Pakistan’s economy is agricultural based in which livestock has a major contribution. Livestock contributes 11.8% to total national GDP. Nili Ravi is established breed of Pakistan. Nili Ravi has high lactation yields (1800-2500 liters with a 6.5% fat) and their males are more suited to ploughing and drafting on dry plane land. Increased calving interval and estrus detection are the biggest bottleneck in achieving the goal “a calf per 13 months” and high conception rate in dairy animals ultimately this leads to in economic losses. To overcome the problem of poor breeding in buffalo various exogenous hormonal intervention have been made to control estrous cycle of buffalo. Several ovulation synchronization protocols offer to bypass the estrus detection and artificially inseminate the animal at pre-established time. Co-synch is modified form of ovulation synchronization. Incorporation of CIDR in Co-synch improves the efficacy of protocol. It is easier in management and cost effective.
Present study was designed to compare the efficacy of 5 or 7 day CIDR + Co-synch in Nili Ravi buffalo and find appropriate time of A.I in Nili Ravi using 5 or 7 day CIDR + Co-synch protocol. Study was conducted on Military Dairy Farm Okara. Selected animals (N = 80) were divided into two treatments. Treatment 1) 7 day CIDR + Co-synch (n =40): The animals received an intravaginal CIDR insert containing 1.38 g of progesterone (P4) for 7 days. On the day of CIDR removal, 150 µg of PGF2α was injected intramuscularly (IM); Half of these animals (n=20) received 100 µg of GnRH IM and TAI after 72 hrs of CIDR removal/ PGF2α administered, the remaining half (n=20) received GnRH and TAI after 84 hrs of CIDR removal/ PGF2α administration. Treatment 2) 5 day CIDR + Co-synch (n=40): The animals received an intravaginal CIDR insert containing 1.38 g of P4 for 5 days. The animals were administered 150 µg of PGF2α IM at the time of CIDR removal. Half of these animals (n=20) received 100 µg of GnRH IM and TAI after 72 hrs of CIDR removal/ PGF2α administration, the other half (n=20) received 100 µg GnRH and FTAI after 84 hrs of CIDR removal/ PGF2α administration. Data is analyzed using IBM SPSS Statistics 20 software program. Follicular growth rate, pre-ovulatory follicular size is analyzed through independent t-test. Interval from CIDR removal to ovulation and interval from GnRH to ovulation is analyzed by Mann Whitney U test. Pregnancy rate is compared by binary linear regression. Ovulation rate and estrus response is analyzed through Chi square. A probability level of (P < 0.05) is considered as significant.
The results of this study showed the pregnancy rates were high (P < 0.05) in buffalo heifers of subgroups of both treatments inseminated after 84 hrs of CIDR removal (50% in 5 day CIDR + Co-synch and 65% in 7 day CIDR + Co-synch) than the subgroup inseminated after 72 hrs interval of CIDR removal (30% in 5 day CIDR + Co-synch and 25% in 7 day CIDR + Co-synch).
Follicular growth rate (mm/day) was tended to be high in 7 day CIDR treatment as compared to 5 day CIDR treatment (1.5±0.3 vs. 1.3±0.4, P=0.06). Pre-ovulatory follicle size in 7 day CIDR + Co-synch was significantly high in animals inseminated after 84 hrs as compared to subgroup inseminated after 72 hrs interval of CIDR removal (12.29mm vs. 10.74mm, P < 0.05). Similar trend was found in 5 day CIDR + Co-synch, the subgroup inseminated after 84 hrs of CIDR removal had larger pre-ovulatory follicular size than subgroup inseminated at 72 hrs interval (10.63mm vs. 11.73mm, P < 0.05). Interval from PG/CIDR removal to ovulation in 7 day CIDR treatment was 99 ± 0.9 hrs while in 5 day CIDR treatment it was 96 ± 1.6 hrs which did not differ significantly (P = 0.14). The interval from A.I/GnRH administration to ovulation in 7 day CIDR + Co-synch was significantly lower in animals inseminated after 84 hrs as compared to subgroup inseminated after 72 hrs interval of CIDR removal (15±1.2 vs. 27.±1.4, P < 0.05). Similar trend was found in 5 day CIDR + Co-synch, the subgroup inseminated after 84 hrs of CIDR removal/PG administration had lower A.I/GnRH administration to ovulation interval than subgroup inseminated at 72 hrs interval (16.2±1.3 vs. 21.6±1.6, P < 0.05). Ovulation rate was significantly high (P = 0.05) in 7 day CIDR treatment (95 %) than the 5 day CIDR treatment (80%). The estrus response in buffalo heifers was not significantly different between the treatments (90% in 7 day CIDR vs. 80% in 5 day CIDR treatments, P > 0.05).
In conclusion higher pregnancy rates were achieved in 7 day CIDR + Co-synch when animals were inseminated after 84 hrs interval of CIDR removal/PG administration. Acceptable pregnancy rates were resulted when timed AI was done after 84 hr of CIDR removal/PG administration using 5 day CIDR + Co-synch regimen. However further studies with larger sample size may be carried out to establish a strong statistical analysis between 5 and 7 day CIDR + Co-synch while inseminating animals after 84 hrs of CIDR removal/PG administration. Results of this study suggest that high pregnancy rate is primarily attributed to larger pre-ovulatory follicular size and appropriate time of AI in relation to time of ovulation. This study provides a way out to large dairy farmer to increase fertility with optimized management.