Comparative foraging behaviour and performance between cattle and horses grazing in heathlands with different proportions of improved pasture area

摘要

The objective of this study was to compare the diet selection and productive performance of beef cattle (Asturiana de los Valles breed) and crossbred horses grazing on heather-gorse shrublands with different available surface of improved pasture (IP): 80% (IP80) or 25% (IP25). Twelve and 10 lactating dams per species with their offspring were managed in IP80 (19 ha) and IP25 (22 ha), respectively, during two grazing seasons (spring-autumn). Visual recordings at IP25 indicated that horses grazed for longer than cattle. Both species grazed preferentially on IP and increased the utilization of shrublands as season advanced and available sward height in the IP area decreased. Diet composition estimates using faecal markers showed greater dietary percentages of white clover in cows than in mares during spring-summer. During autumn cows selected greater percentages of heather and lower of gorse than mares. Mares achieved more favourable body weight (BW) changes than cows during the whole grazing season, although differences were mainly confined to IP80. Calves showed higher BW gains than foals during the whole grazing season, with scarce differences between vegetation mixtures. Mares compete with cattle for the use of quality pastures, negatively affecting BW recoveries of cows when both species graze together.