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    Evaluation of the relationship of some environmental factors and number of inseminations per pregnancy with milk yield in holstein cows
    (Sezer ÖZ, 2024) Erzurum, Onur; Kayar, Tamer
    In order to investigate the relationship between some environmental factors and the number of artificial inseminations per pregnancy with milk yield, data of 90 healthy Holstein breed dairy cows in a private dairy farm in Karapınar district of Konya province were taken. For the utilization of the data, age, number of artificial inseminations, lactation yield, calving season and sequence of lactation records were taken from the herd management program in the enterprise and analysed. As a result of the analysis, the number of artificial inseminations per pregnancy in 2016 was 1.79 and lactation milk yield was 10079,41 kg; the number of artificial inseminations per pregnancy in 2017 was 2.16 and lactation milk yield was 9767.94 kg. There was a statistically significant relationship between the number of artificial inseminations per pregnancy and milk yield during lactation period in both years. As a result, the increase in the number of artificial inseminations per pregnancy negatively affected the average milk yield of lactation period. Genetic and environmental factors are thought to play a major role in this effect.
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    Thiol/Disulphide Homeostasis in the Relationship Between Body Condition Score and Oxidative Stress in Periparturient Period Holstein Heifers
    (John Wiley and Sons Inc, 2025) Kayar, Tamer; Özkurt, Güzin; Erzurum, Onur; Er, Kübra; Büyükgüngör, Beril; Geçgel, Beyza Nur; Karaburç, Muhammet Nureddin
    This study aimed to evaluate the effects of body condition scores (BCSs) on oxidative stress and thiol/disulphide homeostasis (TDH) in Holstein pregnant heifers during the transition period. A total of 36 healthy primiparous heifers in the 7th month of pregnancy, all approaching their first calving, were included in the study. The animals were allocated into three equal groups based on their BCS. The BCS measurements were performed 21 days pre-calving and on the 21st day post-calving. Pre-calving and post-calving serum levels of total thiol (TTL), native thiol (NTL) and disulphide (DSF) were quantified using standard techniques. The study revealed significant differences in BCS, TTL and DSF values among groups both pre- and post-calving (p < 0.05), whereas the changes in NTL values were statistically insignificant (p > 0.05). Overall, a decrease in BCS and NTL levels was observed, accompanied by an increase in TTL and DSF levels. Correlation analysis within groups indicated low-level relationships between changes in BCS and TTL, NTL and DSF levels. Consequently, regression analysis did not yield any statistically significant predictive models. The results showed a differential response between the loss of BCS and the oxidative stress during the periparturient period. The increased DSF levels observed during late pregnancy and early lactation indicate a deficiency in antioxidant substances in the animals. Therefore, supplementing the ration with a premix containing antioxidant substances during the transition period may provide significant benefits in terms of maintaining the BCS balance, animal welfare and herd health.