Estimation of Resilience Parameters Following LPS Injection Based on Activity Measured With Computer Vision

Abstract

Resilience could be referred to as the animal’s ability to successfully adapt to a challenge. This is typically displayed by a quick return to initial metabolic or activity levels and behaviors. Pigs have distinct diurnal activity patterns. Deviations from these patterns could potentially be utilized to quantify resilience. However, human observations of activity are labor intensive and not feasible in practice on a large scale. In this study, we show the use of a computer vision tracking algorithm to quantify resilience based on activity individual patterns following a lipopolysaccharide (LPS) challenge, which induced a sickness response. We followed 121 individual pigs housed in barren or enriched housing systems, as previous work suggests an impact of housing on resilience, for eight days. The enriched housing consisted of delayed weaning in a group farrowing system and extra space compared with the barren pens and environmental enrichment. Enriched housed pigs were more active pre-injection of LPS, especially during peak activity times, than barren housed pigs (49.4 ± 9.9 vs. 39.1 ± 5.0 meter/hour). Four pigs per pen received an LPS injection and two pigs a saline injection. LPS injected animals were more likely to show a dip in activity than controls (86% vs 17%). Duration and Area Under the Curve (AUC) of the dip were not affected by housing. However, pigs with the same AUC could have a long and shallow dip or a steep and short dip. Therefore the AUC:duration ratio was calculated, and enriched housed pigs had a higher AUC:duration ratio compared to barren housed pigs (9244.1 ± 5429.8 vs 5919.6 ± 4566.1). Enriched housed pigs might therefore have a different strategy to cope with an LPS sickness challenge. However, more research on this strategy and the use of activity to quantify resilience and its relationship to physiological parameters is therefore needed.

Pigs behind the technology : individual activity monitoring to assess resilience in pigs

“…The same animals were used as described in Parois et al (2022a) and van der Zande et al (2022).To summarize, a total of 144 Tempo × Topigs-20 pigs (n = 71 females; n = 73 males) were used during the experiment, spread over three batches (n = 48 pigs per batch). During lactation, half of the sows and their piglets were housed in a conventional farrowing pen (CONV) (mean ± SD; sow parity = 4.2 ± 1.8) and the other half in an alternative group housing system (AHS) (parity = 4.0 ± 1.7) at the Swine Innovation Centre (Sterksel, the Netherlands).…”

“…At the other extreme, boredom or negative affective states in barren housed pigs, induced by limited possibilities to show important behaviours, may cause lethargic behaviour (see Bolhuis et al, 2005;Fureix and Meagher, 2015;Luo et al, 2020b). Van der Zande et al, (2022) indeed showed lower activity of barren housed pigs as compared with those in enriched housing. The stress, restlessness or negative affective states that potentially underly the high variation in activity in barren housed pigs, might then exacerbate the cortisol response to LPS.…”

“…It could be hypothesised that this low activity is, in line with the increased basal levels of haptoglobin and cortisol, another indication of chronic stress or heightened immune activation, both of which may lead to (mild) sickness behaviour including lethargy (e.g., Nordgreen et al, 2018). It is not fully clear why animals with higher Factor 1 scores, representing high basal cortisol and haptoglobin levels, showed a smaller AUC and duration of the dip in activity following LPS injection, but this might be related to their low baseline activity level (van der Zande et al, 2022). This baseline activity level of the pigs was considered as their original state and used to calculate duration and AUC of the activity dip.…”

“…Poor resilience is characterized by a slow recovery after exposure to a challenge (Scheffer et al, 2018). Pigs respond physiologically and by changes in behaviour to restore homeostasis (Parois et al, 2022a;van der Zande et al, 2022). These responses might reflect the recovery from a perturbation.…”