Influence of First‐Winter Roughage Source on Subsequent Growth, Reproduction, and Maternal Performance of Replacement Beef Heifers

Forty‐three‐week‐old spring‐born Angus and Angus × Hereford replacement heifers, (n = 75) averaging 480 lb, were randomly allotted to one of five roughage‐based rations following weaning in November to determine the effects of first‐winter ration on subsequent performance of heifers bred to calve initially at 130 wk of age. Rations were (i) bermudagrass‐hay + 1 lb of cottonseed meal, (ii) cottonseed hulls + 2 lb cottonseed meal, (iii) cottonseed hulls + 1.7 lb cottonseed meal + 2.7 lb whole shelled corn, (iv) soybean straw + 1.8 lb cottonseed meal, (v) soybean straw + 1.5 lb cottonseed meal + 2.7 lb whole shelled corn. All rations were formulated to provide 12.5% crude protein with roughages available ad libitum. Winter ending weights after 100 d (March) were affected by treatment; 585, 548, 566, 474, and 522 lb for treatments 1 to 5, respectively. Orthogonal comparisons were: 1 > 2 to 5; 2,3 > 4, 5, and 5 > 4 (P < 0.01). Effects of wintering ration on weight at breeding in December were less but still present (P < 0.06); 767, 765, 742, 710, and 734 lb, respectively. Pregnancy rates were not affected by previous wintering treatments (avg = 87%), nor was average date of calving (P = 0.55). Adjusted weaning weight of calves from heifers receiving ration 1 were lower than those of heifers receiving rations 2 to 5 (431 vs. 481 lb, P < 0.01). Estimated milk yields (weigh‐suckle‐weigh) were not different among rations (P = 0.19). Estimated costs were greatest for ration 3 and lowest for ration 4. Estimated returns favored ration 4. These data indicate that heifers to be bred to calve initially at 130 wk of age in a fall‐calving season can tolerate minimal weight changes during their first winter as weanlings.