One Is the Coldest Number: How Group Size and Body Weight Affect Thermal Preference in Weaned Pigs (3 to 15 kg)

Abstract

Housing pigs within their thermal comfort zone positively impacts productivity and performance. However, fundamental information on behavioral thermoregulatory responses of individual and group-housed pigs is meager. As a gregarious species, pigs prefer to be near one another, touching and often huddling. As pigs huddle together, they decrease their heat loss to the environment by decreasing exposed surface area and increasing mass. Additionally, pigs gain weight rapidly as they age. As an individual grows, their ability to withstand lower temperatures increases. We hypothesized that group size would alter pig thermal preference and that thermal preference would change based upon body weight. Thirty-six groups of pigs (n = 2 pigs/group) were tested in a factorial design based on group size (1, 2, or 4) and weight category (small: 5.20 ± 1.15 kg; medium: 8.79 ± 1.30 kg; and large: 13.95 ± 1.26 kg) in both sexes. Treatment groups were placed inside a chamber with a controlled thermal gradient (4.6 m × 0.9 m × 0.9 m; L × W × H) that ranged in temperature from 18 to 30 °C. Pigs habituated to the gradient for 24 h. The following 24 h testing period was continuously video recorded and each pig’s location during inactivity (~70% daily budget) within the thermal apparatus was recorded every 10 min via instantaneous scan sampling. Data were analyzed using a GLM and log10 + 0.001 transformed for normality. Tukey tests and Bonferroni-corrected custom tests were used for post hoc comparisons. Peak temperature preference was determined by the maximum amount of time spent at a specific temperature. Both group size (p = 0.001) and weight category (p < 0.001) influenced the thermal location choice of pigs. Individual pigs preferred 30.31 °C, which differed from a group of 2 (20.0 °C: p = 0.003) and 4 pigs (20.0 °C: p < 0.001). The peak temperature preference of the small pigs (30.2 °C) differed from the large pigs (20.0 °C: p < 0.001) but did not differ from the medium-sized pigs (28.4 °C: p > 0.05). Overall, heavier pigs and larger groups preferred cooler temperatures.

Perspectivas Do Uso De Gaiola Individual Ou Baia Coletiva Na Gestação De Fêmeas Suínas Em Relação a Instrução Normativa Nº 113/2020

“…De forma geral, é possível observar que há a formação de uma hierarquia social em todas as fases de produção. Quando as fêmeas estão em fase de crescimento, a hierarquia social é instável em todo o período, podendo variar de acordo com o tamanho dos grupos, entrada e saída de fêmeas, assim como os critérios para o agrupamento das mesmas (ROBBINS et al, 2021).…”

Thermal Comfort in Swine

“…The reduction in feed efficiency is mainly reported in finishing pigs kept at a temperature above 30°C. Therefore, there is no doubt that heat stress reduces productive operational efficiency, as it significantly increases the time an animal takes to reach slaughter weight (Robbins et al, 2021).…”

“…Body heat exchanges with the environment occur as the ambient temperature increases, and the animals activate their thermoregulatory mechanisms to maintain homeothermy(Zhang et al, 2021).Swine have few functional sweat glands and a thick layer of subcutaneous adipose tissue, hindering their thermoregulatory capacity. If efforts to lose heat are not enough, they may even have a change in diet among their strategies, aiming to regulate the internal temperature to approach the comfort region(Robbins et al, 2021).…”

Transcriptomic Response of Differentiating Porcine Myotubes to Thermal Stress and Donor Piglet Age

“…As a counterpart, cold stress (CS) lowers young animals' antioxidant capacity and immune system in addition to affecting their growth rate [4,5]. Mammals in cold climates primarily use two methods for producing heat to keep their body temperatures stable: shivering thermogenesis (ST) and non-shivering thermogenesis (NST).…”