Olive oil calcium soaps and rumen protected methionine in the diet of lactating ewes: effect on milk quality

Abstract

Eight Massese ewes were fed 4 diets with alfalfa hay as the forage (73% on the DM basis): 1) control diet (C); 2) diet C supplemented with olive oil calcium soaps, 50 g/d (L); 3) diet C supplemented with protected methionine, 5 g/d (M) or 4) plus both soaps and methionine (ML); the experimenthal design was a 4x4 Latin square with 2 replicates per diet. During the experimental periods, lasting one week each, the ewes were milked twice daily (8:00 a.m. and 7:00 p.m.). Milk yield was not affected by diet quality, but milk fat percentage and 6.5% fat corrected milk yield were higher in diets L, M and ML with respect to diet C (P<0.05). Milk protein content was depressed and blood urea increased following the Ca soap diet alone or with protected methionine. Diet M worsened (P<0.05) Rennet clotting time (r) and curd firmness after 30 minutes (A30). Saturated fatty acids C10:0, C12:0, C14:0 and C16:0 were depressed in milk fat with the Ca soap supplemented diet, some of them significantly. C18:1 increased (P<0.05) with diet L only, whereas the association of Ca salts and methionine in diet ML significantly affected the linoleic acid and CLA content.It is concluded that the use of olive oil fatty acids as a protected fat source seems to improve the milk fatty acid characteristics towards a safer pattern, but the presence of this type of Ca salts in the diet appears to worsen the metabolic utilisation of amino acids.