69 Effect evaluation of two sources of zinc at EU-authorized level on growth performance and gut health of piglets with a low or normal birth weight

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Abstract This study aimed to investigate the effect of ZnSO4 or a porous form of ZnO, at EU-authorized level, on growth performance, gut health and colon microbiota in low and normal birth body weight (BBW) piglets. At birth, 64 piglets were chosen by their BBW and divided into low BBW (LBBW < 1 kg; 32 piglets) and normal BBW (NBBW > 1 kg; 32 piglets). At weaning, 25 d old (d 0), piglets were allocated into four groups (8 piglets/group, 2 pigs/replicate) and fed a standard diet plus 120 ppm of Zn from ZnSO4 or from a porous source of Zn (HZ - HiZox, Animine, France). Groups were balanced for litter of origin and category of BBW. Piglets were weighed weekly until d 21 post-weaning. The prevalence of diarrhea was determined by the fecal index (percentage of animals with fecal score > 3), and feed intake per pen was recorded daily. On d 9 and d 21, one piglet/replicate was slaughtered, and jejunum tissue was collected for morphology, colon content for microbiota analyzes, and distal jejunum pH was measured. Performance, pH, and morphometric parameters were analyzed using a linear mixed model, fecal index using a generalized linear mixed model with a Poisson distribution, including treatment, class of BBW and their interaction as fixed factors, and the litter as random factor. The statistical analysis on alpha, beta diversity and taxonomic composition were carried out using phyloseq, vegan and microbiomeMarker packages. Piglets in the NBBW group had greater BW throughout the study (P < 0.01). The treatment HZ tended to increase the average daily gain (ADG) at d 9-14 (P < 0.10), and significantly increased the gain to feed ratio (G:F) ratio (P < 0.05) at d 0-14. The HZ-fed piglets had a greater G:F in the overall period (P = 0.04). Additionally, the jejunum pH of the HZ-fed piglets was reduced (P = 0.02) at d 21. An interaction was observed between treatment and BBW for fecal index during d 0-14 and d 0-21 (P < 0.01), in which HZ decreased the index in LBBW. An interaction was also observed in villus height (P = 0.05) and absorptive mucosal surface (P = 0.02) on d 21, that resulted greater in NBBW piglets fed ZnSO4. For Beta diversity, using the Adonis test, BBW category tended to affect the microbial structure at d 9 (R2 = 0.04; P = 0.07) and significantly affected the bacterial structure (R2 = 0.05, P = 0.03) at d 21. At d 21, the NBBW piglets fed ZnSO4 had a greater abundance of Succinivibrio which is able to degrade complex carbohydrates, while the NBBW piglets fed HZ had a greater abundance of Ruminococcus gauvreauii which is linked to the production of short chain fatty acids (SCFAs). The use of HZ seems can be a part of the strategy to replace the pharmacological level of ZnO.