Seasonal variation of locomotion and energy expenditure in goats under range grazing conditions

Abstract

Energy cost of various activities can be used in conjunction with direct field observations to estimate energy expended in the daily activities of free-ranging animals. The objective of this study was to estimate the energy expenditure due to locomotion of goats on open range. The study was carried out at the 130-ha "Los Pajares" pilot zone, located in the Filabres mountain-range, Almeria. Average elevation is 865 m above sea level. The area has a Mediterranean climate. The mean annual precipitation is 324 mm. The average daily temperatures range from 8.9 degrees C in January to 23.0 degrees C in August. The landscape is characterized by woody plants and perennial grasses. The experimental flock was grazed on its customary routes for 2 days during 4 seasons. The goats were released to graze during the day and then returned to an enclosed shed. Direct observation was used to simulate the total distance walked, the vertical ascent or descent, and to quantify other grazing activities. The energy expenditure of locomotion was calculated from the horizontal and vertical components of travel and the corresponding costs, which had been previously obtained by calorimetry. Daily travel distances by goats on range fluctuated from 5,763 m in summer to 3,482 m in autumn, with an annual average of 4,295 m, which represents a mean speed of 10.8 m/min. The mean annual vertical ascent or descent was 168 m. Estimated heat production due to locomotion ranged from 56.9 to 34.8 kJ/kg(0.75) per day in summer and autumn respectively. These values account for an increased energy requirement at pasture above maintenance of 14.2 and 8.7%, respectively.