Effect of high dietary zinc oxide on the caecal and faecal short‐chain fatty acids and tissue zinc and copper concentration in pigs is reversible after withdrawal of the high zinc oxide from the diet

Abstract

Summary Zinc oxide (ZnO) used in high (‘pharmacological’) levels to prevent diarrhoea in pigs is assumed to reduce copper (Cu) in tissues and inhibits large intestinal microbial fermentation. To test it, German Landrace pigs were weaned on d28 of age and fed diets containing either 100 (LowZinc, LZn, n = 10) or 3100 mg ZnO/kg (HighZinc, HZn, n = 10). The mixed feed (13.0 MJ ME, 18.5% crude protein) was based on wheat, barley, soya bean meal and maize. After 4 weeks, the HZn group was further fed 100 mg ZnO/kg for another 2 weeks. Caecal contents, faeces and tissues were collected after 4 weeks (n = 5 and n = 10 respectively) and 6 weeks (n = 5 and n = 5 respectively). Faeces and caecal content were analysed for dry matter (DM), pH, ammonia, lactic acid (LA) and short‐chain fatty acids (SCFA) on native water basis. anova was performed to elucidate significant differences at p < 0.05. No diarrhoea occurred. After 4 weeks, the caecal contents’ pH increased (p < 0.001) and butyric (p < 0.05) and valeric acid (p < 0.01) decreased in the HZn group in comparison with LZn. In faeces, a decrease of acetic (p = 0.009), butyric (p = 0.007) and valeric acid (p = 0.046), as well as reduced acetic:propionic acid (A:P) ratio (p = 0.025) was observed in the HZn group in comparison with LZn. Faecal ammonia decreased in HZn (p = 0.018). No differences (p > 0.05) were recorded in caecal contents after 6 weeks. In faeces, acetic acid remained lower in the HZn group in comparison with LZn (p = 0.006), as did the A:P ratio (p = 0.004). Zn concentration in liver, kidneys and ribs, and Cu concentrations in kidneys increased in HZn. Withdrawal of ZnO resulted in reversibility of the changes. The effect on butyric acid should be discussed critically regarding the energetic support for the enterocytes. High Zn and Cu tissue concentrations should be considered by pet food producers.

Potential of a fucoidan-rich Ascophyllum nodosum extract to reduce Salmonella shedding and improve gastrointestinal health in weaned pigs naturally infected with Salmonella

“…Dietary supplementation with the pharmacological dose of ZnO during the first 21 d post-weaning, improved growth performance and faecal consistency similar to previous weaned pig studies with [ 83 , 84 ] or presumably without [ 12 , 85 , 86 ] a concurrent Salmonella infection. In the challenge experiment, no differences in the counts of most bacterial populations were observed between the control and ZnO-residual groups two weeks post ZnO removal, which is in agreement with the assumption of Janczyk et al [ 87 ] that the impact of ZnO on the composition and activity of the gastrointestinal microbiota was reversible after ZnO withdrawal. However, Enterobacteriaceae counts were significantly lower compared to the control indicating that ZnO may have a long-term residual impact on the different members of the microbiota.…”

“…However, Enterobacteriaceae counts were significantly lower compared to the control indicating that ZnO may have a long-term residual impact on the different members of the microbiota. The observed reduction may be attributed to the release of Zn 2 + ions from the liver and kidneys, as Zn concentration was reported to still be high, albeit decreasing, in these tissues two weeks after ZnO removal [ 87 ]. However, prolonged exposure to high Zn levels could potentially increase Zn resistance [ 88 ] and AMR [ 14 , 16 ] within the Escherichia coli population as indicated in previous studies.…”

Zinc overload in weaned pigs: tissue accumulation, pathology, and growth impacts

“…The safety of this short-term, high-dose therapeutic treatment is assumed based upon the lower bioavailability of ZnO relative to other forms of Zn commonly included in feed 10,27 and the reversibility of tissue accumulation after ZnO withdrawal. 14 However, if diet manufacturing errors occur and supra-pharmacologic concentrations of ZnO are fed inadvertently, Zn toxicity may occur.…”

Paternal Zn-deficiency abolishes metabolic effects in offspring induced by diet type

“…Zinc, as a component of over 200 enzymes, participates in many physiological functions in animals, especially playing a pivotal role in the balance of lipids metabolism ( Janczyk et al., 2015 ). In recent years, more and more studies have focused on Zn deficiency.…”