Behavioural changes in weaned piglets orally challenged with Escherichia coli F4 and supplemented with in-feed protected acid salts

Improvement of the intestinal health of piglets at weaning is a principal objective in pig farming in terms of performance and welfare benefits. Early indicators of disease are indispensable for evaluating animal health and the efficacy of interventions such as feed additive supplementation. This study evaluates behavioural changes in weaned piglets that are orally challenged with enterotoxigenic Escherichia coli F4, and which receive or not two different in-feed additives. Two independent trials were performed with early-weaned piglets in pens of three animals, which were fed a plain diet (N = 32) or one supplemented with sodium butyrate (N = 16; Trial 1) or sodium heptanoate (N = 16; Trial 2) and protected with coconut distillates. After one week of adaptation, piglets were challenged with a single oral dose of E. coli F4 (minimum 1.4 x109 cfu). Scan-sampling was used to evaluate individual behaviour (location in the pen, postures, contact with pen mates, and activities) on the day before (d-1) and two days post-inoculation (d+2 and d+3) at 2-min intervals. Behaviours were recorded in mornings (8 am to 10 am) and afternoons (4 pm to 6 pm). Faecal consistency was also recorded for each animal. Diarrhoea peaked at d+ 2. Regarding behaviour, on d+ 2 there was greater frequency of the animals lying inactively under the heat lamp, in contrast to d-1 when they were more frequently present in the feeder, standing and active (P < 0.05). Around the feeder, standing and active behaviour increased at d+ 3, especially in the afternoon (PDayxTime of day < 0.05). Piglets fed sodium heptanoate spent less time around the feeder (P < 0.05). The weight of the animal at weaning was also observed to have an impact on the effect of time or diet on behaviour. Medium size piglets spent more time lying with pen mates in the afternoon (PSizexTime of day < 0.01) and the smallest piglets increased their feeding behaviour when receiving the supplemented diets (PSizexDiet < 0.05). In conclusion, a lethargic response among piglets after the E. coli F4 challenge was evidenced, this response being slightly modified by the supplementation of in-feed additives and the size of the animals. These results are evidence of the potential of behavioural indicators as a useful tool to assess the health status of piglets at weaning and their responses to in-feed supplementation, but they should be regarded with caution before any transfer to farm conditions due to the limitations of experimental models.