ChileanJAR

A study was carried out to evaluate the effect of supplementation in the shade in summer months for cows grazing on a perennial pasture of clover-ryegrass (Trifolium repens L. - Lolium multiflorum L.). Four treatments were compared: I. Day and night grazing without supplementation; II. Day and night grazing plus supplementation; III. Day and night grazing plus supplementation in the shade between 11:30 and 17:00 h; and IV. Day and night grazing plus supplementation in the sun between 11:30 and 17:00 h. Thirty-two Holstein cows with an average production of 20.5 L d^-1 were used, and assigned to the four treatments in a completely randomized block design. There were no significant (P³ 0.05) treatment effects on milk production; highest production was observed on treatment III (19.5 L d^-1). Highest ambient temperatures during January and February where 33.5 and 34.5ºC, respectively. Rectal temperature was significantly higher (P < 0.05) in the treatments where the animals were in the sun, reaching 39.55, 39.00 and 39.43ºC for treatments II, III and IV, respectively. A slight increase in corn silage consumption during supplementation was observed for cows in the shade. The lower silage consumption of animals remaining in the sun was apparently compensated by higher pasture intake during the night. Measurements of animal behavior were made by periodic observation 24 hours a day.