Prolonged postpartum anovulation in mastectomized cows requires tactile stimulation by the calf.

Association of the calf with its dam prolongs the postpartum interval to first ovulation in intact and mastectomized cows indicating that tactile stimulus of the teat and (or) udder is not necessary. Therefore, we conducted the following experiment to determine whether individual calves allowed restricted contact with their mastectomized dam would delay the onset of first postpartum ovulation. Mastectomized cows (n = 21) were allotted randomly and equally to three groups in which cows were 1) allowed unrestricted access to their calves, with unlimited tactile, olfactory, visual, and auditory stimuli (calf present); 2) removed permanently from their calves 24 h after parturition and provided no further association with their calves (calf removed); and 3) remained with their calves for 24 h and then the cow-calf pair was restricted to a pen where tactile contact of the calf was limited to the head and neck region of its dam (calf restricted). Seven udder-intact cows (control) remained with their calves and were allowed to nurse ad libitum. Postpartum intervals to ovulation and first estrus for the calf-restricted cows and calf-removed cows were similar but shorter (P < .05) than those for the calf-present and udder-intact groups. We conclude that restricting tactile stimuli of the calf to the head and neck area of its dam failed to prolong postpartum anovulation in the mastectomized dam and that a cow-calf nursing orientation with tactile stimuli to the inguinal area, but not limited to the teat and(or) udder, was sufficient to prolong anovulation.