Using sounds produced by pigs to identify thermoneutrality zones for thermal environment assessment ratios

Abstract

Although dry bulb temperature (T) is the environmental variable most commonly used to classify thermal comfort in pigs, environmental assessment ratios provide more accurate information. The objective of this study was to correlate the sound pressure levels (SPL) produced by piglet vocalization with the thermal environment observed during the nursery phase, and subsequently establish thermoneutrality ranges. The experiment was conducted on a pig farm where T, relative humidity (RH), and SPL data were recorded between 9 am-5 pm for 42 days. The association between SPL and T in nursery phase piglets was verified; for thermal comfort to be possible, SPLs were 56.3 to 60.3 dB. The SPLs were subsequently used in predictor equations of ratios, and thermal comfort ranges were 74.4-78.3 for temperature and humidity ratio (THI), and 71.6-75.8 for globe temperature and humidity ratio (BGHI). Although the SPL proved to be a convenient indicator of thermal comfort for the evaluation of pigs, further studies developed in different phases of the production system are required.