Effects of Astaxanthin as a Feed Additive on Growth Performance, Intestinal Microbiota and Clinical Parameters in Preweaning Female Holstein Calves: A Preliminary Study

= 12). Treated calves received 40 mg/d of astaxanthin from week 0 to 4 and 80 mg/d from week 4 to 8. Body weight, feed intake, rectal temperature, and fecal consistency score, fecal color score and clinical scores were recorded throughout the trial. Blood samples were collected in weeks 0 and 8 for metabolic profiling, and fecal samples were collected in weeks 0, 4, and 8 to assess fecal consistency and bacterial populations. Astaxanthin supplementation did not affect body weight, average daily gain, or overall feed intake. However, treated calves exhibited a lower frequency of abnormal fecal consistency scores, indicating reduced diarrhea incidence compared with control calves. Fecal microbiological analysis revealed lower coliform counts in astaxanthin-supplemented calves in weeks 4 and 8, whereas total bacterial counts were greater in week 8. Most blood metabolites were primarily influenced by age-related physiological changes; however, circulating calcium concentrations were greater in treated calves. These results suggest that astaxanthin may represent a promising nutritional strategy to support gastrointestinal health during early life, although larger studies are needed to confirm these findings.