Intake, milk production and grazing behaviour responses of strip-grazing dairy goats to daily access time to pasture and to dehydrated lucerne supplementation

Abstract

The ability of grazing dairy goats to adapt to short daily access time to pasture is not well known, while, in practice, access time to pasture (AT) is often lower than 12 h/d. A 3-week trial was carried out in spring with 36 Alpine dairy goats in mid-lactation to study the effect of a restriction of access time to pasture, coupled or not with a dehydrated lucerne supplement. Three treatments were compared: (1) 7 h/d of access time to pasture, between milkings, without dehydrated lucerne (namely AT7); (2) 7 h/d of access time to pasture, between milkings, with 371 g DM/d of dehydrated lucerne, distributed individually after evening milking (namely AT7D); and (3) 11 h/d of access time to pasture, 7 h/d between milkings plus 4 h/d after evening milking, without dehydrated lucerne (namely AT11). The daily pasture allowance was 2.3 kg DM/goat at 4 cm above ground level in each treatment. Each goat received 602 g DM/d of a commercial concentrate, given twice daily at milking. Pasture intake decreased by 433 g DM/d (i.e. 18%) between AT11 and AT7 (P<0.01). Pasture intake also decreased by 259 g DM/d between AT7 and AT7D (P<0.01), which means a substitution rate of 0.72 between pasture and dehydrated lucerne. Milk production, and milk fat and protein concentrations were not affected by AT (P>0.10). Milk production response to dehydrated lucerne was 0.82 kg of milk/kg DM. Grazing time decreased by 2.5 h/d between AT11 and AT7 or AT7D (P<0.001). The pasture intake rate averaged 272 g DM/h and tended to increase between AT11 and AT7 (P = 0.08). It is concluded that an access time to pasture of 7 h/d may be sufficient for lactating dairy goats receiving 600 g/d of concentrate and grazing high-quality pastures. Supplying 400 g/d of dehydrated lucerne has a much stronger positive effect on milk production than an additional grazing period of 4 h after evening milking.