Real Science Exchange: Methyl Donor Nutrition in Transition; Dr. Joe McFadden, Cornell University

This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series. You can find it at balchem.com/realscience.
Feeding rumen-protected choline in early lactation has consistently increased milk yield and energy-corrected milk yield, which is more pronounced when cows are fed diets low in metabolizable methionine. Choline feeding also increases milk fat and protein yield, minimizes body condition loss in early lactation, and reduces postpartum disease incidence. Dr. McFadden presents three topics about choline biology in the dairy cow. (01:45)
Why should we consider fatty acid feeding when feeding methyl donors like choline and methionine?
Choline degradation in the rumen and small intestine, focusing on the role of triethylamine oxide
Why should we consider lysophosphatidylcholine as an immunomodulator in fresh cows and preweaning calves?
Fatty acid nutrition to optimize methyl donor efficiency. (4:02)
Fatty liver is a concern for fresh cows because of its relationship with ketosis, poor fertility and compromised milk production. Cows with fatty liver exhibit low circulating concentrations of phosphatidylcholine, which is a component of very low-density lipoproteins (VLDL) that transport triglycerides out of the liver. Feeding rumen-protected choline lowers liver triglyceride deposition by supporting the synthesis of phosphatidylcholine and thus, VLDL.
Dr. McFadden goes on to explain the two different pathways for phosphatidylcholine in the liver and how those interact with fatty acid metabolism. He describes several experiments that have investigated how rumen-protected choline and supplemental fatty acids interact in lactating cows.
Low phosphatidylcholine supply is a key feature of fatty liver in dairy cows, likely due to low polyunsaturated fatty acid (PUFA) and low choline supplies. Delivery of post-ruminal PUFA may support phosphatidylcholine synthesis with accompanying improvements in insulin sensitivity, body condition maintenance, and inflammation, but interactions with dietary fatty acid digestibility should be considered. Dr. McFadden gives a list of considerations for fresh cow diets incorporating fat and choline supplementation.
Gastrointestinal choline degradation and trimethylamine N-oxide (TMAO) (16:58)
Unprotected choline is almost totally degraded in the rumen. Microbes convert choline into trimethylamine (TMA) which is then converted to TMAO in the liver. Rumen-protected choline allows for a large proportion of choline to reach the small intestine intact. However, research shows that choline can also be degraded by microbes in the small intestine in the same pathway, limiting choline bioavailability. Plasma TMAO accumulation is associated with non-alcoholic fatty liver disease, inflammation, insulin resistance, obesity, oxidative stress, and cardiovascular disease in rodent and human models. Little research was available regarding if the relationship between TMAO and poor health was causative or just associative. Dr. McFadden’s lab infused cows intravenously with TMAO and found that TMAO did not modify milk production or glucose tolerance in early lactation cows.
TMAO does not appear to influence energy metabolism or health in early lactation cows. Choline is subject to both ruminal and lower-gut degradation to TMA, and that influence on choline bioavailability needs to be defined. Data in non-ruminants suggests that unsaturated fatty acid feeding can shift the gut microbes to slow TMA formation.
Lysophosphatidylcholine and immunomodulation (28:45)
Dr. McFadden gives an overview of neutrophil activation and the oxidative burst that contributes to pathogen killing. The ability to elicit the oxidative burst is diminished in pre-weaned calves and transition cows. When cows were given endotoxin to cause an immune response, circulating lysophosphatidylcholine was decreased. In rodent models, lysophosphatidylcholine promotes the oxidative burst and suppresses long-term inflammation in response to bacterial infection. Dr. McFadden cultured neutrophils from pre-weaned calves with lysophosphatidylcholine and observed an enhanced oxidative burst.
Immunosuppression is characterized by low circulating lysophosphatidylcholine concentrations in dairy cows. In vitro data suggests lysophosphatidylcholine can activate neutrophils, and rumen-protected choline increases circulating lysophosphatidylcholine. Future research is likely to define an immunomodulatory role for choline.
Dr. McFadden takes questions from the webinar audience. (38:07)
Please subscribe and share with your industry friends to invite more people to join us at the Real Science Exchange virtual pub table.
If you want one of our Real Science Exchange t-shirts, screenshot your rating, review, or subscription, and email a picture to [e-mail]. Include your size and mailing address, and we’ll mail you a shirt.