Effect of Calving Season and Parity on Productivity, Post-partum Reproductive Parameters and Disorders, and Economic Indices in Holstein Cows Kept Under Subtropical Conditions in Egypt

This research aimed to study the effect of calving season and parity on productivity, post-partum reproductive performance, disorders, and economic impact in Holstein cows kept under subtropical Egyptian conditions. Lactation and health records of high-yielding cows (500 records) in a commercial dairy herd covering the period between 2020 and 2021 were obtained. The studied productive parameters were average daily milk yield (DMY), dry matter intake (DMI), and feed conversion efficiency (FCE) and the reproductive measures were the number of heats, number of services per conception (NSC), days to first heat (DFH), days to first service (DFS), and days open (DO). Summer calvings were associated significantly (P<0.05) with a decline in DMY and DMI (31.8 kg and 22.7 kg, respectively) compared to winter calvings. Cows that calved in summer had significantly higher (P<0.05) NSC and longer DO (3.44, and 199.3 d, respectively) and also had a higher incidence of endometritis than winter calvings. First parity cows had significantly (P<0.05) lower (DMY and DMI) and higher (NSC and DO) than those in higher parities. Parity has no significant effect on the incidence of post-partum ovarian disorders. The economic losses from disease treatments recorded the highest value in summer calving (13280 LE/100 head) and primiparous cows (8218.01 LE/100 head). Revenue and profit/cost ratio were higher in winter calvings and pluriparous cows. In conclusion, good management, suitable nutrition during different parity and seasons also intensive cooling systems during the summer season should be applied for improving the productivity, fertility, and the economic impact on Holstein farms