Growth and cashmere production by Spanish goats consuming ad libitum diets differing in protein and energy levels

Thirty-six Spanish goat wethers (196 12.9 days of age and 17.5 4.60 kg BW at experiment initiation) from a herd previously selected for cashmere growth were used to determine effects and interactions of ad libitum consumption of diets differing in concentrations of CP (10% and 15%) and ME (2.00, 2.35 and 2.70 Mcal/kg; DM basis) on growth and cashmere ®ber production in an 84-day, fall-season experiment. DM intake was greater (P < 0.05) for diets with 15% vs. 10% CP (736 vs. 655 g/day) but similar among ME concentrations (P > 0.10). ADG was greater (P < 0.02) for 15% vs. 10% CP (79 vs. 53 g/ day) and increased linearly (P < 0.10) as dietary ME level increased (58, 62 and 78 g/day for 2.00, 2.35 and 2.70 Mcal/kg ME, respectively). Total ̄eece weight at the end of the experiment was similar (P > 0.10) between CP levels but increased linearly (P < 0.03) as ME concentration in the diet increased (197, 239 and 227 g/day). Guard hair weight was not affected by dietary treatments (P > 0.10); cashmere length was similar among treatments (P > 0.10); and cashmere ®ber diameter was not altered by dietary ME level (P > 0.10) but was greater (P < 0.05) for 15% vs. 10% CP (16.92 vs. 16.06 mm). Cashmere weight was in ̄uenced by an interaction between CP and ME levels (P < 0.05); cashmere ®ber weight with 10% CP was 92, 82 and 95 g, and with 15% CP was 63, 115 and 99 g for 2.00, 2.35 and 2.70 Mcal ME/kg diets, respectively (SE ˆ 10.2). However, the ranking of treatment means for initial cashmere ®ber weight was similar to that at the end of the experiment, although differences at the beginning were non-signi®cant and of lesser magnitude than at the end. In conclusion, further research with in ̄uences of concentrations of CP and ME in diets consumed ad libitum on cashmere ®ber growth of growing US Spanish wether goats is required, and animal numbers and allocation to treatments deserve careful consideration in studies of cashmere ®ber production. # 2000 Elsevier Science B.V. All rights reserved.