Targeted selenium, vitamin E, and iron supplementation to boost nutrient retention and metabolism in calves with anaplasma marginale.

The suckling phase of calves is crucial within the production system. This study aimed to examine the metabolism of selenium and iron, and nutrient digestibility in calves challenged with Anaplasma marginale and supplemented with selenium (Se), vitamin E, and iron (Fe). The experiment was conducted with 33 male Holstein calves inoculated with Anaplasma marginale during the suckling phase, when the animals were 57 ± 5 days of age. The design was completely randomized, with calves allocated to the following treatments: C (control milk replacer, n = 10); SeVitE (milk replacer with 0.6 mg organic selenium/kg + 100 IU vitamin E, n = 11); SeVitEFe (milk replacer with 0.6 mg organic selenium/kg + 100 IU vitamin E + 200 mg Fe chelate/kg, n = 12). Supplemented calves showed higher Se intake, increased urinary concentration, greater Se retention, and higher Se concentrations in the liver and blood. Selenium concentrations in the urine and muscle were higher in SeVitE than in SeVitEFe. Animals receiving SeVitEFe exhibited greater Se retention and higher Se in the blood than SeVitE. Supplemented calves had higher iron concentrations in feces and lower Fe levels in the liver compared to non-supplemented calves. Those supplemented with SeVitEFe had higher Fe intake, lower urinary concentrations, and greater Fe retention compared to SeVitE. Supplementation with selenium, iron, and vitamin E in immunologically challenged suckling calves increased nutrient retention and blood levels without affecting digestibility, demonstrating synergistic interactions between selenium and iron metabolism. These findings reinforce the role of trace mineral nutrition in the health management of early-life dairy calves.