Background

Diarrhea is a common health problem among early weaned piglets 5-6 days after weaning. However, high dietary Zn supplementation of 2500 mg/kg diet 0 to 2 weeks after weaning improves performance and reduces the incidence of diarrhea with up to 50% due to a general improvement in plasma Zn status of the weaned pig (Poulsen, 1995). This strongly indicates that piglets have a considerably higher Zn requirement in this critical period than the recommended level of 100 mg/kg diet (NRC, 2012). At 28 days of age piglets, are weaned and shifted from sow’s milk to a cereal based diet that result in low feed intake and thereby also a low Zn intake. In humans and rodents, Zn absorption is tightly regulated via Zn transport proteins in the intestinal absorptive cells (enterocytes). Mechanisms controlling these transporters are programmed by the Zn intake (Cousins et al., 2006). Recently, it has been suggested that the controlling mechanisms of Zn absorption differ between infants and adults indicating that ontogenesis also plays a role in the development of the Zn transport system in human enterocytes after weaning (Jou et al., 2010). This has never been studied in pigs, but it is speculated that enterocytes of early weaned piglets are not fully developed to be able to absorb adequate amounts of Zn from cereal based diets although the diets are Zn fortified to the recommended level. This theory may also explain why high dietary Zn levels fed to piglets during the first critical days after weaning increase Zn status, protect against diarrhea and increase growth in comparison with piglets fed the recommended 100 mg Zn/kg diet.

 

Cousins, R. J., J. P. Liuzzi, and L. A. Lichten. 2006. Mammalian Zinc Transport, Trafficking, and Signals. J. Biol. Chem. 281:24085-24089.

Jou, M. Y., A. F. Philipps, S. L. Kelleher, and B. Lönnerdal. 2010. Effects of Zinc Exposure on Zinc Transporter Expression in Human Intestinal Cells of Varying Maturity. J. Pediatr. Gastroenterol. Nutr. 50:587-595.

NRC. 2012. Nutrient requirement of swine, 11th rev. Natl. Acad. Press. Washington, DC, USA.

Poulsen, H.D., 1995. Zinc oxide for weanling piglets. Acta Agric. Scand. Sec. A, Anim. Sci. 45, 159-167.

 

Hypothesis

The hypothesis is that Zn absorption in pigs is regulated by Zn transport proteins present in the enterocytes of the small intestine and that the mechanisms controlling the development of these Zn transporters depend partly on the pigs’ Zn intake and partly on ontogenetic development. Consequently, piglets have a specifically higher Zn requirement (expressed as mg Zn per kg diet) during the first physiologically challenging 2 weeks after weaning compared with older pigs (>2 weeks after weaning).

 

Objective

The objective is to achieve basic knowledge about the mechanisms regulating Zn absorption by enterocytes of the proximal small intestine of piglets 0 to 2 weeks after weaning and about the Zn intake- and age-dependent development in the mechanisms controlling Zn absorption after weaning.