Exploring the Zn deficiency hypothesis to explain the beneficial effect of therapeutic ZnO in weaning pigs.

Abstract

The general aim of this PhD thesis is to study Zn status of weaned piglets and whether it is affected by weaning or dietary Zn supplementation, like pharmacological levels of ZnO that are usually administered in post-weaning piglet’s feed to prevent and/or treat diarrhea. To achieve this goal the following experiments (Chapter 3 to 6) were designed. In Chapter 3 we wanted to explore to what extent sow’s age or productive weariness could affect piglet’s Zn status at weaning by an impaired mineral status of sows and consequently an altered mineral colostrum and milk composition. At the same experiment we wanted to assess how low Ca, P and Zn sow’s diet with or without phytase supplementation could affect sow reproductive and litter performance as well as their digestibilities and mineral plasma and milk concentrations. Results showed that colostrum and milk mineral concentrations remain nearly constant meaning that sows make a great effort to provide a constant mineral supply to their offspring regardless of its age and variations in mineral composition and phytase supplementation of its diet. In Chapter 4 (Davin et al., 2013), we wanted to assess whether weaning and dietary pharmacological levels of Zn as ZnO affect piglets Zn status. We intended to evaluate the effect of weaning and dietary ZnO supplementation on plasma, organs (liver, pancreas and spleen) and GIT contents mineral concentrations. Results showed that weaned animals presented lower plasma Zn levels compared to unweaned animals, but ZnO supplementation counteracts this drop. Supplementation with high doses of ZnO during one week increased levels of Zn in liver, pancreas and in the gastrointestinal tract (GIT) contents. Weaned animals showed a similar Zn concentration in the organs but a higher total concentration of Zn in GIT contents compared to unweaned animals. Chapter 5 (Davin et al., 2012), intended to add detail on how Zn, Fe and Cu were distributed into the soluble or insoluble fraction of the different GIT contents obtained from the animals of the previous chapter. Concentration of Zn clearly increased along the GIT for animals receiving high levels of ZnO compared to weaned animals receiving the control diet and to unweaned animals. The proportion of Zn in the soluble fraction in jejunum, ileum and cecum and Fe along the GIT of unweaned pigs was higher than in those weaned animals. In contrast, Cu concentrations were lower in unweaned pigs than in weaned pigs along the GIT and were increased in cecum and colon when dietary high levels of Zn were fed. Chapter 6 includes two experiments in piglets to assess how Zn serum concentration changes around weaning and as affected by different levels, sources and posologies of supplemented Zn. Few days after weaning Zn serum concentrations decreased and pharmacological levels of Zn as ZnO was the only treatment able to rapidly increase Zn serum concentration back to physiological levels. Results exposed in this thesis support the idea that Zn is highly regulated in the sow during lactation to satisfy Zn requirements of piglets. However, Zn status is compromised in piglets after weaning, which could have a role on growth and predisposition to diarrhea during this period. Among the different explored strategies, therapeutic doses of ZnO that are routinely used in commercial farms were the only efficient Zn treatment to counteract this transient situation.

Date of Award	16 Jun 2014
Original language	English
Supervisor	Jose Francisco Perez Hernandez (Director) & Edgar Garcia Manzanilla (Director)