Effect of Dietary Protein Sources on Lamb’s Performance: A Review

Performance of ruminants is influenced by the proportion of nutrients in their daily feed intake. Protein and energy are the main determinants in the ruminant feed that can alter the animal’s performance. However, in developing countries ruminants are mainly fed on crop residues generally receiving only 62% of their crude protein (CP) requirements (Sarwar et al. 2002). Feeding ruminants according to their CP needs not only ensures sufficient protein availability to grazing animals but also reduces the hazards associated with excess and deficiency of this nutrient. Protein sources differ in their chemistry as far as amino acid profile and availability of CP in rumen and post ruminal level (Gleghorn et al. 2004; Bateman et al. 2005). Protein is an expensive but essential nutrient for animal growth (Dabiri and Thonney, 2004). Different protein sources have varying effect on ruminant’s performance and their serum biochemistry (Jørgensen et al. 1984). This varied response in performance may be due to changes in rumen ecology and their different amino acid profiles (Hall and Huntington, 2008) that result in altered nutrient metabolism. Different protein sources in lamb diets like canola meal (CM), cotton seed meal (CSM), corn gluten meal Protein and energy are the two major components of feed that influence performance of the growing and fattening lambs. Provision of the quality of protein in the lamb’s diet does not only improve the animal performance but also ensures profitable animal production. Different vegetable protein sources are used to formulate the rations for growing and fattening lambs. These protein sources differ in amino acid profiles which results in varied responses of the animals. Protein source with a higher by-pass value have been reported to have more intense effects on N-balance, growth and muscle mass accretion than those which are lower in by-pass protein. Inclusion of protein sources with amino acid profiles matching closely to the amino acid needs of the growing lambs results in better growth performance and nitrogen utilization by the animal. Glucogenic amino acids present in some protein sources also improve the energy status of the animal by increasing gluconeogenesis. Presence of anti-nutritional factors may limit the inclusion of protein sources in the diet. Higher fiber contents like in sunflower meal adversely affect the animal performance by decreasing intake and digestibility. Canola meal has higher S contents that are available to the microbes at ruminal level to produce S containing amino acids. Furthermore, ruminal degradability of protein that is synchronized with carbohydrate digestion also results in better feed utilization and animal performance. So, a good protein source, regardless of its escape protein value, should have better amino acid and micronutrient profiles with safe levels of anti-nutritional factors.