For dairy farmers, maintaining the health of your herd and optimising milk production is vital. Changes in the seasons through each year bring about new challenges. The cornerstone of cow wellbeing is maintaining a fully functional rumen - a vital part of the cow's digestive system. Let's break this down according to each season of the year.

Keeping the rumen healthy is all about offering a well-balanced ration. And it’s worth the effort to get it right. Because when you do, you can expect increased feed intake and improved feed efficiency. That means more milk produced at lower cost. So, how’s it done?

What is the rumen and why does it matter?

Think of the rumen as a sort of fermentation vat, teeming with beneficial bacteria that breakdown food into absorbable energy sources. Without a well-functioning rumen, your cows could suffer from a range of expensive health issues.


In the spring, as new grass shoots appear and cows have access to fresh pastures, monitor and slowly introduce any dietary changes to maintain rumen health. Cows at grass have the early season challenge of consuming low fibre, high sugar grass which drives toward low rumen pH and acidosis challenges, as well as high fat, all of which lead to milk fat depression.  

The core elements of a healthy rumen are a thriving microbial population and an optimal pH level, preferably above 6.5. If this balance is lost, the rumen gradually becomes less competent at food digestion, leaving your cows vulnerable to health complications, such as acidosis and laminitis. Buffering with digestible fibre sources will slow down rumen passage rate and encourage rumination as well as provide nutrients for milk fat production. 

Rumen-protected fats provide additional energy, and higher-C16 supplements (such as Mega-Fat 70) improve milk fat while also providing active ingredients to improve fertility.


In the heat, cows need fat in their diet to remain fit and productive, increasing energy supply and more energy per bite. Too much rumen-active fat, however, from sources like vegetable or fish oils can lead to problems. These fats can create an 'oil slick' in the rumen, inhibiting bacteria from digesting fibre.

In addition, unsaturated fatty acids in oils can be harmful to certain rumen bacteria species, leading to decreased fibre digestion, impaired rumen function and poor feed conversion efficiency.


As summer progresses into autumn, increasing unsaturated fatty acids in pasture can lead to the production of trans fatty acids that can negatively impact milk fats.

Maintaining a consistent supply of dietary nutrients is paramount during this period of change. Remember to adjust cow nutrition gradually to allow your herd's microbial populations to adapt.


Supplementing your cows' diets with rumen-protected fats during the winter months can improve milk yield, milk fat percentage, and overall performance.

Products like Megalac can help with this without increasing the acid load in the rumen or impairing the efficient digestion of fibre, and high-C16 supplements such as Mega-Fat 70 and Mega-Fat 88 provide the building blocks for milk fat production.

Three things to stay on top of all year round…

1. Keeping cows hydrated

Regardless of the season, dairy cows need plenty of clean drinking water. Ensure access to water in key areas like paddocks, feed-out areas, and dairy entry and exit points. They're particularly thirsty after milking.

2. Consistent supply of dietary nutrients

For optimal rumen pH and growth of rumen bacteria, you should aim to keep nutrient intake as balanced and consistent as possible. Rumen microbes adapt to dietary modifications slowly, taking up to six weeks to fully adjust to a change of feeds. Make changes gradually to allow your herd’s microbial populations to adapt.

3. Calculating rumen-active fat in diets

Calculating the fat percentage of a cow’s diet can be complex. Dairy cows may require over 6% fat in the diet dry matter (15-20% of the metabolisable energy of a dairy cow’s diet should come from fat). But only around 3.5% rumen-active fat in the dry matter can be tolerated by the rumen before problems begin to develop.

High yielders on high-starch rations will always be at particular risk. Additional fat requirements must be met with rumen-protected fats because they help provide additional energy without adding to risk for acidosis and subsequent milk fat depression.

It's clear that a healthy rumen equals a healthy, productive cow. Carefully monitoring rumen-active fats and supplementing diets with rumen-protected fats as needed is a key way to promote rumen health and improve herd productivity.

For more information on getting the best from your cows, get in touch.