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Rumen Protected Fats

Understanding rumen protected fats in the diet

During lactation stage, dairy cows require a lot of energy to produce milk. Energy can be increased either by higher dry matter intake (DMI), greater energy density in the diet or both. However, there is a limit to DMI. Once the limit is reached, what is needed is to raise the energy density of the dairy cow's diet. Therefore, the goal is to increase the energy intake without consuming more feed volume.

Fats & Oils

This is why fat is such an important component in a dairy cow's diet. Reason being, fat has the most energy among other marcronutrients, namely protein and carbohydrates. Fats has approximately twice the energy value compared to carbohydrates by weight. Therefore, fat is ideal in boosting the total energy of a feed without consuming more feed. However, the problem is that they cannot be utilised fully when being fed in a 'free' or 'unprotected' form such as soyabean oil.

Even a small amount of 'unprotected' fat will coat the fibre in the rumen sufficiently to prevent access by the microbes necessary for fibre breakdown. This will cause sub-optimal rumen fermentation, reduced energy supply and a reduction in butterfat percentage.

Therefore, there is a real need for rumen-protected fats, also known as rumen bypass fats. They are able to pass through the rumen without affecting fermentation, but can still be digested in the cow's intestine.

Silage Quality

During the winter, overall quality of silage is usually pretty average, mostly around 10 MJ ME/kg DM. This results in high yielding cow that had an energy density of approximately 11.5 ME/kg DM during the winter. This makes is hard for a milking cow to produce milk up to her potential. Hence, the role of rumen protected role is very important. Just by adding around 300 - 600 g/cow/day of rumen protected fat to the cow's diet to boost energy was extremely valuable.

Provided the other nutrients are well balance in the cow's diet, just by adding 500g of bypass fat into the ration could potentially raise the overall energy intake to such a level that an extra 2.0 - 2.5 litres of milk is being produced.

You could also add starch to raise the energy intakes. However, this requires adding a significant amount of cereal due to its lower energy content and higher substitution effect, which will likely cause acidosis.

Rumen protected fat looks to be  a very attractive option. The question becomes, which one should you choose?

99% Fats

This form of rumen bypass fat has the highest energy density. As the name suggest, it has a minimum of 99%, and it usually contains around 37 MJ ME/kg DM. It contains high palmitic acid (usually over 70%) and a melting point of around 56°C - 60°C. The rumen temperature is only around 39°C. The fats would pass through the rumen still in their solid state, digested only by the fat-specific enzymes in the small intestine.

These fats have no effect on the palatability, which is crucial when the DMI is near its limit.

Calcium Soap

Calcium soap, also known as calcium salts is made by combining palm oil with calcium oxide. The result is a complex that is predominantly indigestible in the rumen but still digestible in the small intestine. 

Other Fats

There are also many other types of fats in the market. Some of them have only around 50% fats. They will be cheaper, but they will be poorer in value compared to the 99% fats or calcium soap. These products usually combines protected fats and unprotected fats. 

Fatty Acid Profile

An important consideration when looking into buying rumen bypass fats is the fatty acid profile.

Calcium soap products usually contain a well balanced fatty acid profile, thus will be able to drive yield in early lactation cows.


With the 99% fats, there are both balanced fats and those which contain high percentage of palmitic acid, also know as C16 fatty acid. C16 is crucial to boost the butterfat milk content. Typically, 99% fats contain very high C16, usually more than 70% and can go as high as 99%. 

Cost:benefit Ratio

Cost:benefit ratio of several products must be considered. A general rule of thumb is that the higher the fat content, the more it cost.


For some farmers, achieving high butterfat milk content is important. As a result, rumen protected fats containing high C16 is crucial to producers on compositional contract or those who struggle to achieve butterfat minimums.

If a rations lack structural fibre, or a herd is on straightforward grass plus concentrates diet, butterfat levels can drop below the milk level threshold. In such cases, high C16 fat can be a valuable tool in aiding to raise the milk fat percentage. And even if a high-
C16 fat is required to maintain butterfats, but you still want to take advantage of the current opportunities to boost milk output, consider feeding half as much high C16 fat, making up the remainder with a balanced fat to get the best of both worlds.

Maximum Income

In today's market, the main priority for milk producers is to increase the yield so that they can increase their income. Both 99% fat as well as calcium soap can provide a valuable payback.

The best time to feed a dairy cow is during early lactation stage where most milk is being produced. However, that does not meaning feeding a dairy fat during mid lactation stage is a waste. The yield may not be as high as during early lactation stage, but it still provide the cow with a boost. This may be improved general health, higher butterfat milk content or better fertility rates.

In conclusion, feeding rumen bypass fats to dairy cows increases the milk production and thus an economic return.

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