Genetic parameters for milk somatic cell score and relationship with production and udder type traits in dairy Alpine and Saanen primiparous goats

Abstract

Goat milk somatic cell counts have been collected for several years in France by the national milk recording organization. Information is used for health management, because repeatedly elevated somatic cell counts are a good indirect predictor of intramammary infection. Genetic parameters were estimated for 67,882 and 49,709 primiparous goats of the dairy Alpine and Saanen breeds, respectively, with complete information for milk somatic cell counts and milk production traits. About 40% of the goats had additional information for 11 udder type traits scored by official classifiers of the breeders' association CAPGENES. Estimates were obtained by REML with an animal model. The studied trait was lactation somatic cell score (LSCS), the weighted mean of somatic cell score (log-transformed SCC) adjusted for lactation stage. Heritability of LSCS was 0.20 and 0.24 in the Alpine and Saanen breeds, respectively. Relationships with milk production and udder type traits were additionally estimated by using multitrait analyses. Heritability estimates in first lactation ranged from 0.30 to 0.35 for lactation milk, fat, and protein yields; from 0.60 to 0.67 for fat and protein contents; and from 0.22 to 0.50 for udder type traits. Genetic correlations of somatic cell score with milk production traits were generally low, ranging from -0.13 to 0.12. Slightly more negative correlations were estimated for fat content: -0.18 and -0.20 in Saanen and Alpine breeds, respectively. Lactation somatic cell score was genetically correlated with udder floor position (r(g)=-0.24 and -0.19 in the Alpine and Saanen breeds, respectively), and, in Saanen, teat length, teat width, and teat form (r(g)=0.29, 0.34 and -0.27, respectively). These results suggest that a reduction in somatic cell count can be achieved by selection while still improving milk production and udder type and teat traits.

Genetic parameters of somatic cell score and lactose content in goat’s milk

“…Genetic parameters for SCC estimated in the French Saanen, Alpine and New Zealand dairy goat populations (mostly Saanen) were slightly lower than those obtained in our study (0.20 -0.24 - Morris et al, 2011;Rupp et al, 2011). However, repeatability estimated by Morris et al (2011) was almost the same as obtained in our study (0.57 vs 0.55).…”

“…Another New Zealand study on mixed-breed dairy goats (Saanen, Nubian, Alpine and Toggenburg) revealed that heritability of SCS is lactation stage dependent, and increased from 0.12 to 0.25 from the beginning to the end of lactation, while repeatability ranged between 0.46 and 0.59 (Apodaca-Sarabia et al, 2009). The value obtained in our study, higher than in the French population (Rupp et al, 2011), might have been the result of involving different animal populations and using different models. Heritability for SCC was also estimated in Kenya by Bett et al (2012), however their estimates were much lower Table 1; ABC, ab means with different superscripts are significantly different at P < 0.01 and P < 0.05, respectively (0.15) than those previously mentioned and could be explained by the specific system of husbandry (low input smallholder systems in Kenya vs intensive systems in France, New Zealand or Poland).…”

“…Therefore, the prediction of mammary gland inflammation based on SCC in goat is more difficult than in cattle or sheep (Rupp et al, 2011). Many different indicators of the mammary gland subclinical infection have been proposed, but the SCC is still the easiest and most cost-effective means of recording mammary gland health status also in goat breeding (Rupp et al, 2011).…”

“…Many different indicators of the mammary gland subclinical infection have been proposed, but the SCC is still the easiest and most cost-effective means of recording mammary gland health status also in goat breeding (Rupp et al, 2011). In addition, lactose content can also be used as the indicator of the mammary gland health status (Lindmark-Månsson et al, 2006).…”

“…First studies were based on lactation yields, while for the last two decades, the test-day model has been adapted in goat breeding, too. Usually the restricted maximum likelihood (REML) method or the Gibbs sampling with multiple-trait animal models are used to estimate the variance components (Groenewald and Viljoen, 2003;Rupp et al, 2011).…”