Abstract
Various factors influencing reproduction in dairy Holstein cows were routinely evaluated and genetic parameters were estimated for four traits for assessing fertility of artificially inseminated cows: Calving to first service interval (CFSI), calving interval (CI), calving to conception interval (CCI), and number of services per conception (NSC). Data used in this investigation consisted of records of insemination and calving events on Tunisian Holstein cows. Records were registered from 1994 to 2003 in 150 herds to study the effects of non-genetic factors and estimate the heritabilities of those fertility traits. The factors examined were: month and year of calving, herd, parity, and year-month of calving. The effect of month and year of calving (or insemination), herd, parity and year-month of calving were included in the model and were significant (P < 0.01) except for the number of lactations that does not have an effect on the number of services per conception. A decreasing efficiency in cow fertility was observed over the last years, with a longer day for first service interval. Heritability for fertility traits was low ranging from 0.027 for NSC to 0.067 for CI. The results suggested that more attention should be paid to herds with too low fertility traits and that monitoring/alert and intervention schemes should be tested in research/action approaches.
Highlights
Knowledge of reproductive performance in Tunisian dairy herds is limited
Various factors influencing reproduction in dairy Holstein cows were routinely evaluated and genetic parameters were estimated for four traits for assessing fertility of artificially inseminated cows: Calving to first service interval (CFSI), calving interval (CI), calving to conception interval (CCI), and number of services per conception (NSC)
The results suggested that more attention should be paid to herds with too low fertility traits and that monitoring/alert and intervention schemes should be tested in research/action approaches
Summary
Knowledge of reproductive performance in Tunisian dairy herds is limited. Selection for higher yields of dairy cattle has led to a decline in fertility due to unfavorable genetic correlations between yield and fertility (Pryce et al, 2004). During the last two decades, the dairy sector in Tunisia went through major development programs to increase dairy production in order to improve farmer’s life’s whose income comes from milk sale and to ensure the national self-sufficiency in milk and dairy products. These development programs are not in favor of reproductive performances of Holstein which remain low. The deterioration of the fertility in dairy cows during the last two decades today constitutes a major difficulty confronted by the dairy breeders. The objectives of this study were to identify non-genetic factors strongly associated with reproductive performance and to estimate genetic parameters for Tunisian Holstein female reproduction traits
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