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Understanding rumen-protected fats


By Trident’s Daniel Chilvers

Protected fats are an important ingredient in the diets of modern dairy cows, yet a certain amount of confusion exists regarding where they should be used and the various products available.

As milk yields have increased in recent years, the need to raise energy intakes to support additional production has meant either higher dry matter intake (DMI), greater energy density in the diet, or both. But if DMI is constrained, whether by the genetic intake capacity of the cow and/or limitations imposed by the production system (e.g. low energy forage), what’s needed is a way to raise the energy density of the overall ration. The aim is to increase energy intake without the need to consume more feed volume.

Fats and oils

And this is where fats have such a vital role to play. Put simply, fats and oils are the most energy dense feed ingredients available, so are ideal for boosting energy content. The problem is that they can only be utilised by the rumen in small quantities when fed in a ‘free’ or ‘un-protected’ form, such as rapeseed oil or soyabean oil.

Even relatively modest quantities will coat the fibre in the rumen sufficiently to prevent access by the microbes necessary for fibre breakdown. The result is sub-optimal fermentation, reduced energy supply and a cut in butterfat percentage. Hence the need for rumen-protected fats, sometimes called rumen-bypass fats, which pass through the rumen without affecting fermentation, but can still be digested in the cow’s intestine.

Silage quality

Due to the adverse weather conditions this summer, there’s likely to be a good demand for protected fats this year, since overall silage rumen fermentable energy (FME) levels are generally low. And it looks like maize silage energy levels may also be relatively poor, owing to a lack of sunshine and a generally ‘late’ growing season limiting starch production.

The net result is that a winter ration for high yielding cows could have an energy density of only perhaps 11.7MJ ME/kg DM, making it harder for the cow to milk to her genetic potential. So it will be extremely valuable to be able to boost energy content safely by adding relatively small quantities of protected fat – typically 0.200.50kg/cow/day – with minimal substitution effect.

Provided the other nutrients are suitably balanced, adding 0.5kg of protected fat into the ration could raise overall energy intake enough to support an extra 2.02.5 litres of milk. To increase energy intakes by the same amount by adding starch to the diet would require significant quantities of cereal or similar to be included (even more so where cereal quality is lower than usual), and the resulting high level of rapidly available energy in the ration could lead to acidosis problems.

So, if adding a protected fat looks to be the right option for boosting your ration this winter, the question becomes which one to choose?

100% fats

The most energy dense are the 100% fats, at around 37MJ ME/kg. As the name suggests, these consist of fat and nothing else, containing saturated fats with a high melting point. If the melting point is 55°C, for example, compared to a rumen temperature of around 39°C, the fats will pass through the rumen still in their solid state. They will then be digested by the fat-specific enzymes in the small intestine.

These fats have little or no impact on the palatability of the ration, which is particularly important where DMI is near its limits.

50% fats

There are also a number of 50% fat products on the market, and these are a great option for dairy producers looking to gain the benefits of rumen-protected fats without the cashflow commitment required by 100% fat products. However, it’s important to pay close attention to the quality of both the fat and its carrier if problems are to be avoided.

These 50% fat products usually consist of a blend of fats or oils (not always protected) absorbed onto a fibrous carrier. It’s not only important to makes sure the carrier is FEMAS approved, but that it also has a proven nutritional value, such as palm kernel expeller or sugar beet feed.


The second group are known as calcium-soap fats, and are produced by combining palm oil with calcium to produce the ‘calcium-soap’. The result is a product that’s predominantly protected in the rumen, but can still be digested in the small intestine.

Due to the lower fat content (typically 84%), calcium-soaps have a significantly lower energy content. In addition, because these compounds are actually a chemical ‘soap’, their ‘soapy’ smell and taste can affect the palatability of the whole diet, with total DMI reduced by perhaps 45% as a result. Calcium-soaps can also lose some of their effectiveness when rumen conditions are sub-optimal (e.g. acidotic or sub-acute ruminal acidosis, SARA, conditions are seen), with a proportion becoming disassociated (breaking down) and releasing the oil into the rumen.

Clear objectives

Finally, it’s important to be clear about your objectives in feeding a protected fat. Most 100% fats, 50% fats and calcium-soaps, for example, contain a balanced supply of the fatty acids (building blocks of fat) needed to drive yield. Used primarily in early lactation cows to raise milk production, the most effective of these products (usually the 100% fats) are also likely to have a positive impact on body condition (and subsequently fertility) and a small effect on milk fat percentage.

But for those looking to promote the production of milk fat, some 100% fats and 50% fats contain a higher proportion (over 85%) of what are known as C16 fatty acids. These high-C16 protected fats are therefore used where milk fat percentage requires a boost.

In each case, it’s important to ensure the benefits outweigh any additional cost, currently helped by the fact that most protected fat products have come back in price significantly in recent weeks due to falling palm oil prices. Magnapac (a calcium-soap), for example, may be considerably cheaper than the 100% fats Golden Flake (a balanced protected fat), and Butterfat Extra (a high-C16 protected fat), but remember that you’re buying more fat with the 100% products. So do your sums carefully.


High-C16 protected fats still remain a popular product for producers on a compositional contract, or for those who struggle to achieve butterfat minimums. If rations lack structural fibre, or a herd is on a straightforward grass-plus-concentrates diet, butterfat levels can often drop below the milk fat threshold, particularly in the spring.

In these cases, a high-C16 protected fat can be a valuable tool to help raise milk fat percentage. For those also still wanting to push yields, one option is to consider feeding half as much high-C16 protected fat, making up the remainder with a balanced fat product to get the best of both worlds.

However, in the majority of cases, the priority in today’s market is to raise yields to maximise additional income, and the balanced fat products – whether calcium-soaps, 50% fats or 100% fats – can provide a valuable payback.

Table 1 gives an example of feeding 0.5kg of a balanced 100% protected fat such as Golden Flake to early lactation cows to gain an extra 2 litres of milk, producing an additional margin of 30p/cow/day at current prices. That’s a payback of 2:1.

Table 1 – Protected fat payback


0.4kg Golden Flake



0.5kg (DM) TMR @ 14p/kg


Net cost:

29 p/cow/day

Extra yield:

2 litres milk @ 27ppl


Extra milk fat:

0.1% @ 1.7p/% over 30 litres


Net benefit:


Net margin:


But it’s important to remember that in herds managed as two or more groups, protected fats will give better returns when fed to the early lactation or high yielding cows. Not only will yield response from high inclusion levels be greatest, but any extra energy not diverted into milk production will help maintain body condition and subsequently support improved fertility.

Where cows are milked as a single group, most producers are still likely to benefit from feeding a protected fat this winter provided silages, though it’s important to ensure that poor silage energy levels are also supplemented with additional rumen FME. The lower yielding cows in the herd may produce less of a yield response, but additional energy will still provide the cow with a boost, usually in the form of improved body condition or butterfat content. Just be careful to closely manage inclusion rates to prevent late lactation cows becoming overfat.

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