ORGANIC SHEEP MILK PRODUCTION AND QUALITY BY USE OF LEGUME GRAINS AS DIETARY SUPPLEMENT

Abstract

The aim of this study was to evaluate the sheep milk yield and quality as affecting by concentrate dietary supplements prepared on farm by mixing locally produced barley and legume grains, used as alternative to a commercial feed. A total of twelve milking ewes, averaging 92±9 days in milking and 56±6 kg of live weight, were housed in individual pens and divided homogeneously into four groups. Each group was fed ad libitum with a grass-legume hay and received, according to a 4x4 Latin square design with periods comprised of 21 days, one of the following isonitrogenous concentrates: 500 g chickpea and 300 g barley (CP); 450 g faba bean and 350 g barley (FB); 550 g pea and 250 g barley (PE); commercial feed mixture containing maize and soybean meal (CF). The ewes intake of concentrates based on legume grains was higher than that of commercial feed (702, 702, 678 vs. 587 g/d SS for CP, FB, PE and CF, respectively; P0.001). Comparing the different protein sources, the FB and PE increased milk yield in comparison with CP (710, 718 vs. 654 g/d for FB, PE and CP, respectively; P0.001), whereas CF gave intermediate milk level (677 g/d). FB and PE diets improved also the efficiency of dietary protein utilization for milk casein synthesis in comparison with the other diets (96, 99 vs. 89, 88 g casein/kg crude protein intake for FB, PE, CP and CF, respectively; P0.001). Being the same protein intake, these results from FB and PE seem to be attributable to their better amino acid composition, and also to their higher degradability favouring the balance between dietary energy and protein in the rumen for the microbial protein synthesis. Moreover, the diet induced variations in milk fatty acid (FA) profile, especially regarding some healthy polyunsaturated FA. Indeed, compared with FB and PE concentrates, CP increased, similarly to CF, milk contents in linoleic acid (C18:2 n-6 c9 c12) (2.24, 2.25 vs. 1.54, 1.42 % FA for CF, CP, FB and PE, respectively; P0.001), rumenic acid (CLA, C18:2 c9 t11) (0.63 vs. 0.32 vs. 0.25, 0.23 % FA for CF, CP, FB and PE, respectively; P0.001) and total unsaturated FA (24.87, 23.80 vs. 17.19, 16.81 % FA for CF, CP, FB and PE, respectively; P0.001), and improved the value of health promoting index (0.30, 0.28 vs. 0.17, 0.17 for CF, CP, FB and PE, respectively; P0.001). These results demonstrated how, in comparison with CF, the concentrates based on the legume grains were well palatable for the milking ewes and their use did not lead to a milk yield reduction or a worsening in milk composition and clotting ability.