Effect of thermal processing methods on structural, physicochemical and nutritional characteristics of cool-season chickpeas in ruminant systems

The focus of this study was to evaluate the effect of thermal processing methods: Dry Heat, Wet Heat (Autoclave) and Microwave Irradiation on newly developed cool-season adapted CDC chickpeas as an alternative source for protein and energy for ruminant. Three varieties of chickpeas, developed and provided by the Crop Development Center (CDC), were CDC Alma, CDC Cory, and CDC Frontier. All varieties were grown in three different locations in Saskatchewan: Elorse, Limerick, and Lucky Lake. For dry heat related processing, the samples were placed in the oven at 100 °C for 60 min. For wet heat related processing (Autoclave), the samples were placed in the autoclave at 120 °C for 60 min. For microwave irradiation, the samples were microwaved for 3 min (900 W). The results showed that soluble crude protein (SCP) and non-fiber carbohydrate (NFC) were highly decreased by autoclave treatment. Moderately degradable protein fraction (PB1) was greater in autoclave treatment. There was no significant difference in indigestible protein fractions (PC) among all heat processing methods. Autoclave treatment was lower in rapidly degradable carbohydrate fractions (CA4) but greater in slowly degradable carbohydrate fraction (CB3). As to energy value parameters, there were different in total digestible nutrients (TDN) value among processing treatments with greater value in dry heat and microwave treatments. However, there was no difference in net energy for lactation (NE_L3X) among processing treatments. In rumen degradation kinetics, there were no differences in DM rumen degradation kinetics among processing treatments. However, the heat processing affected in situ potential degradable fraction (D) and undegraded fraction (U) of protein. Autoclaving treatment had greater in situ potential degradable fraction but lower undegraded fraction. The processing did not significantly affect rumen bypass protein (BCP) or rumen undegradable protein (RUP) and effective degradation protein (EDCP). For protein intestinal digestion, heat treatments did not affect intestinal digestibility of rumen bypass protein (%dIDP) and intestinal digested crude protein (IDP). For DM intestinal digestion, heat treatments affected digestibility of rumen bypass DM (%dBDM) with greater values in dry heat (90.3%) and microwave (86.5%) and lower value in autoclaving (67.7%). However, total (IDBDM) and intestinal digested dry matter (TDDM) were not significantly affected by processing treatments. For hourly effective degradable ratios (ED_N to ED_DM), microwave showed a greater value. Total true protein supply (DVE value) was not significantly different among processing treatments with average of DVE value of 100 g/kg DM. All three processing methods (dry heating, wet heating, microwave irradiation) had positive degraded protein balance (OEB value) with average of 62 g/kg DM, indicating potential shortage of energy in rumen. Feed Milk Value based DVE value showed no difference among processing treatments. When applied NRC dairy, the results showed that the processing methods also did not significantly affect total Metabolizable Protein supply (MP) to dairy cows with average MP of 82 g/kg DM. But based on NRC model, all treatments had negative degraded protein balance (DPB value) which is different from DVE/OEB system. In conclusion, the response and sensitivity to thermal processing methods of CDC chickpeas showed difference. But important nutrient supply to dairy cows in terms of NE_L3x, DVE, MP, OEB, and FMV were not significantly different among processing treatments.