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Fifty-one yearling Angora doelings (20+/-0.6kg 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 0.7kg/day. During the 94-day experiment, fleece-free ADG was greatest (P0.05) for FI (35, 33, 35 and 50g), whereas greasy fleece weight was greatest (P0.05) for CG (4.4, 3.6, 3.4 and 3.4kg for CG, CT, FT and FI, respectively). Likewise, mohair growth rate was greatest among treatments (P0.05) for CG in each of the three 31- or 32-day periods. Ruminal fluid ammonia N concentration was 8, 11, 6 and 13mg/dl (S.E. 1) immediately before feeding; 10, 18, 11 and 23mg/dl (S.E. 2) at 2h after feeding; 8, 15, 10 and 18mg/dl (S.E. 2) at 4h after feeding; and 4, 6, 5 and 8mg/dl (S.E. 1) at 6h after feeding for CG, CT, FT and FI, respectively. Total VFA concentration in ruminal fluid was similar among treatments (P0.05) at 4 and 6h, but was generally lower for CG and FT than for CT and FI immediately before feeding (29, 33, 26 and 37mM; S.E. 2) and at 2h after feeding (44, 57, 45 and 51mM 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. |
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