Dose- and Time-Dependent Effects of Cobalt Chloride Supplementation on Growth Performance and Intestinal Development in Weaned Piglets

The aim of our study was to evaluate the effect of dietary cobalt chloride (CoCl₂) supplementation on diarrhea, growth performance, and intestinal development in post-weaning piglets. Twenty-six piglets weaned at 21 days of age (d 21) with similar body weights were randomly assigned to three treatments: a control group (<i>n</i> = 10), a low-dose CoCl₂ group (1 mg/kg of diet; <i>n</i> = 8) and a high dose CoCl₂ group (2 mg/kg of diet, <i>n</i> = 8). Piglets were housed individually and fed the experimental diets for 28 days, with a dietary transition at day 15. During the early post-weaning period (d0 to d14), dietary CoCl₂ supplementation was associated with favorable trends in growth performance parameters, including ADG (average daily gain: linear, 0.05 < <i>p</i> < 0.1) and gain to feed ratio (linear, <i>p</i> < 0.05), as well as reduced fecal scores (Linear, <i>p</i> < 0.05). However, during the later post-weaning period (d15 to d28), increasing dietary CoCl₂ levels were unfavorable trends in feed intake (Linear, <i>p</i> < 0.05) and ADG (Linear, 0.05 < <i>p</i> < 0.1). At the intestinal level, CoCl₂ supplementation was associated with dose-related changes in intestinal morphology, epithelial cell differentiation, and luminal pH. Alterations were observed in duodenal crypt depth (CD) and ileal villus height (VH), and duodenal VH/CD (Linear, <i>p</i> < 0.05), without significant effects on ileal epithelial proliferation and apoptosis (<i>p</i> > 0.1). Changes in the numbers of goblet cells in villi (Quadratic, <i>p</i> < 0.05) and crypt (Linear, <i>p</i> < 0.05), and enteroendocrine cells (Quadratic, <i>p</i> < 0.05) in crypt exhibited dose-dependent trends. In addition, with the increase in the CoCl₂ concentration, the expressions of genes related to nutrient transporters (<i>DMT1</i>, <i>GLUT2</i>, and <i>SGLT1</i>) and metabolism (<i>HIF</i>-<i>1α</i>, <i>FBP1</i>, and <i>FBP2</i>), as well as those related to the NOTCH signaling pathway (<i>LGR5</i>, <i>ATOH1</i>, <i>HES1</i>, and <i>NOTCH2</i>), showed a linear decrease (Liner, <i>p</i> < 0.05). This was the case except for <i>LDHA</i> and <i>DLL4</i> (Liner, <i>p</i> < 0.05). The expression of the former was the lowest in the high-dose group, while that of the latter was the lowest in the low-dose group. In vitro, CoCl₂ exposure was associated with reduced organoid budding rates (Quadratic, <i>p</i> < 0.01), the budding numbers (Linear, <i>p</i> < 0.05) per organoid, and altered gene expression of <i>SGLT1</i> and <i>CHGA</i> (Linear, <i>p</i> < 0.05). In summary, dietary supplementation with CoCl₂ exhibited dose- and time-dependent trends in weaned piglets. CoCl₂ supplementation during the early post-weaning period (two weeks after weaning) was associated with favorable trends in growth performance and diarrhea, whereas prolonged supplementation (4 weeks after weaning) or higher dietary level (2 mg/kg of diet) were associated with unfavorable trends in growth performance and intestinal development. These findings suggest that CoCl₂ may have potential as a short-term (two weeks after weaning), low-level (below 2 mg/kg diet) nutritional supplement, while caution is warranted regarding long-term supplementation or higher dietary inclusion levels.