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WS Methods to increase productivity of spring calving production systems in the Nebraska Sandhills
ABSTRACT: A 2-yr study evaluated effects of late-gestation supplementation, post-partum progestin administration, and creep feeding on productivity of March calving cows. In yr 1, 120 crossbred cows (BW 479 ± 57 kg) were assigned to 1 of 4 levels of late-gestation supplementation, 1 of 2 levels of post-partum progestin, and 1 of 2 levels of creep feed in a 4 x 2 x 2 factorial arrangement of treatments in a completely random design. The four supplement levels fed were: 1) 0 kg/d Dec 1 to Mar 1; 2) 0.41 kg/d DM Dec 1 to Mar 1; 3) 0.41 kg/d DM Jan 15 to Mar 1; or 4) 0.82 kg/d DM Jan 15 to Mar 1 while cows grazed dormant upland range. Levels of exogenous progesterone post-partum: 1) controlled internal drug release device for 7 d; or 2) no progesterone administration. Creep feed levels were: 1) unrestricted access by the calf to creep feed which contained an intake limiter; or 2) no access to creep feed. The higher levels of late-gestation supplementation increased cow BW (P < 0.05) and increased cow BCS (P < 0.05) but did not affect (P > 0.12) reproductive measures or calf performance. Exogenous progesterone administration post-partum did not affect (P > 0.13) cow or calf performance. Allowing calves access to creep feed increased (P < 0.01) calf BW at weaning by 21 kg.
Keywords: Key Words:creep feed, progesterone, supplement