Dose- and Time-Dependent Effects of Cobalt Chloride Supplementation on Growth Performance and Intestinal Development...

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 (n = 10), a low-dose CoCl₂ group (1 mg/kg of diet; n = 8) and a high dose CoCl₂ group (2 mg/kg of diet, n = 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 < p < 0.1) and gain to feed ratio (linear, p < 0.05), as well as reduced fecal scores (Linear, p < 0.05). However, during the later post-weaning period (d15 to d28), increasing dietary CoCl₂ levels were unfavorable trends in feed intake (Linear, p < 0.05) and ADG (Linear, 0.05 < p < 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, p < 0.05), without significant effects on ileal epithelial proliferation and apoptosis (p > 0.1). Changes in the numbers of goblet cells in villi (Quadratic, p < 0.05) and crypt (Linear, p < 0.05), and enteroendocrine cells (Quadratic, p < 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 (DMT1, GLUT2, and SGLT1) and metabolism (HIF-1α, FBP1, and FBP2), as well as those related to the NOTCH signaling pathway (LGR5, ATOH1, HES1, and NOTCH2), showed a linear decrease (Liner, p < 0.05). This was the case except for LDHA and DLL4 (Liner, p < 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, p < 0.01), the budding numbers (Linear, p < 0.05) per organoid, and altered gene expression of SGLT1 and CHGA (Linear, p < 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.