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

Similar results were obtained when using THIWS heat stress index (Table 3, Fig 2), except that THIWS had a stronger negative effect on the calf growth rate of males than on females, as indicated by the significant interaction lrc × calf sex (estimate [male] = - 0.001, se = 0.001, p = 0.041). Model predictions on birth weight for females and males were 8.3 kg and 9.0 kg, respectively. Predicted calf body masses at weaning for THIWS = 115 (0.5 quantile) were 41.5 kg (female) and 47.3 kg (male), females were 0.7 kg and males 0.8 kg heavier when they were in an environment of low heat stress THIWS = 96 (0.1 quantile). Contrasting with 0.5 kg and 0.6 kg lighter, females and males respectively, under a high heat stress environment (THIWS = 126, 0.9 quantile) (Table 3, Fig 2). Calf growth rate responded to animal variables in the same fashion that THI index did, that is, male growth rate was higher than female growth rate, calf growth rate increased with mother age, and decreased with mother weight and with calf age (Table 3). Fig 2. Predicted calf growth from birth to forced weaning (day 143) from models in Tables 2 and 3 for three values of THI heat stress index (60, 67, 72) corresponding to its quantiles 0.1, 0.5 and 0.9; and three values of THIWS (96, 115, 126) corresponding to quantiles 0.1, 0.5 and 0.9; f: female calf (magenta); m: male calf (black). https://doi.org/10.1371/journal.pone.0233809.g002 PLOS ONE Heat stress and calf growth in red deer PLOS ONE | https://doi.org/10.1371/journal.pone.0233809 June 1, 2020 8 / 26