A study published online on 9 October 2026 in the Journal of Dairy Science compared two forms of fat supplementation in calf milk replacer — linseed oil and its ethyl esters — measuring their effects across four outcomes: physical properties of the replacer, nutrient digestibility, calf health, and oxidative status.

The authors are M.K. Baba, J. Flaga, K. Dziadek, M. Kasprzak, D. Motyka and Z.M. Kowalski. Their comparison addresses a practical question for dairy producers and calf raisers: whether the chemical form of an omega-3-rich fat source changes how a milk replacer performs once it is mixed, fed, and metabolized by a young animal.

Why the form of the fat supplement matters

Linseed oil is a plant oil valued in ruminant nutrition for its high alpha-linolenic acid content. Ethyl esters are a processed derivative of the same oil, in which fatty acids are esterified to ethanol rather than to glycerol. The two forms can behave differently in at least three respects relevant to calf feeding:

• Physical properties — how the supplement disperses and holds when mixed into a milk replacer, which affects consistency at the nipple or bucket.
• Digestibility — whether the esterified form is broken down and absorbed as efficiently as the triglyceride form native to the oil.
• Oxidative status — polyunsaturated fat sources carry a higher oxidative load, and the study measured whether either form shifted markers of oxidative stress in the calves.

The paper evaluates all three dimensions alongside standard health monitoring, per its published title and scope.

What this means at the feed room

For calf-rearing operations already using fat supplements to raise energy density or modulate fatty acid profiles in milk replacer, the choice between an intact oil and its esterified form is not cosmetic. Processing steps such as esterification change how a fat interacts with the replacer matrix and with the animal's own lipases.

The study's design — a direct comparison of the two supplement forms within the same replacer base — is the type of head-to-head trial that lets a nutritionist or herd advisor judge whether a processed ester delivers the same digestive and physiological performance as the source oil, or whether the two diverge on any of the measured endpoints.

Because the outcomes span physical properties, digestibility, health and oxidative markers, the results speak to both the mixing tank and the calf: a supplement that digests poorly or pushes oxidative status in an unfavorable direction would carry costs that a label-level fatty acid analysis alone would not reveal.

The bottom line

The full results — including species-standard calf growth, digestibility coefficients and oxidative markers for each supplement form — are available in the paper by Baba and colleagues, published 9 October 2026 in the Journal of Dairy Science. Producers and nutritionists weighing fat-source decisions for youngstock milk replacer programs will want to check the reported differences between the oil and its ethyl esters before committing to one form for the coming feeding season.