REVIEW OF LITERATURE

2.1 IMPORTANCE OF SMALL RUMINANTS IN NIGERIA

Sheep and goats are typical cloven-hoofed ruminants of relatively small size collectively referred as small ruminants (Egahi et al., 2012). Ruminant animals are recognized to be among the least tolerant to heat stress, which is caused by one or a combination of environmental factors such as ambient temperatures, relative humidity, solar radiation, and air movement (Uyeno et al., 2010). Ruminant animals help in turning nutrients in the waste into animal products for human use especially when they are fed with poultry litter (Jordaan, 2004). Small ruminants remain popular among the rural populace and resource-poor people. Their importance is primarily associated with their small size, which is of significant advantage for mankind as it favours low investments and minimal risk of loss. Their preference over large ruminants for food, reproductive efficiency and economic use of available marginal land is noteworthy (Omoike, 2006). They have long constituted an integral part of traditional crop-livestock production systems in Sub-Saharan Africa.

Raising small ruminants (sheep and goat) is an important economic activity from which food (meat, milk) and non-food commodities (manure, hides and skins, wool, etc) and cash income are derived. Meat is one of the most important small ruminant products (Seyoum, 1992). Sheep and goat milk is essential as a source of high quality protein and Ca in arid areas, especially for starving or malnourished people, where cattle have difficulties to be maintained (Zervas and Tsiplakou, 2011). The quantities of sheep and goat milk produced represents 1.3% and 2.1% of the total world’s milk production, respectively, with the commercial dairy sheep being concentrated in the Europe and the countries on or near the Mediterranean basin (FAO, 2007). Furthermore, Hooft et al. (2008) stated that small ruminants play risk mitigation, cultural, religious and social roles.

In Nigeria, sheep are kept primarily for meat production. They contribute about 11% of the total meat supply in the country (Adu and Ngere, 1979). Meat constitutes the foremost animal product that is highly explored by the Nigerian households, particularly for direct consumption and as such, the ruminants, especially cattle, constitute the major and cheapest source of meat consumption for most households in the country. Although the small ruminants, especially goats, are as well slaughtered for meat sale, the small size of the animals and high market price of their meats make the animals less demanded for regular meat consumption. However live goats and sheep are much more easily acquired by individuals in relation to cattle owing to market price differentials between the small and large ruminants (Lawal-Adebowale, 2012).

The total world population of 1024 million sheep and 768 million goats are found mainly in developing countries. Asia and Africa together account for as much as

64.5% and 91.5% of the total world’s sheep and goats population, respectively, while the respective figures for Oceania and Europe together is 27% and 2.4%

(FAO, 2007). It was reported that Nigeria had a population of 56,524,100 goats,

33,519,800 sheep, 16,578,000 cattle, 7,471,730 pigs and 192,313,000 chickens (FAO, 2012).

Umeh (2004), using an assumed growth rate of 2.4% and off-take rate of 25%, projected that in the year 2015 Nigerian population of sheep and goats would be 39,991,693 and 63,951,802, respectively, with corresponding meat production of 1,499,688 and 15,987,951 tonnes.

Livestock, especially ruminants, are important contributors to the amount of the

Green House Gas (GHG) emissions from agriculture into the atmosphere (FAO, 2006). The possible environmental pollutants produced by livestock are nitrogen, phosphorus and other organic compounds (e.g., methane and nitrous oxide) (Yang et al., 2010). The amounts of nitrogen excreted in animal manure have increased markedly during the last 2 or 3 decades, causing unacceptable air and water pollution (Hristov and Pfeffer, 2005). Major contribution (37% of global anthropogenic methane) of greenhouse gases comes from methanogenesis during fermentation of feeds in the rumen (FAO, 2006). The types of management systems employed in rearing livestock or in livestock production play an important role in reducing or increasing GHG emissions from the agricultural sector (Aby, et al.,

2013). A number of studies (Beauchemin et al., 2008; Martin et al., 2010 and Patra, 2012 cited by Patra, 2013) have focused on exploring technologies and policies for the mitigation of enteric methane emissions in ruminants. Perhaps, due to lack of appropriate facilities, the amount of contribution to methane production by our ruminant animals has not been documented.

2.1.1 Breeds of Sheep, Population and Distribution in Nigeria

According to Nuru (1985), Nigeria had the highest number of goats (52%) in the West African sub-region, but second to Sahel countries only in the production of sheep and goats. Sheep population in Nigeria was estimated (FAO, 2012 cited by Suberu et al., 2013) to be 33.52 million. Sheep and goats are widely distributed in

Nigeria in rural, urban and peri-urban areas representing about 63.7% of total grazing domestic animals in Nigeria (Gefu, 2002). Sheep are the second most numerous pastoral species in Nigeria, and small flocks often accompany many cattle herds in the north and in the Middle-Belt (Ugwu, 2007). The highest sheep population was recorded in the North West zone, where Kano State has the largest population of about 2.6 million heads and Zamfara recording the lowest sheep population of about 857,000 heads. The South West zone had about 1.1 million heads of sheep with Edo State having the highest population of 668,410 heads (FMARD, 2002).

There are four main breeds of sheep indigenous to Nigeria: They are the Balami, Uda, Yankasa, and West African Dwarf (WAD) sheep. Out of these four breeds of sheep, the WAD breed is mainly found in the southern region of the country. The Balami and Uda are predominant, respectively in the north-eastern and northwestern parts of the country, where they thrive and survive better (LawalAdebowale, 2012). Yankasa breed is the most numerous and widespread in the country, constituting about 50 - 60 % of the national population (Osinowo et al., 1992). According to Aganga et al (1988), Yankasa breed has been the most extensively studied in Nigeria. The coat colour is white with black patches around the eyes and sometimes on the feet. The muzzle and ears are usually black too. Ewes are polled, but the rams have curved horns and hairy white mane. In the wet season, Yankasa sheep do not need daily watering and once-a-day watering suffices in the dry season. Osinowo et al (1992) observed that pre-weaning growth performance of Yankasa sheep was generally better in the wet season than in the dry season while the reverse was true for weaning rate. The authors recorded a birth weight of 2.51 ± 0.01 kg, 90-day weaning weight of 10.87 ± 0.08 kg, average daily gain to weaning of 91.86 ± 0.91 g/d, and weaning rate of 77.8 ± 1.0%. And further observed that dam parity, litter size, month and year of birth significantly affect the birth weight, weaning weight and average daily gain of Yankasa lambs, but sex does not. It was reported (Adewumi and Olorunnisomo, 2009) that Yankasa ewes produce more milk (307.7 ml) than West African Dwarf (WAD) ewes (239.8 ml) when body weight is not considered, but WAD sheep produce more milk (11.5 ml/kg) per kilogram of body weight than the Yankasa (10.5 ml/kg).

2.1.2 Factors Affecting Productivity of Small Ruminants in Nigeria

The Productivity of ruminants is dependent on the potential of a feed to supply, through effective microbial degradation, balanced nutrients for production. Digestible dry matter intake is highly correlated with animal productivity offered individual feeds (Devendra, 1996). Voluntary Feed Intake (VFI) is the single most important factor affecting production in animals and is also associated with digestibility of the feed, and proportion of the digested material that’s absorbed (Devendra, 1996). According to ILRI (1995) during a global consultation to define the priority for livestock research, feeding and nutrition was identified as the major constraint to productivity of the animals.

Goats and sheep rearing in the Mediterranean and Tropical environments, including Nigeria, have been hampered over the years primarily by the seasonal nonavailability of good quality feeds which results into weight losses, low birth weights, lowered resistance to diseases, and reduced animal performance (Onwuka et al., 1989; Winrock international, 1992; Ademosun, 1994; Almeida et al., 2007). Several survey reports (Okorie and Sanda, 1992; Aliyu et al., 2005; Shiawoya and

Tsado, 2011) had indicated that supplementary feeding is rarely practiced by most small ruminant farmers because of the high cost of supplementary feed ingredients.

The resulting preference for extensive and semi-intensive systems of management (Lawal-Adebowale, 2012), is however fraught with some problems (e.g. energy deficit) that affect efficient productivity of sheep and goats (Mohgoub and Lu, 2004; Bushara et al., 2010).

The finding of Aphunu and Okoedo (2011), who investigated small ruminants production constraints in Delta state, was in line with Williams and Williams (1991) assertion that the Livestock Extension Service of the Agricultural Development

Programmes (ADPs) is generally poorly organized and in some cases non–existent.

The authors’ findings also confirmed the assertions made by Omoike (2006) that the major problems of sheep and goats rearing include among other things, the inadequate supply of water and pasture especially in the dry season, as well as problems arising from inadequate veterinary services and infrastructure. Kagira and Kanyari (2001) reported that among several constraints that limit productivity of livestock, diseases and parasites are of major importance. Parasitic gastroenteritis has been noted as major constraint to ruminants’ productivity in terms of pathology and economic importance (Biu et al., 2009). Clarence et al. (1991) also reported that lameness due to diseased condition results in significant reduction in productivity of the livestock. Locomotory soundness is a requirement for effective grazing and reproductive performance in all classes of livestock (Egwu et al., 1994).

According to Ademosun (1994), small ruminant breeds in tropical Africa are characterized by small birth weights, low milk production, slow growth rates and small mature weights. However, it was observed (Rege, 1994) that there has been a tendency to over-emphasize the low productivity of indigenous breeds of small ruminants without due consideration of some important characteristics of these breeds, and that when their small size and the harsh environment under which they are raised are taken into account, their productivity is impressive. The author argued that, indeed, the high-performing temperate breeds cannot survive under traditional management in most African environments. Crossbreeding of exotic breeds with indigenous ones is a strategy that will take the advantage of breed complementarily and/or upgrading to allow gradual improvement in productivity.

2.2 FEED RESOURCES FOR SMALL RUMINANTS

2.2.1 Cereals, legumes and fodder crops

Feed resources are the central components and drivers of production systems. The efficiency of use of the available feed resources is especially important as it is the primary determinant of animal performance and productivity (Devendra and Leng, 2011). Fodder resources (cereals, legumes and fibrous crop residues) in warm climates provide the principal sources of feeds for ruminants (Devendra, 1996). Ruminant livestock survival in Nigeria has depended largely on the extensive native pastures, browses and farm crop residues across and within the various agroecological zones (Shiawoya and Tsado, 2011; Aruwayo and Maigandi, 2013). Traditional farmers in the semi-arid region of Nigeria allow their goats, sheep and cattle to browse on tree forages, in the range lands and they also cut and feed these tree foliages as supplements based on experience and convenience (Njidda, 2010).

2.2.2 Sugar Beet and Citrus Pulps

In China, some ingredients such as sugar beet and citrus pulps are widely used as sources of energy for ruminant animals. These ingredients are either fed sole or mixed with molasses (Onwuka et al., 1997; Zhao et al., 2013). Most of these ingredients have high content of neutral detergent soluble fibre (NDSF; largely pectin substances) and sugars. In addition, Molasses and urea are known as sources of readily available energy and nitrogen, respectively, used in feeding ruminants (Preston and Leng, 1987). For example, Salem et al. (2013) investigated the addition of urea, molasses or mixture of both to ensiled fodder trees’ forage. They observed increased metabolisable energy (ME), organic matter degradability (OMD), as well as increased gas production (GP) when molasses was added, and suggested that addition of molasses to forage from fodder trees might improve nutrient utilization in ruminants. Increased flow of microbial crude protein to the small intestine and higher efficiency of microbial synthesis (EMS) were observed

(Huhtanen, 1988) when molasses was supplemented to cattle fed grass silage. However, it was found (Hemingway et al., 1986) that dried molassed sugar-beet pulp, containing either 200 or 400 g of molasses per kg, did not affect either milk yield or milk components when given to cows receiving grass silage and hay.

2.2.3 Lignocellulosic Agricultural By-products

In tropical countries of the world, the ruminants are fed on lignocellulosic agricultural by-products like cereal straws, stovers, sugarcane bagasse and tree foliages, and cakes of oil seeds like groundnut, cotton, mohua, neem and mustard (Kamra, 2005). Cassava and maize leaves have also been found to be valuable feed materials for ruminants, meeting the nutritional requirements for growth, reproduction and maintenance of ruminants year round (Wanapat et al., 2000). Cassava leaves can be fed in mixture with maize leaves and can be used in the diet mixtures of up to 75% of DM fed. This was found to improve feed intake, nutrient digestibility and N utilization leading to a better weight gain in sheep. Therefore, cassava and maize leaves which are otherwise waste materials can be used as substitute to hay in the seasons when grass forage supply is scarce, especially in the smallholder sheep production system (Fasae et al., 2012).

2.2.4 Wheat Middling

These are by-products from wheat milling and are used as feed for animals. They consist mostly of wheat pericarp, germ, and a small amount of endosperm tissue from various mill streams including the bran, shorts, germ and flour streams (Reed et al., 2006). Tufarelli et al. (2011) in trial fed a diet containing 600 g/kg dry matter

of wheat middling (WM) as total mixed rations for lambs and observed improvement in final live weight and gain, feed conversion ratio, slaughter weight and cold-carcass dressing, and concluded that WM maintained lamb performance and had no negative effect on lamb performance and carcass traits.

Fodder trees and shrubs constitute an important feed resource in harsh environments with long dry periods, because they provide forage for grazing ruminants throughout the year or at specific critical periods of the year, particularly when herbage is scarce or when the quantity and quality of herbaceous species sharply decline (Devendra, 1990). The use of fodder trees and shrubs to ameliorate problems of inadequate feed supply in small ruminant production has long received research attention (Paterson et al., 1999; Aregheore, 2004). Some indigenous species have been selected to serve as supplements to the low quality forage fed to animals (Pezo et al., 1990). Adegun et al. (2011) reported that most trials in the Humid Zone of

West Africa (HZWA) conducted by the International Institute for Tropical

Agriculture (IITA) and the International Livestock Centre for Africa (ILCA), now

International Livestock Research Institute (ILRI), involved Gliricidia sepium and Leucaena leucocephela which have shown benefits to crop production and animal improvement through alley farming and feed gardens. For instance, Ademosun et al. (1985) reported an improved daily dry matter intake (DDMI, 42.3 g/kg0.75/d), and significantly higher growth rates (36.0 g/d), when WAD goats were fed Gliricidia supplemented with Leucaena, than when only Gliricidia was fed (37.9 g/kg0.75/d and 23.3 g/d, respectively), with the latter being similar to those reported for goats at village level. However, these species may have limitations in terms of productivity, palatability, presence of toxic substances (e.g. tannins) and adaptability (Akingbamijo et al., 2006), and also, the reluctance of smallholder farmers to adopt these tree species as supplements for small ruminant nutrition (Adegun et al., 2011). In spite of being an excellent source of nutrients, a number of toxic constituents which severely limit livestock performance are contained in Gliricidia (e.g. Coumarine, O-coumaric acid, hydrochloric acid and tannin) and Leucaena (e.g. mimosine, phytin and tannin) (Manoji and Samiran, 2007; Aye, 2012; Chisowa and Mwenya, 2013).

There are many agricultural crop residues [e.g. maize, wheat, rice, sorghum, millet and barley (straw), maize, millet and sorghum (stover), maize cob, sorghum panicle, cowpea (husk and hay), cowpea and groundnut (shell, and haulm), e.t.c.] with great potentials for ruminant animal feeding (Bello and Tsado, 2013). Others include sugar cane tops, bagasse, cocoa pod husks, pineapple waste and coffee seed pod pulp, all of which are generally produced with high biomass in humid and subhumid regions (Devendra, 1996). They have been used mostly as roughage for cattle, sheep, goats and horses (Alawa and Umunna, 1993). According to Lufadeju

(1988), over 111.5 million tons of crop residues are produced annually in Nigeria.

Fibrous crop residues (FCR) form the main base in feeding systems throughout countries with warm climates (Devendra, 1996). Sibanda and Said (1993) cited by Otaru et al. (2011) also reported that crop residues and agro-industrial by-products constitute the bulk of ruminants’ diets in developing countries and they are limiting in the nutrients such as amino acids, long chain fatty acids (LCFAs) and glucogenic precursors required by the animals.

In the northern grassland ecology of Nigeria, pastoralists use significant quantities of crop residue while their livestock return manure to the soil. Small-scale ammonification treatment of maize and sorghum stovers known as CRUPROCESS is being extended to farmers in Kano to improve the feeding quality of the straw (Onwuka et al. 1997). Large scale use of crop residues is not common in southern part of Nigeria, due to low level of livestock husbandry, even though a lot of crop residues are being generated from cropping and from households (Onwuka et al.

1997).

2.3 FORAGE RESOURCES IN NIGERIA

Forage and fodder crops include pasture and range vegetation, as well as crop residues derived from farm crops. Nigeria has a land area of 92.4 million hectares of which about 44% constitutes rangeland or natural pasture, which support its domestic ruminants of over 101 million (FMAWR, 2008; Shiawoya and Tsado, 2011). Shiawoya and Tsado (2011) observed that forage and fodder crops production is a very important component of Nigeria’s farming systems, not only from the perspective of cereal and pulses production for human consumption, but also from the perspective of providing adequate feed for the livestock sub-sector of the economy. Some of the important forage species in various agro-ecological zones in Nigeria include: Andropogon gayanus (Gamba grass), Cenchrus ciliaris (Buffel grass), Pennisetum pedicellatum (Kyasuwa), Digitaria decumbens (Pangola grass), Digitaria smutsii (Woolly finger grass), Setaria sphacellata (Golden blue grass),

Panicum maximum (Guinea grass) and Pennisetum purpureum (Elephant grass). These grasses which are fibrous in nature are rich in cellulose and provide the ruminants with high level of structural carbohydrate and some measures of vitamins and minerals (Kallah, 2004).

Important browse plants common across the agro-ecological zones in Nigeria include: Cajanus cajan (Pigeon pea), Butyrospermum paradoxum (Shea butter tree),

Gliricidia sepium (Almond blossom), Gmelina arborea (Gmelina), Ficus thoningii (Ficus), Zizyphus mauritiana, Hibiscus rosa-sinensis (Chinese hibiscus), Acacia albida (Ana tree), Acacia seyal (Shitting wood) etc. (Shiawoya, 2006). For instance, significant increases were found in intake and digestibility of barley straw fed to sheep when dried Gliricidia and Calliandra calothyrsus were offered as supplements (Ahn, 1990). Otaru (1998) investigated the effects of replacing fresh gamba grass with wilted Ficus leaves in the diet of Red Sokoto bucks, and concluded that Ficus thoningii leaves could be included in the diets of goat up to

30% without any adverse effects on intake, digestibility of nutrients and growth. Inclusion of Zizyphus mauritiana leaf meal in the concentrate diets of Yankasa ram lambs at 10-20% inclusion levels was found to produce best result in terms of performance than when the leaf meal was fed at higher levels of inclusion to ram lambs (Abdu et al., 2012).

Given the distinct nature of the ruminants’ stomach, the farm animals heavily depend on forage or roughage as major feeds. Forage availability problems can limit herbivore populations, and affect foraging behavior and growth rates (Therrien et al., 2008). Reduced foraging time can limit energy gained by an animal, adversely affecting body condition and subsequent reproductive success (Belant et al., 2006 cited by Severud et al. 2013). Forages are a vital part of total mixed rations (TMR) for dairy cattle providing them with physically effective fibre (e.g. forage particle size) needed to maintain proper rumen health and functioning. A fine particle size may adversely affect stratification of ruminal digesta, providing fewer stimuli for chewing activity and ruminal contractions (Mertens, 1997), which may result in a reduced ruminal pH, depressed fibre digestion and feed intake as well as lowered feed efficiency (Tafaj et al., 2007). In addition, the use of higher proportions of high-quality forages in the diet of dairy cows can help in maintaining high digestible energy intake of the cows despite decreasing concentrate inclusion level, plus the associated cost of feeding (Zebeli et al., 2010). Maize silage and grass silage are conserved forages mostly used in the feeding of dairy cows in many parts of the world. They are fed as single forage components, or together, depending mainly on the region, availability, and feeding purpose (Zebeli et al., 2010).

2.3.1 Limitations of Forage Feed Resources

Forage digestibility in ruminants is constrained by the extent of cell wall neutral detergent fibre (NDF) digestion (Van Soest, 1994). Another cell wall component, lignin, is generally accepted as the primary component responsible for limiting the digestion of forages (Traxler et al., 1998). In tropical regions like Nigeria with two different seasons, the quality of grass changes with seasons. For example during the rainy season tropical forages under grazing have good quality, in the dry season its nutritive value is severely reduced, with increased lignin content in the cell wall and a decreased total content of nitrogenous compounds. These modifications can compromise the availability of energy from forage (Paulino et al., 2006) by reducing the neutral detergent soluble compounds and decreasing neutral detergent fibre (NDF) digestibility (Van Soest, 1994 cited by Detmann et al. (2009). Lowquality tropical forages are deficient not only in nutrients for animal performance, but also in substrates (e.g. nitrogen) for microbial metabolism (Detmann et al., 2009).

The nutrition of sheep in tropical and sub-tropical countries is mainly based on lowquality crop residues and natural pastures. Most of the roughages in these regions are deficient in crude protein, metabolizable energy and some minerals (Ash, 1990 cited by Patra, 2009). Adamu et al (1993) showed that the CP content of the native grasses during the dry season is about 1.5 to 3%. This is below the minimum of 7% CP required in forages to enhance voluntary intake, digestibility and utilization by ruminants (Smith, 1993). Crop residues are characterized by high content of fibre usually above 40%, low content of nitrogen (0.3-1.0%) and low content of essential minerals such as Sodium (Na), phosphorus (P) and Calcium (Ca), which result in reduced feed intake and low performance by the ruminant animals (Adegbola, 1998).

Leguminous trees and shrubs often have thorns, fibrous foliage and growth habits which protect the crown of the tree from defoliation. Many plants also produce chemicals which are not directly involved in the process of plant growth (secondary compounds) but act as deterrents to insects and fungal attack. These compounds also affect animals and the nutritive value of the forages. Mycotoxins (fungal metabolites) produced by saprophytic and endophytic fungi are also a potential source of toxins in forages (Norton, 1994). The utilization of the browse is limited by the high lignin content and the presence of anti-nutritional factor which may be toxic to ruminants (Njidda, 2010).

Feeding of forages alone does not support full expression of genetic potentials of ruminant animals. From an experiment conducted by Singh et al. (2011) to evaluate the effect of feeding crop residues of cereals and legumes on weight gain of Yankasa rams, it was concluded that feeding the residues of cereals alone resulted in a mean weight loss of 14% for sorghum, 16% for maize and 11% for millet, while feeding the residues of cowpea or groundnut alone resulted in the weight gain of about 13 and 12%, respectively. Researchers (Alhassan et al., 1984; Alhassan, 1985; Bello and Tsado, 2013) who fed Sorghum Stover to sheep and goats suggested supplementation with a minimum of 60 g of cottonseed cake (CSC head / day) for sheep and 50 g/ head/ day for goats to reduce weight losses.

2.4 FEED SUPPLEMENTS

The availability of supplements is an important prerequisite in enhancing the utilization of fibrous crop residues irrespective of whether these are treated or untreated with alkali to improve digestibility and voluntary feed intake (Devendra, 1996). Bowman and Sanson (1996) defined supplements as feedstuffs added to the basal diet to provide nutrients required to support the desired level of production. To meet the nutritional needs of ruminants, supplemental CP is often provided to increase forage intake (Lintzenich et al., 1995), DM digestibility (Delcurto et al., 1990), and body weight (BW) gain (Bodine et al., 2001). Supplementation of crop residues with rumen degradable nitrogen (RDN) is necessary in order to meet the protein requirement of rumen microbes for microbial growth and optimum rumen fermentation, and digestion of crop residue based diets. The efficiency with which the RDN in diet is converted to microbial protein, determines the overall efficiency of ruminant diet on one hand and loss of nitrogen in the urine on the other (Chen et al., 1999). Olson et al. (1999) and Mathis et al. (2000) have well established that supplementation of low-quality forages with concentrate supplements can boost intake of low-quality forages, enhance the utilization, and increase productivity of ruminants. Stockdale (2008) reported that over the last two decades, the increasing use of supplementary feeds, particularly cereal grain-based concentrates and byproducts has contributed to increased production per cow and per farm in the Australian dairy industry.

Fat supplementation is a common practice for increasing energy density in diets fed to high-producing dairy cows without sacrificing fibre content (Kargar et al., 2010). Fat sources have played important roles in increasing energy density of diets and offer alternatives to feeding excessive amount of cereals, and thus prevent problems of ruminal acidosis, off-feed, lameness and low milk yield (Groehn et al., 1992 cited by Otaru et al. 2011). Supplementation of natural protein to ruminants consuming low-quality forage (<6% CP) improved forage intake, nutrient digestibility, animal performance and reproductive efficiency compared with non-supplemented controls, (Wiley et al., 1991; Bandyk et al., 2001; Bohnert et al., 2002 cited by McGuire et al., 2013).

Providing supplement to grazing animals is another way of compensating for the absence of good-quality forage (Van Soest, 1994); it can improve performance and carcass quality, but its high cost can limit its usage. Mamani-Linares and Gallo

(2013) fed wheat bran/sorghum grain concentrate supplement overnight at rate of

0.30 kg/animal/day to young llamas grazing native pasture and observed greater live weight, greater carcass weight, greater fat deposits and improved carcass characteristics, and concluded that supplementation with concentrate was a good alternative in the production of llama meat, especially in the dry season where there is poor pasture availability. Several studies have shown that concentrate ration supplementation during prepartum period had impact on growth and improved goats productivity (Totanji and Lubbadeh, 2000; Madibela and Segwagwe, 2008).

Bushara et al. (2010) fed 350 g/head/day of concentrate supplement to grazing Taggar goats to investigate effect of type of ration on productive and reproductive traits. The authors observed higher birth weight, higher weaning weight, lower milk fat, higher milk total solid, shorter kidding intervals and reduced incidence of abortions for the supplemented groups.

2.4.1 Concentrate Supplements (Energy, protein, vitamins and minerals) The use of conventional feedstuffs such as maize, soybean cake, fish meal and others as supplement to low quality feed may not be cost effective in the present day Nigeria to intensify ruminant animals production, owing to their high cost, their irregular supply (Akintunmi, 2004) and the competition over them with both humans and monogastric animals (Adama, 2008; Ajayi et al., 2008; Ukpabi and Abdu, 2009). Effective and economical sources of nitrogen (N) are needed as supplements for better use of crop residues in dairy diets (Sarwar et al., 2002). Due to its lower cost per unit of N compared with most sources of natural protein, urea (non-protein N; NPN) is a popular source of supplemental N (McGuire et al., 2013).

Supplements serve essentially to promote efficient microbial growth in the rumen, and/or increase nutrient supply for digestion in the small intestines. Protein supplement could be from non protein nitrogenous sources such as urea, and natural protein e.g. cottonseed cake, or multi-nutrient mixtures involving molasses and mineral sources made into liquid mixtures or solidified into blocks and served as multi-nutrient block licks (MNBL) or leguminous forages that have a low level of tannins (1-3%), dried or heat treated e.g. Acacia spp., Gliricidia maculata and Leucaena leucocephela (Devendra, 1996). To ensure better use of forage-based diets, the recommended supplements have to be energy-and protein-based supplements (Hersom, 2008). When conditions in beef cattle production demand increased energy intake, grain supplementation is often practiced (Carey et al., 1993). Corn supplementation at levels as low as 800 g/d in mature cattle has decreased in vivo cellulose digestibility and forage intake (Lusby and Wagner, 1986). However, increased concentrate intake increases the production of shortchain fatty acids and lowers rumen pH, possibly resulting in ruminal acidosis (e.g. Plaizier et al., 2008). This can even generate tympany (Lowman and Lewis, 1991), and increase the incidence of laminitis and liver abscesses (Nocek, 1997 cited by Manninen et al., 2010).

Readily digestible fibre sources such as soybean hull and immature forages fed as energy supplements to ruminants have increased forage intakes (Ørskov, 1991) and increased digestibility. For instance, brown midrib corn silage and sorghum silage have been shown to have less lignin and greater fiber digestibility than parent stock and have produced more milk when fed to cows (Oba and Allen, 1999; Aydin et al., 1999). Supplementation of energy may alter energy requirements of grazing ruminants by altering grazing behavior or by influencing efficiency of nutrient use (Caton and Dhuyvetter, 1996). Pordomingo et al. (1991) reported that cattle supplemented with corn while grazing summer pasture had reduced forage intakes.

The commonest protein supplement used for ruminant feed in northern Nigeria is cottonseed cake (CSC). Cottonseed cake is obtained from cotton after the removal of the lint, followed by oil extraction from the seed. It has a protein content of 3844% (Milo, 2010) depending on the efficiency of oil extraction but deficient in lysine, methionine, leucine and isoleucine (Ramesh, 2000 cited by Aruwayo and Maigandi, 2013). In forage-fed ruminants, supplementation of energy or N sources can improve rumen fermentation since carbohydrate and N degradation rates in forages are normally imbalanced (Van Soest, 1994). Nutrient supplementation may enhance rumen microbial population and VFA production (Mould et al., 1983).) Sawyer et al. (2012) cited by Mulliniks et al. (2013) reported that the use of small quantities of high supplemental ruminally undegradable protein (RUP) ingredients combined with salt and minerals sustained ruminal function of animals on low quality warm season forage diets. Mulliniks et al. (2012) reported lower calf morbidity in the feedlot by feeding dams small quantities of a high RUP supplement during late gestation. Thus, protein supplementation in a small quantity of high RUP may have the potential to decrease production costs while optimizing cow and calf performance (Mulliniks et al. 2013). The authors indicated that calves born from dams receiving a self-fed high RUP supplement, consumed at relatively low quantities, were treated less for sickness had decreased death loss, and had increased feedlot net profit.

Robinson (1994) reported that many dairy producers supplement a basal totally mixed ration (TMR) with mixed concentrates or grains to meet the nutritional requirements of higher producing dairy cows because of difficulties in formulating a single mixture for all lactating cows within a herd, with various levels of milk production at various stages of lactation. Adegun et al. (2011) have shown that provision of Moringa-based multinutrient blocks in small ruminants’ diet can enhance better performance and pose no health challenges to the animals.

2.4.2 Supplementary Feeds and their Combinations for Efficient Use of Roughages

The inclusion of supplemental feeds creates a complexity in the feeding scenario that may result in an improved or detrimental animal response (Moore et al., 1999). Supplemental feeds often times have physical structure, solubility, degradation, and chemical characteristics that are different from the base forage utilized. The respective differences may be advantageous to the manipulation of nutrient synchrony. In contrast, the properties of the supplement may exacerbate an asynchronous dietary nutrient supply. In that regard, negative associative effects would be detrimental to the process of dietary nutrient synchrony (Hersom, 2008).

Rumen microorganisms use carbohydrate as the main energy sources although protein also can be used. When adequate energy sources are supplied in the rumen, ammonia N can be converted to microbial protein. If the rate of protein degradation exceeds that of carbohydrate fermentation, large quantities of N are converted to ammonia, and likewise, when the rate of carbohydrate fermentation exceeds that of protein degradation, inefficient microbial protein synthesis may occur (Bach et al., 2005). Therefore, synchrony between the supply of energy and N to the rumen microorganisms should improve the efficiency of the rumen microbes in capturing

N and use of energy for microbial growth (Yang et al., 2010). Since anaerobic fermentative digestion in the rumen provides microbial cells which supply the protein to the animal, the efficiency of microbial growth therefore influences the protein: energy (P/E) ratio in the rumen. Poor microbial growth due to inadequate dietary N for example will result in a low P/E ratio and, conversely, adequate supplementation and good rumen function enables a good P/E in the nutrients available to the animal (Leng, 1982).

According to Hersom (2008) the most frequent supplement strategies include controlling the timing of feed and nutrient delivery, the form in which the nutrients are supplied and supplement types, and finally, attention to the balance of energy to protein in the diet. An important observation is that each particular type of supplement (i.e., energy or protein) also generally supplies other ancillary nutrients. The complement of energy and protein in supplements may increase the likelihood of dietary nutrient synchrony in forage fed cattle (Hersom, 2008), but more important is the synchronization of the rate of degradation of feed nitrogen and carbohydrate or organic matter components (Rusell and Hespell, 1981; Orskov, 1982).

The strategic supplementation with limiting nutrients become the best option for cattle management, especially when this supplementation is based on feeding nitrogenous compounds, which stimulates the cellulolytic activity in the rumen and increases the utilization of low-quality fibrous carbohydrates (Costa et al., 2008; Detmann et al., 2008 cited by Detmann et al., 2009). Also, Currier et al. (2004) studied the effects of urea or biuret supplementation on ruminants consuming lowquality forages and found that total DM, OM, and N intake; DM, OM and N digestibility; N balance; and digested N retained were greater for supplemented groups than for unsupplemented control group. However, decrease in voluntary intake associated with excess use of nitrogenous compounds supplements such as urea and ammonium sulfate were also observed by other authors when they fed cattle with low-quality forage supplemented with ammonium sulfate, urea and albumin (Lazzarini, 2007; Sampaio, 2007).

Mertens and Loften (1980) reported that supplementation of forages with starch decreased fiber utilization in vitro. Rapid fermentation characteristics of starch supplements often exceed the ability of ruminants to maintain a stable ruminal pH (Orskov and Fraser, 1975) and as pH decreases, cellulolytic bacterial function is often impaired and fiber digestion decreases. Sanson et al. (1990) demonstrated that increasing levels of cornstarch supplementation decreased forage intake in steers. These reductions have been attributed to either depressions in ruminal pH or a carbohydrate effect (Bargo et al., 2002). Declining ruminal pH associated with increasing dietary starch should affect the ruminal bacteria toward greater amylolytic and lower cellulolytic population. Resulting bacteria shifts are thought to reduce fibre digestion and negatively affect intake of grazed forage (Caton and Dhuyvetter, 1997). However, increased forage intake had been reported when sheep were fed low levels of corn supplement (7.8% of DM intake) (Henning et al., 1980; Matejovsky and Sanson, 1995).

Maximum fermentation rates are attained when all factors required by the ruminal microorganisms are available, namely- a source of energy (sugars, cellulose), nitrogen (N), sulphur (S) and minerals. When the rate of fermentation is restricted feed intake decreases; and nutrient availability to the animal is likewise limited

(Norton, 1994). Sharma, et al. (2008) evaluated the feeding value of Oak (Quercus incana) leaves (OL) as a supplement to wheat straw (WS) in calves. The authors observed that supplementation of WS/OL ratio of 44:56 enhanced DMI, digestibility, efficiency of N utilization and body weight gain compared with a WS/OL ratio of 100:0. The increase in total DMI was reported to be associated with improved N and energy supply to cellulolytic bacteria (Chakeredza et al., 2002), leading to increased degradation rate of poor quality roughage, and to a higher digesta passage rate (Goodchild and McMeniman, 1994). Manipulating rumen fermentation through strategic supplementation with concentrate and forages could improve rumen efficiency through maintaining optimum pH, optimizing volatile fatty acids (VFAs) and ammonia-nitrogen (NH3-N) utilization for microbial protein synthesis and reduction of methane (CH4) production thereby enhancing the productivity of ruminants in the tropics (Khampa and Wanapat, 2007).

One way of utilizing fodder trees is to use them as feed to small ruminants as part of, or along with, multi-nutrient blocks (MNBs) (Agbede and Aletor, 2004; Aye, 2007). According to Habib et al. (1991), MNBs create an effective ecosystem and increase intake and digestibility of low quality, high fibre grasses usually consumed by the small ruminants. Exogenous fibrolytic enzymes hold a lot of promise as mean of increasing forage utilization, milk production, average daily weight gain and improving the productive efficiency of ruminants. They are, however, limited by their hydrolysis in the rumen environment (Peters et al., 2010). Fon and Nsahli, (2013) stated that as a result of banning the use of antibiotics in ruminant feeds to improve feed efficiency and promote growth, supplementing fibrous forages with probiotics that can survive in the rumen has become a substitute. They further stated that if these microbes can colonize and establish in the rumen, fibrolytic enzyme availability would be continuous. Milk production, average daily weight gain, dry matter intake, microbial population, fibre utilization and animal performance have shown marked increase when ruminant animals are supplemented with direct-fed microbial consortia (Aydin et al., 2009). However, Raeth-Knight et al. (2007) did not observe any significant change in the digestibility parameters of Holstein dairy cows when supplemented with direct-fed microbial consortia.

2.5 RUMEN ENVIRONMENT AND NUTRIENT SYNCHRONY

The rumen is an environment with a diverse population of microorganisms, consisting of bacteria (1010-1011 cells/ml, of more than 50 genera), ciliate protozoa (104-106/ml, of 25 genera), anaerobic fungi (103-105 zoospores/ml, of five genera) and bacteriophages (108-109/ml) (Kamra, 2005). The rumen microorganisms ferment dietary carbohydrates and protein to obtain energy and N for maintenance and growth. Through this process, the two major nutrients or products (i.e. VFA and microbial protein) for the host animal are produced (Yang et al., 2010). Microbial protein synthesis (MPS) is important in ruminants because microbial protein synthesized in the rumen provides from 50% to nearly all amino acids required by ruminants, depending on the rumen undegraded protein (RUP) concentration of the diet (NRC, 2000). Non-structural carbohydrate (NSC)-fermenting microorganisms usually represent a predominant population of rumen microbial flora in highproducing ruminant animals, such as lactating dairy cows and feedlot beef cattle. The nitrogen requirement of NSC-fermenting microbes can be met by either ammonia or peptides and amino acids (Russell et al., 1992).

Microbial processes in the rumen confer the ability on ruminants to convert fibrous feeds and low quality protein, even non-protein nitrogen, into valuable nutrients for the ruminant animal (Dewhurst et al., 2000 cited by Chandrasekharaiah et al., 2012). Microbial proteins synthesized within the rumen provide a major source of amino acids to ruminant animals. The ruminal microbial ecosystem can be divided into two groups, microbes that ferment structural carbohydrate and those that ferment non-structural carbohydrate (NSC, Russell et al., 1992).

According to Kung (2011), the optimum pH of the rumen for efficient and effective fermentation or degradation of feeds (especially fibre) ranges from 6.2 to 6.8. At pH below 6.0 - 6.2, fibrolytic bacteria in the rumen become less active and fiber digestion is decreased. Further decrease in pH to between 5.8-5.9 causes mildly acidic rumen environment and cessation of fiber digestion. Excessive feeding of concentrate, especially grains has been implicated as the cause of acidosis in ruminants when rumen pH falls below 5.0 – 5.2 (Allen, 1997; Carro et al., 2000). Kanjanapruthipong and Leng (1998) reported that ruminal fluid ammonia is the major source of nitrogen for microbial synthesis and growth and that critical levels of has been from 50 to 250 mg of ammonia-nitrogen/ litre of rumen liquor.

The term “synchrony” derived from Greek for “together” and “time”, means simultaneous occurrences in general (Hall and Huntington, 2008). In ruminant nutrition, “nutrient synchrony” means parallel occurrence of both rumen degradable protein (RDP; non protein N and rumen degradable true protein) and energy (ruminally fermentable carbohydrates) for the ruminant animal to consume or be present in the diet and rumen, so that an increase or optimization of microbial efficiency would occur (Hersom, 2008; Yang et al., 2010). The synchronic ingestion of protein and energy is important for the ruminant micro flora (Schilcher, et al.,

2013).

Feeding cows excessive amounts of physically effective fibre decreases feed intake and lowers feed efficiency due to reduced microbial protein synthesis (Yang and Beauchemin, 2006). The synchronization of the ruminal degradation rate of carbohydrates and protein has been shown to increase ruminal microbial protein synthesis (MPS), improve efficiency of N usage and animal performance, and decrease urinary N excretion (Cole and Todd, 2008) because of simultaneous capturing of N and use of ATP (adenosine triphosphate) by microbes for their growth (Richardson et al., 2003; Elseed, 2005; Chumpawadee et al., 2006; Baah et al., 2011)). Some experimental evidences indicated that low nitrogen content of low-quality forages could limit the availability of microbial fibrolytic enzymes in the rumen. Thus, the main effect of the supplementation with nitrogenous compounds would be the higher supply of nitrogenous precursors for the synthesis of microbial enzymes (Costa et al., 2008; Detmann et al., 2008; Souza, 2007 cited by Detmann et al., 2009).

According to Hersom (2008), parameters such as ruminal pH, total VFA and individual acid concentrations, and ammonia concentration, microbial nitrogen yield, and body weight (BW) gain, milk production, or carcass weight accreted are useful indicators of synchrony of release of nitrogen and energy in the rumen during dietary degradation. For example, Chumpawadee et al. (2006) fed diets containing 3 levels of synchrony index (0.39. 0.56 and 0.74) to Brahman cattle at the rate of 2.5% body weight by separate concentrate and roughage. The authors observed linear increase in average daily gain, dry matter, organic matter and neutral detergent fibre digestibility, and ruminal total volatile acids concentration at 6 h post feeding. They concluded that synchronized rate of dietary energy and nitrogen degradation improved ruminal fermentation and digestibility which led to higher growth rate in Brahman cattle fed with straw-based diets.

A rapid release of nitrogen not matched to the release of organic matter from the carbohydrate source could lead to a high absorption of ammonia from the rumen. In that regard, ammonia not captured in the rumen is absorbed and converted into urea in the liver (Baah et al., 2011). According to Yang et al. (2010), there are several ways to supply energy and N to the rumen synchronously. These include: i) changing the concentrate: forage ratio; ii) supplementation of energy or protein sources; iii) using index values and; iv) change in feeding frequency or pattern. Newbold and Rust (1992) suggested that even if the total amount of rumen degradable protein supplied each day meet the requirement of rumen microbes, difference between feeds in rate of degradation of protein or energy substrate may cause short-term imbalances between nitrogen and energy supply to rumen microorganisms. Sinclair et al. (1993) and Khorasani et al. (1994) recommended synchronizing the rate of organic matter and nitrogen degradation for optimal microbial protein synthesis in the rumen.

Studies in sheep (Trevaskis et al., 2001; Richardson et al., 2003) and dairy cows (Kim et al., 1999) indicated an improvement in microbial efficiency and yield when provided with synchronized nutrients. Richardson et al. (2003) examined the effect of calculated dietary synchrony index on growing lamb performance and observed no difference in the ADG (0.187 kg/d) and efficiency of gain (0.178 kg/kg). The authors, however, recorded lower retained energy (0.079 MJ retained/MJ of intake) for lambs fed asynchronous diet compared with lambs fed the intermediate or synchronous diet (0.095 MJ retained/ MJ of intake). Also, Kim et al. (1999) fed carbohydrate supplement (sucrose) to dairy cows in a continuous, synchronous or asynchronous pattern and observed no effect on ruminal pH or total VFA production compared with basal diet of grass silage.

2.6 FEEDING REGIMES IN SMALL RUMINANT PRODUCTION

In ruminant production, feeding regime is used to describe a regulated system/pattern of what meals are been offered, how frequently they are offered, what sequence is followed, and during which particular period they are offered. In Nigeria, small ruminants’ management system may be extensive, intensive or semiintensive. According to Oludimu (1992) and Lakpini (2002), under the extensive management system, goats and sheep graze on large expanse of land or scavenge all day to feed themselves. At best, they are offered feed supplements such as kitchen refuse, cassava/yam/ banana peelings, bean husks and maize chaff. The animals raised under this system are very destructive to crops, and are prone to diseases, risk of theft and parasites infestation which result in low productivity (Weaver, 2005). In intensive type of management system, animals are completely confined and provided feed using the cut-and-carry (zero-grazing) method in which leguminous trees planted in alley farms or intensive feed gardens provide a high-protein diet to small ruminants. Intensive system of management ensures higher growth rate, carcass yield, milk yield, litter sizes and survival rates. But, it is not advised for the rural poor due to the level of input on feeding and health care (Gefu, 2002; Lakpini, 2002). Huijsman (1987) remarked that there is a substantial increase in reproductive performance of dwarf goats when the animals are kept under intensive management.

The author recorded productivity of 10.9 kg liveweight/doe/year under extensive management compared to 24.2 kg liveweight/doe/year in the intensive management system.

Semi-intensive system of management involves allowing the animals to graze for 6 to 8 hours and supplementing them with concentrates after returning to the pens in the evening. Growth and survival rates of animals are high under this system, though it can only be practiced where grazing land is available or during the dry season when crops have been harvested (Lakpini, 2002; Ugwu, 2007). For instance, Osinowo et al. (1992) reported that sheep managed under semi-intensive system are allowed to graze on improved and sown pasture for 6-8 h daily, with 0.3-0.5 kg/day of 15-20% CP concentrate supplement throughout the year, depending on the animal’s physiological status. In addition, changing the frequency of concentrate supplementation such as feeding the supplement in alternate days or every third day (e.g. Tellier et al., 2004) is another feeding regime being employed in ruminant animals production.

Supplementation in most areas where domestic ruminants graze is a major factor to consider when making management decisions. Providing nutrients to offset deficiencies or to meet production demands is more often practiced during the dry season in the tropics and in the periods of summer dormancy or in the fall and winter months in temperate regions (Caton and Dhuyvetter, 1997; Detmann et al., 2009). In situations where optimum sward conditions cannot be maintained, and the nutrient intake of animals falls below the required level, one option available is to provide supplementary feeding. Supplements are usually offered in the morning, when the animals have just completed the first grazing season (Carro et al., 1994). However, irrespective of the management system, it is important to increase the proportion of forage in the diet to reduce or minimize cost (Bouwman et al., 2005) bearing in mind the production objective. Feeding regime, like the number of meals and the sequence of feeding roughage and concentrates during feeding is important to prevent sub-acute ruminal acidosis (Nordlund et al., 1995). The levels of rumen metabolites (VFAs, NH3-N) and pH are closely related with feeding regime (Steger et al., 1970).

2.7 RESPONSE OF RUMINANTS TO SEQUENCE AND FEEDING INTERVAL OF SUPPLEMENT AND ROUGHAGES

Schilcher et al. (2013) investigated the rumen health of different wild ruminant species in relation to feeding managements. In the morning, the test animals were offered with a mixture of concentrates, vegetables and fruits, and at the same time hay. They observed severe lesions on the rumen mucosa of the animals which are fundamental characteristics of subacute ruminal acidosis (Krause and Oetzel 2006). This is because of initial low hay intake as the animals usually eat the concentrate mixture in preference before hay. The authors, therefore, suggested that roughage be offered in the morning before the concentrate meal. Earlier, Morita and Nishino (1991) offered diets to steers separately by feeding hay before concentrate and observed greater DMI in steers fed hay before concentrate compared to their counterparts fed concentrate before hay. Similar results were obtained when this sequence of feeding (concentrate supplement fed 40 min before or after feeding hay) was compared with feeding mixed diet of hay and concentrate (Morita and Nishino, 1993). However, Nocek et al. (1986) observed that the amount of DM intake increased when the mixed ration was offered. On the other hand, some reports pointed out that offering the mixed ration had no effect on DM intake (Holter et al., 1977). Voight et al. (1978) cited by Morita and Nishino (1993) reported that cellulose digestibility in the fore stomach increased when chopped ryegrass was fed before feeding barley or corn.

Zeyner et al. (2004) studied the effects of hay intake and feeding sequence on variables in faeces and faecal water of horses. They found that the horses fed forage 30 min before the concentrate instead of the opposite had higher faecal pH (6.6) and higher faecal buffering capacity (108 mmol/l), compared to faecal pH (6.4) and buffering capacity (84 mmol/l) of horses fed concentrate 30 min before forage. The concentration of acetic acid was higher, the propionic acid lower, and the ratio acetic/propionic acid was higher in the faecal water of horses fed forage before concentrate. The authors concluded that feeding forage before concentrate gives a higher buffering capacity in the hindgut which might protect against acidification of the colon content upon decrease in pH sequel to ingestion of concentrate.

Nocek (1992) showed that manipulating feeding sequences alone can impact performance of primiparous cows. Changing feeding frequency or pattern was employed in some nutrient synchrony studies to assess the effects of feedstuffs on simultaneous availability of energy and N. Because these studies use the same ingredients and alter feeding pattern only, any change in metabolite patterns in the rumen may be due to variation in degradation rates of nutrients in the rumen (Yang et al., 2010). Kaswari et al. (2007) studied the relationship between synchronization index and microbial protein synthesis in the rumen by using different feeding frequency and pattern, and observed that when energy sources (maize grain, grass silage, grass hay, wheat grain or maize silage) were offered first before protein sources ( soyabean meal or peas+ urea), microbial activity was improved although synchrony index (i.e. measure of synchrony between N and energy supply throughout the day which is derived from laboratory chemical analysis and degradation kinetics using nylon bag technique) was low.

Robinson (1989) implicated rapid fermentation of starch in an unbuffered rumen as the cause of rapid decline in rumen pH when concentrate feeding preceded that of forage. In a related study, Beauchemin and Buchanan-Smith (1990) showed that feeding supplemental grains prior to forage can reduce overall forage intake. This could be as a result of rapid decline in pH value of the rumen. Voight et al. (1978) cited by Robinson (1994) recommend feeding of forages before concentrates in order to optimize rumen function. Robinson et al. (1992) showed that changing the feeding strategy of protein supplements can modify rumen outflow patterns leading to modified diurnal patterns in nutrient flow to the intestine. However, Robinson (1994) fed rolled barley or a mixture of rolled corn and soyabean meal 1 h prior to, or after feeding mixed ration to primiparous dairy cows. He observed that the influence of modifying the sequence of feeding grain and forage on productivity of dairy cows was not consistent. The author stated that the numerical differences in virtually all production parameters favoured feeding grain subsequent to the foragebased mixed ration, regardless of rumen fermentability of the supplemental grain. He further observed that the magnitude of the numerical differences were too small to be of productive benefit and attributed it to relatively small amount of grain fed(less than 20% of total DMI) separately from the mixed ration and concluded that the differences between treatments might have been larger if the amount of grain fed had been greater.

It was concluded (Robinson, 1994) that the productivity of late lactation primiparous cow was not modified by changing the sequence of feeding supplemental grain relative to a forage- based mixed ration, and in addition, the effect of the feeding sequence on animal performance was not influenced by the rumen fermentability of the grain. But, Beauchemin (1992) recommended to dairy producers that forages should be fed before starch-rich concentrates, particularly in the morning, in order to increase rumen buffering capacity. And alternately, less rapidly fermentable starch sources, such as corn, should be substituted to reduce the rate of production of volatile fatty acids and lactic acids. Both of these practices have been reported (Robinson, 1989; Beauchemin, 1992) to result in higher intake of forage and increased overall animal productivity. Furthermore, Carro et al.

(1994) studied the effect of time of supplementary feeding on performance of sheep. The authors offered cereal-based concentrate supplement 1 h after feeding hay in the morning and 30 min before feeding hay in the afternoon, at the rate of 700 g/sheep/d, and observed a higher total OM intake when concentrates were given after rather than before a period of ingestion of hay. This suggests that feeding supplement after rather than before a major grazing bout may be an effective means of minimizing reduction in forage intake as a consequence of feeding concentrate.