Hard butter is in the headlines – is the way we feed dairy cows to blame?
At the end of February 2021, the issue of hard butter started to hit the news headlines in Canada, coining the term, “buttergate.” Since then, it has gained widespread interest and concern. In this video, I address some of the background to this concern and discuss the biology of how cows make milk fat and what influences milk fatty acid composition.
The mammary gland must make a milk fat that is fluid at body temperature and has a number of mechanisms in place to handle this (short chain de novo fatty acids and desaturation of saturated to monounsaturated fatty acids). Milk fat melts over a wide temperature range, from approximately -40°F to 104°F. This is illustrated by the firmness of butter at refrigerator temperature vs. room temperature. At refrigerator temperature butter is approximately 50% solid, but is only about 20% solid at room temperature, which is why it spreads more easily as the temperature increases. Butter therefore does not have a single melting point but rather a range that is related to the melting points of the individual fatty acids that make up milk fat and their arrangement on the triglyceride molecules. These influence the texture and hardness of butter.
Many different factors can alter milk fatty acid profile, including stage of lactation, season, individual cows, nutrition, geography, and management. Palm oil and palmitic acid supplements have been fed to dairy cow for many years and provide an important source of energy and nutrients to the cow. Dietary palmitic acid is a key driver for milk fat synthesis and can result in small changes in fatty acid profile; palmitic acid content of milk general increases which is compensated for by reductions in other saturated fatty acids. However, research needs to be done to relate dietary and management changes to functional properties of milk fat, which is lacking at present. These small changes should be kept within the context of the established variations observed across farms, different diets and management practices, geographies, and seasons.