The mission of the Tri-State Extension Dairy Team is to unite Maine, New Hampshire, and Vermont in advancing dairy management through collaborative educational programs, addressing shared industry challenges, and fostering innovation across northern New England. Since January 2025, the team has been hosting live monthly webinars on the last Wednesday of each month from 11:30 AM to 12:30 PM. Sessions have focused on current dairy research and program updates, including interviews, presentations, and roundtable discussions. All recorded sessions are available to watch on the UVM Extension Northwest Crops & Soils YouTube Channel.
In July, the Tri-State Extension Dairy team hosted a webinar focused on rumen biochemistry and function of dairy cattle with guest independent nutrition consultant, Kurt Cotanch.
Kurt believes that “our job in feeding dairy cattle is to facilitate microbial growth.” Microbial fermentation produces volatile fatty acids (butyrate, propionate, and acetate) and hydrogen. The cow needs these metabolites to produce milk as well as support muscle and body condition and reproductive function – including fetal growth.
Dairy rations supply nutrients in the form of sugars, starches, and fiber. Sugars are fermented into butyrate, which is utilized by the rumen epithelium and by the cow as an energy source. Starches are fermented into propionate, which is utilized in the liver to produce blood glucose through the process of gluconeogenesis. Fiber fractions are fermented into acetate, which is a precursor for milkfat production. The quality, digestibility, nutrient profile, and fermentation status of the feed ingredients (including forage sources) being fed dictates the proportions of volatile fatty acids produced by the rumen microbes.
Milk is 4.7% lactose, which is a sugar. Therefore, a cow making 85lbs of milk per day is actually producing about 4lbs of sugar per day. Blood glucose made in the liver during gluconeogenesis is then used not only to make lactose, but is also used for red blood cell production, mammary tissue production, and by the cow’s immune system. Activated immune systems get priority use of blood glucose, meaning cows experiencing stress and reduced feed intake will revert to mobilizing nutrients from muscle and adipose for energy, which further stresses the system. This explains why a cow can tolerate heat stress, overcrowding stress, or even illness for a short period of time before production will drop noticeably.
Rumen fill and flow are determined by fiber fractions, which are in turn determined by forage maturity stage at harvest. Pasture and less mature forages have a faster passage rate and are more digestible. More mature forages pass through the rumen more slowly and take longer to digest. Diets that are high in fast fiber may pass through the cow without getting fully digested. Diets that are high in slow fiber pass through the cow more slowly, which may hinder intake.
Rations that provide nutrient synchrony by supplying the right amino acid profile, fiber fractions, and carbohydrates allow cows to maximize production efficiency. Nutrients fed above animal requirements, particularly nitrogen sources, utilize extra energy to expel excess nutrients in the form of urinary nitrogen and milk urea nitrogen (MUN). Milk components, including fat and protein percentages and ratios, milk fatty acid profiles, and MUNs, can all be used to assess and troubleshoot rumen function and nutrient efficiency.
Click here to access the full recording of this webinar and all other webinars in this series. Register for upcoming Tri-State Dairy Exchange webinars here.