The effect of blocking angularis oculi and facial veins on daily water intake in euhydrate and dehydrated Tswana goats under field conditions during summer
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The aim of this study was to assess the importance of selective brain cooling (SBC) in the water economy of Tswana goats by blocking angularis oculi and facial veins in euhydrate and dehydrated goats under outdoor conditions in Botswana during summer. Eighteen male goats were assigned randomly to three treatments of six animals each: nonoperated controls (NOC), blocked facial veins (BFV) and blocked angularis oculi veins (BAOV) groups. Daily water intake (DWI) was determined for 65 days in all animals to establish a baseline water intake. The goats were then dehydrated for 24, 48 and 72 hrs. Ambient temperature (Ta) was recorded hourly at the experimental site. DWI data on days with mean ambient temperatures (Tas) of 28, 29 and 31oC were analysed. DWI increase with increasing Tas. At Tas of 28 and 31oC, BAOV and BFV groups had higher DWI than NOC group. No differences were observed after the goats were dehydrated for 24 hours. However, BAOV and BFV groups had higher DWI than NOC group after 48 hours of dehydration with BAOV group consuming 7 % more water than the other two groups. The 2-way interaction between DWI and Ta as well as hours of dehydration tended to be significant at P < 0.075 and P < 0.0650 respectively. It is concluded that SBC contributes to the water economy of goats by saving on DWI. This saving is particularly important during short term dehydration periods.