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

RESEARCH ARTICLE Heat stress reduces growth rate of red deer calf: Climate warming implications F. J. Pe´ rez-Barberı´aID*, A. J. Garcı´a, J. Cappelli, T. Landete-Castillejos, M. P. Serrano, L. Gallego Game and Livestock Resources Unit, University of Castilla-La Mancha, IDR, IREC, Albacete, Spain * j.perezbarberia@gmail.com 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 impor- tant during the first months of life, when most growth takes place. Red deer (Cervus ela- phus) 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 indi- ces 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 demand- ing 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 environ- ment 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 ani- mal welfare, geographical clines in body size and adaptation to climate change. Introduction Climate projections from computer models indicate that by 2100 average global temperature is highly likely to rise between 1 and 3.7˚C [1]. Under this scenario, ruminants are expected to be affected, directly and indirectly, because of changes in quantity and quality of food, water avail- ability, agro-ecological zones, increase in heat stress and diseases [2]. Simultaneously, rumi- nants impact on climate change, because of their enteric methane emissions [3, 4], which PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0233809 June 1, 2020 1 / 26 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Pe´rez-Barberı´a FJ, Garcı´a AJ, Cappelli J, Landete-Castillejos T, Serrano MP, Gallego L (2020) Heat stress reduces growth rate of red deer calf: Climate warming implications. PLoS ONE 15

(6): e0233809. https://doi.org/10.1371/journal. pone.0233809 Editor: Daniel E. Naya, Universidad de la Republica Uruguay, URUGUAY Received: January 17, 2020 Accepted: May 12, 2020 Published: June 1, 2020 Copyright: © 2020 Pe´rez-Barberı´a et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Data are available from Zenodo: http://doi.org/10.5281/zenodo. 3828442. Funding: This work was supported by Ministerio de Economı´a y Competitividad, Spain Project INCYDEN, RTC-2016-5327-2 and by Junta de Comunidades de Castilla-La Mancha SBPLY/19/ 180501/000115. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.