Effect of gestation on GnRH-induced LH and FSH release in buffalo ()

LH peak and ovulation after two different estrus synchronization treatments in buffalo cows in the daylight-lengthening period

The aim of this study was to determine the timing of ovulation in relation to the LH peak after synchronization using PRID or Ovsynch protocols, to assess the effects of the period of treatment on these parameters and to provide information concerning how to use the two main protocols for fixed-time artificial insemination in buffalo. Forty-eight lactating Italian Mediterranean buffalo cows were used. The buffaloes were treated in various periods as follows: February to March (n = 12 PRID, n = 12 Ovsynch), end of the breeding season, May to June (n = 12 PRID, n = 12 Ovsynch), beginning of low-breeding season according to Italian environmental conditions. To determine the LH, blood samples were taken at 4-hour intervals, starting 24 hours from PRID removal (PRID group) or 12 hours from (PGF2α) injection (Ovsynch group) up to 108 hours. The ovaries were monitored by transrectal ultrasonography to verify ovulation. The LH-ovulation interval was similar in both groups (30.10 ± 1.05 and 32.77 ± 1.15 hours, respectively, in PRID and Ovsynch group). In the PRID group, the timing of ovulation in relation to device removal was 76.83 ± 3.65 hours with a high level of variability among the animals. In the Ovsynch group, we observed a better synchronization of LH peaks and ovulations, and the timing of ovulation in relation to the last GnRH injection was 35.67 ± 1.15 hours. The percentage of animals reaching the LH peak and ovulation was lower (P ≤ 0.05) in May to June (respectively 75.0% and 54.1%) compared to February to March (respectively 95.8% and 83.3%), indicating a reduction of hypothalamus-pituitary responsiveness to the synchronization treatments in the daylight-lengthening period.

The postpartum buffalo: I. Endocrinological changes and uterine involution

To maintain a calving interval of 13-14 months in buffaloes, successful breeding must take place within 85-115 days after calving. Disturbances during this period due to delay of uterine involution or resumption of estrous activity are likely to prolong the calving interval and reduce the lifetime reproductive and productive efficiency. In this article literature on endocrinological changes in the peripartum period and on factors affecting uterine involution are reviewed. The available information indicated that although the availability of releasable FSH does not appear to be a limiting factor for resumption of postpartum cyclicity a substantial increase of releasable LH and replenishment of pituitary stores occurred around Day 20 in dairy and Day 30 in swamp buffaloes. There is evidence that follicular activity is resumed early (15-30 days) in the postpartum period. However, the factors which initiate release of appropriate LH pulses, follicular maturation and ovulation in the postpartum buffalo need further studies. The mean interval to complete uterine involution varied widely between 19 and 52 days. Assessment of cervical and uterine horn diameters by rectal palpation alone is not satisfactory to diagnose delayed uterine involution and possible subclinical uterine infection. Vaginal inspection can be included as a fundamental part of postpartum genital examination for diagnosis of such case. Uterine involution, however, does not seem to be a limiting factor for achievement of satisfactory fertility in the postpartum buffalo but the main determinant is resumption of estrous activity.