Effects of dietary protein level on performance of weaned Boer crossbred and Spanish wethers

I. Prieto¹, A. L. Goetsch¹, S. Soto-Navarro^*,1, V. Banskalieva¹, M. Cameron¹, R. Puchala¹, T. Sahlu¹, L. J. Dawson¹, and S. W. Coleman²

¹E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK
²Grazinglands Research Laboratory, USDA, ARS, El Reno, OK

Boer (3/4) × Spanish (1/4) (BC; n = 23) and Spanish (SP; n = 22) wethers, approximately 4.5 mo of age and 17.6 and 19.4 kg initial BW, respectively (SE = .57), were used to determine effects on growth of protein level in 70% concentrate diets consumed ad libitum for 30 wk. Diets offered were 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), with supplemental protein 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 diets (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 = .07) and P4 (P < .05) than for P1 (76, 90, 85, and 100 g/d for P1, P2, P3, and P4, respectively; SE = 5.3) and for BC vs SP (97 vs 78 g/d, SE 3.7; P = .05). Similarly, ADG:DMI was lowest (P < .05) among diets for P1 (.106, .126, .121, and .132 for P1, P2, P3, and P4, respectively; SE .0053) and greater (P < .05) for BC than for SP (.135 vs .108; SE .0037). In conclusion, with 70% concentrate, dietary protein levels above 14% DM did not improve performance for either weaned Boer crossbred or Spanish wethers.