Effect of floor type on salivary cortisol of fattening pigs

Animal welfare is a growing concern in intensive pig production; on this kind of production system, pigs are exposed to various stressors among which can be found the housing conditions. The salivary cortisol concentration, which follows a circadian rhythm conditioned by age, is a useful biomarker to evaluate the animals response to stress situations. The aim of this work was to evaluate the effect of the floor type in a partially slatted floor facility, on the salivary cortisol concentrations, in the morning and in the afternoon, in fattening pigs, at two different weights (and ages): 60 kg and 100 kg of live weight (3.6 and 5.0 months of age, respectively). 144 pigs (72 entire males and 72 females) were used. Pigs were housed in 24 single-sex pens (6 pigs/pen; 1.2 m(2)/pig) with partially slatted floor (60% continuous and 40 % slatted). The pens floors were of two types: one with concrete continuous floor and concrete slats (HH), and the other with concrete covered with epoxy resin continuous floor and metal slats (RM). In younger animals, salivary cortisol concentrations in the morning were higher than in the afternoon; however, the opposite happens for older animals. Salivary cortisol levels in the morning and in the afternoon were numerically higher in pigs housed in RM floor than in HH floor, both at 60 and 100 kg live weight, but only significant differences were found for 60 kg live weight and morning sampling (p = 0.0393). In addition, in animals housed on RM soil the circadian rhythm was more flattened than in animals housed on HH floor. It could be concluded that RM floor was more stressful for pigs than HH floor.