Cafeteria trials to determine relative preference of six desert trees and shrubs by sheep and goats

Abstract

Six fodder plants consisting of two leguminous trees, Acacia salicina and Acacia saligna, a leguminous shrub, Cassia sturtii and three halophytic shrubs, Atriplex canescens, Atriplex halimus and Atriplex nummularia were offered ad libitum in cafeteria trials to four fat-tailed Awassi sheep (41.1 ± 3.2 kg) and four local Negev goats (36.5 ± kg). Leguminous plants are characterized by high tannin contents and halophytes by high ash contents. The animals, aged 1.5–2.0 years, were randomly picked from a large free-grazing Bedouin flock of sheep and goats that had access to the fodder plants while grazing. They were penned for three weeks prior to measurements during which time they were provided with a maintenance diet. After a 12 h fast, the animals were offered the six feeds over a 15 min period each day for 5 consecutive days to determine (1) fodder selectivity by these small ruminants and (2) whether the ranking and proportionate feed intakes were similar between sheep and goats. Time-series analyses showed that the intakes and ranking of intakes did not change over the five days. Total DMIs per 15 min were similar in sheep (95.6 ± 10.1 g) and goats (92.6 ± 17.8 g) and feed selection in goats tended to be positively correlated with that of sheep (Mantel test: n = 15; r 2 = 0.48; P = 0.071). A. saligna was the most preferred feed in both small ruminants (by Jacobs' selectivity index) and the two Acacia species comprised more than 86% and 70% of dietary intakes in goats and sheep, respectively.