Transportation stress reduced serum vitamin E from 7.10 µg/ml to 1.95 µg/ml, below the critical 2 µg/ml level indicating inadequate antioxidant levels. Calves exposed to a dust-stress environment continued to have lower serum vitamin E concentrations (1.88 µg/ml vs. 2.11 µg/ml) throughout the trial. Micotil protected calves from transportation stress (as measured by serum vitamin levels), but had no effect on calves in the dust-stress environment. In a similar study, shipping stress and exposure to dust decreased total antioxidant capacity (TACA) and increased lipid peroxidation (MDA), a measure of lipid breakdown from cell membranes.
Average daily gains showed a similar pattern to antioxidant levels. On day 28 of the study, mean average daily gain of the tent and dust groups was lower than that of the controls (0.77 kg/day vs. 1.26 kg/day). In other studies, the tent (no dust) group performed similarly to controls.
Data showed that as serum vitamin A and vitamin E fell, calf rectal temperatures increased. Incidence of BRD increased as well, hinting at the link between low antioxidant status, a suppressed immune system and illness. As incidence of BRD increased, serum vitamin A and vitamin E concentrations decreased, as did average daily gain.
A study at Louisiana State University examined the effects of supplemental vitamin E alone or with lasalocid on disease severity and immune responses of calves. Thirty-two male Holstein calves were challenged with coccidiosis, which was experimentally induced with Eimeria bovis oocysts when the calves were 2 weeks old.
Calves that received lasalocid had higher (P = 0.06) levels of total immunoglobulins from week 3 until the end of the 8-week study. The control calves had lower IgM levels throughout the study (P > 0.05), while calves supplemented with vitamin E alone had increased levels of IgM at weeks 6 and 8 (P < 0.05). There were no differences in IgG1 and IgA levels between treatment groups (P > 0.05). Average daily gain tended to be greatest in calves supplemented with both lasolicid and vitamin E.
Future studies will attempt to identify antioxidant supplementation strategies to reduce the health and performance effects of transportation and feedlot acclimatization stress.
The complete text of this article with complete references is available to registered users in the online edition of NutraFacts, Volume 7, Number 1
