Pig production has reduced ammonia emissions by 45% per pig place, AFBI research finds

Date published: 11 August 2026

Pig production in Northern Ireland has reduced ammonia emissions by 45% per pig place over the last two decades through the adoption of lower protein diets, research from the Agri-Food and Biosciences Institute (AFBI) has found.

Dr Elizabeth Ball, from AFBI’s Monogastric Research Group, told a recent pig research seminar at AFBI Hillsborough that targeted nutrition and improved pig efficiency had helped cut emissions.

Modern pigs, housed in modern finishing houses and being fed modern diets, emit significantly less ammonia per pig place per year than they did 20 years ago.

Pigs previously emitted 2.8kg of ammonia per pig place, according to the UK Ammonia Inventory. Pigs on lower protein diets now emit 1.55kg of ammonia per pig place.

This new figure has been accepted by the UK Ammonia Inventory and Northern Ireland Environment Agency (NIEA), which helps farmers operate within the confines of environmental legislation.

Nitrogen excretions have also reduced by more than 36% - from 12.6kg per pig place before 2010 to 8kg per pig place according to the most recent figures.

Dr Ball said environmental improvements have been achieved by a reduction in the amount of protein in pigs’ diets. AFBI work has shown that for every 1% drop in dietary protein, nitrogen excretion reduces by up to 10%.

The percentage of protein in diets for finishing pigs has been reduced from 19% to 15% in recent years, lowering the amount of nitrogen excreted per pig and reducing ammonia emissions from production.

“This significant reduction has been mainly achieved through the adoption of lower protein diets coupled with advancements in genetics,” Dr Ball said.

“Confidence to reduce the protein of the diets has been underpinned by the scientific work, and industry collaborations, undertaken by AFBI.

“The pig industry has led the way in addressing environmental challenges and has adopted scientific solutions put forward by AFBI in collaboration with the Pig Research Consortium with Devenish Nutrition Ltd, John Thompson and Sons and Preferred Capital Management.”

Dr Ball said scientific trials at AFBI and on commercial farms have shown that pig performance can be maintained on lower protein diets if they are carefully formulated with amino acids to prevent any impairment in growth rate and efficiency.

She said if a pig is not given enough protein and amino acids, its performance will be negatively affected, and excretion of environmental pollutants will increase.              

The seminar also heard details of a large-scale AFBI study to further assess performance of pigs on very low protein diets.

The study found it would be beneficial to house boars and gilts separately and offer them different diets to further reduce nitrogen excretion while maintaining performance.

In the AFBI trial, boars and gilts were fed two different diets, one with 15% protein and the other with 13% protein.

The 13% diet also contained a lower level of lysine (0.9%) and other essential amino acids to test whether this affected pig performance.

Regardless of the dietary protein content, boars significantly outperformed gilts in growth rate and feed conversion efficiency due to their higher genetic capacity to lay down lean growth as expected.

However, boars given the lower protein/lysine diet grew significantly slower and were less efficient than boars offered the higher protein/lysine diet.

There was no difference in the performance of gilts given either 15% or 13% protein diets.

Dr Ball said: “The reduction in dietary protein offered to gilts, while maintaining their performance, resulted in nearly 20% reduction in nitrogen excretion per pig due to their lower nitrogen intake. This figure is in addition to the environmental gains already achieved.

“AFBI has shown that substantial reductions in nitrogen and ammonia excretion can be achieved through the use of targeted protein nutrition, with further reductions possible through careful diet formulation and strategic pig management.”

All of the above research was funded by the Department of Agriculture, Environment and Rural Affairs (DAERA) with contributions from the Pig Research Consortium with Devenish Nutrition Ltd, John Thompson and Sons and Preferred Capital Management.