Perhaps the most underrated nutrient in the dairy cow's diet, fat is  essential for ensuring your herd's overall health and optimum productivity. And while the feeding of liquid oils and oily by-products are commonplace throughout the dairy farming community, in this blog, we'll explore why the type of fat really matters, as well as why it needs to be rumen-protected to achieve those optimum results.

>>> What do we mean by 'rumen-protected fat?'

What happens when you feed an unprotected fat?

While it's tempting to simply add liquid vegetable oils and high oil by-products to the diet to get that fat boost, this can lead to an ‘oil slick’ forming over the fibre in the rumen. And like all oil slicks, this is bad news. Not only does the thick coating of oil reduce fibre digestibility and milk fat, but many of the fatty acids present in these oils kill the good fibre-digesting bacteria in the rumen - further impeding fibre digestion. These fatty acids – the building blocks of fat – can also be converted into different fatty acids in the rumen which can cause major milk fat depression.

So how does rumen-protected fat differ?

Long story short, we convert these sticky oils into solid particles that can pass through the rumen without any negative consequences to fibre digestion. This enables the fat, or more specifically, those all-important, targeted fatty acids, to be delivered right where they need to be - the small intestine.

>>> Learn more about rumen-protected fats here

Let's take a look at how rumen-protected fats benefit the whole cow…


Fat is by far the most energy-dense nutrient available, supplying 2.5 times more energy than cereals. With forages containing around 3.5% fat, and cereals around 1.5-2.5% fat, and the average high-yielding dairy cow requiring 6%+ fat in her diet for optimum productivity and fertility, there's an obvious shortfall in a typical grass and cereal-based diet. Adding rumen-protected fat to the diet is an extremely efficient means of making this up, as well as having a multitude of other benefits to overall cow performance. Research recommends that 15-20% of the metabolisable energy in a cow's diet comes from fat.

Improving dairy cow fertility

Did you know? Fertility falls by around 10% for every 0.5 unit loss in Body Condition Score (BCS). With this in mind, it's essential to keep your dairy cow in prime BCS in order to be successful in getting her in calf. In this instance, a rumen-protected fat with higher levels of C18:1 (oleic acid), which is proven to aid both BCS and fertility, comes into its own.

Increasing milk fat percentage

When aiming for increased milk fat, C16:0 fatty acids are fundamental for stimulating production. Feeding a rumen-protected fat which is high in this fatty acid delivers these milk fat boosters through the rumen to the small intestine intact, ensuring that the cow can make the most of the nutrition delivered.

Optimising milk yield

In early lactation, when energy demands are high, it makes sense to deliver nutrition with the greatest bang for its buck. Feeding rumen-protected fat ensures maximum energy is delivered and available for milk production. A rumen-protected fat that is higher in C18:1 fatty acid is most appropriate at this stage.

Need help working out which rumen-protected fat is right for your herd? Click here for our handy decision-making tree.

>>> Learn more about rumen-protected fat supplements, product types and categories.

Delivering energy without acid

There's no denying the energy boost that feeding cereals can offer. However, this superficial gain can lead to long-term pain as the rapid fermentation of these starch-rich feeds generates acid in the rumen, which impacts rumen function, fibre digestion and ultimately, your milk cheque. A rumen-protected fat not only delivers an energy boost that packs a punch, but it does it without upsetting that delicately balanced pH in the rumen, avoiding the risk of acidosis.

Reducing the risk of heat stress

Supplementing your dairy cow's diets with rumen-protected fats is the most effective way to help meet the energy requirements of your herd, particularly when dry matter intake is in decline. With rumen-protected fats passing through the rumen to be efficiently digested in the small intestine, the heat generated by the metabolism of these fats is far lower than that generated by the digestion of fibre and cereals. In the rumen, fibre and cereals have a fuel-on-a-furnace-like effect inside your dairy cow and can increase the risk of heat stress as well as acidosis.

Reduced methane production

It's no secret that methane production is a natural consequence of the digestive process within the dairy cow – created via complex microbial activity within the rumen as it rapidly digests feed material. Methane production accounts for between 2 and 12% of energy loss from the diet in the dairy cow, and this energy could otherwise be used for milk production, meaning losses for the dairy farmer.

Unlike other ingredients, fat isn't fermented in the rumen. Therefore rumen-protected fats offer the ultimate source of energy to mitigate methane production – benefiting both farm profits and the environment in one hit.

Enhanced feed efficiency

As we mentioned earlier in the blog, by rumen-protecting our fats, we can deliver this vital energy source, right where it needs to be in order for the dairy cow to make the absolute most out of every mouthful. With the bonus of not upsetting that delicate microbial population within the rumen, we are able to ensure that she can enjoy the nutritional benefits of her fibre sources too.

Find out more about the benefits of feeding fats in rumen-protected form.

Optimised metabolic effect

Ultimately, by feeding rumen-protected fats, we can reduce the digestive stress imposed on the dairy cow, minimising energy loss through metabolic heat production, as well as the negative consequences that can occur with other energy sources. Offering a true powerhouse energy source, enabling the cow to direct energy into body condition, fertility and milk production, fats boast benefits that go above and beyond the basis of any other diet and are a key piece of the nutritional puzzle.