РИЗИК ФАКТОРИ ЗА НАРУШЕНА ПЛОДНОСТ КАЈ ВИСОКОМЛЕЧНИТЕ КРАВИ: RISK FACTORS AFFECTING FERTILITY IN THE HIGH-PRODUCING DAIRY COWS
2011
Metodija Trajchev | Dimitar Nakov | Goran Mitrov
The fertility of lactating dairy cows is economically important, but the mean reproductive performance of dairy cows has declined during the past 3 decades. Traits such as first-service conception rate and the lenght of the service period are influenced by numerous explanatory factors common to specific farms or individual cows level A one years retrospective study was carried out to identify risk factors affecting the reproductive performance of black-white lactating cows. The data for reproductive, health and production events were obtained from farm reproductive board. The first breeding of haifers was at average on 479.48±78.521 days of age, and the first calving was at average on 756.99±78.661 days of age. The first service conception rate was 97.30%. The average number of days in lactation to conception was 112.10±56.262. The annual calving rate was 47.42%, the high calving rate was evidented in the winter calving season (57.73%), and the low was evidented in the summer calving season (42.80%). The average lenght of calving interval was 437.35±101.94 days. The average length of the pregnancy was 276.96±27.920 days. The average lenght of the lactation was 320.54±61.698 days. The univariate GLM was used to analyze risk factors responsible for reproductive efficiency. Among the risk factors that were found to affect the lenght of the service period, statistical significance at level p<0,001 showed the lenght of lactation. The cow parity and season of calving did not show statistical significant influence on lenght of the service period.
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