Beef cattle performance and hair cortisol accumulation in silvopastoral and pastoral systems: a 2-year assessment

The Mediterranean area is highly vulnerable to climate change. Silvopastoral practices, such as integrating trees into pastureland or grazing in woodland areas, are potential mitigation strategies to improve microclimate conditions and reduce heat stress risks. We conducted a 2-year on-farm experiment to compare growth performance, measuring average daily gain (ADG), hair cortisol accumulation, and blood glucose concentration in Maremmana breed steers and heifers reared in either a silvopastoral (SP) or pastoral (PA) system during spring and summer. Additionally, we monitored microclimate conditions in both systems via the black globe humidity index (BGHI) as a heat stress proxy for outdoor-reared animals. In both years, the highest ADG values were recorded in spring: 1.49 kg/day in PA and 1.25 kg/day in SP in 2021 and 1.24 kg/day in PA and 1.17 kg/day in SP in 2022. During spring, PA-reared animals performed best, likely because of favourable microclimate conditions and abundant pasture, making tree shade unnecessary. Conversely, in summer, as heat stress risk increased-indicated by higher BGHI levels-tree presence in the SP system mitigated heat stress impacts on ADG, resulting in superior SP performance over PA. The hair cortisol levels increased in both groups during the summer, with a significantly greater increase in the PA animals. In 2021, cortisol levels reached 35.04 pg/mg in PAs and 26.62 pg/mg in SPs. In 2022, cortisol levels rose further to 46.56 pg/mg in PAs and 42.94 pg/mg in SPs. A decrease of glucose levels in PA group was determined but further research is needed to clarify the effects of heat stress on physiological mechanisms that lead to a change in glucose levels. Effective pasture and system management have been shown to increase productivity, with higher spring stocking rates in open pastures improving animal performance in both years.