Although the ban on using processed animal protein in pig diets has now been lifted, the historical ban lead to the use of soybean products as the key protein source in pig diets. In Europe, domestic production of soya is minimal and so most soya is imported from Brazil and Argentina. As a result the environmental footprint of pig diets are high due to the high percentage of imported ingredients, land use change associated with soya production and local gas emissions. Yet, alternative protein sources exist in the domestic market (Beans, peas, rapeseed etc), so why are these products not as widely adopted?
Following on from the last study Trabue et al. (2021) investigated various protein sources to see if there was any environmental or performance related impacts. In this trial, the protein level (17.6%) remained equal across all treatments along with SID Lysine levels (0.85). The control diet used soyabean meal as the protein source, while the three treatment diets used maize gluten, canola meal or poultry meal as the protein source.
Table 1: Animal performance for 45-d feeding trial of pigs fed maize-based diets with different sources of dietary protein
| Protein Source | Soyabean Meal | Maize Gluten Meal | Canola Meal | Poultry Meal | SEM | P-Value |
| Average Weight | 112.1 | 117.5 | 114.3 | 114.1 | 2.10 | 0.47 |
| ADFI (Kg d-1) | 2.79 | 2.79 | 2.80 | 2.69 | 0.03 | 0.24 |
| ADG (Kg d-1) | 0.74 | 0.76 | 0.77 | 0.67 | 0.02 | 0.37 |
| Gain:Feed (Kg:Kg) | 0.27 | 0.27 | 0.25 | 0.25 | 0.01 | 0.74 |
“Pig performance was similar when diets containing soya or non-soya were offered”
Elizabeth Magowan, AFBI (Scottish Farmer, 2017)
Despite the alternative proteins providing lower levels of SID Isoleucine, Threonine, Tryptophan and Valine, the performance across all treatments did not differ significantly. Thus, altering the protein source of pig diets appears to have no detrimental impact on animal performance. Similar results have been found by other research institutes such as AFBI, AHDB and Teagasc. Environmentally, there were also limited differences on the concentration of ammonia in manure and air samples.
If there is no benefit what’s the point in changing?
Despite having no benefit to performance or domestic emissions, changing pig diets from soyabean meal to a locally produced protein source can still provide environmental benefits. Reducing reliance on soyabean reduces the volume needing to be imported into Ireland and the UK. As a result, Irish and UK pork can be produced with a lower carbon footprint than other countries which may provide a competitive edge to locally produced pork. For the producer, imported soya is expensive so by switching to a locally produced protein diet costs can be reduced. This may also become more favourable as most retailers requiring producers to use sustainably produced soya only – a similar approach to the palm oil certification may be used which will increase administrative costs for soya production.
The Hidden Benefit
Another study published this year into protein sources (Soyabean vs Peas/Rapeseed) in pig diets focused on the meat quality and health-promoting indicators (Sonta et al., 2021). Similar to Trabue, there were no differences in animal performance and meat quality was similar with a slight increase in protein content of the pea/rapeseed fed pork compared to soyabean meal.
The pea/rapeseed pork was shown to have improved dietary value. High levels of saturated fats measured through the degree of saturation in meat products is linked to an increased risk of coronary heart disease; the experimental pigs produced pork with a lower degree of saturation due to reduced SFA content. Furthermore, the content of Polyunsaturated fats, known to prevent coronary heart disease, were increased in these pork products.
By adopting a different protein source, the pig sector can produce pork that has a lower environmental footprint, supports the local rural economy and aids the improvement of food security by providing a source of pork that has a higher dietary value.
References
SCOTTISH FARMER. 2017. Pig and Poultry Thrive of Rapeseed Meal. Available at: Pig and poultry thrive of rapeseed meal | The Scottish Farmer [Accessed 15/11/21]
SONTA, M., REKIEL, A., WIECEK, J., BATORSKA, M. & PUPPEL, K. 2021. Alternative Protein Sources vs. GM Soybean Meal as Feedstuff for Pigs-Meat Quality and Health-Promoting Indicators. Animals (Basel), 11.
TRABUE, S. L., KERR, B. J., SCOGGIN, K. D., ANDERSEN, D. & VAN WEELDEN, M. 2021. Swine diets impact manure characteristics and gas emissions: Part II protein source. Science of The Total Environment, 763, 144207.