Dezetter Charlotte

Abstract :

Robustness of Holstein (HO) cows has decreased over the past decades while crossbreeding might be a way to improve it. The aim of this thesis was to assess, with a simulation model, the interest of the introduction of a crossbreeding mating plan in HO herds. From a preliminary estimation of crossbreeding parameters for production and reproduction traits in HO, Montbéliarde (MO) and Normande (NO) cows from the national database, we concluded that breed differences and heterosis effects were significant. Then, we simulated, over 15 years, three different crossbreeding scenarios with HO, MO, NO or Scandinavian Red (SR) breeds, in comparison to pure HO mating for several types of dairy operations. Given the parameters values of our study, in high milk-yielding herds with low prevalence of reproduction and health disorders, the introduction of crossbreeding was not more profitable than keeping on pure HO mating. However, in high milk-yielding herds with high prevalence of reproduction and health disorders, crossbreeding was more profitable than keeping on pure HO mating, especially for the 3-way rotational HOxMOxSR scheme, which increased the gross margin by 100€/cow/year compared to pure HO mating. In moderate milk-yielding herds, profitability advantage of crossbreeding was smaller but cows’ robustness was improved and led to fewer treatments per cow. As shown in an initial step of this study and despite of our quite favorable results, French dairy producers are still widely reluctant to implement crossbreeding. Therefore, the study highlights the need of a more elaborated advice to producers on this subject.

Key words :

Dairy cow, Crossbreeding, Animal performance, Profitability, Genetic evaluation, Modelling, Holstein, France