This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
In today’s Science Page Karolína Steinerová, John Harding, Sarah Parker, Heather Wilson, Arthur Nery Finatto and Yolande Seddon take a look at the connection between rearing pigs with play opportunities and infection resilience.
Introduction
Emerging evidence suggests beneficial effects of positive emotions on health during infectious challenges in farm animals. There is also an increasing societal demand for improved welfare of intensively farmed pigs, but welfare improvements can be costly and laborious for producers. Therefore, it is essential to evaluate approaches that are feasible to implement in existing management systems. Play is a natural behaviour that spontaneously occurs in piglets and has been associated with positive emotional states. Our previous research confirmed that play can be promoted and sustained in grow-finish pigs through targeted enrichment in the standard commercial rearing environment, demonstrating play promotion could be a means to support positive welfare in commercial pig farm operations. On the basis that we assume play to be positive and it can be stimulated in rearing systems, the current study investigated if rearing pigs with regular intermittent play opportunities would enhance their resilience to infectious challenge with porcine reproductive and respiratory syndrome virus (PRRSV) as measured through their response to the challenge and speed to return to pre-challenge status.
Methods
Nine litters were assigned to either play (PLY; n=5) or control (CON; n=4) treatments (trt) at birth. In PLY, play was promoted with temporary access to extra space (1.3m2/pig) and enrichment items (cardboard, rope, burlap, dog rubber toys, straw) for three hours daily from five days of age (doa). At weaning (25±2 doa; mean±SD), 30 pigs (14/trt for disease challenge, 1/trt sentinel pigs) were selected. At 34±2 doa, pigs were transported to a disease containment facility at the WCVM and were in two groups of seven pigs/trt, with pens balanced for weight, sex, and sow. At 43±2 doa, 28 pigs were inoculated with PRRSV (day 0 post-inoculation, DPI), and two sentinel pigs were sham-inoculated. Skin lesions, blood, clinical signs, average daily gain (ADG, kg), and behaviour were collected pre- and post-inoculation at regular intervals each week between day -1 to 22 DPI. Within the disease containment facility, PLY pigs continued to receive play opportunities every other day until euthanasia of all pigs at 65±2 doa (22 DPI). Blood was analysed for PRRSV load and complete blood count.
Results
The PRRS viral load and rate of clearance day 0 – 22 DPI did not differ between treatments. PLY pigs had a lower probability of experiencing moderate and severe respiratory distress (PLY: 35%, CON: 91%, p≤0.001), for fewer days (PLY: 4 days, CON: 12 days, p≤0.001). PLY pigs had a higher ADG (Figure 1A) and numerically greater feed efficiency (feed-to-gain ratio PLY: 1.40 kg ± 0.12; CON: 1.78 kg ± 0.34; mean ± S.D.). PLY pigs had fewer monocytes on 8 DPI than CON, with levels returning to baseline by 21 DPI, whereas CON levels exceeded baseline (Figure 1B). Play pigs maintained play activity throughout infection, whereas CON pigs reduced activity, demonstrating more sickness behaviour. Sentinel pigs remained free of PRRSV.
Conclusions and implications
This study demonstrates that rearing pigs in an environment supporting positive experiences through provision of play opportunities can enhance resilience against infectious challenge, underscoring the value and importance of promoting positive welfare in intensive pig farming.
For more details, please refer to the following links to complete papers of the group on this topic:
Rearing pigs with play opportunities: The effects on disease resilience in pigs experimentally inoculated with PRRSV. https://doi.org/10.3389/fvets.2024.1460993
The promotion of play behaviour in grow-finish pigs: The relationship between behaviours indicating positive experience and physiological measures. https://doi.org/10.1016/j.applanim.2024.106263