Abstract
Climatic models predict scenarios in which ambient temperature will continue increasing worldwide. Under these climatic conditions, fitness and animal welfare of many populations are expected to suffer, especially those that live in captive or semi-natural conditions, where opportunities of heat abatement are limited. We undertook an experimental design to assess the effect of heat abatement that water sprinkling might have on Iberian red deer calf growth and behaviour from birth to weaning (135 days). One group of ten mother-calf pairs lived on plots with water sprinkling (treatment) available during summer’s hottest time of the day, while the control group (nine mother-calf pairs) occupied plots with no available water sprinkling. Treatment and control groups were fed ad libitum and swapped between plots every seven days to minimise any plot effect. Body weight was monitored weekly and individual behaviour was recorded once or twice a week at mid-day. We observed that calves had showers under the sprinklers and wallowed in mud puddles. The results clearly indicated that calves of the treatment group showed a significant increase in body weight at weaning in comparison with the control group, with no differences between sexes (treatment: male = 56.5 kg, female = 50.3 kg; control: male = 50.3 kg, female = 46.5 kg). Mother weight and mother age effects were negligible on calf body weight at weaning. The heavier the mother the faster was the rate of growth of its offspring, irrespective of calf sex. The model indicated that although males grew significantly slower than female calves in the control group, males grew faster than females when exposed to the treatment. Calves of the treatment group spent less time drinking, less time in the shade, similar time eating and more time in motion than calves of the control group. There were no behavioural differences between calf sexes of treatment and control groups. The results indicate the importance of providing animals with opportunities of heat abatement in hot environments to improve animal growth and welfare in farmed Iberian red deer.
Highlights
Climate models predict a rise in land surface temperature between 1 and 3.7 ̊C for the period 2046–2100 [1], with direct negative consequences on livestock production, prevalence of diseases and parasites [2] and body growth [3].Heat stress is the result of an imbalance between metabolic heat production inside the animal body and its dissipation to the surrounding physical environment [4, 5]
This is an increment of 10% in body weight over the predicted weaning weight of the control group (Fig 2), which corresponds to 46 g/d and 28 g/d in male and female calves over the daily growth of the control group
Our results clearly indicate that calves of the treatment group had lower water turnover than those of the control group
Summary
Climate models predict a rise in land surface temperature between 1 and 3.7 ̊C for the period 2046–2100 [1], with direct negative consequences on livestock production, prevalence of diseases and parasites [2] and body growth [3].Heat stress is the result of an imbalance between metabolic heat production inside the animal body and its dissipation to the surrounding physical environment [4, 5]. These are based on reducing direct sun radiation, improving air convection and providing animals with cooling opportunities, such as water sprinklers and atomizers [11, 12] The efficiency of these methods has been measured using behavioural and metabolic proxies of animal heat stress, such as changes in behavioural activity, food intake, rectal temperature, metabolites and stress-related hormone concentrations (Bell et al, 1989 [13]; Dussault et al, 2004 [14]; Lopez et al, 2018 [15]; Spiers et al, 2004 [16]; Correa-Calderon et al, 2004 [17]; Strickland et al, 1989 [68]; Turner et al, 1992 [11]), and assessing animal condition and production [6, 18]. Perez-Barberıa et al [3] hypothesised that calves of the most costly sex to produce, ie. males, are more sensitive to limitations in energy supply than female calves [19, 24, 25], and probably more affected under conditions of heat stress
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