Comparison of Response to Estrus synchronization and artificial insemination in heifers and lactating dairy cows by application two protocols: OvSynch and Two PGF2α injections

This study was conducted on 60 heifers and 60 cows from different production seasons in the private Al-Bustan farms in Jableh and the Fideo Cows affiliated to the Ministry of Agriculture between 1/1/2021 and 1/10/2022 ,to compare the effect of applying the OvSynch protocol and two doses of PGF2α on reproductive indicators (Insemination index, service period, pregnancy rate, period between two births, period between two inseminations) for each of the heifers and Holstein-Friesian milk cows reared in local conditions. The heifers were distributed randomly in two groups (30 heifers for each group), and the cows were also divided into two groups (30 cows for each group Then, each group was divided into three categories according to the productive season, in each category 10 cows). The hormonal treatment was completed, as 2ml of the synthetic GnRH compound (Lecirelinum) was injected intramuscularly at a concentration of 0.025 per 1ml of the dose. As for PGF2α, it was treated with cloprostenol-Na and injected at a rate of 2ml at a concentration of 0.25mg in 1ml into the semitendinosus muscle. The PGF2α protocol excelled in reducing the service period, which amounted to an average of (133.6)day compared to the group of dairy cows on which the OvSynch protocol was applied (140.7)day, but it was not statistically significant between the two protocols at the probability value P≤0.05. The study recorded a higher insemination rate in heifers after applying the OvSynch protocol (3,9) compared to heifers that underwent PGF2α protocol (3,6). Likewise, the insemination rate was higher for dairy cows after applying the OvSynch protocol, as it reached (3.5) compared to cows that underwent the PGF2α protocol (3.3), but without any significant differences in the insemination index for both heifers and dairy cows between the two protocols. When the probability value is P≤0.05. When applying the OvSynch protocol, the study recorded a 30% decrease in the pregnancy rate in the heifers compared to 60% in dairy cows at a probability value of P≤ 0.001, while the pregnancy rate in dairy cows that responded to treatment with two doses protocol of PGF2α was 73.3% and that of calf was 60%. With regard to the interval between two births, the study recorded the lowest period (402) days when applying the PGF2α protocol compared with the OvSynch protocol (411) days. However, there were no statistically significant differences between the two protocols (OvSynch and PGF2α) at the probability value of P≤ 0.05. As for the interval between two vaccinations before and after the treatment with the OvSynch protocol, it decreased significantly in all groups, but this decrease was greater in the third season cows and heifers, as it reached a very high significance. P ≤ 0.001, while the PGF2α protocol did not show any significant differences in the interval between two injections. That is, this protocol did not show effectiveness in expressing estrus in both heifers and cows.