Effect of substitution of barley and tickbean to maize and extruded soybean in the diet on milk and cheese from ewes grazing under two different stocking rates.

This experiment aimed to verify the effects of a concentrate supplement based on barley and tickbean (BT), compared with a concentrate of maize and extruded soybean meal (MS), on milk and cheese yield and composition of ewes grazing with different stocking rate (SR). Thirty two Comisana ewes, divided into four groups, for 50 days in spring were allowed to graze plots of a mixed sward of Italian reygrass and berseem clover with a low (LSR, 23 ewes/ha) or a high SR (HSR, 38 ewes/ha) and fed BT or MS. Herbage allowance per ewe was more than double at LSR compared to HSR (P<0.001), and daily milk yield was 10 to 15% higher (P<0.01) in the LSR-BT ewes than in the other groups. Milk composition, cheese yield and composition were not influenced by treatments. Curd firming time (k20) was higher (P<0.05) for LSR-BT milk. Milk fatty acid composition of ewes fed MS, compared to BT, had a higher level of C18:0 and a lower level of C16:0 and C18:3 n-3. Milk trans-10 C18:1 and trans-13 C18:1 fatty acids were higher (P<0.05) at HSR and with BT, while trans-12 C18:1 was higher at LSR (P<0.05). LSR increased (P<0.05) the cheese content of odd and branched chain fatty acids compared to HSR. The results suggest that both concentrate type and pasture availability influenced milk and cheese composition, whereas milk yield was positively affected by the interaction LSR*BT.