Effect of Protein Levels and Degradability in the Ration on Awassi Lambs Performance 1-Productive Parameters
ABSTRACT : Factorial experiment was carried out using forty eight individually fed Awassi male lambs weighing 26.5 kg ± 1.1 and 5 months of old were used to investigate their responses to feeding concentrate diets containing three levels of dietary crude protein (CP, 11.5, 13.5 and 15.5%) each level was formulated with high and low nitrogen degradability[rumen degradable N (RDN): undegradable dietary N (UDN) ratio]. Concentrates were offered once a day at rate of 3% of live body weight with free choice of barley straw. Results revealed that neither straw nutrient intakes, nor the total intake were significantly affected by increasing levels of dietary CP or RDN: UDN ratios, However, total nitrogen (N) intake was increased significantly (P<0.01). Better intake of digestible dry matter (DDM) and organic matter (DOM) intakes were achieved (P<0.05) by lambs fed the medium level of dietary CP. Gain was not significantly affected by RDN:UDN ratio, However, lambs fed medium and high levels gained higher (P<0.05) than those fed the low level of dietary CP. Feed conversion ratio (FCR) based on DM and OM intakes was not significantly affected by level of dietary CP or RDN:UDN ratio, Even though, less amount of N required per unit of gain was achieved with low and medium as compared to high levels. Higher DM, nitrogen free extract (NFE) and hemicellulose (P<0.05), OM, CP, crude fiber (CF) and cellulose (P<0.01) digestibilities were achieved by lambs fed the medium level of CP, whereas, no significant effect was observed on ether extract (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibilities. Lambs fed diets formulated with low RDN: UDN ratio digested its dietary nutrients at higher rate than those fed diets formulated with the high ratio. Effect of interaction between levels of dietary CP and RDN: UDN ratio revealed that productive parameters of lambs fed diets containing medium level of CP and formulated with low RDN:UDN ratio was somewhat tended be better.
Keywords: protein ,degradability, digestibility, growth ,sheep