Environmental and genetic factors for fatty acid contents in goat milk

Summary Fatty acid (FA) composition has an important influence on the nutritional quality of milk and on the technological properties for cheese making.The aim of the study was, at first, to estimate the environmental effects of diet, breed,parity number, stage of lactation, month of calving, season of control and day of testing within each herds (HTD) on the milk fatty acid content. Secondly, the genetic parameter estimation of the major FA and protein and fat yield. The apparent relationship between FA traits as well as between FA and production traits were also studied.The data set for the effects analyse (except from breed effect) included 141 397 testday records of 46 289 goats (Alpine and Saanen breeds). These results confirmed that diet effect need to be more precisly studied to show a true impact on the FA composition. For the other effects, goats in first stage of lactation as well as goat at first lactation produced more unsaturated FA than at middle stage or at 2nd and 3rd lactations. Milk fat produced during automn had greater unsaturated fatty acid content compared with the other season of control. The differences between breeds was also estimated, on a restricted data set included 40 674 test-day records of 13 101 goats, when the herds used both breeds. Variance components were estimated with single trait animal models using REML (VCE) on a smaller data set of 14 237 Alpine goats and 13 892 Saanen goats. Concerning heritabilities, those estimate for fat content are more underestimated than for protein content. FA heritabilities take values from 0.20 to 0.40 which seem in accordance with cattle results. Generally, they are higher in Saanen goats, whereas repeatabilities are higher in Alpine goats.