Methionine-supplemented diet increases the general performance and value of Rahmani lambs.

Feed additives such as probiotics, chelated minerals, and protected amino acids have been introduced into the market over the past years to improve the nutrient availability, utilization, and consequently, the general performance of ruminant livestock. Interest in the use of probiotics as feed supplements for ruminants has particularly increased in most recent years. Methionine and lysine are the most limiting amino acids for ruminants because of their low concentrations in feed proteins. Indeed, methionine is the most limiting amino acid for protein synthesis in growing lambs (Storm and Orskov, 1984; Nolte et al. 2004) and steers (Greenwood and Titgemeyer, 2000). However, the bioavailability of methionine is limited due to its degradation in the rumen (Schwab et al. 2001). Supplementing ruminant diets with ruminally undegradable proteins can increase the flow of nitrogen and amino acids to the small intestine (Titgemeyer et al. 1989) and result in improved growth and efficiency of nitrogen utilization (Goedeken et al. 1990). However, feeding ruminally undegradable proteins can decrease the efficiency of microbial protein synthesis and flow of microbial amino acids to the small intestine (Cecava et al. 1991) Compared with feeding more degradable protein sources. Plant proteins deficient in methionine (Schwab et al. 1986) and rumininat animals cannot synthesize methionine and, therefore, meEssential amino acids such as methionine have been increasingly included into diets of lambs. However, few studies have determined the effects of methionine supplementation in the general performance and economic returns of lamb production. To address this question, 21 weaned male Rahmani lambs were allotted to 3 dietary treatments: control diet (C), control diet plus 3.30 g of methionine/kg concentrate feed mixture (T1), and control diet plus 3.63 g of methionine/kg concentrate feed mixture (T2). T1-fed lambs showed significantly higher (P<0.05) total body weight gain than those fed diets C. The digestibility coefficients of dry matter (DM), organic matter (OM), crude protein (CP), ether extract, (EE), and nitrogen free extract (NFE) for T1 and T2 were significantly better (P<0.05) than for C. Economically, dietary feed T1 and T2 increased the net profit by 329.64 Egyptian pounds EGP/lamb and 305.76 EGP/lamb, respectively, as compared with the control diet. In addition, the economic efficiency (average feed cost/kg of body weight gain) was 10.02 for C and T1 and 10.48 for T2. Total costs were similar between the 3 dietary treatments. In conclusion, feeding growing Rahmani lambs with 3.30 g of methionine/kg concentrate feed mixture improved their growth performance and raised their economic value.