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In this study, the effect of adding progesterone (PRID) to the presynchronization (G6G/Ovsynch) protocol on first insemination pregnancy rates in cows and heifers was investigated. Holstein cows (n:181) and heifers (n:100) were used in the study and divided into four groups as follows: Cow G6G (cow control group, n:79), Cow G6G/PRID (cow treatment group, n:102), Heifer G6G (heifer control group, n:50), and Heifer G6G/PRID (heifer treatment group, n:50). The animals in the treatment groups were subjected to the G6G/PRID protocol; namely, the G6G/Ovsynch protocol together with intravaginal progesteron administration between days 8-15 of the protocol. Pregnancy examinations were performed between days 30–35 after AI. When First insemination pregnancy rates obtained after AI were evaluated, it was determined that pregnancy rates in cows were 56.96% in the control group and 51.96% in the treatment group, in heifers were 64% in the control group and 68% in the treatment group, and there was no statistical difference between the groups (p>0.05). When pregnancy rates at first insemination were evaluated in primiparous and multiparous cows, it was found that multiparous cows had numerically higher pregnancy rates compared to primiparous cows in both the control and study groups. When pregnancy rates at first insemination were evaluated in cyclic and non-cyclic animals in cows and heifers, it was found that cyclic cows and heifers had numerically higher pregnancy rates in the study group, while non-cyclic cows and heifers had numerically higher pregnancy rates in the control group. According to the obtained results, it was determined that adding progesterone to the G6G protocol in cows did not have a positive effect on pregnancy rates. The pregnancy rates obtained in heifers using the G6G protocol were quite good, and based on the data obtained, it was concluded that successful results can be achieved in heifers using modified presynchronization method.

This study investigated the dynamics of maternal humoral immunity in Hisex laying hens subjected to prolonged Newcastle disease (ND) vaccination by evaluating IgM, IgG, and IgA concentrations in egg yolk and egg white. Hens aged 28, 31, 37, and 61 weeks were examined, and antibody levels were quantified using commercially available ELISA kits at four time points, days 3, 7, 10, and 14, within collection period. IgM responses were most pronounced in younger hens (28 and 31 weeks), which exhibited early peaks (p≤0.05) followed by significant declines (p≤0.05), consistent with the transient nature of primary antibody responses. Older hens (37 and 61 weeks) showed attenuated or delayed IgM activity, and egg‑white IgM declined progressively with age, suggesting reduced early‑phase immune responsiveness. IgG was predominantly yolk‑associated. In 28‑ and 31‑week‑old hens, yolk IgG remained high and stable; egg‑white IgG showed a day‑10 decrease in 31‑week‑old hens (p < 0.001). In 61‑week‑old hens, yolk IgG increased at day 10 (p < 0.01) but decreased by day 14 (p < 0.05). IgA showed early increases but declined sharply by days 10 and 14 in most age groups (p < 0.05). These reductions were most pronounced in older hens, indicating that mucosal immune responses were short‑lived and more susceptible to age‑related decline. Overall, prolonged ND vaccination effectively supported long‑term IgG‑mediated maternal immunity but was less successful in sustaining IgM and IgA levels, particularly in older hens. These findings highlight significant age‑dependent differences in maternal antibody deposition and underscore the importance of optimizing vaccination programs to enhance protection in newly hatched chick.