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Upper Critical Temperature of Iberian Pigs
Department of Nutrition and Sustainable Animal Production, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, CSIC, San Miguel 101, 18100 Armilla, Granada, Spain
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Animals 2025, 15(10), 1374; https://doi.org/10.3390/ani15101374
Submission received: 20 December 2024
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Revised: 11 April 2025
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Accepted: 17 April 2025
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Published: 9 May 2025
(This article belongs to the Section Pigs)
Simple Summary
Pigs are sensitive to heat, producing large economic losses in pig production due to a lack of welfare. Iberian pigs (Sus mediterraneus) are a rustic breed that thrives in the Mediterranean forests in the southwest of the Iberian Peninsula where temperatures can be very hot. There are a range of temperatures where animals feel comfortable, known as the thermoneutral zone (or thermoneutrality). Into this zone, heat production reaches a minimal value, and it is constant and independent of the ambient temperature. This zone is delimited by the lower critical temperature and the upper critical temperature which are, respectively, the lowest and highest temperatures at which the heat loss of animals is minimal and the retained energy reaches its maximum. Cold stress (at least moderate) is well dealt with by most homeotherm animals, but heat stress is not. The aim of this study was to determinate the upper critical temperature of Iberian pigs.
Abstract
The effect of ambient temperature on various physiological parameters were obtained to determine the upper critical temperature (UCT) in Iberian pigs. After an adaptation period at 28 °C, eight barrows (99 kg) were individually moved to two respirometry chambers and fed ad libitum (standard diet). The heat production (HP) and respiratory quotient (RQ) were measured over 24 h and some physiological parameters were measured every two days at 24, 26, 28, 30 and 32 °C. No differences (p > 0.05) were found in the heart rate (HR; 97.7 beats/min) and rectal temperature (RT; 39.7 °C) between ambient temperatures. Breathing rate (BR) and skin temperature (ST) increased (272 and 2.4%, respectively; p < 0.05) along with the temperature; whereas voluntary feed intake (VFI), retained energy (RE) and respiratory quotient (RQ) decreased (40.3, 65.8 and 10.5%, respectively; p < 0.001). Overall, HP slightly decreased (19.2%; p < 0.01) when the temperature increased. The reduction in RE when the temperature increased was related more to the decrease in VFI rather than to the concomitant reduction in HP. The UCT can be established at 28 for BR, 30 for VFI and RE, and 32 °C for ST, HP and RQ. Overall, the UCT was stablished at 28–30 °C, indicating the good adaptation of Iberian pigs to heat.
