Relation between the somatic cell count and the success of first insemination in East Frisian dairy herds on the basis of logistic models analysis

Abstract

The purpose of this project was to study the impact of the somatic cell count measured at different test days on pregnancy rates of Holstein cows located in Eastern Frisland applying logistic models. Test days observations for somatic cell count were defined as follows: the last test day before the insemination, the first test day after the insemination and the geometrical average from the whole lactation. In statistical models, somatic cell count was considered in classes of fixed effects, whereas the impact of protein yield and service interval on pregnancy rates was tested as regression coefficients of different polynomial structure. Somatic cell counts above 400000 indicate mastitis whereof 10% of cows were affected. Especially chronic diseased cows over the whole lactation and cows with a somatic cell count above 400 000 in their first test day after the insemination showed about 4% lower pregnancy rates compared with cows in somatic cell count classes below 150000. In conclusion, our study revealed a strong impact of udder health on success of first insemination after calving. The somatic cell count should be considered in selection decisions. An adequate measure in this context seemed to be the relative breeding value for somatic cell count, recently available for the selection on the cow dam path. High protein yield next to the date of insemination decreased the pregnancy rate of cows. A longer service interval is recommended for dairy producers to circumvent the phase of metabolic stress in the first stadium of lactation. Heifers producing in the first lactation and actually in a period of growth have distinct problems to reach a balanced stadium of energy. The success of first insemination in heifers was lower than it was in adult cows. The results from the present study indicated that information collected at different test days, especially the somatic cell count, are informative to characterize the status of fertility from individual cows. Detailed physiological relationships concerning mastitis and fertility should be investigated in further studies.