Peripartum supplementation of rumen-protected choline has been shown to improve cow health and milk
production by improving liver function through a reduction in hepatic lipidosis. However, the optimal dose
range remains undetermined. To evaluate the effects
of supplemented choline chloride on lactation performance and health of dairy cows, a systematic review
and dose-response meta-analysis were conducted. This
meta-analysis followed the preferred reporting items for
systematic reviews and meta-analyses guidelines and
used the population (dairy cows), intervention (choline
supplementation), comparison (control group vs. choline
supplementation), and outcome framework to select studies on dairy cows supplemented with choline. A total of
30 studies from 19 articles and 1 dissertation, identified
through Web of Science, Scopus, Google Scholar, and
PubMed, were included. The analysis focused on DMI,
milk yield and composition, BW, and BCS. Study quality
and risk of bias were evaluated using systematic review
center for laboratory animal experimentation’s risk of
bias tool. A 1-stage random-effects meta-analysis with
a restricted cubic spline model was employed to assess
dose-response relationships, with REML used for variance estimation. Subgroup and sensitivity analyses were
performed to address heterogeneity and robustness, and
publication bias was assessed using funnel plots and adjusted with the trim-and-fill method. This meta-analysis
showed the significant effects of choline supplementation on intake and lactation performance of dairy cows.
Optimal DMI was reached at 13 to 14 g/d, resulting in
an increase of 0.48 kg/d (95% CI: 0.10, 0.87), whereas
milk yield peaked at 13 g/d, with an increase of 1.29
kg/d (95% CI: 0.17, 2.41). A significant dose-response
relationship for 3.5% FCM yield was observed across
21 trials, with efficacy significantly increasing steadily
between 15 and 21 g/d, and a predicted mean difference
of 2.19 kg/d at 21 g/d (95% CI: 0.48–3.90). Milk fat
yield increased significantly by 0.09 kg/d at a dose of
24 g/d (95% CI: 0.01, 0.17), whereas milk protein yield
improved significantly in the 13 to 20 g/d range despite
considerable heterogeneity (>50%). A subgroup analysis
showed that factors such as parity and level of milk yield
had no significant effect on milk protein yield. However,
the effects on milk protein yield were only significant
in studies conducted between 2012 and 2024 compared
with studies conducted between 2000 and 2011. In addition, choline chloride supplementation fed postpartum
after 21 DIM had a significant effect compared with
feeding before 21 DIM, and the commercial brand of
rumen-protected choline also had a significant effect on
milk protein yield. No significant effects were observed
on milk composition (fat, protein, lactose), MUN, BCS,
or prepartum BW, although overall BW increased significantly at a choline chloride dose of 11 g/d, reaching
a peak of 12.5 kg (95% CI: 0.01, 24.96). Based on the
res
