Why does feeding cows high amounts of concentrated feed lead to lower milk fat and protein levels and shorter lifespans?

Australian dairy farmers carefully balance what their cows eat to provide enough energy for milk production while keeping them healthy. If a cow is fed too much high-energy ‘concentrated’ feed without enough fibre, it can upset her digestive system. This may reduce milk fat and protein levels and, if ongoing, affect her health and lifespan.

Producing milk requires a lot of energy. To produce one litre of milk, a cow needs around 6 megajoules of energy. While grass is the foundation of most Australian dairy cows’ diets, grass alone doesn’t always provide enough energy, particularly for modern dairy cows bred to produce milk efficiently.

That’s why farmers may supplement pasture with concentrated feeds such as grains, high-energy crops, or by-products from other food industries. These feeds help meet the cow’s energy needs, especially during certain seasons or stages of lactation.

The key is balance. Cows also need enough fibre in their diet to keep their rumen (the main part of their stomach) functioning properly. If a diet contains too much rapidly fermentable, high-energy feed and not enough fibre, it can lead to a condition called sub-acute ruminal acidosis (SARA). This can cause discomfort, reduce milk fat and protein levels, and if not addressed, it can impact a cow’s overall health and lifespan.

Importantly, this is not standard practice in Australian dairy farming. Farmers work closely with nutritionists and veterinarians and adjust feed rations based on factors such as:

• seasonal pasture availability
• climate conditions
• stage of lactation 
• cow genetics 
• herd health and body condition  

Balancing cow nutrition is both a science and a skill, and maintaining rumen health is a core part of good dairy management.  

Supporting cows to live longer, healthier lives is also a focus for the industry. Dairy Australia invests in research and practical tools that help farmers optimise nutrition, animal health and longevity outcomes.  

When diets are properly balanced, as they are on the vast majority of Australian dairy farms, cows can produce milk efficiently while maintaining good health and wellbeing.