Effects of hair sheep breed and region of origin on feed dry matter required for maintenance without and with a marked feed restriction

摘要

Effects of hair sheep breed and region of origin on feed required for maintenance without and with a substantial restriction were determined with 46 Dorper, 47 Katahdin, and 41 St. Croix females (initial BW of 62, 62, and 51 kg, respectively, SEM = 1.43; 3.8 +/- 0.18 yr of age, 1.2-11.7) from 45 commercial farms in Midwest, Northwest, Southeast, and central Texas regions of the USA. A 50% concentrate pelleted diet was fed, with the amount varied in the first 4 wk for stable BW and average DM intake in wk 3-4 relative to BW0.75 considered DM required for maintenance without restriction (DMm-m). Feed offered in wk 6-10 was 55% of DMm-m, with DM intake relative to BW0.75 in wk 9-10 considered the requirement with feed restriction (DMm-r). Region had little effect on any measure. DMm-m was slightly greater (P 0.05) for St. Croix than for Dorper and Katandin (49.4, 48.9, and 50.9 g/kg BW0.75 for Dorper, Katandin, and St. Croix, respectively; SEM = 0.48). The decline in BW during the restriction phase was relatively small and similar among breeds (wk 9-10 vs. 3-4: 3.6, 3.2, and 2.9 kg for Dorper, Katandin, and St. Croix, respectively; SEM = 0.21). DMm-r averaged 43% less than DMm-m, again being greater (P = 0.056) for St. Croix than for Dorper and Katandin (28.3, 27.9, and 29.1 g/kg BW0.75 for Dorper, Katandin, and St. Croix, respectively; SEM = 0.28). DMm-m and DMm-r were highly related, indicating that animals would rank similarly at both levels of intake, and variation was similar among breeds. In conclusion, the amount of feed required for BW maintenance was greatest for St. Croix regardless of feed restriction, but differences were minor. The hair sheep exhibited considerable capacity for decreasing the feed requirement for maintenance when offered feed was markedly restricted.