Effects of restricted feed intake on blood constituent concentrations in Dorper, Katahdin, and St. Croix sheep from different regions of the USA

Forty-six Dorper, 47 Katahdin, and 41 St. Croix female sheep (initial BW = 62, 62, and 51 kg, respectively, SEM = 1.43; 3.8 ± 0.18 yr) from farms in Midwest, Northwest, Southeast, and central Texas regions of the USA were used to evaluate effects of feed restriction on blood constituent levels. The amount of feed offered varied in the first 4 wk to achieve stable BW, and that in wk 5–10 was 55% of intake in wk 3–4. Blood was sampled at the end of wk 3, 4, 6, 8, and 10. There were relatively few effects and interactions involving region and no breed × time interactions. Breed affected the concentration of a small number of constituents, including urea N (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). Also, the concentration of triglycerides in wk 4 and 10 was lowest for St. Croix (29.8, 29.5, and 26.7 mg/dl for Dorper, Katahdin, and St. Croix, respectively; SEM = 0.88). There was a trend for a difference (P = 0.051) between wk 4 and 10 in the glucose concentration (51.9 and 54.2 mg/dl; SEM = 0.90), and there were differences (P < 0.05) in 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), and cholesterol (67.5 and 74.7 mg/dl, respectively; SEM = 1.66). In conclusion, similar responses in blood constituent levels of different hair sheep breeds to feed restriction is in accordance with comparable effects on the maintenance energy requirement.