Low birth weight and early-life iron deficiency in piglets: Post-weaning effects on cognition, development, and motivation

Abstract

Proper cognitive, physical and anatomical development depend on the correct orchestration of developmental processes and the factors influencing them. Complications and disturbances around birth and during early development may negatively affect development permanently. In this thesis, we studied two complications during the early development of piglets, both as a model for these conditions in humans, and for gaining knowledge on and improving the welfare of pigs. The first part of this thesis focused on low birth weight and litter size, and their effects on physical and cognitive development (measured by growth and memory performance in a holeboard task). Additionally, we studied the motivation for food of low and normal birth weight pigs. Although low birth weight causes numerous welfare problems in young piglets, we surprisingly found an improved memory performance compared to normal birth weight siblings, though no difference in food motivation. We found that litter size affects growth and cognitive performance in pigs, although this effect was supplier or breed dependent. Furthermore, supplier or breed had a strong effect on emotionality responses of piglets. The second part of this thesis focused on the effects of early-life iron deficiency in piglets on physical and cognitive development, hematology and brain iron concentration. Early-life iron deficient animals showed retarded growth, impaired memory performance and reduced brain iron levels weeks after treatment and iron repletion. Moreover, early-life iron deficiency reduced hippocampal synaptic plasticity. Our findings suggest that iron is essential for the development and normal functioning of brain structures involved in memory and learning. These lasting effects of severe early-life iron deficiency are in line with findings in human and rodent iron deficiency research. However, in a follow-up study, ID piglets did not become anemic during treatment and did not show impairments in growth nor in cognitive performance. Thus, development of anemia seems essential in retarding growth and developing long-term impairments of memory performance due to iron deficiency. We conclude that the piglet is a suitable animal model for early-life iron deficiency in humans, provided that the induced early-life iron deficiency leads to anemia.