Effect Of Salinity Of Drinking Water And Dehydration On Thermoregulation, Bloodand Urine Composition In Nubian Goats

Abstract

The studies were performed to investigate the effects of salinity of drinking water, state of body hydration and seasonal changes in the tropical thermal environment on physiological responses of Nubian goats. In experiment 1, the effects of salinity of drinking water (0.8, 1.2, 1.6, and 2% NaCl) on physiological responses of Nubian goats have been investigated in winter and summer. Tr was not affected by salinity of drinking water, RR during summer at 2:30 p.m, was significantly higher with all groups receiving saline water compared to respective groups receiving tap water. The values of Tr and RR were higher during summer and showed significant diurnal changes in both seasons. In both seasons, water intake by treated groups was significantly higher compared to respective control group values and the increase in NaCl concentration from 0.8 to 1.6% NaCl in drinking water increased water consumption by the goats but at 2% NaCl, water intake decreased. The intake of NaCl in drinking saline water increased significantly with increase in NaCl concentration. The high concentrations of NaCl (1.6 and 2%) in the drinking water resulted in a significant decrease in food intake of the goats. The mean body weight change was significantly lower in the group receiving 1.6% NaCl during winter compared to respective control group. The packed cell volume (PCV) level during summer was significantly lower for groups receiving 1.2 and 1.6% NaCl in drinking water compared to respective groups offered tap water. The highest value of PCV for treated groups was recorded during winter in the group offered 2% NaCl in the drinking water. The highest values of Hb for treated groups were recorded during winter in the group offered 2% NaCl in the drinking water. The plasma glucose level was not affected by salinity of drinking water in both seasons, but in winter the mean plasma glucose level for control as well as treated groups was slightly higher compared to values obtained in summer. The serum total protein (Tp) and albumin (Alb) concentrations increased significantly by gradual increase in NaCl concentrations in drinking water during winter. In both seasons, Tp and Alb were higher for the groups offered 1.2, 1.6 and 2% NaCl compared to respective control groups. In both seasons, the serum urea level was significantly lower in the groups receiving high concentrations of NaCl (1.6 and 2%) in the drinking water compared to the lower concentrations. In both seasons, the serum concentration of Na was significantly higher in all groups offered saline water compared to the respective control groups. The increase in NaCl concentration in the drinking water increased the serum Na level significantly during summer. The serum K level in both seasons decreased significantly with increasing NaCl concentration in the drinking water. In both seasons, the serum Mg level was not affected by gradual increase in the concentration of NaCl in drinking water. In both seasons, there was a significant increase in urine urea level with increasing NaCl concentration in the drinking water. The urine urea values in both seasons were significantly higher in treated groups compared to respective control groups. In both seasons, there was a significant increase in urine Na concentration with increasing NaCl concentration in the drinking water. The urine Na values were higher signifacntly in treated groups compared to respective control groups during winter. The urine K level was increased significantly with increasing NaCl concentration in the drinking water during winter. The urine Mg levels in both seasons were higher in treated groups compared to respective control groups. There was a significant increase in urine Mg concentration with increasing NaCl concentration in the drinking water during summer. In experiment 2, the effects of saline water drinking (1.2% NaCl) and the state of body hydration on the physiological responses of Nubian goats have been investigated in wet summer. The combined effect of saline water drinking and dehydration significantly increased Tr of the goats. Following rehydration Tr decreased in the treated goats. RR was not affected significantly by the group receiving saline water (1.2% NaCl) compared to respective control group values, but during the first day of dehydration there was a significant increase in RR for both control and treated group. While on the second day of dehydration there was a significant decrease in RR for both control and treated groups. The salinity of drinking water significantly increased water consumption by the treated group compared to respective control group values. For both control and treated groups, water intake by the goats in the first day of rehydration was significantly higher compared to the normal hydration value. Dehydration resulted in a marked decline in food intake of both control and treated groups, but this decrease in food intake was significant only in the group offered tap water. 1.2% NaCl in drinking water had no effect on food intake by the goats compared to control group (tap water). The salinity of drinking water (1.2% NaCl) did not influence significantly the PCV and Hb concentration during experimental phases, but water deprivation increased the PCV and Hb concentration in both groups. On rehydration, the PCV and Hb concentration returned to the normal hydration level on the second day. The plasma glucose level tended to decrease during the dehydration period. The combined effect of saline water drinking water and dehydration significantly increased the serum Tp, Alb and urea level of the goats. Serum Tp and Alb levels of the treated group were not significantly different compared to respective control group values. The serum urea level increased significantly for treated group compared to respective control group values. The serum concentration of Na was significantly higher in the treated group compared to the respective control group value during the normal hydration period, while the K level was significantly lower in the treated group compared to the respective control group value during the normal hydration and rehydration periods. The serum Mg level was significantly higher in the treated group compared to the respective control group value during the second day of dehydration and the rehydration period. The results presented in this thesis for the Nubian goats were discussed and compared with previous studies on the goat and other domestic animals.