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.

Cow-calf association delays postpartum ovulation in mastectomized cows.

Eleven 3-yr-old crossbred Angus cows that had raised one calf each were mastectomized at 6 to 7 mo of their second gestation. All calves were removed from cows within 12 h after birth. Cows were kept in a drylot with a fertile bull for 60 d after parturition. Cows were observed for estrus every 6 h, and blood serum was collected daily and assayed for progesterone. The average first ovulation and first estrus occurred at 13.9 and 20.1 d after parturition, respectively. Nine of 11 cows conceived, and the average time of conception was 34.3 d after parturition. The next year, eight of the same mastectomized cows were allocated to two equal groups. In one group, calves were removed from cows within 12 h after birth, whereas in the other group, calves remained with cows for 46 to 53 d. Calves that remained with their dams were hand fed from a bottle or bucket every 12 h. The two groups of cows were kept in separate drylots about 50 m apart, and a fertile bull was kept with each group. Blood samples were obtained from all cows, and they were observed for estrus as before. Cows withcut calves ovulated before 22 d (average 16.0), exhibited estrus by 33 d (average 24.0), and conceived by 40 d (average 30.5) after calving. None of the cows with calves ovulated or exhibited estrus earlier than 49 d after calving. However, all cows ovulated by 4 d (average 3), exhibited estrus by 10 d (average 5.5), and conceived by 11 d (average 9.3) after calf removal. We conclude that cow-calf interaction can suppress ovulation and estrus even when suckling and lactation do not take place.

Multiple embryo-transplant offspring produced from quartering a bovine embryo at the morula stage.

A non-surgical embryo collection was completed on a day 7 superovulated Chianina donor cow. Because all but two of the ova from the collection were unfertilised and a surplus of potential recipients was available, one embryo (an excellent quality late morula) was dissected into four equal portioned 'quarter' embryos using a simplified micromanipulation procedure. Each quarter embryo was then placed in a 0.25 ml French straw and non-surgically transplanted to four different crossbred beef recipient females. The remaining embryo was similarly transplanted to a herd mate recipient as an intact embryo. One recipient returned to oestrus, one recipient had an extended post transfer cycle and the two remaining recipients produced a live quarter embryo transplant calf each within 24 hours of the other. The intact embryo placed in a herd mate recipient did not produce a transplant calf. To the authors' knowledge, these transplant offspring are the first live births reported from a non-surgically collected later-stage bovine morula (day 7), which had been dissected into quarters and then individually transplanted non-surgically to recipient females. The procedure was relatively simple to perform and was completed in less than one hour.