Effect of tree density on predatory behavior of weaned calves in Eucalyptus grandis silvopastoral systems during winter

Abstract

Silvopastoral systems combine forestry and grazing, potentially improving land use efficiency and animal welfare. However, livestock predation on trees is a challenge. To compare the predatory behavior of calves (Bos taurus × Bos indicus) grazing native grassland with different Eucalyptus grandis densities, 71 calves were randomly allocated at weaning (Day 0) to 3 treatments: (1) Full sun (0 trees/ha), (2) low tree density (160 trees/ha), and (3) high tree density (240 trees/ha). The live weight of the calves was measured monthly, and blood samples were collected once to evaluate serum minerals. Tree severity damage was assessed using a visual scale (0 = no damage to 4 = severe damage). Variables were analyzed using SAS mixed and proc freq procedures, being significant if P < 0.05. On Day 66, damage was found in 16% of trees, with significant differences (P < 0.05) in severe damage between low (6%) and high (3%) tree densities. Daily weight gain and serum profiles of Ca, P, K, Na, Cl, Fe and Cu were similar (P > 0.05) between treatments, but Cu was below reference values. At Day 66, all calves were fitted with nose plates, halting predatory behavior for 54 days. On Day 120 a second attack was observed only in high tree density (17%), most with severe damage (P < 0.01). Live weight, daily gain and stocking rate were similar between treatments. We concluded that weaned calves exhibited predatory behavior towards E. grandis, not associated with weight loss but with mild Cu deficiency. An oscillating nose plate design effectively stopped predatory behavior.