A new PhD thesis shows that alternative fat sources cannot replace palm fat in Norwegian milk production without reducing the amount of milk fat. However, they can contribute to a healthier fatty acid profile.
Criticism of the use of palm oil in animal feed, particularly due to environmental and health concerns, raised the question of whether rapeseed and soya could replace palm fat without compromising production.
In his research, PhD student David Galmeus has investigated how different fat sources in feed affect digestion, the absorption of fatty acids and the composition of milk.
The cows were fed a diet containing, amongst other things, palm fat, rapeseed fat and soya fat, and he examined how these fat sources affect rumen fermentation, nutrient uptake and, ultimately, milk production.
It turned out that the total milk yield remained stable regardless of the type of fat the cows were fed. It was primarily the fat content of the milk that changed. Palm-based fat yields the highest amount of milk fat in cows, whilst rapeseed and soya-based fat sources increase the proportion of unsaturated fatty acids. Nevertheless, they cannot replace palm fat if production levels are to be maintained.
One of the clearest conclusions of the study relates to palmitic acid (C16:0), which is found in high concentrations in palm fat.
When the cows were fed palm-based fat, the milk fat content increased significantly – by between 0.12 and 0.89 percentage points. This also resulted in an increase in daily milk fat production of up to 208 grams per cow. The explanation lies in the very structure of the fatty acids. Fatty acids with the correct chain length function better as building blocks for milk fat in the rumen. By contrast, it made little difference whether the fat was in the form of free fatty acids, triglycerides or calcium soaps. It was the type of fatty acid that was decisive.
Galmeus also found that the degree of saturation in the fat influenced how the fatty acids were broken down and absorbed by the cow’s body. Hydrogenated triglycerides from rapeseed had lower digestibility, which limits how much nutrition the cow actually derives from the feed.
A balance between fat quantity and quality
The relationship between the quantity and quality of the fat is crucial. If the aim is to achieve a high level of milk fat, palm fat is the most effective. If the aim is to increase the level of unsaturated fatty acids in the milk, rapeseed and soya yield better results
Nevertheless, the study shows that rapeseed- and soya-based fats cannot replace palm fat if the aim is to maintain current levels of milk fat production. The use of calcium soaps can help to combine a high fat content with a more favourable fatty acid composition, but this still requires a fat source rich in palmitic acid.
The findings provide important insights for Norwegian milk production and for the development of future feeding strategies. The question going forward is not just how much fat we can produce, but what type of fat we want in the milk.
David Galmeus will defend his doctoral thesis: "Lipid supplementation in dairy cow feed: Replacing palm oil fatty acids with alternative lipid supplements " on 25 June 2026 at NMBU.
Galmeus’s main supervisor has been researcher Margrete Eknæs, NMBU. His co-supervisors have been Professor Egil Prestløkken, NMBU, and Professor Harald Volden, NMBU.