Evaluation of the Grazing Behavior of Hair Sheep in the Tropics

The objective of this study was to evaluate the grazing behavior of tropically adapted hair sheep. Non-pregnant, non-lactating, multiparous St. Croix White (5.6 y of age, 43 kg, n = 10) and Dorper x St Croix White (3.8 y of age, 43 kg, n = 10) ewes were evaluated for 5 consecutive d each mo for a yr to monitor grazing behavior in a 0.6 ha pasture. At the start of each wk large numbers were painted on both sides of each ewe to aid in identification from a distance using a spotting scope. Three times each day (0830-0930 h, AM; 1200-1300 h, MID; 1500-1600 h, PM) visual observations were conducted by two observers to record location (sun or shade), activity (grazing, walking, resting, drinking or masticating), proximity to other ewes (within 1 m or >1 m) and posture (standing or laying) of the ewes. The frequency of observed behaviors within time of day, between breeds and across months was analyzed using PROC FREQ and Chi-squared of SAS. Over the entire year mean THI and solar radiation during the AM, MID and PM were 76.3, 80.5, 77.2 and 182, 714, 113 W/m², respectively. There were no differences in frequency of any behaviors between breeds or across months of observation (P > 0.10). In the AM ewes were observed laying down 86.8 % of the time compared to 36.6% and 10.9 % in the MID and PM, respectively (P < 0.0001). Ewe were within 1 m of another ewe 64.1 and 58.8 % of the time in the MID and PM, respectively, and 41.2 % of the time in the AM (P < 0.0001). Ewes were in the sun 89.5% of the time in the AM and 49.7 and 23.1 % of the time in the MID and PM, respectively (P < 0.0001). Ewes were observed grazing 63.4 and 87.4% of the time in the MID and PM and 13.2% in the AM (P < 0.0001). Ewes were masticating 77.1% of the time in the AM and 36.2 and 11.7% of the time in the MID and PM, respectively (P < 0.0001). These results show that these breeds of sheep are adapted to the tropical climate and can graze during the time of day with elevated THI and solar radiation.