3 August 2001

How to predict effect of intakes on milk quality

By Jessica Buss

KNOWING what milk quality changes will result from a dairy cow ration will be a useful weapon in the armoury of producers seeking to meet a variety of contract requirements.

UK rationing systems calculate a diet for cows giving a specified milk quantity and quality at least cost, but cant really predict what milk composition will result, says Nick Offer, of SAC Auchincruive. "These programmes give no clue how milk composition will alter when an ingredient is changed."

But as part of the LINK-funded Feed into Milk project, Dr Offer has been working on producing a number of decision support systems including one for milk composition prediction. The project will launch a new rationing system for the UK this autumn.

He developed the computer-based decision support model using information on a number of research projects which show how different diets influence milk output and quality.

The model reviews the diet and calculates scores for both fat and protein yield and percentage. This prediction is based on the intake and level of protein, starch, sugar, neutral detergent fibre (NDF) and oil in the diet.

It must also take into account the type of fat, says Dr Offer.

The model will accurately predict the difference in milk composition resulting from different diets fed to a group of cows.

As a result, it will be possible to immediately predict the change in fat % and protein % by replacing barley with beet pulp in a dairy cow ration. This will help answer important questions, such as whether a particular ingredient change will increase milk fat %.

Predict changes

"An experienced feed adviser may be able to predict these changes when reviewing a ration, but with the decision support model everyone can benefit and it is more scientific."

However, Dr Offer says that while scores given are based on constituent yield in kg and percentages, cow factors on farm and genetics will also have an effect on milk quality.

"Cows fed the same diet on different farms will perform differently because of these factors."

The model also reveals that small changes in diets, such as replacing a byproduct with 1kg of wheat, will often only have a small effect on milk quality, says Dr Offer.

"The only big changes possible through a small diet addition are in milk fat %, which can fall by up to 1% when feeding a fat source such as fish oil."

This decision support system will be widely available to producers within a few months. With most of the UK dairy cow feed industry co-sponsoring the Feed into Milk project, alongside DEFRA and MDC, it is likely to be incorporated in the rationing programmes used by most feed advisers, he says.

FEED INTO MILK