Heat stress reduces growth rate of red deer calf: Climate warming implications

Abstract

Climate models agree in predicting scenarios of global warming. In endothermic species heat stress takes place when they are upper their thermal neutral zone. Any physiological or behavioural mechanism to mitigate heat stress is at the cost of diverting energy from other physiological functions, with negative repercussions for individual fitness. Tolerance to heat stress differs between species, age classes and sexes, those with the highest metabolic rates being the most sensitive to stressing thermal environments. This is especially important during the first months of life, when most growth takes place. Red deer (Cervus elaphus) is supposedly well adapted to a wide range of thermal environments, based on its worldwide distribution range, but little is known about the direct effect that heat stress may have on calf growth. We assessed the effect that heat stress, measured by heat stress indices and physical environment variables (air temperature, relative air humidity, wind speed and solar radiation), have on calf and mother body weights from calf´s birth to weaning. We used 9265 longitudinal weekly body weight records of calf and mother across 19 years in captive Iberian red deer. We hypothesised that (i) heat stress in hot environments has a negative effect on calf growth, especially in males, as they are more energetically demanding to produce than females; and that (ii) the body weight of the mother through lactation should be negatively affected by heat stress. Our results supported hypothesis (i) but not so clearly hypothesis (ii). By weaning (day 143) calves growing under low heat stress environment grew up to 1.2 kg heavier than those growing in high heat stress environment, and males were more affected by heat stress than females. The results have implications in animal welfare, geographical clines in body size and adaptation to climate change.

Physicochemical, Microbiological and Technological Properties of Red Deer (Cervus elaphus) Milk during Lactation

“…Considering that, over the study, hinds were fed equally and that protein concentration increased as a consequence of a milk concentration effect, this decrease in urea at the end of the lactation could be explained by a lower protein intake by hinds in these last weeks, coinciding with the hottest period during lactation. Studies on heat stress in hinds and calves at our farm have shown that increased heat stress leads to a lower growth in calves and, in the case of higher values of thermal stress indices, also in lactating females [ 36 ]. The literature on cattle shows feed intake reduction and lower protein in milk during high thermal stress in cows [ 37 ], but while the latter study showed no effect of heat stress on urea, Costa et al [ 38 ] showed in buffalo that urea had one of the strongest correlations with heat stress indices, although a positive one and not the postulated negative one of our results.…”

Rainfall decrease and red deer rutting behaviour: Weaker and delayed rutting activity though higher opportunity for sexual selection

“…A delay in conception date might produce a mismatch between actual births and optimal calving date, which may increase calf mortality [ 105 , 106 ]. Moreover, nutritional stress during pregnancy and lactation has been shown to affect calf body mass and immune system which are related to their future survival and reproductive success [ 97 , 104 , 107 , 108 ].…”

Water sprinkling as a tool for heat abatement in farmed Iberian red deer: Effects on calf growth and behaviour

“…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 ].…”

“…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 ]; López 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 ]. In polygynous species, such as red deer [ 19 – 21 ], males are larger than females from birth and their sexual dimorphism in body size increases with age [ 3 , 22 , 23 ]. Pérez-Barbería et al [ 3 ] hypothesised that calves of the most costly sex to produce, ie.…”

“…Red deer are well adapted to a variety of habitats and abiotic environmental conditions [ 26 ], as indicated by their worldwide distribution and the success of many introductions outside their native range [ 27 , 28 ]. A prime habitat is Mediterranean woodland, which is characterised by hot and dry summers, making this season the limiting period for red deer population growth [ 3 , 29 , 30 ]. Despite deer adapting well to a variety of climates, deer suffer thermal stress under certain physical environmental conditions [ 3 , 8 , 31 , 32 ].…”