PALATABILITY OF SHRUBS AND FODDER TREES MEASURED ON SHEEP AND DROMEDARIES .1. METHODOLOGICAL APPROACH

Experiments were performed to study the effect of measurement duration on the palatability of 11 range species and to define a palatability index. The range species were randomly distributed in five combination s (C1-C5) each containing four species. Each combination was tested ov er a 15 day experimental period on four 1-year-old sheep and five 2-ye ar-old dromedaries (Camelus dromedarius). Animals received the four ra nge species ad libitum daily at 08: 00 h and were supplemented at 17:0 0 h with spineless cactus. Barley hay (standard food) was offered with the range species only during the first 5 days of each experimental p eriod. Food intakes measured on the first day (I1), average food intak es in the first 5-day period (I5), the second 5-day period (I10) and t he third 5-day period (I15) were compared. Significant correlations we re found between I1 and I5 (r = 0.93, P<0.01), I5 and I10 (r = 0.75, 0 .01) or I15 (r = 0.61, P<0.05), and I10 and I15 (r = 0.87, P<0.001) fo r sheep. These correlations were higher for dromedaries, and intakes m ay be predicted by the following regression equations: 15 = 1.09I1+0.0 7 (r = 0.96, P<0.001); I10 = 1.15I1+0.25(r = 0.85, P<0.01); I15 = 1.42 I1+0.32(r = 0.78, P<0.01). As the range species were not offered in th e same amounts, intakes were expressed as a percentage of the relative quantities offered daily (I1/D1, I5/D5, I10/D10 and I15/D15). The sam e trend as reported above was observed between I1/D1 and I5/D5, I1/D1 and I10/D10, and I1/D1 and I15/D15. Such results suggested that for dr omedaries 1 day of measurement may be sufficient for palatability asse ssment while for sheep this period should be extended to 5 days for be tter accuracy of intake prediction. As all the range species were not offered at one time, I1/D1 and I5/D5 ratios were expressed in relation to hay intake (HI)/hay distributed (HD) ratio. Two indices were then calculated: R1 = (I1/D1)/(HI1/HD1) and R2 = (I5/D5)/(HI5/HD5). R1 and R2 were found to be highly correlated for sheep (r = 0.94) and dromeda ries (r = 0.92). Therefore, R1 was chosen as a palatability index. The range species were ranked using this index and animal preferences wer e established.