Feeding frost-damaged or non-frost-damaged, hulled or dehulled, mid- or low-tannin faba bean on diet nutrient digestibility and growth performance of weaned pigs.

In cool climates with a short cropping season, faba bean production can be affected by frost. Crop fall frost damage is not uniform, causing blackening in the upper part of the plant. Naturally occurring tannins in faba bean, concentrated on the outer hull, confer field frost tolerance but may reduce starch and protein digestibility. The quality of frost-damaged faba bean may be improved by optical color sorting to segregate blackened beans and dehulling to remove the hull tannins. Therefore, a frost-damaged low-tannin cultivar (Snowbird) was color-sorted into frost-damaged (blackened-colored) and non-frost-damaged (tan-colored). A mid-tannin cultivar (Florent) that was not frost-damaged served as control. One-half of each cultivar sample was dehulled. In a randomized complete block design, 240 pigs (8.9 ± 1.2 kg) housed 4 per pen were fed 1 of 6 diets: (1) Snowbird, (2) dehulled Snowbird, (3) frost-damaged Snowbird, (4) dehulled, frost-damaged Snowbird, (5) Florent, or (6) dehulled Florent. Diets including 20% in phase 1 and 30% faba bean in phase 2 were fed over two 14-day (d) growth phases. Individual pigs, feed added to pen feeders, and non-consumed orts were weighed weekly. Pen fecal grab samples were collected on d 12, 13, 26 and 27. Tannin content averaged 0.74% in Snowbird and 1.02% in Florent. Color sorting separated >80% of beans blackened by frost with a 12% lighter specific weight than non-frost-damaged, tan-colored beans. Feeding diets including frost- vs. non-frost-damaged Snowbird did not reduce the apparent total tract digestibility (ATTD) of dry matter (DM), gross energy (GE) and crude protein (CP) or digestible energy (DE) and predicted net energy (NE) values or growth performance in weaned pigs. Regardless of dehulling, feeding diets including low- vs. mid-tannin faba bean increased (P < 0.005) the ATTD of DM, GE and CP for both phases by an average 2.1%. Feeding diets including dehulled vs. hulled beans increased (P < 0.05) the ATTD of DM, GE and DE and NE values for both phases by an average 2.5%. Feeding diets including mid- vs. low-tannin or dehulled vs. hulled faba bean increased (P < 0.05) overall gain-to-feed (G: F) ratio by an average 2.0%. In conclusion, feeding diets including frost-damaged Snowbird did not reduce diet nutrient digestibility or growth performance in weaned pigs. Regardless of cultivar or frost damage, dehulling faba bean increased diet nutrient digestibility and overall trial G: F ratio.