Effect of Percentages Calluna vulgaris Cover and Cow and Ewe Physiological Status on Animal Production on Mountain Pastures

The effect percentage cover of Calluna vulgaris (30 or 70%) on performance of dry and lactating ewes and cows with their lambs and calves was studied during 1990 and 1991. Lactating cows had greater body weight losses than dry ones, the difference being 0.3 and 0.S kg/day for 1990 and 1991 respectively. Percentage C.vulgaris cover (30 or 70%) caused differences in body-weight losses· similar to those caused by physiological status. Milk production from the cows, and therefore calf live-weight gain, were significantly higher in the group grazing on the plot with 30% Calluna (0.62 and 0.71 kg/day for 1990 and 1991, respectively), than in that with 70% (0.44 and 0.3S kg/day in 1990 and 1991). The changes in live-weight and body condition in the sheep as a result of percentage Callina cover, and the physiological status, follow similar trends to those for cattle, although they are of lesser magnitude, and the effect of Ca/1,ma cover was stronger than physiological status. Lamb live-weight gain was relatively good (80-100 g/day) during the first part of the grazing season, but when preferred posture height fell below 2S-30 mm the lambs were just able to maintain their weight.