Effect of GnRH treatment during different times post-mating on pregnancy rate of buffalo heifers

الملخص EN

To evaluate the efficiency of GnRH injection, on day of mating (Day 0) or during different days post-mating (Day 10 or Day 12),on conception rate of repeat breeder buffalo heifers, a total of 20 cyclic Egyptian buffalo heifers (2-4 years of age and 350-400 kg LBW was allotted to four experimental groups.

All heifers had mature CLs and were injected i.m.

with 2.5 ml PGF2α analogue (Estrumate)/h.

Heifers in heat were naturally mated by fertile buffalo bull and allotted randomly to four experimental groups, 5 animals in each.

On day of estrus, heifers were injected with 2.5 ml saline (G1, control), or a single dose of 2.5 ml Receptal on days 0, 10 and 12 post-mating in G2, G3 and G4, respectively.

Blood samples were collected for determination of P4 concentration in blood serum.

Pregnancy was diagnosed on day 25 post-mating of each animal using ultrasound examination.

Results showed that conception rate (CR) was the highest (P<0.05) in G3 and G4 (80%), moderate in G2 (60%) and the lowest in G1 (40%).

Serum P4 concentration was the highest (P<0.05) in G4 on most sampling days.

There were insignificant differences in serum P4 on day of estrus, being ≤0.5 ng/ml in all groups.

Concentration of P4 was the highest (P<0.05) in G2 as compared to other groups.

Heifers in G4 showed the highest response to GnRH injection on day 12, whereas P4 concentration tended to increase on day of GnRH injection.

There were marked group differences in P4 concentration on days 22 and 24, but P4 concentration was always ≥2 ng/ml in all groups.

Level of P4 was higher (P<0.05) in pregnant than in non-pregnant heifers within each group.

In conclusion, GnRH administration (2.5 ml Receptal/h) on day 12 of estrus/mating had positive effect on pregnancy rate of repeat breeder buffalo heifers as compared to those injected on day 0 and 10 of mating.