September 2014: Information on the label isn’t enough

When it comes deciding between two pig diets, the information on the label isn’t quite enough to make an informed decision. Two diets may look very similar from the label, and it’s tempting to let price be the determining factor, but this may not be best and I would advise getting help from a trusted salesman or nutritionist.

I say this because, by law, only certain characteristics need to be declared. These are based around the “proximate analysis” of the feed; an analysis first developed in Germany in 1860. This gives us an indication of moisture, crude oil, crude protein, crude fibre and ash – otherwise known as MOPFA. Furthermore, the label also tells us total lysine, total methionine, sodium, calcium and phosphorus levels.

Understanding the relationships between these declarations will, in part, indicate the suitability of that diet for a certain class of pig. Higher oil, protein, lysine and lower fibre would tend to suggest that the diet is aimed at a younger and more digestively sensitive animal.

Lower oil, protein and lysine would suggest more a finishing pig or dry sow diet. The key message here is that these components “suggest” the class of animal the diet was designed for, but we have to rely on the advice of the salesman or nutritionist to confirm this, as the reality is considerably more complicated.

The MOPFA levels are from a very basic analysis. The result is reported as a number that is a useful tool for the likes of Trading Standards to audit feed manufacturers. MOPFA still forms the basis of this testing.

But protein and lysine declarations tell us only part of the story of the feed. Nutritionally, what we need to know is how much of this protein or lysine is actually digestible and available for use in all metabolic processes such as growth, immunity and reproduction. This is not something that’s legally declarable on a label, but it’s vital for efficient pig performance.

The same can be said for fibre levels. Crude fibre analysis is derived by taking a sample of the feed, treating it sequentially with ether, acid and then alkali to obtain a “crude fibre” number.

However, the actual fibre and types of fibre in feed is considerably more complicated and have profound impacts on performance and behaviour. We’ve all the plant cell wall components to consider – such as lignin, cellulose and hemicellulose – and these can be found as neutral detergent fibre, acid detergent fibre and acid detergent lignin – none of which needs to be declared on a label.

So, for the time being we’re reliant on the crude analysis information that’s legally required on a label declaration to compare feeds. Until we’ve further detailed information available on the diets, we must complement the label detail with advice from the supplier or nutritionist that the ration suggested will meet the demands of the pig and producer respectively.

> Born in Essex, schooled in Suffolk and a graduate of Reading University, Dr Phil Baynes has spent his career in pig welfare and nutrition. Now based in Cheshire, he runs Baynes Nutrition and is a consultant nutritionist to Provimi

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