Chapter 2 6
2.11 DIETARY SUPPLEMENTATION AND THE NEED FOR IT
Fertilized or young and succulent grasses as forage diets readily contain soluble nitrogen such that with moderate available energy, productivity is enhanced; as such no supplementation is required (Nsahlai et al., 1998). Contrary to this, in period of nutritional constraints, supplementation with crop by-products may be necessary as this result from high seasonal and yearly fluctuations in forage quality and feed availability. Moderate supplementation stimulates intake while biomass availability and vegetation quality is low on slightly
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degraded forage land (Schlecht et al., 1999). Invariably, when legumes are introduced into pastures to increase the supply of protein in the GIT, their ability to do so is largely dependent on the escape properties of legume particles within the rumen if dominated by grass particles. A strong assertion, according to Nsahlai and Apaloo (2007) counting on the recommendation of in sacco method of degradation, attributes of feed are mostly known in the rumen of animals whose feed is well supplemented with protein which is the first nutrient that restricts the potency of rumen microbial fermentative activity for low quality roughages.
Related to this, is the double advantage of increased degradation and passage rates when forage legumes were used for supplementation as confirmed by others (Abule et al., 1995;
Bonsi et al., 1995; Nsahlai et al., 1998).
Solaiman (2006) asserted that protein is the most high-priced portion of animal feed and it often varies between 12-16% of ration dry matter based on two main factors namely; animal physiological state (growing, pregnancy or lactating) and quality of forage. Therefore, to provide high protein supplements to ruminants when feeding with low-quality roughages tend to stimulate intake, digestion and performance (Chanjula et al., 2004a, 2008b). Urea and other non-protein nitrogen sources have been found useful in this aspect (Solaimon, 2006).
By their use, voluntary feed intake is increased (Archibeque, 1999), microbes of the rumen produce microbial protein which is a good source of nitrogen for the host animal and nutrient digestibility and passage of feed from the rumen are improved positively. For example, when Bohnert et al. (2007) supplemented steers with protein in cool season and warm season forage, he established an intake increase by 47% on warm season forage compared with 7%
on cool season forage. In addition, not only intake and digestibility of the two forages were different but also that the physiological response of ruminants to supplemental protein is partly dependent of the cell wall structure of the diet. Nsahlai (1991) also asserted that when
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increase in intake resulted from increased digestion rate of low-quality roughage, then diet digestibility rises by 4-40% depending on the quality of the basal feed.
Another cogent reason for the requirement of a supplemental nitrogen source in ruminants, is the proper functioning of the rumen most especially when the diet component is of very low quality (Hernandez and Sanchez, 2014). When straw or hay has been ammoniated with urea, ammonia gas or ammonium bicarbonate at a condition it is not needed, then only a source of by-pass nutrients is used to heighten animal performance (FAO, 2002). To buttress these assertions, Wickersham et al. (2004) noted that trial studies take advantage of protein supplementation since nitrogen requirements of rumen microbes may not be met and thereby resulting to poor use of roughage and poor performance. Although rumen degradable protein improves animal performance, nitrogen available for this function still include absorbed nitrogen or mobilized endogenous nitrogen from source like recycled urea. Likewise, status of nitrogen in ruminants can also be improved by providing rumen un-degradable protein as it also has potential to make nitrogen available for microbes in the rumen (Lobley et al. 2000), it was established that ruminally degradable protein is more efficient than un-degradable one (Bandyk et al. 2001). Complementary to all these, multi-nutrient blocks of molasses are also important supplements when low nitrogen basal feed are offered to ruminants (FAO, 2007).
Nsahlai et al. (1998) observed that the intake of roughages without supplementation is within 17 to 29 g/kg body weight and 16 to 23 g/kg body weight for sheep and cattle, respectively, and thus elicit varied levels of productivity. As such, the amount of supplement required by these animals may be a function of basal roughage quality. Ordinarily, animals on poor quality diets do mobilize their energy reserve to cater for their nutritional needs but this results in reduced body condition. With the range of body condition score of goats between 2.1 for poor and 3.8 for fair, Lengarite et al. (2014) observed that goats offered long grass
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without supplement were poor while those fed mixed grass hay with whole Acacia pods as supplement, were fair.
Tafaj (2005) observed that it is not a strategy to overcome limitation of low quality forage by feeding concentrates as supplement to ruminants, rather the quality of the roughage should be increased. A reduction of concentrate level from 50 to 20% in the diet of low fibre forage improved rumen conditions as the rumen solid passage rate and fibre digestibility increase with decrease concentration of large particles and of the mean particle size of the rumen digesta and of the faeces. Besides, Lengarite et al. (2014) reported that with supplementation, there was an increase in milk production of goats, similar daily weight gain of suckling goat kids, improved digestibility with milled Acacia and increased feed intake with chopped grass hay. Lengarite et al. (2014) highlighted that supplementation can alleviate nutritional constraints, increase milk yield and maintain body condition of pastoral goats in dry land, if included as milled Acacia or whole one in mixed grass hay.
2.12 UREA TREATMENT AND OPTIMIZATION OF LOW QUALITY