Effect of dietary linseed supplementation on milk fatty acid profile in dairy goats with different alphaS1-casein (CSN1S1) genotype
In this study, the effects of dietary supplementation with extruded linseed on milk fatty acid profile of dairy goats with different alpha-s1 casein (CSN1S1) genotype are investigated. A flock of 68 Alpine goats were genotyped by IEF at the CSN1S1 locus. Ten were selected for the experiment: 5 homozygous for the weak F allele (FF) and 5 heterozygous for a strong allele (AA or BE). Goats of each genotype (weak and strong) were allocated into two groups: one was the control (CON) and one was supplemented with 150 g/d of extruded linseed (LIN). The trial lasted 8 weeks. Data were analyzed using a mixed linear model that included the period, diet, genotype and diet × CSN1S1 genotype interaction as fixed factors, and the goat as random factor. Results confirmed the lower protein content (-11%) and higher milk yield (+26%) in weak genotype. A significant interaction diet x genotype was found for fat content: it was higher in LIN compared to CON only in the strong genotype (3.4 vs 4.0%), whereas it did not change in weak genotype (3.3 vs 3.2%). Goats fed LIN had greater proportions of vaccenic acid (18:1 trans11), CLA c9t11 and 18:3n-3 than goats fed CON. The genotype affected some FA: in particular the weak group showed a higher proportion (P<0.05) of linoleic (2.5 vs 2.1 g/100 g total FA), CLA c9t11 (0.8 vs 0.6 g/100 g total FA), C16:1 and C22:4n6, and a lower proportion of stearic (7.4 vs 8.6 g/100 g FA) compared to strong. Furthermore, the delta9 desaturation ratios were higher in weak CSN1S1 genotypes for C14 and trans11 C18:1. This study evidenced the impact of genetic variants of CSN1S1 on milk fat content and composition. Acknowledgements: research funded by Fondazione Banco di Sardegna project.
Keywords: goat milk; alphaS1-casein; linseed diet by genotype interaction