Integration of extruded linseed into dairy sheep diets: effects on milk composition and quality and sensorial properties of Pecorino cheese

The objective of this work was to study the influence of including extruded linseed at different supplementation levels in dairy sheep feed on the chemical, organoleptic and nutritional quality of milk and Pecorino cheese. Three hundred and thirty multiparous Sarda ewes, three weeks before their expected date of parturition, were divided into three groups of 110 animals each. Ewes were fed one of three different concentrates: a control concentrate (CTR) without linseed and two concentrates supplemented with different levels (100 and 200 g/kg as fed; EL-10 and EL-20, respectively) of extruded linseed. The experimental concentrates were fed to the ewes during late pregnancy (400 g per head per day) and early lactation (60 days after parturition; 800 g per head per day). All animals had unlimited access to pasture and hay. Milk production was recorded, and milk samples were collected for the analysis of chemical composition and clotting properties. Cheeses were made with bulk milk from the three groups using a traditional cheese-making technique. After 60 days of ripening, the chemical composition and organoleptic properties of the cheeses were analysed using a Panel test. Milk yield and all major milk components, except milk fat yield, were both linearly (0.01<P<0.001) and quadratically (0.05<P<0.001) related to the level of linseed in the diet. Except for the urea content, which decreased at a decreasing rate (linear P<0.001 and quadratic P<0.05), milk components increased at an increased rate with increasing EL supplementation. The fatty acid composition of milk and cheese was affected by dietary linseed supplementation. Milk fat of groups receiving feed that included extruded linseed showed higher levels of monounsaturated fatty acids and lower levels of saturated fatty acids. Linseed administration linearly increased milk polyunsaturated fatty acid content (P<0.001). The C18:3 n-3 milk content increased by 36 and 87% (P<0.001) for the EL-10 and EL-20 groups, respectively. The higher content of total n-3 fatty acids in milk caused a linear decrease of the n-6/n-3 fatty acid ratio in the EL groups (P<0.001). Dietary treatments affected the chemical composition of cheese; the increase in the level of extruded linseed was negatively correlated with the moisture content of cheeses. Modifications to the fatty acid profiles of the cheeses were similar to those observed for milk. Sensory properties of cheese were not negatively affected by dietary treatments. Cheeses produced from groups fed diets with added linseed had higher scores for overall and ripe cheese flavour