Convention de collaboration technique et scientifique dans le cadre des évaluations génétiques bovines laitières pour la Wallonie. Rapport d’activités pour l’année 2006.

Report (2007)

Within and across breeds differences in fatty acids profiles of milk and milk fat in dairy cows

Poster (2006, August)

Différences intra- et inter-races du profil en acides gras du lait

in 11ème Carrefour des Productions Animales (2006, January 25)

Variation in fatty acid contents of milk and milk fat within and across breeds

in Journal of Dairy Science (2006), 89(12), 4858-4865

The aim of this research was to study the potential for selection of cows with a higher nutritional quality of milk fat by studying the differences in fatty acid profiles within and across the following ... [more ▼]

The aim of this research was to study the potential for selection of cows with a higher nutritional quality of milk fat by studying the differences in fatty acid profiles within and across the following breeds: Dual Purpose Belgian Blue, Holstein-Friesian, Jersey, Montbeliarde, and non-Holstein Meuse-Rhine-Yssel type Red and White. Six hundred milk samples from 275 animals were taken from 7 herds. Several types of fatty acids in milk and milk fat were quantified using midinfrared spectrometry and previously obtained calibration equations. Statistical analyses were made using a mixed linear model with a random animal effect. The variance components were estimated by using REML. Results showed breed differences for the fatty acid profile. The repeatability estimate obtained in the present study may suggest the existence of moderate additive genetic variance for the fatty acid profile within each breed. Results also indicated variation for each analyzed milk component in the whole cow population studied. Genetic improvement of the nutritional quality of milk fat based on fatty acid profiles might be possible, and further research and development are warranted. [less ▲]

Inbreeding depression for global and partial economic indexes, production, type, and functional traits

in Journal of Dairy Science (2006), 89(6), 2257-2267

The objective of this research was to examine the effects of inbreeding in the population of Holstein cattle in the Walloon region of Belgium. The effects of inbreeding on the global economic index and ... [more ▼]

The objective of this research was to examine the effects of inbreeding in the population of Holstein cattle in the Walloon region of Belgium. The effects of inbreeding on the global economic index and its components were studied by using data from the genetic evaluations of February 2004 for production, somatic cell score (SCS), computed from somatic cell counts and type. Inbreeding coefficients for 956,516 animals were computed using a method that allows assigning an inbreeding coefficient to individuals without known parents. These coefficients were equal to the mean inbreeding coefficient of contemporary individuals with known parents. The significance of inbreeding effects on the different evaluated traits and on the different indexes were tested using a t-test comparing estimated standard errors and effects. The inbreeding effect was significantly different from zero for the vast majority of evaluated traits and for all of the indexes. Inbreeding had the greatest deleterious effects on production traits. Inbreeding decreased yield of milk, fat, and protein during a lactation by 19.68, 0.96, and 0.69 kg, respectively, per each 1% increase in inbreeding. The regression coefficient of SCS per 1% increase in inbreeding was +0.005 SCS units. The inbreeding depression was thus relatively low for SCS, but inbred animals had higher SCS than non-inbred animals, indicating that inbred animals would be slightly more sensitive to mastitis than non-inbred animals. Estimates of inbreeding effects on evaluated type traits per 1% increase were small. The most strongly affected type traits were chest width, rear leg, and overall development on a standardized scale. For several type traits, particularly traits linked to the udder, the estimates suggested a favorable effect of inbreeding. The global economic index was depressed by around 6.13 Euro of lifetime profit per 1% increase in inbreeding for the Holstein animals in the Walloon region of Belgium. [less ▲]

Qualité nutritionnelle du lait - Etude de la variabilité intra- et inter-races du profil en acides gras du lait

in Le Bulletin (2006), (2), 8-10

Within and across breeds differences in fatty acids profiles of milk and milk fat in dairy cows.

in Proceedings of the 8th World Congress on Genetics Applied to Livestock Production (2006)

Integration of longevity into the Walloon genetic evaluation system

in Interbull Bulletin (2006), 35

Correlations of longevity evaluation with type traits in Walloon Region.

Poster (2006)

Approximated genetic correlations between direct longevity and type traits were computed for a sire Holstein population. Data were based on results for type traits (77,965 records) and for direct ... [more ▼]

Approximated genetic correlations between direct longevity and type traits were computed for a sire Holstein population. Data were based on results for type traits (77,965 records) and for direct longevity (74,289 records) from the INTERBULL routine run of November 2005. Most of type traits presented a high relationship with direct longevity (from 0.06 up to 0.29). The strongest positive correlation with longevity was for udder depth (0.29) and the strongest negative correlation was for chest depth (-0.21). According the different results, an animal with a good direct longevity seemed to be smaller and less heavy than an animal with a shorter longevity. [less ▲]

Genetic evaluation of cow survival using a lactation random regression model

in INTERBULL Bulletin (2005), 33