Effects of dietary protein sources on mohair growth and body weight of yearling Angora doelings

Abstract

Fifty-one yearling Angora doelings (20±0.6 kg initial body weight (BW)) were used to determine effects of different dietary protein sources on BW change and mohair growth. Diets consisted of approximately 40% roughage and 18–19% CP (DM basis), of which two-thirds was supplied by corn gluten meal (CG), cottonseed meal (CT), hydrolyzed feather meal (FT) or menhaden fish meal (FI); DM intake was restricted at approximately 0.7 kg/day. During the 94-day experiment, fleece-free ADG was greatest ( P<0.05) for FI (35, 33, 35 and 50 g), whereas greasy fleece weight was greatest ( P<0.05) for CG (4.4, 3.6, 3.4 and 3.4 kg for CG, CT, FT and FI, respectively). Likewise, mohair growth rate was greatest among treatments ( P<0.05) for CG in each of the three 31- or 32-day periods. Ruminal fluid ammonia N concentration was 8, 11, 6 and 13 mg/dl (S.E. 1) immediately before feeding; 10, 18, 11 and 23 mg/dl (S.E. 2) at 2 h after feeding; 8, 15, 10 and 18 mg/dl (S.E. 2) at 4 h after feeding; and 4, 6, 5 and 8 mg/dl (S.E. 1) at 6 h after feeding for CG, CT, FT and FI, respectively. Total VFA concentration in ruminal fluid was similar among treatments ( P>0.05) at 4 and 6 h, but was generally lower for CG and FT than for CT and FI immediately before feeding (29, 33, 26 and 37 mM; S.E. 2) and at 2 h after feeding (44, 57, 45 and 51 mM for CG, CT, FT and FI, respectively; S.E. 3). In conclusion, the different protein supplements had dissimilar effects on ADG (greatest for FI) and mohair growth (greatest for CG). Factors responsible for these results are unclear, and the range of experimental or production conditions under which comparable findings might occur are unknown and deserve further study.