Protein digestibility: The next frontier in feed efficiency.

Research by Topigs Norsvin has shown that protein digestibility is heritable and represents a promising new trait for future inclusion in the breeding program. New findings confirm that large-scale measurement of this trait is both feasible and practical. 

A key question has been whether fecal samples need to be dried before NIRS analysis. Sample drying is a time-consuming and costly laboratory step that would limit how many animals can be screened for this trait. New research in collaboration with the University of Manitoba, provides an encouraging answer: fresh fecal samples work.  

In a study of over 300 Large White pigs, fresh samples proved a feasible alternative to dried samples for estimating how much protein a pig absorbs from the intestines. Fresh fecal samples were slightly less precise than dried samples but still identified meaningful genetic differences between pigs. Importantly, the estimates of heritability remained high, demonstrating that fresh samples are sufficiently accurate for large-scale breeding. 

This finding removes a significant practical barrier: farms and testing stations can collect fresh feces directly, without the added laboratory step of drying, making large-scale data collection for the breeding program more realistic. 

Efficient protein digestibility has far-reaching benefits across the production system. Feed accounts for up to 75% of production costs and 40–80% of climate impact in pork production, so even small improvements in how well pigs absorb protein can deliver substantial gains. These include lower feed costs, reduced need for high-protein feed ingredients such as soy and rapeseed, and greater opportunity to use locally sourced ingredients. Better protein digestibility also leads to reduced nitrogen excretion in manure, lowering nitrous oxide emissions, and contributing to a reduced environmental footprint from pork production. 

If Topigs Norsvin is able to improve protein digestibility by 2.2 percent (one genetic standard deviation), this is expected to increase the proportion of protein absorbed in the intestine. By this improvement, it is predicted that a slaughter pig will use approximately 1.3 kg less protein to reach slaughter weight. This improvement is also expected to reduce total greenhouse gas emissions by around 0.8 percent, primarily through reduced nitrous oxide emissions from housing, manure storage, and manure application. 

The improvement is also expected to reduce nitrogen excretion in manure by approximately 10.5 percent, resulting in lower nitrous oxide (N₂O) emissions during manure storage and field application. Assuming a carcass weight of 90 kg and a carbon footprint of 4 kg CO₂e per kg carcass, the calculated reduction corresponds to approximately 0.8 percent of total greenhouse gas emissions, or 2.8 kg CO₂e per slaughter pig. 

When protein digestibility increases by 2.2 percent, a larger proportion of dietary protein is absorbed and utilized by the animal. Assuming that nutrient requirements for maintenance, growth, and protein deposition are met, the protein content in feed can be reduced by approximately 5 grams per kilogram. 

This improved efficiency enables greater use of locally sourced feed ingredients, such as barley, while reducing reliance on imported protein sources like soy and rapeseed. As protein-rich raw materials are among the most expensive components of feed, this creates clear opportunities to lower feed costs.