The influence of early age mastectomy and unilateral ovariectomy on reproductive performance of the bovine.
The effects of mastectomy and unilateral ovariectomy and their interaction during the postpartum period 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 (PP1, 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 (PP1, 32.1 vs 52.5, P less than .01; PP2, 21.6 vs 59.9, P less than .01; PP3, 20.6 vs 46.7, P less than .01) The interval from parturition to first estrus was shorter for heifers in the mastectomized group (PP1, 45.3 vs 76.2, P less than .05; PP2, 28.7 vs 69.9, P less than .01; PP3, 32.4 vs 62.3, P less than .05) as was the interval from parturition to conception during PP2 (60.0 vs 104.9, P less than .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 less than .01). Mastectomy reduced the standard deviation for the interval between parturition 2 and parturition 3 (55.9 vs 15.9; P less than .01), the interval between parturition and return to estrus in PP2 (56.3 vs 11.4; P less than .01) and the interval from calving to conception PP1 (92.2 vs 31.4; P less than .01). Unilateral ovariectomy did not have a significant influence on any of the postpartum intervals, nor were there any significant interactions.
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