Influência da suplementação no comportamento, desempenho e variáveis fisiológicas de ovinos negros da raça Santa Inês, em condições de pastejo

Abstract

The objective of this study was to evaluate effects of concentrate supplementation on thermoregulatory responses, grazing behavior, the average daily weight gain, estimated consumption and tolerance to the heat of the Santa Inês sheep. The experiments were conducted at Riachão farm, located in the municipal district of Sairé, Agreste region of Pernambuco state during the spring and summer seasons. The trial lasted six months, starting in august 2009 and ended in february 2010. The group of animals, both in spring and in summer seasons, consisted of 20 lambs of Santa Ines sheep, with mean age of six months, raised on pasture, 10 of which were concentrated feeding and the other 10 formed the control group. The physiological parameters rectal temperature, respiratory rate, skin temperature and body surface area were measured from 06 to 07h, after which the animals were loose in the pasture and collected at 13:30 for a corral where they stayed for half an hour to rest before the start of the measurements of the afternoon at 14 o'clock, the same physiological parameters. Sheep from the treated group were taken back to the paddock at 17:30 and individually fed with concentrate based on soybean meal, ground corn and mineral salt. The physiological parameters were evaluated once more from 19 to 20h. Behavioral activities as leisure, grazing and rumination of sheep submitted to sun or shade were evaluated through the instantaneous scan method. Evaluations were conduced weekly in the summer for two consecutive days every 10 minutes. Drinking activity was observed by continuous recording. The environment was continuously monitored every hour, through an automatic weather station with the capacity for data logging of temperature and humidity, dew point temperature, wind speed and direction, maximum and minimum temperatures. Black globe temperature was measured in the shade and sun throughout the experimental period. Thermal comfort indices were calculated (temperature and humidity index, global temperature index). The nutritional plan influenced the heat balance of sheep only in the morning (7h) and provoked an increase in rectal temperature of sheep without causing hyperthermia. Rectal temperature was greater in the winter-spring than summer regardless the period of the day in which evaluation was carried out. Rectal temperature, respiratory frequency, and epidermal temperature presented significantly higher values in the afternoon (14h) than the other periods of evaluation, regardless season of the year. Animals underwent heat stress in the afternoon in both season of the year and the greater magnitude of such stress took place in the winter-spring. Time spent with grazing, leisure and rumination by sheep was not influenced by concentrate supplementation, which promoted a better performance in live weight gain of ewe-lambs. Heat tolerance was not influenced by supplementation, even though supplemented animals showed higher sudation rate and superficial body temperature.