Respiration Rate Associations with Temperature and Relative Humidity and Preliminary Model-Derived Reference Points in Korean Native Black Goats

Quantitative evidence on the associations of temperature, relative humidity, and skin temperature (ST) with respiration rate (RR) in Korean native black goats remains limited, including potential sex- and growth-stage differences. Twenty-four goats (six per sex-by-growth-stage group) were repeatedly measured on 35 dates at a single farm over 15–33 °C, yielding 840 repeated animal-date observations. Natural-log-transformed RR was analyzed using a linear mixed-effects model accounting for animal-, date-, and pen-level dependence. Within the observed conditions, each 1 °C increase in temperature and 1 percentage-point increase in relative humidity were associated with 9.23% and 0.79% increases in RR, respectively. At 24 °C, mean relative humidity, and mean baseline body weight, adult goats had higher predicted RR than growing goats, while temperature-associated RR slopes did not clearly differ by sex or growth stage. Adding ST modestly improved in-sample model fit. Model-derived temperatures corresponding to RR criteria of 40, 60, and 80 breaths/min were 21.2–23.1, 25.8–27.7, and 29.0–31.0 °C, respectively, conditional on mean relative humidity and mean baseline body weight. These preliminary population-level reference points are not validated thresholds of heat-stress severity, welfare impairment, or production loss and require external validation in larger, multi-farm studies using independent physiological, behavioural, welfare, and production outcomes.