IMPIEGO DI GONADOTROPINA CORIONICA EQUINA NEL PROTOCOLLO DI SINCRONIZZAZIONE DEGLI ESTRI IN BUFALE SOTTOPOSTE AD INSEMINAZIONE STRUMENTALE

Equine chorionic gonadotropin (eCG) is secreted by specific areas of the chorion of the equine placenta, i.e., the endometrial cups, from the 36th up to the 140th day of pregnancy. ECG plays an FSH- and LH-like activity, with prevalence of the latter in equine species and of the former in other livestock. This hormone has been widely used to enhance follicle growth in estrus synchronization and superovulatory regimes. We evaluated the effect of eCG on pregnancy rate in buffalo cows which were submitted to a regime for timed artificial insemination (TAI). During the interruption of sexual promiscuity outside the breeding season, from January to February, 80 buffalo cows, reared on one farm in the Salerno district, were submitted to gynaecological examination by rectal palpation in order to select animals with an empty, disease-free genital tract. These animals were separated into two groups (n= 47 and 33) which were submitted to TAI 20 days apart. Each group was further subdivided into control and eCG-treated groups. All the animals received a first dose of GnRH, i.e., 50 ug lecirelin acetate, which marked day-0 of the treatment. After 7 days, a PGF2 treatment, i.e., 150 ug D-cloprostenol, was administered and 2 days later all the animals received another 50 ug lecirelin acetate dose. Two dosages of eCG (Ciclogonina, Fort Dodge Animal Health), i.e., 400 vs 800 IU, were administered at the time of PGF2-induced luteolysis in the eCG treated subgroups of the first and the second experimental period, respectively. Approximately 17 and 41 hours after the last GnRH injection, all the animals were artificially inseminated twice with frozen/thawed semen of two buffalo bulls. The animals were homogeneously distributed within groups, i.e., treated vs control and bull 1 vs bull 2, in relation to age, parity and number of days open. Pregnancy was diagnosed by rectal palpation after 50 days post-TAI. Statistical analysis was performed by the Yates’ Chi square test. Pregnancy rate significantly differed between the two experimental periods (42.6% vs 72.7%; P< 0.02). Since apart from the eCG dosage, we did not change the experimental procedure from the first to the second period, we can argue that the higher pregnancy rate recorded in the second experimental period may be due to either a change in climatic conditions or to the biostimulatory effect played by the cows in heat in the first estrus-induced group versus the cows from the second group. The administration of eCG did not significantly affect pregnancy rate at either 400 IU (35% vs 50% in eCG-treated and control groups) or 800 IU (82% vs 63% in eCG-treated and control groups) dosages. However, the increase in the pregnancy rate using 800 IU of eCG suggests repeating the trial with a higher number of animals in order to establish a definitive result. On the other hand, the repeated use of this treatment in the same animals may have some limitations due to anti-eCG antibody formation. In conclusion, neither 400 UI nor 800 UI eCG administration at the time of PGF2 treatment in a timed artificial insemination regime affected pregnancy rate in buffalo cows. The good results recorded with 800 UI eCG administration, however, encourage us to replicate this trial in the future with a larger number of animals