ABSTRACT
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.