Pros and cons of the supplementation with oilseed enriched concentrates on milk fatty acid profile of dairy sheep grazing Mediterranean pastures

Abstract

The aim of this research was to study the effects of dietary supplementation on the composition and fatty acid (FA) profile of milk from grazing dairy sheep. Forty-eight lactating Sarda ewes were randomly allocated to four homogeneous groups: PAS – control group grazing for 22h/d without supplementation; NFS – group supplemented with a cereal based concentrate; SLNA – group supplemented with a concentrate enriched with sunflower seeds (106g/kg DM); and SALA, group supplemented with a concentrate enriched with linseeds (105g/kg DM).Milk from groups receiving the oilseed enriched concentrate (SLNA and SALA) showed increased total C18:2 non-conjugated dienes, C18:1 t9 and total trans C18:1 by 106% (P<0.01), 152% (P<0.01) and 50% (P<0.01) respectively, compared to the PAS group. The supplementation with linseed concentrate enhanced the level of milk CLA c9, t11, (2.90 vs 2.27g/100g of FAME; P<0.01), compared to the PAS group. An increase in PUFA level was also detected in oilseed supplemented groups (9.58, SALA; 9.84 SLNA vs 6.68g/100g of FAME in PAS; P<0.01), whereas the n-3/n-6 ratio was decreased (2.08 (PAS) vs 0.60 (SLNA) and 0.90 (SALA) P<0.01). In addition, the supplementation with sunflower seed decreased the I-Harris index (EPA+DHA=0.13 vs 0.10g/100g of FAME; P<0.01 in PAS and SLNA, respectively). Results from the NFS group were either undifferentiated from PAS or intermediate between those of oilseed supplemented groups and the PAS group. Overall, these results suggest that oilseed enriched supplementation in grazing dairy sheep, while enhancing the content of some putatively beneficial FA such as PUFA or CLA c9, t11 in milk, also resulted in some counters effects on milk nutritional quality, compared to grazing without supplementation.