Milk production, composition, and milk fatty acid profile from grazing sheep fed diets supplemented with chestnut tannin extract and extruded linseed

tTannins are bioactive compounds able to interfere with protein and lipid metabolism in the rumen, byforming undegradable complexes with dietary proteins and by modulating several bacterial activities,including the biohydrogenation of polyunsaturated fatty acids. The aim of this trial was to study theeffect of dietary supplementation with chestnut hydrolysable tannin extract on ewes milk yield andquality. Ninety-six multiparous Sarda ewes in their mid-lactation phase were allotted to two homoge-neous groups (control group, C group; group fed concentrate supplemented with chestnut tannin extract,CHE group), each of 48 animals, for a feeding trial. Animals of both groups grazed 8 h per day on the samepasture based on a mixture of Lolium multiflorum, Avena sativa and Trifolium repens (1:1:1). The two dietsdiffered only in their concentrate supplement. The control group received 450 g/head per day of a con-centrate feed without chestnut tannin extract, whereas the CHE group received 500 g/head per day ofa concentrate feed formulated with the same ingredients of the control concentrate plus 80.0 g/kg DMof chestnut tannin extract. The amounts of concentrate offered to the animals of both groups were cal-culated in order to obtain isoproteic and isoenergetic dietary treatments considering the expected DMintake of animals. The inclusion of chestnut tannin in the concentrate resulted in a greater productionof milk (+18.64%; P < 0.001). Moreover, no differences in casein fraction profile between milks from bothgroups were found while the casein index was greater (P = 0.034) in milk from ewes fed CHE than milkfrom ewes fed C. As regard fatty acid composition, milk from CHE group had a greater concentration ofomega-3 fatty acids if compared to milk from C group (alpha-linolenic acid: 2.18 vs 2.57 g/100 g of totallipids in C and CHE group, respectively), whereas the percentage of CLA and of C18:1 trans11 in milk fatfrom CHE group was smaller (CLA: 2.20 vs 1.85 g/100 g of total lipids, in C and CHE group, respectivelywith P = 0.001; C18:1 trans11: 3.89 vs 3.57 g/100 g of total lipids in C and CHE group, respectively withP = 0.001). The use of practical doses of CHT in the diet of grazing ewes may improve the response todietary linseed supplementation, resulting in milk with a greater concentration of alpha-linolenic acid.