Comparison of different zinc sources at EU authorized level for sustaining gut health in weaned pigs in different physiological conditions

Pharmacological level of zinc oxide (ZnO) was one of the most used strategies during weaning transition. However, its therapeutic use was banned in the European Union in 2022; hence, the evaluation of different sources of zinc (Zn) that can be as effective at lower inclusion is essential and challenging. This thesis included a meta-analytical and literature review regarding the Zn effects on post weaning piglets as well as two in vivo trials where piglets with different intestinal maturity received different sources of Zn at EU authorised level. Additionally, a study investigating different Zn and copper sources and doses in post-weaning piglets’ diets is included. The meta-analysis confirmed the pharmacological ZnO positive effects, and identified promising alternatives, such as porous, nano, or chelated Zn forms. The second and third study revealed how physiological variations observed may be merely associated to the age at weaning or birth body weight. Therefore, to reduce these discrepancies, novel nutritional strategies should focus on fulfilling the piglets’ Zn requirements while alleviating post-weaning recovery. Additionally, these trials demonstrated that porous ZnO effectively mitigated weaning-associated stress, particularly in early weaned or low birth weight piglets. Both trials revealed a positive influence on the gastrointestinal microbial composition and morphology, which contributed to enhanced activation of the gut immune system and overall health. The last trial confirmed the greater positive outcomes of pharmacological dose of ZnO in piglets’ diets but also highlighted increased fecal Zn concentration as drawback. Notably, supplementation of 300 mg/kg of a porous form of ZnO showed growth performance similar to those of the pharmacological ZnO. In conclusion, despite promising alternatives, no direct replacement for pharmacological ZnO is currently available. Further research is needed to identify Zn sources that can address both local and systemic effects, ultimately improving post-weaning strategies for piglets’ health and performance.