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Discipline: supplementation; Keywords: choline, health, milk yield, transition cow
Choline is a known essential nutrient as it is required for synthesis of essential membrane phospholipids, acts as a precursor for synthesis of acetylcholine, and in particular, has a role in lipid intermediary metabolism. In ruminants, however, almost all dietary choline is degraded by ruminal microbes and requires choline to be supplemented in a rumen-protected form.
Dairy cows in the last weeks of gestation and first few weeks of lactation are prone to negative nutrient balance, which induces extensive catabolism of fat depots and can result in up to 50% developing moderate to severe fatty liver. Cows in this state have compromised health such as increased risk of ketosis, displaced abomasums and reduced milk yield. At the same time that cows undergo negative nutrient balance, the concentrations of choline metabolites in plasma are at their lowest during the first weeks of lactation, and supplementing rumen-protected choline increases plasma concentrations of choline metabolites in cows pre-calving. Improving choline status pre-calving has the potential to reduce the risk of fatty liver and improve health and lactation. However, little is known about the optimum dose of choline fed as rumen-protected choline on post-calving performance. Furthermore, the effect of rumen-protected choline on risk of health disorders is mostly unknown. Also, because both choline and methionine participate in the metabolism, it is possible that responses to choline are dependent on the supply of methionine. To study this further, the first objective of the meta-analysis investigation of reputable publications by Dr U. Arshad and colleagues was to to evaluate the effects of supplementing rumen-protected choline on the production and health of dairy cows. A second objective was to identify an optimal dose of choline fed in the rumen-protected form, and thirdly whether responses to rumen-protected choline depend on pre-calving dietary energy content and pre- and post-calving supplies of methionine. The authors published their results in the Journal of Dairy Science, Volume 103 of 2020, page 282 to 300, the title being: Meta-analysis of the effects of supplemental rumen-protected choline during the transition period on performance and health of parous dairy cows.
The literature was systematically reviewed and 21 experiments, with up to 66 treatment means and 1313 pre-calving cows, were included. All experiments had a treatment with no supplemental choline (0 g per day), and the amount of choline supplemented to treated cows ranged from 5.6 to 25.2 g per day. The data collected included the ingredient composition and chemical analyses of pre- and post-calving diets, amount of choline supplemented, number of cows per treatment, frequency of health events, production responses, liver composition, and blood parameters.
The results showed that increasing supplementation of choline during the transition period increased pre- and post-calving dry matter intake, and yields of milk, energy-corrected milk (ECM), fat, and protein. An interaction between choline and post-calving methionine was observed for yields of milk, ECM, and protein because as methionine increased, the positive response to choline on yields of milk, ECM, and protein decreased. Supplementing choline during transition tended to reduce the risks of retained placenta and mastitis, but it had no effect on metritis, milk fever, displaced abomasum and ketosis. The median amount of choline supplemented was 12.9 g per day (close to optimum) and responses in post-calving dry matter intake and yields of milk, ECM, fat, and protein to that amount of supplementation were 0.5, 1.6, 1.7, 0.07, and 0.05 kg per day, respectively.
Collectively, the results showed that feeding rumen-protected choline during the transition period improved performance of the cows. Increases in yields of milk and milk components were observed in spite of differences in pre- and post-calving dietary compositions in the experiments, but the increments in milk, ECM, and protein yields with supplementing choline, decreased as the concentration of methionine in the post-calving diets increased.