Odd- and branched-chain fatty acids in goat milk as indicators of the diet composition

Abstract

This work aimed to determine if the milk fat contents of odd- and branched-chain fatty acids (OBCFA) could be linked to the diet composition in goats, by canonical discriminant analysis (CDA). The OBCFA contents of 32 milk fat samples from two feeding trials (two treatments per trial) were used. In both experiments, the goats were fed a diet, with the same forage/concentrate ratio and nutritive value, which was supplemented or not with 30 g/d of linseed oil. The starch/non-forage NDF ratio of the diet was 3.1 in the first experiment and was lowered to 0.8 in the second experiment by replacing part of the cereals in the concentrate with soybean hulls. Milk fat composition analyses were grouped into four classes in the CDA. Stepwise backward selection identified C13:0 iso, C14:0 iso, C17:0 anteiso, C18:0 iso and C17:0 + cis-9 C17:1 as valid predictors. The first two discriminant functions (DF) explained 82.2 and 13.9% of total variance. DF1 and DF2 differentiated milk samples by the non-forage NDF content and linseed oil supplementation of the diet, respectively. C14:0 iso and C17:0 anteiso were indicative of the diets with high non-forage NDF and starch contents, respectively. C17:0 + cis-9 C17:1 and both C18:0 iso and C13:0 iso contributed to identify the diets with and without added linseed oil, respectively. In conclusion, CDA allowed to identify which milk OBCFA were the best indicators of the starch/non-forage NDF ratio and the presence of linseed oil in the diets fed to dairy goats.