A meta-analysis and meta-regression of the effects of vitamin E supplementation on serum enrichment, udder health, milk yield, and reproductive performance of transition cows

摘要

Vitamin E is an essential nutrient for cows, but theeffect of vitamin E supplementation is often controversiallydiscussed in the published literature. The maingoal of this meta-analysis was to evaluate the effects ofvitamin E supplementation on its serum and colostrumenrichment, milk yield (MY), and somatic cell counts(SCC), as well as on various reproductive variables oftransition cows, by considering a large set of variablesthat might influence the responses to vitamin E supplementation.After a broad search in journals and databaseswith keywords related to transition cows supplementedwith vitamin E and appropriate filtering of theresults, 36 papers including 53 trials were selected, andtheir data were extracted into a database. A meta-analysiswas conducted on the extracted data. The analysisshowed enrichment of serum vitamin E both at parturition(effect size: 2.423) and postpartum (effect size:0.473), but no effects of vitamin E supplementationon IgG concentration in colostrum (effect size: −0.05)were found. There was a tendency for supplementedcows to produce more milk (effect size: 1.29) during thefirst month of lactation. Because of large heterogeneity,a meta-regression was performed but none of the presumedinfluencing factors was identified as a potentialvariable affecting MY. Milk SCC, as an indicator ofudder health, was unaffected by vitamin E supplementation.Vitamin E supplementation tended to decreasethe calving to first estrus period (CFP), wherebysupplementing Se and taking parity into account in theanalysis significantly lowered the CFP. Cows receivingadditional vitamin E had, on average, 6.1% fewer casesof retained placenta, whereby Se supplementation andbreed were key factors improving the effect of vitaminE to reduce retained placenta. In this regard, breedsother than Holstein responded better and these cowsshowed a lower incidence of retained placenta. Thesupplemented cows showed fewer days open (effect size:−0.31), and this improvement was affected linearly byincreasing the dosage administered. Also, cows showedfewer services per conception with increasing dosageof vitamin E. In conclusion, this analysis showed thatsupplementing vitamin E did not affect SCC or colostrumquality but improved reproductive performanceof transition cows, an effect consistent with increasedlevels of serum vitamin E and, for some variables, beingmodulated by Se supplementation.