Effects of restricted time allocation to pasture on feeding behaviour, intake and milk production of dairy sheep rotationally grazing Italian ryegrass (Lolium multiflorum Lam) in spring

Abstract

The effects of restricted time allocation (2, 4 or 6 h/day) to pasture and grazing day (Day 1, initial; Day 4, intermediate; Day 7, final) on feeding behaviour, intake and performance were assessed in Sarda dairy ewes, rotationally grazing Italian ryegrass plots for 7 days, with 21 days of regrowth. A randomised block design with two replicates per access time was used with six groups of six ewes each. The ewes were supplemented daily with 400 g/head of a commercial concentrate at milking, 300 g/head of lupin after grazing and 700 g/head of ryegrass hay overnight. Pasture variables, feeding behaviour, herbage and supplement DM intake, and milk yield and composition were measured on 12 days (4 per target grazing day). Plot average data were analysed by a bifactorial model with interaction, which was not significant. Sward height and herbage mass decreased between Day 1 and Day 4 (P < 0.05). Leaf area index dropped from Day 1 to Day 7 (P < 0.05). Eating time, as proportion of access time, and intake rate were higher in 2 h/day groups than in the others (P < 0.05). Nevertheless, herbage and total intake were higher in 6 h/day than in 2 h/day groups, being 4 h/day groups intermediate (P < 0.05). Herbage intake decreased with grazing period (P < 0.05). Fat normalised milk yield was higher in 6 h/day groups than in the others (P < 0.05) and in Day 1 and Day 4 than in Day 7 (P < 0.05). To conclude, time restriction below 6 h/day and pasture depletion, in terms of herbage quality, constrained intake and performance of rotationally grazing dairy ewes.