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

lactation due to the high energy demands of producing milk, but especially under heat stress ambient conditions. Methods Study area and animals Data collection was carried out at the University of Castilla-La Mancha (UCLM) deer farm experimental facilities (38˚57’32.8"N 1˚52’51.8"W, Albacete, Spain,) between 2000 and 2018. The UCLM deer farm is a scientific facility orientated to the study of life history traits, repro- duction, nutrition and antler growth in Iberian red deer. The study used 583 mother-offspring pairs (Table 1), comprising 150 different mothers. Mothers age ranged between 1 and 17 years (mean = 5.9, sd = 3.64). Mother-calf pairs were split into 2–3 groups and each was allocated to different fields of approx. 0.5 ha. The animals relied entirely on supplementary feed, as the amount of grass pro- vided by the fields was negligible. The base diet year-round was a well-balanced mixture of chopped alfalfa hay and orange pulp supplied ad libitum three times a week, and between March and October was supplemented with pelleted feed. Feed was presented to deer on both- side access 14 m long belt feeders to minimise aggressions during feeding. Animals had free access to water at all times. Each plot was fenced with a stock-proofed wire 2 m height that sup- ported a corrugated metal sheet 1.2 m height. Shade was provided by the projection created by the corrugated metal sheet, two roofed bin-feeder sheds in each plot (51 m2) and a line of trees around one third of the perimeter of each plot. This meant that shade was available all day

long but it was reduced to approx. 200 m2 in each plot at solar noon during the experimental period. Water sprinklers were available during summer. The farm complied with Spanish ani- mal welfare legislation. It was daily attended by qualified personnel and an expert deer veteri- narian looked after the animals on a weekly basis. Age and body weight Body weight of calves and mothers was monitored between 10 and 22 times (mean = 17.7, sd = 3.08, S1 Fig) through a period of 143 days between births and forced weaning. Monitoring of body weight took place weekly (mean = 8.2 day, sd = 3.52, range = 1–22, S2 Fig), comprising a total of 9265 body weights across 486 monitoring events. At each monitoring event animals were gathered in the fields and driven to the handling facility through a system of alleys, where they were weighed on a plate platform scale fitted with a motion hold sensor. Calves at birth were weighed in the field, in close presence of their mothers to minimise stress, using a digital portable scale (all weights ± 0.01 kg). The procedure was supervised by a veterinarian specialised on deer. Body weight monitoring was part of the farming activities to control the condition and welfare of the animals. It was a procedure under no experimental license requirements. The animal work carried out in this study was approved by the Animal Welfare and Ethical Review Body of the scientific establishment (Comite´ de E´tica en Experimentacio´n Animal CEEA, UCLM). Table 1. Number of mother-calf red deer pairs across the study.

year 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 n 10 7 7 6 35 35 51 65 71† 52 41† 39 38 15 15 20 23 21 28† † one mother bearing twins. https://doi.org/10.1371/journal.pone.0233809.t001 PLOS ONE Heat stress and calf growth in red deer PLOS ONE | https://doi.org/10.1371/journal.pone.0233809 June 1, 2020 3 / 26