Infrared thermography as a non-invasive method for the evaluation of heat stress in pigs kept in pens free of cages in the maternity

Abstract

Infrared thermography is a non-invasive method of body surface temperature analysis in pigs. This study aimed to evaluate the body surface temperature of sows and piglets kept in individual pens free of cages with or without cooling system with the use of infrared thermography. The study was conducted during the summer and autumn in Pirassununga, Brazil. Twenty-six sows during lactating phase and 281 piglets until 21 days-old were evaluated in two treatments: cooled pens with fans and water sprinklers on the roof and non-cooled pens. Both areas had ceramic roof tiles. Thermographic images were collected at intervals of seven days in the morning and afternoon in sows and randomly in five piglets per litter, and salivary cortisol were collected only on sows. The thermographic images were analyzed using the software IRSoft Version 3.6 Testo. Every three days respiratory rate and rectal temperatures were collected from sows and five piglets per litter. It was included fixed effect of treatment, period of the day, seasons and their interactions, besides the correlations of Pearson. In summer and autumn, the hottest surface area of sows was the mammary gland and the coldest the vaginal. For the piglets, the hottest area in the summer was the head and the coldest the snout. Summer presented the highest surface temperatures of the sugarcane bagasse bed, concrete floor and roof. No correlations were found between air temperature of and facilities. The respiratory rate presented moderate correlation with the back and with the snout of the sows. Rectal temperatures were higher in summer and in the afternoon, but it was similar between treatments. Although the cooling system had reduced the air temperature of the pens free of cage, it was not enough to reduce body superficial temperatures of the sows and piglets during lactating phase. Nevertheless, the use of infrared thermography allows to identify the hottest and coldest surface body areas of pigs and can be a tool to assess pig facilities and animal welfare.