Respostas de novilhas Jersey em pastejo de milheto sem e com acesso à sombra

Abstract

The objective was to evaluate the behavioral and physiological responses of 20 heifers Jersey purebred origin, aged between 12 and 14 months and average live weight of 198.35 ± 28.7 kg in millet grazing in experimental design completely randomized design with two treatments (without access to shade - with access to shade) and ten repetitions (cows). The study was conducted in an area of Embrapa Temperate Climate - Experimental Station Lowlands, for 33 days (01.10.2014 to 02.12.2014). There were three reviews where the behavioral variables were observed for 24 hours, evaluating grazing time, ruminating time (standing and lying), while in other activities (standing and lying) and search time by the water cooler. And physiological variables were evaluated respiratory rate and the hair coat surface temperature. Animal performance was evaluated by weighing the animals at the beginning and end of the experiment. Animals with access to shade showed a larger total grazing time (P = 0.0012) and day (P = 0.0002). Rumination activity did not suffer effect of the treatments (P> 0.05). Long been observed in other activities overall (P = 0.0063) and day (P = 0.0001), for animals without access to shade. There was a significant difference (P = 0.0026) between the hours of the day for respiratory rate, with higher values at 13: 00h. For hair coat surface temperature, there was a significant interaction treatment x time of day (P = 0.0001), with higher values at 13: 00h in the treatment without access to shade and at 8: 00h and 18: 00h in treatment access the shadow. Treatment effects (P = 0.0038) on the average daily gain (ADG), where animals with access to shade achieved major. No replacement daytime grazing by night nor change in the pattern of daytime grazing by dairy heifers in heat stress conditions. The use of shadow on the grassland improving the physiology and improved animal performance.