EVIDENCE FOR MATERNAL-BEHAVIOR AS A REQUISITE LINK IN SUCKLING-MEDIATED ANOVULATION IN COWS

Some component of the suckling process inhibits LH secretion and delay s postpartum ovulation in beef cows. To investigate a possible role fo r maternal behavior in suckling-mediated anovulation, 27 crossbred bee f cows were randomly allotted to 1 of 3 groups: 1) alien (dam suckled by alien calf; n = 11); 2) own (dam suckled by own calf, n = 8); and 3 ) weaned (calf removed for 6 days; n = 8). Beginning 14-17 days after parturition (experimental Day 0), cows were control suckled (10 min ev ery 6 h) in stanchions for 6 days by either their own calf or by an al ien calf or were weaned. Mean LH pulse frequencies in the alien and we aned groups were similar but were elevated (p < 0.02) on experimental Days 2 and 4 compared to those in the own group. The incidence of lute al activity by experimental Day 10 was greater (p < 0.01) for the alie n (72.2%) and weaned groups (75.0%) than for the own group ( 12.5% ). Frequency of oxytocin release following suckling was greater (p < 0.01 ) in the own group than in the alien group (Day 2: 100% vs. 36.4%; Day 4: 100% vs. 54.6% ), whereas suckling-induced release of prolactin wa s similar for both groups. Data provide evidence that the mother-offsp ring bond is an important link in suckling-mediated inhibition of LH s ecretion and ovulation.