PSXI-29 - Effects of feed restriction on blood constituent concentrations in hair sheep

Forty-six Dorper, 47 Katahdin, and 41 St. Croix female sheep (initial body weight of 62, 62, and 51 kg, respectively, SEM=1.43; 3.8±0.18 yr of age) from 45 commercial farms in Midwest, Northwest, Southeast, and central Texas regions of the United States were used to evaluate effects of feed restriction on concentrations of blood constituents. A 50% concentrate pelleted diet was fed, with the amount varied in the first 4 wk to achieve stable BW. The amount of feed offered in wk 5-10 was set at 55% of that consumed in wk 3-4. Blood was sampled at the end of wk 3, 4, 6, 8, and 10, with constituent levels in wk 4 and 10 assumed relevant to conditions with different maintenance energy requirements (i.e., fed at maintenance and approximately 43% lower with restricted intake). There were some differences among breeds such as ones based on samples collected at all times in urea nitrogen (14.0, 13.7, and 15.4 mg/dl; SEM=0.31) and creatinine (0.945, 0.836, and 0.809 mg/dl for Dorper, Katahdin, and St. Croix, respectively; SEM=0.0253) but relatively few among regions and only one interaction between week and breed or region. There was a trend for a difference (P = 0.051) between wk 4 and 10 in the concentration of glucose (51.9 and 54.2 mg/dl; SEM=0.90), and there were differences (P < 0.05) in levels of lactate (23.9 and 20.3 mg/dl; SEM=0.89), urea N (16.4 and 13.0 mg/dl; SEM= 0.25), creatinine (0.808 and 0.919 mg/dl; SEM=0.0165), triglycerides (31.8 and 25.5 mg/dl; SEM=0.63), cholesterol (67.5 and 74.7 mg/dl; SEM=1.66), and cortisol (10.55 and 8.31 ng/ml for wk 4 and 10, respectively; SEM=0.0542). In conclusion, similar responses of different hair sheep breeds in blood constituent levels to feed restriction is in accordance with comparable effects on body weight and the maintenance energy requirement previously reported.