Source and level of supplemental protein for growing lambs1

Abstract

Two 3 x 2 factorial growth trials and a companion metabolism trial with 13, 15, or 17% dietary CP (DM basis), with or without 3% of the DM replaced with slowly degraded menhaden fish meal, were conducted to determine if level of dietary protein influences whether slowly degraded protein improves lamb growth and protein use. The growth trials included 32 and 34 pens of two weanling lambs initially weighing 23 to 26 kg and fed for 42 d. The metabolism trial included 12 additional lambs fed in metabolism cages with a 2-wk adjustment period, a 1-wk preliminary period, and a 7-d collection period. Plasma urea N (PUN) was measured in all lambs at the conclusion of the second growth trial and at the end of the metabolism trial. There was a protein level x protein source interaction (P = 0.05) for PUN of the 12 lambs in the metabolism trial but not for the 68 lambs in the second growth trial. Replacement of part of the soybean meal protein with protein from fish meal did not affect ADG or G:F at any protein level, but it lowered (P = 0.08) PUN in the second growth trial. Plasma urea N values were higher (P = 0.002) in lambs fed diets with 15 or 17% CP; however, ADG (P = 0.037 in Exp. 1 and P = 0.055 in Exp. 2), and G:F (P = 0.094 in Exp. 1 and P = 0.003 in Exp. 2) were lower for lambs fed the diets with 13% CP. There was little difference in ADG or G:F between lambs fed the diets with 15 or 17% CP, suggesting that a CP level of 15% with supplemental protein from soybean meal would be optimal for 25- to 40-kg growing Finnsheep x Dorset lambs.

Effects of barley grain processing and dietary ruminally degradable protein on urea nitrogen recycling and nitrogen metabolism in growing lambs1

“…Plasma urea N concentration was unaffected (P = 0.27) by barley processing, but it tended (P = 0.06) to be greater in lambs fed the low dietary RDP compared with those fed the high dietary RDP. Lambs fed high-concentrate diets with N contents comparable to those used in our study (≥27.2 g of N/kg of DM) had similar PUN concentrations (Dabiri and Thonney, 2004;Marini et al, 2004). The greater PUN concentration in lambs fed the low-RDP diet was unexpected, especially considering that these lambs had lower intake of ruminally fermentable N, which would have decreased postabsorptive NH 3 -N supply for hepatic ureagenesis; the reasons for this observation are unclear.…”

Effect of energy and protein levels on nutrient utilization and their requirements in growing Murrah buffaloes

“…There was no significant difference in faecal N among the diets with different CP levels . The N excretion through urine apparently showed a positive relationship with the intake (Dabiri and Thonney 2004;Tatsapong et al 2010). Higher CP intake than the optimum or imbalance between energy and protein intake or rapid protein degradation than synthesis leads to more ammonia production in rumen, and the ammonia absorbed into the blood is carried to the liver and converted to urea and excreted via urine N. Hussain et al (2001) observed that energy level had a significant effect on N retention as a percentage of N intake in male buffalo calves.…”

Effect of different levels of raisin waste on performance, nutrients digestibility and protozoal population of Mehraban growing lambs

“…The lower DMI in the R 3 -fed lambs compared to the other lambs may also explained by the lower dietary protein of R 3 . Dabiri & Thonney (2004) reported a lower DMI in lambs receiving 13% protein compared to those received diets containing 15% protein. The CP content of diets is often related positively to DMI (Roffler et al, 1986).…”