Making pigmeat carbon-neutral with Irish protein

Last week the Irish Farmers Journal brought you the news story that Irish protein can reduce the carbon footprint of pigmeat by 30% without affecting performance.

This wasn’t as simple as it sounds, as anti-nutritional factors in beans can vary from year-to-year and result in a decrease in pig performance, but this article provides more background to the findings which Peadar Lawlor of Teagasc described at an Adesco conference last week.

One thing that was abundantly clear at the conference was the acknowledgement that the sector can no longer be dependent on soya as a protein source and if the amount of soya used declined it could significantly reduce the carbon footprint of pigmeat.

Some in the audience stated the sector could become carbon neutral through the use of solar panels and other measures.

However, it is important to remember that soya will not be replaced on all pig farms across the country, but there are opportunities to create sustainable brands. Approximately 7000,000t of soya was imported into Ireland in 2020 and the majority of this was used in pig and poultry feed according to Peadar. A large amount of soya imported into Ireland comes from Argentina and is produced on deforested land and so carries a high carbon footprint.

Anti-nutritional factors

Many tillage farmers will have heard about anti-nutritional factors in beans, such as tannins. Others have vicine and covicine anti-nutritional compounds and there are some varieties, like Victus, which have lower levels of these substances.

From listening to Peadar it appears these anti-nutritional factors are not the problem they once were.

A large proportion of anti-nutritional factors are in the pod for starters, and so having the combine set properly and delivering clean beans can take out a significant amount. Improvements in varieties have taken out more.

Field beans

30% reduction in carbon footprint

Peadar described an experiment carried out in 2016. The beans in this case were rolled and treated with propionic acid. Diets were formulated after chemical analysis of the ingredients and were formulated to 8.9 MJ NE and 8.9g SID Lys/kg. Animals had ad-lib access to feed.

Some of the beans were raw and some were extruded. Irish beans had an inclusion rate of 40% in a cereal bean mix and were compared with a cereal soya bean mix. There was no significant difference between diets when looking at average daily gain, intake or feed conversion ratios. Feed intake increased on the native-beans diet. There was also little difference in carcase weights or kill-out percentages.

Work from Shane Maher in UCD placed the carbon footprint of the pigs on the native protein diet at 1.53kg CO2eq/kg gain, 30% lower than those on the soya-based diet which had a carbon footprint of 2.2kg CO2eq/kg gain. There was little difference between the raw and extruded beans.

From this experiment Peadar concluded that field beans could replace soya bean meal in grower-finisher pig diets. However, more work was needed.

Performance reduction

In a second experiment, the anti-nutritional factors of beans appeared to have more of an impact. The beans from the 2020 harvest were fed dry and were not treated as a result. The carcase weight was lower in pigs fed native protein when compared to the soya bean-based diet.

Variety seemed to play a role in this study too, as Lynx beans had a much poorer feed efficiency than Victus. Victus has low anti-nutritional factors (low vicine and covicine).

This experiment also raised the question if the propionic acid had an impact on performance as it was included in the first study and not this one.

Drying and treatment of beans

A further experiment examined the impact of propionic acid and enzymes on pig performance when using beans. It should be noted that the beans were low in moisture and so a low level of treatment was needed on the beans, and for this reason Peadar described them as conditioned beans.

Feed conversion was similar between dried and treated beans, but the carcase weight was 2.3kg lower in the pigs fed acid-conditioned beans. It was also lower in pigs fed beans treated with an enzyme compared to those without an enzyme.

Upper limit on beans inclusion

In conclusion Peadar said an upper limit on inclusion is needed for beans due to anti-nutritional factors. He suggested this might be 25-30%. However, this limit may be increased if anti-nutritional factors are low or varieties with low anti-nutritional factors are used. He said to completely replace soya in the diet the following is needed:

However, a proportion of the soya in the diet could also be replaced with Irish beans to reduce the carbon footprint.

Irish bean production

In 2022, approximately 10,270ha of beans were grown in Ireland at an estimated average yield of 6.1t/ha. That equates to 62,647t. By 2027, the target is to have 20,000ha of protein grown in the country, equating to about 100,000t. Increased protein payments are being paid to encourage farmers to grow the crop. The majority of the protein crop area is made up of spring beans.