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Effects of Early Weaning on Postpartum Reproduction of the Dam and Growth of Calves Born as Multiples or Singles¹

United States Department of Agriculture and Montana Agricultural Experiment Station, Miles City, 59301

Abstract

Two studies were conducted to produce multiple births in beef females and determine growth performance to 90 days of age of early weaned and artificially reared calves. The effects of early weaning on postpartum reproductive activity of dams producing single or multiple births were also determined. The studies involved 52 nulliparous heifers treated with 6.2 mg FSH and 55 lactating 2-year-old dams treated with either 6.2 or 9.4 mg FSH. Estrus was synchronized with MAP and estradiol. Calves were removed from their dams at 3, 10, 35 or 90 days of age. Calves weaned before 35 days were fed cold (1.7 to 2.8 C) whole milk or cold milk replacer ad libitum to 35 days of age. Net calf production from dams in the superovulated groups ranged from 71 to 111%. Gestation lengths of single calves were longer (P< .01) than those of multiples and incidence of retained placenta increased in dams producing multiple births. Weaning calves early resulted in a shortening (P< .01) of the postpartum interval to first estrus, regardless of type of birth. Weight gains of early weaned calves were normal and digestive problems were minimal.

¹ This study was conducted at the U. S. Range Livestock Experiment Station, Miles City, Montana 59301. Publication has been approved by the Director of the Montana Agricultural Experiment Station, Journal Series No. 472. Parts of these data have been reported previously at the X Biennial Symposium on Animal Reproduction.

² Authors express appreciation to: The Upjohn Company, Kalamazoo, Michigan, for financial aid that partly supported this study; Armour-Baldwin Laboratories for furnishing FSH-P; Cache Valley Breeding Association, Logan, Utah, for semen used on Experiment 1; N. H. Wiltbank, H. E. Traweek and W. E. Wolf for assistance in data collection and care of experimental animals. Mention of trade names or specific equipment does not constitute a warranty by the U. S. Department of Agriculture and does not imply approval to the exclusion of other products that may be suitable.