Heat tolerance of goats to increased daily maximum temperature and low salinity of drinking water in tropical humid regions.

OBJECTIVE: The daily maximum temperature and seawater level continuously increase as global warming continues. We examined the adaptability and production performance of heat-stressed goats with a supply of low-saline drinking water. METHODS: Twelve Kacang and Kacang Etawah cross goats were exposed to two climatic conditions (control, 25°C to 33°C, 83% relative humidity [RH], temperature humidity index [THI]: 76 to 86; and hot environment, 26°C to 39°C, 81% RH, THI: 77 to 94) and two salt levels in drinking water (0% and 0.4% NaCl). The experimental design was a Latin Square (4×4) with four treatments and four periods (28 days each). RESULTS: Temperature of the rectal, skin, and udder, and respiration rate rose, reached a maximum level on the first day of heat exposures, and then recovered. Plasma sodium rose at 0.4% NaCl level, while the hot environment and salinity treatments increased the drinking water to dry matter (DM) intake ratio. Water excretion was elevated in the hot environment but lowered by the increase in salinity. Total lying time increased, whereas change position frequency decreased in the hot condition. Lying and ruminating and total ruminating time increased and explained the enhanced DM digestibility in the hot conditions. CONCLUSION: The goats exhibited a high level of plasma sodium as salinity increased, and they demonstrated physiological and behavioral alterations while maintaining their production performances under increasing daily maximum temperatures.

Physiological changes and behavioral responses in heat-stressed goats under humid tropical environment.

Kacang (K) and Kacang Etawah (KE) cross goats are the major goat breeds that are important for farming livelihood and income and recognized for their tolerance to hot and humid tropical climates. As global warming progresses, the daily maximum temperature (Tmax) is predicted to be continuously increased, which will challenge goat production in the future. The objective of this study was to evaluate the physiological and behavioral responses of the goats to the elevated Tmax. Six K and six KE female goats were housed in a normal environment (average Tmax: 33°C; temperature humidity index (THI): 76 to 86) for 6 weeks and then in a hot environment (average Tmax: 38°C; THI: 76 to 92) for 7 weeks. During hot conditions, rectal, rectal surface, and skin temperature, respiration rate, hemoglobin, and cholesterol increased (p < 0.05), whereas glucose blood levels decreased (p < 0.01). Dry matter (DM) intake was lowered (p < 0.01), and DM digestibility was elevated (p < 0.01), whereas drinking water and body water retention were lowered but varied (p < 0.05) during hot weeks. Lying time increased during the hot weeks in both breeds (p < 0.01), whereas lying and ruminating as well as total ruminating time was longer (p < 0.05) in KE goats compared to K goats, which explain the greater (p < 0.05) DM digestibility in KE goats. The effect of the elevated Tmax might be less severe since it also depends on the duration of the Tmax and the variation of daily THI.