I. Prieto et al., Effects of dietary protein concentration on postweaning growth of Boer crossbred and Spanish goat wethers, J ANIM SCI, 78(9), 2000, pp. 2275-2281
Boer (3/4) x Spanish (1/4) (BC; n = 23) and Spanish (SP; n = 22) goat wethe
rs, 4 to 4.5 mo of age and 17.6 and 19.4 kg initial BW, respectively (SE =
0.57), were used to determine effects on growth of protein concentration in
70% concentrate diets provided for ad libitum intake for 30 wk in confinem
ent. Offered diets contained 10.2, 14.2, 18.3, and 23.6% CP (DM basis), and
CP concentration in consumed DM was 9.3, 13.8, 17.1, and 22.1% (P1, P2, P3
, and P4, respectively); supplemental protein was from soybean meal for P1
and P2 and from soybean meal plus a blend of blood, fish, and feather meals
for P3 and P4. Dry matter intake was similar between breeds and among diet
s (732, 712, 698, and 740 g/d for P1, P2, P3, and P4, respectively; SE = 27
.0). Average daily gain was greater for P2 (P = 0.07) and P4 (P < 0.05) tha
n for P1 (76, 90, 85, and 100 g/d for P1, P2, P3, and P4, respectively; SE
= 5.3) and for BC than for SP (97 vs 78 g/d, SE = 3.7; P = 0.05). Similarly
, ADG:DMI was lowest (P < 0.05) among diets for P1 (0.106, 0.126, 0.121, an
d 0.132 for P1, P2, P3, and P4, respectively; SE = 0.0053) and greater (P <
0.05) for BC than for SP (0.135 vs 0.108; SE = 0.0037). In conclusion, wit
h 70% concentrate diets, the protein requirement for both BC and SP seemed
to have been met by consumption of diets with at least 14% CP, with no appa
rent benefit from addition of ruminally undegraded protein.