What do you need from your feed fat?

Start with the cow, not the fat

A cow in early lactation doesn’t have the same nutritional priorities as she does later in lactation. When milk production outpaces feed intake, energy supply becomes particularly important, both for maintaining body condition and supporting fertility. Later in lactation, the focus may shift towards milk yield or milk fat production, depending on the farm’s production objectives.

The same applies at herd level. What you need from supplementary fat will depend on the cows in front of you and the production targets you’re working towards. So, before looking at the fat itself, it’s worth asking: what do I need this supplement to achieve?

High-yielding dairy cows can require 400 MJ or more of metabolisable energy (ME) per day, depending on their stage of lactation, with around 15–20% of that energy supplied from fat for optimal milk production efficiency. But meeting that energy requirement is only the starting point. Different fatty acids influence how nutrients are used within the cow, creating opportunities to tailor supplementation to changing nutritional priorities throughout lactation.

What are you trying to achieve?

The answer starts with what’s happening in the herd. Four questions can help:

1. Where are the cows in lactation?
2. Is body condition being maintained?
3. Is fertility currently a priority?
4. Are you targeting milk yield or milk fat production?

The answers will help establish the nutritional priority before considering which fatty acid profile is best suited to the job. Early in lactation, that may mean prioritising energy supply while protecting body condition and fertility. Once cows have recovered from those demands, the focus can move towards other production goals, depending on what the farm is trying to achieve.

Is body condition telling you something?

The first 100–120 days in milk place the greatest energy demand on the cow, as milk production outpaces feed intake. During this period, keeping a close eye on body condition can provide a useful indication of whether cows are getting the energy they need.

Excessive body condition loss has implications beyond the condition of the cow herself.

Research from the University of Nottingham indicates that every 0.5-unit loss in body condition score can reduce conception rates by around 10%, making it harder to get cows back in calf.

Fatty acid profile becomes particularly relevant. Supplements containing higher levels of rumen-protected C18:1 improve total fat digestibility, increasing the amount of energy cows can extract from the diet while directing nutrients towards body condition. C18:1 has also been shown to support egg and embryo development, helping prepare cows for the breeding period.

Looking at body condition alongside stage of lactation can therefore help farmers decide whether their current fat supplementation strategy is aligned with what cows need at that point in the production cycle.

Are you targeting litres or milk fat?

Once cows have recovered from the demands of early lactation, the priorities for fat supplementation may change. At this point, it’s worth looking at the response you want from the ration and, importantly, what your milk contract is rewarding.

If milk fat production is an important target, supplements containing higher levels of C16:0 can be particularly relevant. C16:0 directs nutrients towards the udder, supporting increased milk fat and milk yield.

That doesn’t mean reaching a particular point in lactation should automatically trigger a change in supplementary fat. The decision should come back to the cows and the production goals of the farm. If the response you’re looking for has changed, it’s worth considering whether the fatty acid profile you’re feeding still matches that objective.

Don’t solve an energy problem by creating a rumen problem

Whatever the production objective, increasing dietary energy needs to go hand in hand with protecting rumen function. Cereals can be a useful source of dietary energy, but their high starch content means inclusion levels need to be managed carefully. Rapid starch fermentation increases acid production in the rumen, which can increase the risk of acidosis.

Rumen-protected fats offer a different way to increase energy density. Proven products such as Megalac contain around 2.5-times more energy than cereals and are manufactured to pass through the rumen before being digested in the small intestine. This enables more energy to be supplied without adding to the acid load associated with rapidly fermentable starch or compromising rumen function.

“Energy supply and rumen function cannot be separated,” says Dr Richard Kirkland, Global Technical Manager for Volac Wilmar Feed Ingredients. A ration may provide more energy on paper, but if the way that energy is supplied compromises rumen conditions, the cow may ultimately receive less energy from the total diet.

Three questions to take back to the ration

Choosing a supplementary fat comes back to three questions:

1. Where are my cows in lactation?
2. What response am I trying to achieve?
3. Does the fatty acid profile I’m feeding match that objective?

There’s no single fatty acid profile that’s right for every cow throughout lactation. "Ultimately, the goal is not simply to maximise milk yield, but to maximise lifetime performance," concludes Dr Kirkland.

Want to make sure your feed fat is delivering the right response for your herd? Explore Megalac’s technical resources or speak to your nutritionist about matching your fat supplementation strategy to your cows’ changing needs.

Proven by science. Trusted by farmers.