Influence of dietary nitrogen sources with different ruminal degradability on growth performance of Comisana ewe lambs

The effect of diets with different ruminal degradability on growth performance of Comisana ewe lambs was studied. Forty-five ewe lambs, with average live weight of 16 ± 0.55 kg (mean ± sem), were allocated randomly to three isocaloric (2.19 Mcal/kg), isonitrogenous (15.5% of crude protein) diets for 18 weeks. Pelleted total mixed rations (PTMR) were formulated in order to provide N sources with different ruminal degradability: (1) urea (46% N) associated to soybean meal (high-degradability diet, HD), (2) soybean meal (medium-degradability diet, MD) and (3) corn gluten meal associated to soybean meal (low-degradability diet, LD). In vivo nutrient apparent digestibility of the three PTMR was determined using Comisana rams (mean LW 68 ± 3.8 kg) and indicated significant (P < 0.05) differences for protein, ether extract, N-free extract, neutral detergent fiber (NDF) and hemicellulose fractions. The results from the current trial using Comisana ewe lambs showed that average daily gain was unaffected by ruminally degradable protein and ruminally undegradable protein ratio in diets (P > 0.05). Final body weight in ewe lambs fed the MD diet was significantly greater (P < 0.05) compared with the HD and LD treatment groups. Feed conversion ratio was lower in MD diet than HD and LD diets (P < 0.05).