Protein Supplementation as Related to Protein Sources for Growing and Finishing Lambs

The production of high-quality foods continues to offer an important challenge to livestock producers and animal scientists. People in many countries of the world consume diets which are inadequate in quantity and quality of nutrients. The animal industry plays a major role as a supplier of high-quality foods such as meat, milk and eggs for human nutrition. Protein is perhaps the most important nutrient provided by animal products because of its quality and availability in relation to human needs. Ruminants such as cattle and sheep have the unique ability to convert low quality feedstuffs to high quality food as animal products. However, the nature of the digestive system and the processes which occur in the rumen during fermentation contribute to a lower efficiency of feed conversion in comparison to nonruminants. Protein metabolism is also inefficient in ruminants which contributes to a low conversion rate of feed protein to higher quality animal protein. Dietary proteins intact and at different stages of degradation, nonprotein nitrogen compounds and microbial protein pass to the small intestine. The amount of feed protein which has not been degraded to ammonia or synthesized into microbial protein is influenced by factors such as source of dietary protein, solubility of the proteins, particle size of the feed and amino acid composition as well as the level of protein in the diet. A number of experiments have been conducted to determine the protein requirements of beef cattle and sheep under various types and levels of production. Because of changes in animal; feed and management factors affecting the need and utilization of nutrients, protein and other nutrient requirements need to be constantly evaluated. Such studies form the basis for recommended daily allowances which appear to give good performance under practical feeding conditions. Many of the studies have been concerned with protein requirements using feedstuffs rich in protein as supplemental sources to diets low in this nutrient. Research with protein sources indicates that solubility, rate of degradation in the rumen and availability of carbohydrates in the diet are important factors affecting bacterial protein synthesis. Sources of preformed protein such as soybean meal, peanut meal and corn gluten meal have been shown to be degraded at different rates in the rumen, affecting the total level of utilization of this nutrient by the ruminant. The objective of this study was to evaluate some commercially available sources of protein supplements in the diets for growing and finishing lambs. The supplements used were expected to be degraded at different rates in the rumen. If the principles concerning protein solubility and ruminal degradation of proteins reported by other investigators would be applicable, then response in terms of growth and feed utilization would be a measure of the suitability of the supplements for productive purposes. Utilization of nutrients during adaptation to the supplements and following adaptation were also objectives undertaken to study the effect of these different protein supplements on digestibility and nitrogen retention