Investigation of the Role of Amide I to Amide II Ratio and Alpha Helix to Beta Sheet Ratio of Faba Bean Seeds in the Determination of Microbial Protein Synthesis and Animal Performance and Metabolism in Ruminant Livestock Systems.

The food and feed industries have benefited from the application of Infrared Spectroscopy as spectral features have been associated with nutrient quality and degradation characteristics. To our knowledge, the effects of steam pressure toasting (SPT) duration on spectral features of Faba bean seeds (FBS) have not been previously evaluated, and the influence of amide I to amide II ratio, and α-helix to β-sheet ratio (α_β) on the protein quality (solubility and digestibility), metabolism, and bioavailability in dairy cows has not been established. Thus, the objective of this research was to evaluate the role of the protein-related spectral ratios on the nutrient quality and protein metabolism of FBS in high lactating dairy cows through the application of laboratory and spectroscopic analysis, feed evaluation models (CNCPS, NRC2001, DVE), in situ nylon bag incubation, and in vitro batch culture techniques. Data were analyzed with Procedure MIXED of SAS 9.4 software using a RCBD model with the significance declared at P 0.05). The fat yield (kg/cow/day) tended to be lower with TMR_15 and TMR_30 compared to the other treatments (linear P = 0.05), milk urea nitrogen (MUN) was reduced from 12.2 to 11.1 mg/dl with TMR_0 to TMR_30, respectively (P < 0.01). The fat corrected milk (FCM3.5%) and energy corrected milk (ECM) tended to be slightly increased with TMR_7.5 than TMR_0 (P = 0.07, P = 0.08, respectively). Both parameters had a tendency to be reduced with TMR_15 and TMR_30 compared to the other treatments (P = 0.07, P = 0.08, ii respectively). Moreover, the actual milk yield, averaged pH, averaged NH3, and total VFA’s concentration were not significantly different among the dietary treatments (P > 0.05) with corresponding values reaching 39 kg/cow/day, 6.32, 102.7 mg/L, and 76.7 mmol/L, respectively. The feed efficiency (ECM/DMI) was reduced with TMR_15 and TMR_30 compared to TMR_0 (linear P = 0.02). In the rumen simulation technique (RUSITEC), CP disappearance decreased (linear P < 0.01) from TMR_0 to TMR_30, and the total microbial nitrogen (MN) increased (quadratic P = 0.03) from TMR_0 to TMR_15 (73.5 to 88.4 mg/day, respectively). In the present study, the application of mid-Infrared molecular analysis was helpful to determine changes in the protein molecular structures of FBS induced by SPT duration. Hence, the peak heights of α-helix, β-sheet, and the area ratio of amide I to amide II found in the present study were increased over SPT duration in the endosperm of FBS determined with Synchrotron radiation-based Infrared (IR) micro-spectroscopy (SR-IMS). Moreover, the areas of total amide, amide I, and amide II and the peak heights of α-helix and β-sheet were reduced over SPT duration when a mixture of the FBS’ pericarp, seed coat, aleurone cell, and endosperm was analyzed using Attenuated total reflectance- Fourier transformed IR spectroscopy (ATR-FTIR). A decreased ratio of α_β in FBS was found with increasing SPT duration with both SR-IMS and ATR-FTIR techniques. Additionally, SPT at 121 °C was effective to reduce protein and starch degradability in the rumen with different responses observed with different SPT duration in FBS among the treatments. The truly digested protein in the small intestine (DVE-MP) increased with SPT. Cows fed TMR’s with 10% inclusion of raw FBS yielded 39.1 and 43.9 kg/cow/day of milk and FCM, respectively, with 3.90% fat, 2.98% protein, and 4.55% lactose contents in the milk. Cows fed TMR’s with 10% inclusion of steam-pressure toasted FBS for 7.5 min yielded 39.9 and 44.4 kg/cow/day of milk and FCM, respectively, with 3.95% fat, 2.97% protein, and 4.53% lactose contents in the milk. Finally, cows fed TMR’s with 10% inclusion of steam-pressure toasted FBS for 15 and 30 min yielded on average 39.4 and 41.2 kg/cow/day of milk and FCM, respectively, with 3.79% fat, 2.98% protein, and 4.56% lactose contents in the milk. The optimal processing, time, and level of inclusion should be considered when FBS are used in combination with more traditional sources of protein and starch to improve the production performance of high lactating dairy cows