Effect of injectable vitamin E on incidence of retained fetal membranes and reproductive performance of dairy cows.

Vitamin E, being an antioxidant, has various protective functions at the tissue level and therefore is included on a routine basis in dairy cow diets. However, if other antioxidants are not included in the diet, Vitamin E may take on that function during storage of the feed, resulting in some of the activity being lost. Irrespective of this possibility, the protective role of vitamin E during pregnancy in protecting the integrity of vital membranes may be underestimated, and therefore nutritionists and veterinarians often recommend injection of vitamin E since the supplements provided during late pregnancy may not contain sufficient. The question is, is this really necessary? This was the topic of a study of Dr G.C.S. Pontes and colleagues, which they published in the Journal of Dairy Science, Volume 98 of 2015, pages 2437 to 2449. The title is: Effect of injectable vitamin E on incidence of retained fetal membranes and reproductive performance of dairy cows.

The objective of their study was to evaluate the effects of injectable vitamin E during the last three weeks before calving on the incidence of retained foetal membranes and reproductive performance. They assigned a total of 890 dairy cows of which 390 were Holsteins (respectively 132 first-calf heifers and 258 with more lactations) and 500 were crossbred Holstein × Gyr cows (respectively 199 first-calf heifers and 301 with more lactations), from three dairy farms in Brazil to the study. On all three farms, from October to March, the cows before calving grazed tropical grasses and received 2 kg per day of a mixture of finely ground maize, soybean meal, and minerals and vitamins. From April to September the other cows before calving received a total mixed ration composed of maize silage, finely ground maize, soybean meal, and minerals and vitamins. During this pre-calving period, cows were fed 280 (farm 1), 390 (farm 2), and 480 international units (IU) (farm 3) of supplemental vitamin E per day, and throughout post-calving, cows were fed 370 (farm 1), 500 (farm 2), and 600 (farm 3) IU of supplemental vitamin E. Within each farm, cows were randomly assigned to be untreated controls or to receive three injections in the muscle of 1,000 IU each of dl-α-tocopherol (a derivative of vitamin E), administered at about 19, 13 and 6 days before calving. Blood was sampled from 141 cows immediately before the start of the experiment to determine the α-tocopherol and cholesterol baseline status. Blood was also sampled and analyzed for concentrations of cortisol and non-esterified fatty acids in the last three weeks of pregnancy.

The blood results showed that the serum concentration of α-tocopherol and the α-tocopherol:cholesterol ratio did not differ between treatments. In total, 53% of the cows had an inadequate concentration of serum α-tocopherol. The risk of retained foetal membranes decreased as serum α-tocopherol increased. Milk production did not differ between control and vitamin E cows. Treatment with injectable α-tocopherol decreased the retained foetal membranes from 20 to 13.5%, decreased the incidence of stillbirth from 15 to 7%, and tended to decrease death by 200 days post-calving. Vitamin E cows tended to have improved pregnancy per insemination at first AI (37 versus 30%), because of decreased pregnancy loss from 31 to 62 days of pregnancy (12.5 versus 20.5%). Furthermore, despite a similar insemination rate, vitamin E cows had a 22% greater pregnancy rate than control cows. Also, cows receiving vitamin E had decreased circulating cortisol and non-esterified fatty acids around calving.

In summary, the control cows, depending on season, were supplemented with 28 to 48% of vitamin E recommendations. The results convincingly showed that pre-calving supplementation with injectable α-tocopherol decreased the incidence of retained foetal membranes and improved reproduction.