Effects of dietary Schizochytrium spp. alone or combined with Nannochloropsis gaditana on milk fatty acid profile and oxidative status in lactating ewes

Abstract

The objective of this study was to evaluate the effects of dietary supplementation with Schizochytrium spp., either alone or combined with Nannochloropsis gaditana, on milk yield and composition, milk fatty acid profile, and oxidative status in lactating ewes. Thirty-two crossbred dairy ewes in early lactation (50 ± 5 d in milk) were allocated to four groups (n = 8 per group) balanced for milk yield, body weight, and age. The control group (CON) received a concentrate without microalgae, whereas the supplemented groups received concentrates providing 30 g/ewe/d of Schizochytrium spp. (SC30) or 30 g/ewe/d (MB30) or 40 g/ewe/d (MB40) of a 70:30 blend of Schizochytrium spp. and N. gaditana. The experiment lasted 90 d, and milk and blood samples were collected on d 18, 36, 54, 72, and 90. Dietary treatment did not affect milk yield, fat-corrected milk (FCM), energy-corrected milk (ECM), milk fat yield, or milk protein yield (P > 0.10), although milk fat percentage tended to be lower in MB30 than in CON (P = 0.083). Milk C18:0 and cis-9 C18:1 concentrations were lower in all supplemented groups than in CON (P = 0.006 and P < 0.001, respectively). Trans-11 C18:1 and cis-9, trans-11 CLA were greater in SC30 and MB40 than in CON and MB30 (P = 0.012 and P = 0.015, respectively). Milk C20:5 n-3 increased in all supplemented groups and was greatest in MB40 (P < 0.001), whereas C22:6 n-3 was greater in all supplemented groups than in CON, with the greatest concentrations observed in SC30 and MB40 and an intermediate concentration in MB30 (P < 0.001). Similarly, total polyunsaturated fatty acids (PUFA) and n-3 PUFA were greater in SC30 and MB40 than in CON, with MB30 showing intermediate values (P < 0.001), whereas the n-3/n-6 ratio increased in all supplemented groups compared with CON (P < 0.001). In plasma, catalase activity tended to be greatest in MB40 (P = 0.066), glutathione transferase activity was greatest in MB40 and higher than in SC30, with CON and MB30 showing intermediate values (P = 0.036), and protein carbonyl concentrations were lower in MB30 than in CON and SC30 (P = 0.015). In milk, ABTS radical-scavenging capacity and glutathione peroxidase activity were lower in all supplemented groups than in CON (P = 0.003 and P = 0.043, respectively). Overall, microalgae supplementation, particularly treatments supplying greater amounts of Schizochytrium spp. (SC30 and MB40), enriched ewe milk with long-chain PUFA without impairing milk yield or major production traits.