EFFECT OF GENOTYPES, TANNIN LEVEL AND PROCESSING METHODS ON THE PHYSICOCHEMICAL, NUTRITIONAL AND STRUCTURAL CHARACTERISTICS OF FABA BEAN GROWN IN WESTERN CANADA

Abstract

The general objective of this study was to determine the effect of genotypes, tannin levels (low and normal) and heat processing methods on the structural, physicochemical, and nutritional characteristics of faba bean grown in western Canada as an alternative protein and energy source for ruminants. The faba bean used for this research were grown in three different locations in Saskatchewan and included three low tannin types: Snowbird, CDC Snowdrop, CDC 219_16 and five normal tannin types: CDC Fatima, Vertigo, 346_10, FB9_4, and CDC SSNS_1. Chemical analyses, energy parameters, rumen degradation kinetics, intestinal digestion and FTIR molecular spectroscopic analyses were presented in this research. Statistical analyses were performed using the MIXED procedure model of SAS 9.4 with RCBD in Study 1 (genotypes as a fixed effect and locations as a random block effect). CRD was used in Study 2 (with 2 x 3 factorial design including two tannin levels and three treatments (Control, Steam Pressure and Microwave Irradiation). Significance in all studies was declared at P < 0.05 with tendency at P ≤ 0.10. In Study 1, the results of chemical profiles showed no significant differences in total protein (CP) and total carbohydrates (CHO) contents among genotypes. Low tannin types of faba bean (LT) showed higher (P < 0.05) soluble crude protein (SCP), rumen bypass starch (BSt), intestinal digestibility of rumen bypass protein (dIDP) compared to normal tannin (NT). On the other hand, normal tannin types had greater organic matter (OM), lignin (ADL), slowly degradable protein fraction (PB2), and total tract digested starch (TDST) compared to low tannin. No significant difference (P > 0.10) was observed on total digestible nutrients (TDN1x), metabolizable protein (MP), rumen degraded protein balance (DPB), feed milk value (FMV), and rumen undegraded crude protein (RUP). In Study 2 (Heat Processing), Steam Pressure (SP) and Microwave Irradiation (MI) increased (P < 0.05) the indigestible crude protein (PC) and decreased the rapidly degradable CHO fraction (CA4), indigestible fiber fraction (CC), and undigestible neutral detergent fiber (uNDF288h). Steam Pressure reduced (P < 0.05) the digestibility of bypass starch (dBST) and total digested starch (% TDST) and increased (P < 0.05) the intestinal digested crude protein (IADP) compared to the Control and Microwave Irradiation. The metabolizable protein (MP), truly digested protein in the small intestine (DVE), and feed milk value (FMV) were higher with Steam Pressure treatment. In Study 3, a higher absorbance in normal tannin genotypes for amide I and amide II peak height and area, structural CHO (STCHO), total CHO (TCHO) area and peaks (H_1015, H_1076, H_1145) and cellulosic compounds (CEC) to total CHO (TCHO) ratio. Amide I area and α-helix absorbance were not different among low tannin genotypes; however, higher ratios for α-helix to β-sheet height and CEC to STCHO were observed. Related to heat-induced changes, Steam Pressure treatment in low tannin genotypes increased (P < 0.05) the absorbance in amide I and amide II areas and α-helix peak height. Steam Pressure treatment also increased (P < 0.05) the absorbance in amide I and amide II area, the absorbance in the structural CHO (STCHO) area, cellulosic compounds (CEC) area and peak height (H_1235), CEC: TCHO ratio, and CEC: STCHO ratio and decreased the absorbance of all parameters related to total CHO (TCHO) spectral profiles. On the other hand, Microwave Irradiation increased (P < 0.05) the absorbance of all parameters related to total CHO spectral profiles, it reduced (P < 0.05) the absorbance in STCHO: TCHO ratio and showed similar results to Control in the rest of spectral parameters. In general, based on the available data in this research both low and normal tannin types grown in western Canada could be a suitable protein and energy source ingredient to combine with other common feedstuffs in diet formulations for ruminants.