Protein quality, digestibility differ among pulses

By Swine Innovation Porc

Editor’s note: This article is a project summary prepared for Swine Innovation Porc, as part of a series of articles covering SIP’s work. For more information, contact ‘’

Selection of Canadian pulse varieties tested to determine protein quality and digestibility for Canadian pigs.

Given ever-rising feed costs and the volume required on-farm, especially for growing and finishing pigs, scientists are investigating new options to diversify the ingredient supply and methods for getting the most from nutrients in pig diets. To give producers the greatest return on their investment, those ingredients must be high-quality and able to maximize pig performance.  

As part of Swine Innovation Porc’s (SIP) Cluster 3 research activities, Kate Shoveller from the University of Guelph worked with a PhD student, Cara Cargo-Froom, and Dan Columbus at Prairie Swine Centre to characterize the nutrient content of Canadian-grown pulses for inclusion in swine diets, including two varieties of field peas, as well as lentils, chickpeas and faba beans.

Assessing protein quality and digestibility

Table 1: Comparing the protein quality and digestibility of the pulses tested.

To evaluate the overall quality of protein-dense feed elements, a digestible indispensable amino acid score (DIAAS) was created for each ingredient, which uses amino acid digestibilities measured at the end of the small intestine to provide an accurate measure of the amounts of amino acids absorbed by the body (Table 1). The higher the DIAAS score, the greater the protein quality of an ingredient. The project also measured the digestibility of amino acids in the tested ingredients. Since pigs are unable to synthesize all amino acids required for optimal performance, feed plays a key role. 

The researchers also aimed to understand how pelleting and extrusion under different conditions affect the nutrient content of the ingredients. Pelleting is the process of converting finely ground mash feed into dense, free-flowing pellets. Pelleting a diet makes it easier to handle feed and helps reduce feed waste, while supporting optimal performance. Research has demonstrated that pelleted feed supports a roughly seven per cent increase in feed efficiency. Extrusion, which involves applying heat, moisture, and pressure to an ingredient, can improve energy and protein digestibility for pigs, and the heat treatment increases the storage life of pulses by reducing water content. 

Overall, however, there were no extreme detrimental effects of processing on nutrient content of the pulses, specifically in relation to protein and amino acid content.

Though it was not part of the official study, researchers also observed the pigs’ eating behaviours. They noted that while every pig consumed all of the diets provided, there was a clear preference, based on the enthusiasm with which they ate. Pea and faba bean diets seemed to be more popular than lentil options.

Initial results provide much to consider

Although scientists can now make some credible assumptions about changes in nutrients across pulses or within a pulse category, there is more work to be done. A better understanding of how processing can affect each category of pulse – and the varieties within the category – can provide much needed insight on the specific varieties of interest.

For nutritionists and producers, these results may help inform their choices on alternative feed ingredients. Additionally, different processes, such as extrusion, can be considered to improve nutrient digestibility and availability.