Is insect oil an alternative fat source for calf milk replacer?

Using oil derived from black soldier flies as the fat source in calf milk powder could offer a more sustainable solution to current alternatives – without compromising on youngstock performance.

Cargill Animal Nutrition ruminant nutritionist Bianca Theeruth said fat mattered for young calves because they were born with minimal fat reserves – typically just 3-4% body fat.

This means the energy provided by milk replacers is critical in the early weeks of life.

See also: What are the benefits of milk replacer for calf rearers?

“Fat is required for thermoregulation, for basic metabolism, and more importantly, it’s required to fuel the immune system and immune development,” she explained.

Dietary fat also plays a vital role in digestive health, vitamin absorption and gut development.

So matching the fatty acid profile of cows’ milk (rich in a combination of short-, medium- and long-chain fatty acids) is a key aim in milk replacer formulation.

Historically, animal-derived fats such as lard and tallow were common in calf nutrition.

Today, milk replacers commonly include palm and coconut oil. These provide the required saturated fats, but carry a high environmental footprint.

Bianca Theeruth © Charlotte Cunningham

“Palm oil gives us palmitic acid, while coconut gives us lauric acid. Both are digestible,” said Bianca.

“But tropical oils are subject to price volatility, and concerns around deforestation and biodiversity loss are growing.”

(Rapeseed oil has a high polyunsaturated fat content which increases the risk of oxidation, meaning antioxidants must be added to maintain stability in storage and transport.)

Insect oil potential

Among the emerging options is black soldier fly larvae oil.

It has a fatty acid profile very similar to coconut oil and contains high levels of lauric acid, known for its antimicrobial properties.

“It’s highly digestible and has functional benefits in the gut, providing intestinal protection,” Bianca said.

Black soldier fly larvae were reared on plant-based by-products, making the oil a circular, low-waste option, she added.

A commercial-scale trial on a dairy farm in Italy compared black soldier fly larvae oil with palm and coconut oil in terms of calf performance, health, and feed intake.

Bianca said there was no effect on performance across all inclusion levels.

This means no differences in daily weight gain, total weight gain or feed efficiency – or changes in palatability.

Calves accepted the feed well, and no reduction in milk intake was observed in any treatment group.

However, during the first three weeks, calves receiving the 20% insect oil inclusion had fewer diarrhoea events compared with those on the standard palm/coconut mix.

She said this could be from the antimicrobial effect of a high lauric acid content, or it could mean that the palm and black soldier fly oil combination was more digestible for young calves.

Emissions concerns

While the study shows promising potential, a recent life cycle assessment commissioned by Defra assessed insect protein – not oil – and raised concerns about its emissions compared with soya or fish meal as a protein source.

The report did not assess the nutritional or antimicrobial value of insect oil, nor its use as a fat source in replacers.

Insect oil and processing leftovers were not included in the report, said Bianca.

“Also, as production in insect products scales up and greener energy is used, the carbon footprint will look very different,” she added.