Relationship between Protein Structural Characteristics and Supply of Metabolizable Protein to Dairy Cattle from New Cool-Season Forage Corn Varieties in Western Canada

Abstract Text:  The objective of this study was to find out the relationship between protein inherent molecular structural characteristics of cool-season forage corn and supply of metabolizable protein (MP) to dairy cattle. Six new corn cultivars, including 3 Pioneer (PNR) and 3 Hyland (HL), coded as PNR-7443R, PNR-P7213R, PNR-7535R, HL-SR06, HL-SR22, HL-BAXXOS-RR, were sown in 24 plots on in the research fields of Canada-Saskatchewan Irrigation Diversification Centre (Outlook, SK, Canada). The 24 plots were blocked within 4 fields, and all cultivars were sown in each field (4 block x6 varieties). Whole crop samples were collected after a target of 2160 CHU was achieved. The MP supply to dairy cattle, and energy synchronization properties were modeled by the DVE/OEB system and the NRC-2001 model. The parameters evaluated were protein molecular structures in terms of amide I, amide II, amide I to II ratio, α-helix, β-sheet and α-helix to β-sheet ratio, which were determined using vibrational molecular spectroscopy (VMS). The data analysis were performed using SAS with Proc Mixed and Proc Corr.  The Normality test was used Proc Univariate with Normal and Plot options. Multivariate molecular spectral analyses were performed with Statistica (StatSoft Inc., Tulsa, OK). The Tukey method was used for multi-treatment comparison. The significant level was declared at P<0.05. There were no-significant differences (P>0.05) among the cultivars in molecular-spectral intensities of protein molecular structures. The amide II had a significant positive correlation with truly absorbable rumen undegraded feed protein (ARUP) (r = 0.30; P < 0.001), and had a significant negative correlation (r = 0.18, P < 0.05) with truly absorbable endogenous CP (AECP). Whereas, both amide I and amide II, and protein secondary structures (α-helix and β-sheet) were inversely correlated with rumen available N per insoluble rumen available OM (r= ~-0.30; P < 0.001). In summary, protein molecular structure in the new cool-season corn varieties significantly link to the supply of metabolizable protein to dairy cattle.

Keywords: Corn varieties, supply of metabolizable protein, protein molecular structures