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

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 (A(30)). Saturated fatty acids C-10:0, C-12:0, C-14:0 and C-16:0 were depressed in milk fat with the Ca soap supplemented diet, some of them significantly. C-18:1 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.