The impact of the dietary supplementation level with Schizochytrium sp. on milk chemical composition and fatty acid profile, of both blood plasma and milk of goats

Abstract

• 20 g Schizochytrium sp./goat/day enhances milk PUFA. • 20 g Schizochytrium sp./goat/day didn’t affect negatively the milk fat. • Both 40 and 60 g Schizochytrium sp./goat/day induce milk fat depression. • Both trans-10, cis-12 C 18:2 and c is-9 C 18:1 have pivotal role in goats’ milk fat. Microalgae, have gained significant attention as a source of beneficial biomolecules such as long chain n-3 polyunsaturated fatty acid (PUFA), and are considered to be an effective strategy to enhance ruminant milk with PUFA. However, milk fatty acids (FA) profile is affected by ruminant biohydrogenation process and consequently by possible adaptations of rumen microbiome related with the duration of diet supplementation. Thus, the aim of the present study was to investigate a long-term response of dietary inclusion of microalgae Schizochytrium sp., at three different levels with moderate forage to concentrate ratio (50/50) on milk chemical composition and fatty acid profile of both goats’ blood plasma and milk. For this purpose, twenty-four dairy goats were divided into four homogeneous sub-groups. All the goats were fed individually with alfalfa hay and concentrates. The concentrates of the control group (CON) had no microalgae, while those of the treated groups were supplemented daily with 20 (ALG20), 40 (ALG40) and 60 (ALG60) g Schizochytrium sp./kg concentrates. The mean milk yield was not affected, while the fat content was decreased in ALG40 and ALG60 groups, compared with the CON and ALG20 ones. In blood plasma the proportions of C 16:0 , C 18:0 , cis-9 C 18:1 and C 18:2n6 c decreased (P < 0.05), while those of trans-11 C 18:1 , C 20:3n3 , C 22:2n6 , C 22:5n6 and C 22:6n3 were increased in the microalgae treated groups compared with the CON. The proportions of C 14:0 , C 16:0 , trans-10 C 18:1 , trans-11 C 18:1 , cis-9, trans-11 C 18:2 , trans-10, cis-12 C 18:2 , C 22:6n-3 (DHA), C 22:5n-6 (DPA) and the total n-3 fatty acids were increased significantly in the milk of treated goats, while those of C 18:0 , cis-9 C 18:1 and C 18:2n6c were decreased. In conclusion, the dietary inclusion of 20 g Schizochytrium sp./goat/day, combined with a forage to concentrate ratio of 50/50, enhances the PUFA of goats’ milk without negative effects on its chemical composition.