Effectiveness of Oestrus Induction and Fertility Indices in Cows Depending on Biochemical Blood Parameters

The aim of this study was the evaluation of the relationship between values of selected biochemical blood parameters at the moment of cloprostenol (PGF2α) administration and the effectiveness of oestrus induction and fertility indices in dairy cows. Examinations were conducted on 121 cows with the corpus luteum between 45 and 120 d post calving. These animals were injected with 500 μg/cow of PGF2α. Blood samples were collected directly before the injection. Artificial insemination (AI) was made in cows with stimulated oestrus, and in cows with spontaneous oestrus noticed afterwards. Oestrus has been observed in 71.9% cows up to 7 d after injection of PGF2α. Pregnancy rate after AI in induced oestrus was 43.7%. Pregnancy following the first AI in spontaneous oestrus that appeared later than 7 d after PGF2α injection amounted 47.1%. Animals with visible signs of oestrus after injection of PGF2α had shorter calving-pregnancy period (111±43 vs. 162±63, P<0.05), lower percentage of “repeated breeders” (23.0% vs. 38.2%, P<0.05), and lower culling rate (6.9% vs. 14.7%) in comparison to cows, that did not exhibit oestrus post PGF2α. Significant differences were found in the values of non-esterified fatty acid (NEFA), total protein, NH3, and ammoniacal nitrogen and serum urea nitrogen index (N-NH3/SUN) in cows from groups that differed in response to PGF2α and fertility parameters. Relationships between the average concentration of aspartate aminotransferase, β-carotene, NEFA, and index of N-NH3/SUN were correlated with the average length of calving-pregnancy period in groups of cows that differed in the reaction to PGF2α and in the effectiveness of AI after subsequent inseminations.