Impacto productivo del acceso a sombra en la parcela de pastoreo de sorgo forrajero tendiente a mitigar el efecto del estrés por calor en novillos hereford.

The objective of this project was to evaluate the effect that the access to shade in the plot of land has on the mitigation of heat stress and summery animal performance in steers fed with forage sorghum, with an assignation of 8% of the PV. The experiment was held in the Experimental Station Mario A. Cassinoni, Paysandú, Uruguay, between 12/1/2021 and 23/3/2021. We used thirty Hereford steers, approximately 18 months old, and with an initial weight of 347 ± 5,5 kg, which were randomly assigned to two treatments: free grazing with and without access to shade. The animals grazed on forage sorghum of the type ADV 2800, rotating weekly. Pastures were used in grazing with an average availability of 10727 ± 3637 kg DM/ha and 119 ± 39.8 cm in height. The average gain of the treatments was 0.617 kg/a./day for the animals with access to shade and 0.523 kg/a./day for those without access to shade; in this way, a significant effect of the shade on the performance of the animals was determined (P=0.02), defined by the second stage of the experimental period (0.717 vs. 0.570 kg, P=0.012), The shade improved the HLI average (67 vs. 72) notoriously improving animal performance, reduced rectal temperature (40.1 vs. 37.3 °C, P=0.0076), respiratory rate (83.3 vs. 63.2 rpm, P<.0001) and panting intensity when compared to treatments without access to shade.