Prédiction des performances potentielles de la vache laitière à partir des caractéristiques de la robe et de paramètres biologiques

Abstract

The aim of our study was to study a relationship between reproductive efficiency and heat stress in dairy cows, particularly when animals are raised under conditions of high temperatures and intense solar radiation. so how can thermal stress affects on reproduction performances. Selection of a hair, adapted to warm environments, could be a strategy to improve the reproductive function of cows in Algeria. The investigations in this thesis aimed to understand the relationship between reproductive performance, the characteristics of the coat of cows born in Algeria or imported from Europe and their relationship to the level of hair cortisol in 95 cows (28 Fleckvieh FL and 67 Montbéliarde MB ). The results showed that the imported cows had a whiter coat than the cows born locally for the MB breed, but an opposite trend was observed for the FL cows. The significant effect of total hair diameter was observed on the design calving interval (IC) for imported MB cows, suggesting less impact of heat stress on the reproductive efficiency of cows with a thin hair. Although, for the FL breed, the darkest cows were born locally, they performed significant reproductive performance for all parameters. In the Montbéliarde breed, HD was negatively correlated with SPC in winter (r = -0.34, p = 0.01), whereas in summer, the coat characteristics were not correlated with all fertility parameters. In Fleckvieh cows, coat color was correlated with ICS and IC (r = 0.67, p = 0.02; r = 0.60, p = 0.04, respectively) during the summer and with SPC in winter (r = 0.86, p = 0.01). No association between the level of hair cortisol and fertility was observed. The characteristics to select here could be: MB cows with large hair diameters, FL cows with a dark coat for the best reproductive and adaptation performance. This adaptation results in the expression of higher reproductive performance.