Diet selection of dry and lactating beef cows grazing extensive pastures in late autumn

The diet selection, made by twelve dry and twelve lactating spring-calving Salers beef cows at the end of the grazing season on an extensively grazed natural mountain pasture in central France, was compared. Sward structure, selection bites, daily grazing time and digestibility of the diet were measured in mid-October (P-1) and mid-November (P-2). Live weights were measured twice monthly throughout the experiment. Daily milk production was assessed in the week before the grazing behaviour measurements. Lactating cows grazed more selectively than dry cows: they took more bites on green patches (0.20 vs. 0.13 of total bites, P < 0 01; Jacob's selectivity index: 0.13 vs. -0.25, P < 0.001), which is consistent with the higher overall nitrogen concentration in faeces (18.1 vs. 17.3 g kg(-1) DM, P < 0.05). Lactating cows tended to slightly increase their daily grazing time compared with dry cows (on average 9.9 vs. 9.5 h, P = 0.07) and grazed faster in mid-November (74 vs. 69 bites min(-1), P < 0.05). The lactating cows lost more live weight (-24 vs. -12 kg cow(-1), P < 0.05) between P-1 and P-2. A positive correlation was found between consumption of green patches by lactating cows and their daily milk production in P-2 (r = 0.574, P = 0.05), whereas no correlation occurred between individual milk production and liveweight loss. Dry cows were less selective, which supports management practices that promote the use of cows with low requirements on extensively grazed pastures in late season.