Abstract
Simple SummaryPhysiological stress increases the activity of the hypothalamic-pituitary-adrenal (HPA) axis and the secretion of cortisol, which might cross the placenta and affect foetal development. Stress in sows can be affected by management factors such as enrichment, different feed systems of the housing accommodation, and is reflected in the salivary cortisol concentration. It is unclear how stressed the sow must be before there is an impact on foetal growth, but higher levels of cortisol might affect the maturity of piglets at birth as well as their birth weight. Therefore, it could be beneficial to accommodate gestating sows in the least stressful manner, not only for piglet performance but also for sow welfare. Cortisol concentration in sows seems to be influenced by a combination of parity and feed systems, but its connection to those factors, as well as to foetal development, warrants further investigation.The aim of this study was to investigate herd cortisol levels as an indicator of stress during gestation in three different feeding systems. Twelve commercial Danish herds with 800 to 3050 sows were included, with either free-access feeding stall (Stall), floor feeding (Floor), or electronic sow feeding (ESF; n = 4 herds per system). Saliva samples were collected from 30 sows/herd in the gestation unit for cortisol analysis with an average of 67.2 gestation days for ESF, 72.4 days for Floor, and 68.6 days for Stall. Data on piglet birth weight (PBW) and the percentage of intrauterine growth restricted (IUGR) piglets from 452 litters (9652 piglets, 8677 liveborn) from all 12 herds were obtained on the saliva collection days. The cortisol levels in saliva increased throughout gestation (p < 0.01), and lower concentrations were observed among sows belonging to Stall (4.80 nmol/L), compared to Floor (7.03 nmol/L) and ESF (7.87 nmol/L), and that difference was significant as an independent effect in the case of ESF (p < 0.01). There was no difference between Floor and ESF or Stall and Floor (p > 0.05). An interaction was observed between parity and feeding system, with parities 4–5 in ESF herds having lower levels than other parities within the ESF system (p = 0.02).
Highlights
Piglet mortality is an ongoing concern of the Danish pig production, and piglets that have a low piglet birth weight (PBW), suffer from intrauterine growth restriction (IUGR) or are born of litters with a high within-litter variation of PBW (PBWCV ) have an increased risk of dying before weaning [1,2,3]
Piglets suffering from IUGR have not received enough nutrients during development, and their brain is prioritised for the survival of the organism [4], giving them their characteristic head shape [2,5,6]
The average salivary cortisol concentrations across the feed systems at different parities are presented in Table 2, and the results of the linear mixed-effects regression can be found in Supplementary Table S2
Summary
Piglets suffering from IUGR have not received enough nutrients during development, and their brain is prioritised for the survival of the organism [4], giving them their characteristic head shape [2,5,6]. It is not known when during gestation this takes place recent studies suggest differences in the development of porcine foetuses already at day 28 of gestation (Strathe et al, unpublished)
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