Energy, protein, and amino acid digestibility of mid- and zero-tannin faba bean differing in vicine and covicine content fed to growing pigs

Abstract

Novel faba bean cultivars vary in nutrient content, digestibility and antinutritional factors that must be characterized to realize predictable growth performance in growing pigs. Therefore, four diets including 950 g faba bean/kg of either one of two zero-tannin cultivars (Snowbird, Snowdrop; both with vicine and covicine) or one of two mid-tannin cultivars (Fabelle, low vicine and covicine; Florent, high vicine and covicine) were fed to eight ileal-cannulated barrows (37.5 kg) for four 9-day periods to establish energy and nutrient digestibility. A nitrogen-free diet was fed to correct for basal endogenous losses of protein and amino acids. Mid-tannin cultivars had double the tannin content of zero-tannin cultivars (14.0 vs. 6.9 g/kg as is). Fabelle had the least vicine (0.6 g/kg) and covicine (0.4 g/kg) whereas zero-tannin cultivars contained the most vicine (6.8 g/kg) and covicine (3.4 g/kg). Starch ranged from 329 to 356 g/kg in faba bean cultivars. Resistant starch ranged from 124 to 150 g/kg. Crude protein (CP) ranged from 247 to 293 g/kg. Total dietary fibre ranged from 157 to 163 g/kg and was 96 % insoluble. The coefficient of apparent total tract digestibility of dry matter and gross energy were greatest (P < 0.05) for Snowbird and Snowdrop, intermediate for Fabelle and lowest for Florent. The coefficient of apparent ileal digestibility of starch was greater (P < 0.05) for zero- than mid-tannin cultivars. Diet and cultivar digestible energy values were greatest (P < 0.05) for Snowbird, intermediate for Fabelle and lowest for Florent; Snowdrop was not different from the latter two. Diet and cultivar net energy values were greater (P < 0.05) for Snowbird but not different among Snowdrop, Fabelle or Florent. The coefficients of standardised ileal digestibility (CSID) of CP, lysine, threonine, and methionine were generally greater (P < 0.05) for Snowbird, Snowdrop or Fabelle than Florent. The CSID of tryptophan was greater (P < 0.05) for Fabelle than Snowbird, Snowdrop or Florent. In conclusion, Florent with mid-tannin and vicine and covicine content, had lower energy, protein and amino acid digestibility than zero-tannin cultivars. Fabelle with mid-tannin but least vicine and convicine content, was intermediate in energy but not different in protein or amino acid digestibility than zero-tannin cultivars. Cultivar variation in content of macronutrients including total and resistant starch, protein and dietary fibre contributed to differences in energy, protein and amino acid digestibility that should be considered in diet formulation.