Sophie Mattalia

Inbreeding and crossbreeding parameters for production and fertility traits in Holstein, Montbéliarde, and Normande cows

Breed differences and nonadditive genetic effects for milk production traits, somatic cell score (SCS), conception rate (CR), and days to first service (DFS) were estimated for Holstein × Montbéliarde and Holstein × Normande crossbreds, using an animal model adapted from the French genetic evaluation and extended to across-breed analysis. Inbreeding and breed differences were estimated from all purebred recorded cows. Only records from 1,137 herds with Holstein × Montbéliarde crossbred cows and from 1,033 herds with Holstein × Normande crossbred cows were used to estimate crossbreeding parameters. In these herds, crossbred cows represented about 13% of the total number of recorded animals compared with <1% when all herds were considered. Compared with the Montbéliarde and Normande breeds, the Holstein breed was genetically superior for production [+951kg and +2,444kg for 305-d mature-equivalent (305ME) milk, +40kg and +102kg for 305ME fat, +17kg and +54kg for 305ME protein, respectively] and inferior for fertility traits (-12 and -9% for CR, respectively). Inbreeding depression caused loss of yield for production traits (from -32 to -41kg of 305ME milk, -1.4 to -1.7kg of 305ME fat, and -1.1 to -1.3kg of 305ME protein per inbreeding percentage), a small increase in SCS (+0.001 to 0.006) and DFS (+0.12d), and a decrease in CR (-0.27 to -0.44%). Favorable heterosis effects were found for all traits (+494 to 524kg of 305ME milk, +21 to 22kg of 305ME fat, +15 to 16kg of 305ME protein, -0.05 to -0.04 SCS, +2 to 3% for CR, and -3 to 6d of DFS), to such a point that F1 crossbreds could compete with Holstein cows for milk production while having a better fertility. However, recombination losses suggested that some F1 heterosis was lost for backcross cows.

Évolution des objectifs et des méthodes de sélection des bovins laitiers

Over the last decades, the dairy stock has undergone major changes, and the selection of dairy cattle has become an internal business.With current prospects of milk quota removal, falling prices, increasing herd sizes, changes in the farmers’ way of working and diversification of demand, the ideal cow of the future will have to demonstrate autonomy, robustness and feed efficiency, and will have to produce a rich milk whose composition meets the requirements of humans. Selection methods will change radically with the ongoing development of genomic selection. Animal identification, pedigree and performance recording will remain, but progeny testing of bulls will diminish. Resources will be pooled between research and supervision organisations, breeding companies and other operators, and there will be an increased need for training.

La sélection dans l’espèce bovine et ses perspectives

Cet article présente la sélection bovine dans les deux filières bovines laitière allaitante qui ont chacune leurs particularités, en particulier la place de l’insémination animale ou le développement de la base de sélection, mais aussi des propriétés communes, pour la plupart issues de la Loi sur l’Élevage qui a défini l’organisation de la sélection. Progressivement, les objectifs de sélection ont évolué vers la prise en compte d’un nombre croissant de caractères et la diminution du poids de la productivité au profit des caractères fonctionnels. La Loi d’orientation agricole de 2006 et l’émergence de la sélection génomique à partir de 2009 ont profondément modifié l’organisation de la sélection avec l’abandon du testage sur descendance, la mise en place de populations de référence, la concentration des acteurs économiques, une mutualisation nationale moindre au profit d’initiatives d’entreprises mais aussi d’accords internationaux. Un nouveau changement majeur est attendu avec la mise en application en 2018 du Règlement Zootechnique Européen qui modifie le cadre organisationnel de la sélection.