Investigations were carried out on the effects of water and food deprivation on the milk yield, body weight, blood composition and urine volume of lactating Nubian goats. The animals survived 4 days of deprivation of either food or both food and water, but these treatments resulted in about 10 per cent loss in body weight, 85 per cent drop in urine volume, and cessation of milk production, but no significant changes in packed cell volume, serum sodium, potassium and total protein. The change in body weight could be reversed within 1 day, but the initial milk yield was not resumed during the 2 weeks immediately following restoration of food and water.

Energy conservation is a clear function of torpor. Although many studies imply that torpor is also a water-saving strategy, the experimental evidence linking water availability with torpor is inconclusive. We tested the relative roles of water and energy shortages in driving torpor, using the Siberian hamster Phodopus sungorus as a model species. To account for the seasonal development of spontaneous heterothermy, we used male hamsters acclimated to short (8L:16D, SP; n = 40) and long (16L:8D, LP; n = 36) photoperiods. We continuously measured body temperature (Tb) during consecutive 32 h of complete removal of water, food, or both, separated by 7.5 d recovery periods. We predicted that all deprivation types would increase the frequency of spontaneous torpor in SP, and induce torpor in LP-acclimated hamsters. Individuals underwent each deprivation type twice in random orders. Food and water deprivation did not induce torpor in LP-acclimated P. sungorus. Patterns of torpor expression varied among deprivation types in SP individuals. Torpor frequency was significantly lower, but bouts were ∼2 h longer and 2.5 °C deeper, during water deprivation compared to food and food-and-water deprivation. Heterothermic responses to all deprivation types were repeatable among individuals. Different torpor patterns during water and food deprivation suggest that water and energy shortages are distinct physiological challenges. Deeper and longer bouts during water deprivation likely led to higher energy and water savings, while shorter and shallower bouts during fasting may reflect a trade-off between energy conservation and food-seeking activity. The lack of a difference between food- and food-and-water-deprived hamsters suggests a higher sensitivity to food than water shortage. This supports the traditional view that energy conservation is the major function of torpor, but suggests that water shortages may also modulate torpor use. The high repeatability of thermoregulatory responses to resource deprivation suggests that these may be heritable traits subject to natural selection.

To determine if Campylobacter jejuni grown at 37 and 42 °C have different abilities to survive on beef and chicken, and in water. Beef, chicken and water were separately inoculated with four Camp. jejuni (two poultry and two beef) strains grown at 37 or 42 °C. The matrices were stored at ~4 °C and Camp. jejuni numbers were monitored over time by plate counts. On beef there was a greater decrease in number for two strains (P < 0·05; ~0·7 and 1·3 log CFU cm⁻²) grown at 37 °C as compared with 42 °C. By contrast on chicken there was a decrease in numbers for two strains (P < 0·05; ~1·3 and 1 log CFU g⁻¹) grown at 42 °C as compared with 37 °C. In water there was a greater decrease in numbers for all strains (P < 0·05; ~3-5·3 log CFU ml⁻¹) grown at 42 °C as compared with 37 °C. Growth temperature influences the survival of Camp. jejuni on food and in water. Campylobacter jejuni survival studies need to consider growth temperature to avoid erroneous results. Campylobacter jejuni grown at 37 °C, the body temperature of humans and cattle, may represent a greater public health risk in water than those grown at 42 °C, the body temperature of poultry.

The optimum growth, food intake, food conversion efficiency, final body composition and mortality of juvenile Cichlasoma urophthalmus (Günther) was studied at different temperatures, ranging from 22.5 to 36.3°C. The results showed that food intake and specific growth rate increase rising to an apparent optimum at about 33.1°C. Multiple regression equations were derived which can be used to predict food intake and specific growth rate when temperature and initial body weight are known.

The young larvae of insects living on dry food produce large amounts of water by the metabolic combustion of dietary lipids. The metabolic production of water needed for larval growth, previously known as hypermetabolic responses to juvenile hormone (JH), is associated with a 10 to 20-fold increase in the rate of O2 consumption (10,000 microL O2/g/h in contrast to the usual rate of 500 microL O2/g/h). Growing and moulting larvae are naturally hypermetabolic due to the endogenous release of JH from the corpora allata. At the last, larval-pupal or larval-adult moult there is no JH and as a consequence the metabolic rate is much lower and the dietary lipid is not metabolized to produce water but stored in the fat body. At this developmental stage, however, a hypermetabolic response can be induced by the exogenous treatment of the last larval instars with a synthetic JH analogue. In D. vulpinus, the JH-treated hypermetabolic larvae survive for several weeks without moulting or pupating. In T. castaneum and G. mellonella, the JH-treated hypermetabolic larvae moult several times but do not pupate. All these larvae consume dry food and the hypermetabolic response to JH is considered to be a secondary feature of a hormone, which is produced by some subordinated endocrine organ. The organ is most probably the controversial prothoracic gland (PG), which is a typical larval endocrine gland that only functions when JH is present. According to our hypothesis, PG activated by JH releases an adipokinetic superhormone, which initiates the conversion of dietary lipid into metabolic water. This type of metabolic combustion of dietary lipid produces large quantities of endothermic energy, which is dissipated by the larvae in the form of heat. Thermovision imaging revealed that the body of hypermetabolic larvae of G. mellonella can be as hot as 43 deg C or more. In contrast, the temperature of "cold" normal last instar larvae did not differ significantly from that of their environment. It is highly likely that thermovision will facilitate the elucidation of the currently poorly understood hormonal mechanisms that initiate the production of metabolic water essential for the survival of insects that live in absolutely dry conditions.

Effect of evaporative cooling of pregnant dairy cows under heat load conditions during the dry and close-up period, on mammary gland enzymatic activity and intake of food and water, BCS, and milk performance after calving were measured in two consequent experiments. In experiment 1, 18 dry cows held in tie-stalls in a closed aerated barn under heat load conditions were used to measure the effect of evaporative cooling on the respiratory rate and body temperature, individual intake of food and water, enzymes expression level in mammary gland and adipose tissues, and BCS changes until calving. In experiment 2, two groups of 36 dry cows each, held in a commercial loose housing barn, were used to measure the effects of evaporative cooling under heat load conditions on calves' birth weight, colostrum quality and quantity, BCS changes and milk yield during 90 DIM. The non cooled (NC) cows responded to heat load by increasing their respiratory rate and daily water intake, while elevating their rectal temperature by 0.2-0.3 °C as compared with the cooled (C) cows. The external relief of heat load by the C cows in both experiments was expressed in increasing their voluntary DMI during the dry period as compared with the NC group. In experiment 2 the calves' birth weight of C cows was higher, and their colostrum quality and quantity were improved as compared with the NC group. Cooling also improved significantly BCS gain during the last 21 days until parturition, accompanied with higher cell proliferation process (based on enzymes expression at mRNA level) in the mammary gland of the C cows. Consequently, a significant increase in milk production by 5.3%, protein yield by 5.1%, ECM yield by 4.2% and FCM yield by 4.5%, was demonstrated in the C cows during 90 DIM as compared with the NC group.