Lightweight pigs are surprisingly resilient to shipping stress

Why this research is being done

Based on historical trends, and our understanding of uterine crowding, the population of low-birth-weight pigs will increase along with litter size. If these low birth-weight pigs survive, they become lightweight pigs at weaning and may be more sensitive to transport stress. The objective of this research is to understand the impact of specific management decisions on animals at the lower end of the weight distribution. Intensive and ongoing genetic selection has produced an incredible increase in litter size which on paper seems to be a major benefit for the swine industry (Figure 1). However, this increase in litter size has come at the expense of greater within litter variation for critical factors such as birth weight (Figure 2). The animals on the lower end of this distribution are typically the smallest at weaning, exhibit poor lifetime performance, and high morbidity and mortality. To better manage this population, we need to understand how they respond to various stressors such as transport.

Results

We evaluated the impact of transport at weaning in outwardly healthy animals from the top and bottom of the weight distribution. Unsurprisingly, pigs that are larger at weaning outperform smaller ones in the nursery phase. What is surprising is that when pigs are weaned at 21 days, we find no statistically significant effect of transport on nursery performance in the form of weight gain, regardless of starting weight (Figure 3).

Conclusions

In our experimental design, shipping for nine hours had no negative effect on performance, suggesting weaning alone is maximally stressful at this age. Our results also show that lightweight pigs are remarkably resilient to shipping stress. If shipping stress is not a major factor in the poor performance of lightweight pigs, then the question remains, why do these animals perform poorly? And what management strategies can we employ to offset these effects? Our ongoing work will look to better understand the fundamental physiology of these animals in order to identify and address their unique needs.

Contact Information

Alex Pasternak jpastern@purdue.edu | 765-701-0548

Isabel Turner ibturner@purdue.edu