Decreasing phosphorous excretion: A nutritional approach
The animal article of the month for April is entitled ‘Quantifying the consequences of nutritional strategies aimed at decreasing phopsphorus excretion from pig populations: a modelling approach‘
Although pigs need Phosphorus in their feed in order to thrive, this can pose environmental problems. Any surplus is excreted and is likely to become agricultural runoff that can cause serious pollution of watercourses. It also represents an unnecessary cost to the farmer. How can producers ensure that they avoid feeding excess Phosphorus to their stock? Previous approaches to the problem have involved modelling nutritional needs based on the average pig within the population, with mixed results. Our team at Newcastle University’s School of Agriculture, Food and Rural Development have tried a different method, developing a tool that could have wider applications for livestock nutrition.
We developed a mathematical model that took into account the variation that may exist within a batch of pigs. This was the only way that would allow us to predict the consequences of different management solutions on Phosphorus excretion and pig performance. Two management approaches were investigated. In the first, the whole batch received the same diet, based on current evidence of how their need for Phosphorus varies during their growth, but the composition of the feeding regime changed more frequently than would normally be the case, as we were aiming to adjust the amount of Phosphorus closely with the growing and fattening pigs’ needs.
When modelling the diet of the second group of pigs, we took into account the varying size and consequent differing nutritional requirements of individuals in the batch, dividing them into “large” and “small” and providing different feeding regimes, more closely tailored to the average bodyweight of each group. For this population the composition of the feed remained constant throughout their growth.
Both approaches demonstrated reductions in Phosphorus excreted, whilst maintaining pig performance, and, more significantly, showed how a population based approach to modelling could prove more useful than one based simply on an average animal.
Our research shows that management of nutrition remains the most effective means of reducing Phosphorus excretion, but in order to do this effectively we have to be able to model the individual pig needs more closely. Changing the feeding regime is certainly an effective technique in reducing Phosphorus excretion, as we have demonstrated, although we do seem to see the law of diminishing returns operating as the number of changes is increased, and one has to question how practical this is in a commercial context. Dividing the population into the ‘large’ and ‘small’ groups also has some effect, particularly for the lighter pigs and this could be more feasible. The model is capable of predicting the consequences of other management approaches.
It may be that in the future precision farming techniques could enable a completely individualised approach to feeding pigs, but at the moment the industry has to be able to predict the consequences of management at population level, using an approach that goes beyond the ‘average’ animal and takes more variables into account. Our work has shown that this is possible and it could be applied in a range of contexts within livestock production.
Authors: V. Symeou, I. Leinonen and I. Kyriazakis
The animal Article of the Month is selected by the Editor-in-Chief and is freely available for one month