Phosphorus is one of those things which we can’t live with nor live without. It is essential for bone strength and growth in pigs. Unfortunately pigs are not very efficient at phosphorus digestion and absorption, hence we have to manage phosphorus nutrition very efficiently and be conscious of phosphorus excretion and the potential impact this may have on local waterways.
To answer this issue definitively the research consortium set out to establish the true phosphorus requirements of pigs. Growing and finishing pigs were offered diets formulated to contain 0.45, 0.5 or 0.6% of phosphorus. There was no effect of phosphorus level on the growth performance of pigs but pigs offered diets with low phosphorus (0.45%) had weaker legs which would lead to an increase in breakages and compromise animal welfare. When the diet containing 0.5% phosphorus was offered soluble phosphorus excretion was reduced by 50% compared to when a diet containing 0.6% was offered. These findings were adopted by the pig industry and as a result the soluble phosphorus being excreted to the environment has been halved. This reduction means that soluble phosphorus excretion is currently over 80 tonnes less per year than if this research had not been completed.
Work followed on phytase which showed that inclusion of phytase was not a simple matter of addition but many factors influence its effectiveness i.e. level of inorganic phosphorus in the diet, level of inbound organic phosphorus in the diet, form of phytase, heat stability of phytase and level of inclusion. Get any of these wrong and phosphorus excretion can increase and pig performance can be compromised.
Sam Smyth (John Thompsons), Dr Violet Beattie (Devenish) and Dr Elizabeth Magowan (AFBI) discussing how to reduce the impact of pig production on the local environment.
Early work by the consortium showed that the crude protein in diets could be reduced from 21% to 19% for pigs up to 40kg. Later work took this onto finishers and successfully dropped crude protein in the later period down to 16%. What was evident in the research was the importance of amino acid balance and the importance of knowing the transfer weights of finishers. Introducing pigs onto low protein finisher diets with an inadequate amino acid balance too early was found to be costly in terms of pig performance, nitrogen excretion and economics. However, this work showed that getting diet formulation right in the finishing period reduced nitrogen excretion by 680g of N/pig. This locally produced research data was taken to DEFRA and Brussels and resulted in the acceptance of a 25% reduction in land required for spreading pig slurry and revised Nitrates Action Plan Figures for Northern Ireland (Table 1).
| Original NAP Figures (2007) | Revised NAP Figures (2011) | |||
| Nitrogen Excretion per pig | Land required for 2000 pigs | Nitrogen Excretion per pig | Land required for 2000 pigs | |
| Finishing Pig | 2.69 kg | 31.7 Ha | 2.01 kg | 23.7 ha |
| Wean to Finish | 3.41 kg | 40.1 Ha | 2.39 kg | 28.1 ha |
Table 1 the consortium’s research changed the land requirements in the NI Nitrates Action Plan.
Nitrogen and Phosphorus are fundamental nutrients supporting pig performance. To reduce these vital nutrients with the aim of improving the environment and not impacting on pig performance or welfare requires knowledge. Get it wrong and the pig, the environment and the producer’s pocket will suffer. Get it right and everyone wins.
It is only through research that we can be confident in making radical changes in diet formulation to meet the requirement of legislation. For further guidance and advice on environmental management of pig diets, please contact Devenish, John Thompsons or AFBI.
Back to Press Releases