The effect of lift crate on piglet survival rate and sow stress level during farrowing

In intensive farms, the mortality of newborn piglets during farrowing is a critical aspect that represents a significant cause of economic loss in pig production, and the deaths, representing 5–25% of newborn piglets, depend mainly on starvation and crushing [1]. The term “crushing” implies that death is due to trauma to the piglet’s body by the sow; however, many piglets are killed by suffocation when trapped under the body of the sow for a prolonged time. The first days of farrowing are the most critical for piglets: in the first 72 h, the mother can crush some newborns due to the significant size difference and her rolling movements [2]. In the present study, the aim was to determine the effect of lift farrowing crates on piglet mortality by crushing and on sow welfare, using hair cortisol to assess chronic stress in animals, pioneered by Koren et al. in 2002 [3], it represents a reliable tool to obtain information on long-term HPA axis activity in a non-invasive way. The lift farrowing crates (Nooyen Balance frame, Nooyen pig flooring, Deurne, The Netherlands) is an innovative farrowing crate equipped with a self-propelled floor that uses sensors to detect where the animal is standing or lying down. The floor of the sow is raised by an air-hydraulic system 28 cm higher than the creep area, when she stands, to limit the probability to crush her newborn piglets. The experimental study was conducted in a pig farm located in Northern Italy, using eighty-four sows (Landrace X Large White X Duroc) in a one-year experiment organized in in three monitoring sessions. The number of piglets crushed by the mother within 48 h, 72 h, and at weaning (28th day) was assessed by the farm’s veterinarian. In each session, 14 sows were housed in a room with conventional crates (CC), and 14 sows were lodged in a room equipped with lift crates (LC). The sows were randomly distributed in CC and LC rooms. No primiparous sows were considered in the study to avoid sows unexperienced with the dynamics of lift crates. Hair cortisol concentration (HCC) was measured upon entry and exit from farrowing to evaluate stress level variation. Also feet diseases and backfat thickness were evaluated to assess sows’ potential diseases induced by lift crates and potential metabolic problems. The results show that the number of crushed piglets, per sow, up to weaning, was higher in the CC rooms than in the LC rooms (0.50 vs. 0.37; p < 0.05). Mean values of HCC variation in sows during farrowing were significantly different in the two housing systems and higher for the LC sows (0.53 pg/mg vs. 0.22 pg/mg; p < 0.05). No significant differences were detected for backfat variation and feet disease scoring between LC and CC sows. In conclusion, LC sows evidenced an increase in hair cortisol values during farrowing, probably caused by a higher stress status induced by the dynamics of the lift crate, along with the benefit of the higher survival rate of piglets before weaning.