Follicular diameter and ovulatory response to GnRH and HCG administration in buffalo.

The intravenous administration of 12 μg Buserelin acetate (GnRH) causes a ready pituitary response, increasing LH and FSH levels. However, only 57.1% of treated buffaloes show a significative increase of progesterone blood levels (Neglia et al., 2005). The aim of this study was to verify the follicular diameter and the incidence of ovulations after the treatment with GnRH or hCG, performed on day 26 of pregnancy. The trial was carried out between January and March on 109 pluriparous buffaloes (DIM =163 ± 75 days). The animals were synchronized by using the Ovsynch-TAI Program. Buffaloes diagnosed pregnant by ultrasound on day 25 after AI, were randomly assigned in two treatment groups GnRH (12 μg of Buserelin Acetate i.m) and HCG (1000 I.U. i.m.) after measurements of follicular diameter. Two days after treatment the ovulation was evaluated by ultrasound of the ovaries and on day 45 of pregnancy it was verified the presence of an accessory corpus luteum. Differences between the follicular diameters of responsive and not responsive buffaloes were tested by ANOVA. The incidences of animals which responded to the two treatments were analysed by chi square test. No significant differences between the two treatments were found in terms of ovulatory response, which was present in 57.3% of animals. The mean follicular diameter which results sensible to the hormonal treatment was 8.9mm (Table 1) in both treatments, with varying between 4.2 and 1.3 mm. It is interesting to observe that the dimensions of the follicles recorded in buffaloes responsive to the treatments were similar to those of buffaloes in which ovulation did not occurr. These data are in accordance with those reported in bibliography in buffalo and in cattle regarding the incidence of subjects responsive to the treatment with GnRH and the dimensions of responsive follicles. In conclusion, the treatment with GnRH or HCG may be utilised in order to induce the formation of an accessory corpus luteum and, hence, to increase P4 levels, which are critical for maintaining the gestation