LAUSR

Abstract An experiment was implemented to examine differences between sheep and goats in the utilization of open arid-area rangelands when provided with different concentrate supplement levels. Fifty-two non-lactating females (Abu-duleik sheep, n = 26 and Balady goats, n = 26) were employed in a 90-day experimental period. Animals of each species were allocated randomly into two treatments, according to a 2 × 2 factorial arrangement, with animal species (goats and sheep) and concentrate level (low and high) as main factors. They were grazing widely over the arid-area rangelands with a limited amount of a concentrate supplement, low (1 % BW) or high (2 % BW) (DM basis). Total energy expenditure was estimated by heart rate (HR) monitors for 48 h after its calibration by oxygen consumption with a face mask open-circuit respiratory system. However, the significant interaction between animal species and concentrate levels of supplement indicated that increasing the concentrate level had a negative effect (P