Milk Protein Concentration

Milk Protein Concentration – How can we influence it?

We need good levels of protein in our milk as consumer taste trials have shown that higher protein levels make the milk taste better. So how can we maintain or improve our milk protein concentration? To answer this questions we need to understand what factors affect our milk protein concentration.

Milk protein percentage (%) can be affected by genetics, nutrition, environment, and management to name a few.

Genetics: Improving milk protein % by genetic strategies may take many years. However one trial has shown that the selection of a particular genetic merit can rapidly increase casein yields in milk. Cows can be blood tested to determine if they have this genetic merit (Jerseys have shown to have greater incidence of this than Friesians!).

Nutrition: Generally it is believed increasing energy intake in the lactating cows diet only directly increases milk yield not milk protein %. However there does appear to be a direct relationship between feed quality and milk protein %. Increased feed quality increases energy intake per kilo of dry matter (kgDM) consumed, and ensures there is an increase in total dry matter consumed. Starches and sugars are important in maintaining milk protein % as they promote rumen available energy and microbial protein. What we feed our cows pre-calving has a big influence on the protein yield post calving. A pre-calving diet which has a protein source added (especially in the last 2-3 weeks before calving) can improve milk protein % post calving. High levels of oil/fat (greater than 5%) in the diet can suppress milk protein %. Better body condition at calving will improve milk protein and milk fat percentage.

Environmental: Higher milk protein yields are observed during the cooler months in Autumn/Winter and early Spring. Heat stress (which we experience in the summer) can adversely affect milk protein %. The highest increases in milk protein % are related to higher rainfall (spring/autumn) as a result of more ‘young pasture’ or higher energy pasture.

Management: The quality of the feed offered to our cows is one of the most important determinants for our protein test. By maintaining good pasture quality throughout the year we can maintain better milk protein %. As pasture quality deteriorates production of milk solids falls. Feeding quality legumes (clover, lucerne) and low levels of starch based concentrates at the time when pasture quality drops off (October/November) are shown to help maintain milk protein %. Generally poorer milk protein percentages are seen on farms with big daily fluctuations in milk yield.

In summary the best means to ensure higher milk protein concentrations is by ensuring we feed our cows a high quality diet (good quality silage and pasture) 2-3 weeks pre-calving with good cow body condition at calving (5 condition score). To maintain this higher protein test once the cows have calved we need to ensure that whatever the cows are being fed is of good quality to increase the intake of energy per kgDM consumed.

Nicky Bramwell
Intelact Consultant/Director