Assessment of Lactational Performance in Dairy Cows Receiving a Rumen Protected B Vitamin Blend during Lactation: Part 1: A Meta-Analysis of 50 Studies

The objective of this research was to evaluate the impact of a dietary supplemental rumen protected B vitamin blend (RPBV: Folic acid, B12, pyridoxine, pantothenic acid, and biotin; Jefo, St. Hyacinthe, QC Canada) on milk, fat, and protein yield in cows past peak lactation. Results from 50 double reversal design trials (control-test-control) were evaluated using meta-analyses. All herds participated in monthly milk recording services, and all were Holstein herds. Within each of the 50 trials, cows included in the statistical analysis were over 45 days in milk (DIM) at the first milk test, averaged 159 ± 26 DIM on the first test date, and were available for all milk collection periods. A total of 6483 cows from 7 countries were represented in the 50 studies, with an average herd size of 129.7 ± 118.0. Meta-analyses were conducted to determine effect size for milk, fat, and protein yield based on the treatment differences and standard errors (SE) from the individual trials. Results indicated that dairy cows responded positively to the inclusion of the rumen protected B vitamin blend. Forest plots revealed trial-to-trial variation and might be related to age, level of milk production, and stage of lactation of the cows.