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The Influence of Early Age Mastectomy and Unilateral Ovariectomy on Reproductive Performance of the Bovine¹

University of Wisconsin, Madison 53706

Abstract

The effects of mastectomy and unilateral ovariectomy and their interaction during the postpartum poeriod were examined in 26 Angus heifers. At birth, the animals were assigned to a 2 x 2 factorial arrangement of treatments: mastectomy and unilateral ovariectomy, mastectomy, unilateral ovariectomy and unoperated suckled control. Surgeries were performed at approximately 2 months of age, and animals were observed through three consecutive postpartum intervals (PPl, PP2 and PP3). There were no significant influences of mastectomy or ovariectomy on age at puberty, age at first conception or services required for first conception. Mastectomy reduced the number of days from parturition to ovulation (PPl, 32.1 vs 52.5, P<.01;PP2, 21.6 vs 59.9,P<.01; PP3, 20.6 vs 46.7, P<.01). The interval from parturition to first estrus was shorter for heifers in the mastectomized group (PPl, 45.3 vs 76.2, P<.05; PP2, 28.7 vs 69.9, P<.01; PP3, 32.4 vs 62.3, P<.05), as was the interval from parturition to conception during PP2 (60.0 vs 104.9, P<.05). The interval between calvings was shorter for heifers in the mastectomized group than for controls, but the difference was significant only between the second and third parturitions: 338.5 vs 399.2 (P<.01). Mastectomy reduced the standard deviation for the interval between parturition 2 and parturition 3 (55.9 vs 15.9; P<.01), the interval betweenparturition and return to estrus in PP2 (56.3 vs 11.4; P<.01) and the interval from calving to conception PPl (92.2 vs 31.4; P<.01). Unilateral ovariectomy did not have a significant influence on any of the postpartum intervals, nor were there any significant interactions.

¹ Dept. of Meat and Anim. Sci. Paper No. 750. Research supported by the College of Agricultural and Life Sciences, Univ. of Wisconsin and American Breeders Service, DeForest, WI.

² Present address: Agr. Bldg., P.O. Box 120, Monroe, WI 53566.

³ The authors express appreciation to Ed Hoch, Paul Bringle and John Kane for their assistance in the care and feeding of the experimental animals and collecting the data, and to Sue Kading and Wendy Winkler for preparing the manuscript.