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FLUID BALANCE DURING HEAT STRESS IN LACTATING GOATS
Author(s) -
Olsson Kerstin,
Dahlborn Kristina
Publication year - 1989
Publication title -
quarterly journal of experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0144-8757
DOI - 10.1113/expphysiol.1989.sp003317
Subject(s) - plasma osmolality , dehydration , lactation , zoology , urine osmolality , thermoregulation , excretion , chemistry , endocrinology , vasopressin , water balance , thirst , urine , heat stress , medicine , biology , pregnancy , biochemistry , genetics , geotechnical engineering , engineering
Fluid balance and thermoregulation were studied during an acute heat load (maximal daily temperature, 38 ± 1 °C; night temperature, 27 ± 1 °C) in six goats during lactation and nonlactation. The goats had free access to water for 1 day, followed by 29·5 h of water deprivation and then water was returned. With water available the goats increased water intake and urinary and milk water losses, while plasma and milk osmolality decreased. Water deprivation caused plasma osmolality and vasopressin concentration to increase most in lactating goats. Milk osmolality rose to values similar to plasma osmolality. Plasma cortisol increased in lactating goats at the end of dehydration. Renal Na + excretion increased during dehydration in lactating goats. Evaporative heat loss was larger in lactating goats when hydrated, but became less than in non‐lactating goats during dehydration. Lactating goats exhibited higher respiratory frequency and rectal temperature than non‐lactating goats. In conclusion, our results show that goats increase the water turnover during heat stress if allowed to drink ad libitum, but when they are deprived of water lactating goats reduce water loss in urine, milk and by evaporation, and rectal temperature reaches higher levels than in non‐lactating animals. This saving of water could allow milk production to be maintained for a longer time during heat stress.