Growth performance by Alpine, Angora, Boer and Spanish wether goats consuming 50 or 75% concentrate diets

Forty-five weaned wether goats (12 Alpine, 12 Angora, 10 Boer (87.5%) and 11 Spanish) were used to determine effects on growth performance of consumption of a 75% concentrate diet (DM basis) for 24 weeks (75C) or for 12 weeks subsequent to 12 weeks of feeding a 50% concentrate diet (50C). Initial BW was 20.2, 12.2, 20.7 and 19.2 kg (<F>S.E.=0.73</F>) for Alpine, Angora, Boer and Spanish, respectively, and age was 4 months when the experiment began. There were no interactions between genotype and dietary treatment in DM intake, ADG or gain efficiency in weeks 1–12 or 13–24. DM intake in weeks 1–12 ranked Alpine and <F>Boer>Spanish>Angora</F> (703, 689, 567 and 436 g per day; <F>P<0.05</F>) and in weeks 13–24 was significantly greater for Alpine and Boer versus Angora and Spanish (712, 702, 515 and 456 g per day; <F>P<0.05</F>). DM intake was similar between dietary treatments. In week 8, OM digestibility was 79.3 and 71.3% (<F>S.E.=1.57</F>) and NDF digestibility was 54.2 and 52.1% (<F>S.E.=3.46</F>) for 75C and 50C, respectively. Total VFA concentration was similar between diets; the acetate:propionate ratio was greater (<F>P<0.05</F>) for 50C versus 75C (4.12 versus 2.56). ADG in weeks 1–12 was greatest (<F>P<0.05</F>) for Boer (59, 59, 90 and 49 g per day for Alpine, Angora, Boer and Spanish, respectively); in weeks 13–24 ADG was lowest (<F>P<0.05</F>) for Spanish (25 g per day) and tended to be greater (<F>P<0.10</F>) for Boer versus Alpine (82 versus 58 and 63 g per day). Gain efficiency (ADG:DM intake) was greater (<F>P<0.05</F>) for Angora and Boer than for Alpine and Spanish in weeks 1–12 (132 and 127 versus 85 and 85 g/kg), and in weeks 13–24 was lower (<F>P<0.05</F>) for Spanish than for Angora and Boer (80, 121, 104 and 51 g/kg for Alpine, Angora, Boer and Spanish, respectively). ADG and gain efficiency were greater (<F>P<0.05</F>) for 75 versus 50% dietary concentrate in weeks 1–12 (ADG: 73 and 55 g per day; gain efficiency: 122 and 92 g/kg), and tended to be greater (<F>P<0.11</F>) for 50C than for 75C in weeks 13–24 (ADG: 49 and 65 g per day; gain efficiency: 77 and 101 g/kg for 75C and 50C, respectively). In conclusion, differences in growth performance among Alpine, Angora, Boer and Spanish wether goats were similar with 50 and 75% concentrate diets, and the genotypes responded similarly to the change in dietary concentrate level from 50 to 75%. [Copyright &y& Elsevier]