Effects of Synovex C implants on growth rate, pelvic area, reproduction, and calving performance of replacement heifers.
Two trials were conducted to evaluate effects of Synovex C implants on replacement heifers, given at two different ages. Crossbred heifer calves (n = 370) were allotted to four treatments: 1) nonimplanted controls, 2) implanted at 2 mo, 3) implanted at 6 mo, and 4) implanted at both 2 and 6 mo of age. Heifers implanted at 2 mo gained 7 kg more (P = .01) by 6 mo than those not implanted at 2 mo. No differences were found in 22-mo weights. All implanted heifers had larger (P = .01) yearling pelvic area than controls. All heifers implanted at 6 mo continued to have larger (P = .01) pelvic area at 22 mo. All implanted heifers had higher (P = .05) occurrence of non-ovulatory estrus. No differences were found among treatments in percentage of heifers puberal before breeding, in estrus first 21 d of breeding, or in first-service conception rate. In only one trial, pregnancy first 21 d and total pregnancy in 63-d breeding season were decreased (P = .05) by implanting at 6 mo. At subsequent calving, an interaction existed between the effects of the 2- and the 6-mo implant for calf birth weight and pelvic area:birth weight ratio. A single implant at either 2 or 6 mo decreased (P = .01) calving difficulty score; and implanting at both 2 and 6 mo showed the greatest reduction in calving difficulty. Implants had no significant long-term effects on reproduction or calf production of 2-yr-old cows.(ABSTRACT TRUNCATED AT 250 WORDS)
Hancock
R F
RF
West Central Research and Extension Center, University of Nebraska, North Platte 69101.
Deutscher
G H
GH
Nielsen
M K
MK
Colburn
D J
DJ
D000818:Animals; D001724:Birth Weight / Q000187:drug effects; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D002418:Cattle Diseases / Q000517:prevention & control; D004338:Drug Combinations; D004343:Drug Implants; D004420:Dystocia / Q000517:prevention & control / Q000662:veterinary; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005298:Fertility / Q000187:drug effects; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000254:growth & development; D010053:Ovary / Q000187:drug effects / Q000254:growth & development; D010384:Pelvic Bones / Q000187:drug effects* / Q000254:growth & development; D010387:Pelvimetry / Q000662:veterinary; D011247:Pregnancy; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D011897:Random Allocation; D012098:Reproduction / Q000187:drug effects*; D012741:Sexual Maturation / Q000187:drug effects; D013997:Time Factors; D015430:Weight Gain / Q000187:drug effects*
D004338:Drug Combinations; D004343:Drug Implants; D011374:Progesterone; D004958:Estradiol; C025370:estradiol benzoate, progesterone drug combination