Physiochemical, Nutritional, Molecular Structural Characterization and Dairy Cow Feeding Value of Oat Grain in Comparison with Barley Grain: Impact of Varieties and Processing Methods

Abstract

The general objectives of this study were to determine the impact of varieties and processing methods on the physiochemical, nutritional and molecular structural characteristics of CDC oat grain, as an alternative to barley grain in dairy cows diets. In the first study, three CDC varieties of oat, CDC Nasser (feed type), CDC Arborg and CDC Ruffian (milling type), were used and compared to CDC Austenson barley grain (feed type). In the second study, commercial oat and barley were tested, the oat was processed using three different methods (dry-rolling, steam-flaking, and pelleting) while barley was dry-rolled. In studies 1 and 2, the chemical profile, energy value, rumen degradation kinetics of nutrients, hourly effective rumen degradation ratios/potential N-to-energy synchronization, and intestinal digestion of nutrients were analyzed, the truly absorbed protein supply to dairy cattle and feed milk values were evaluated using on the DVE/OEB system and the NRC Dairy model, and the protein molecular spectra were analyzed. In study 3, the samples from different processing methods were used in a dairy trial, to evaluate production and milk composition as well as metabolic parameters, such as blood BHBA and urea. In study 1, CDC Nasser showed significantly higher percentage of EE in relation to the other varieties of oat. Degradation of starch and CP in the rumen was higher for all varieties of oat when compared to barley. On the other hand, starch, sugar, and NFC content were higher for CDC Austenson barley grain, that also showed the highest bypass CP and starch. No significant difference was observed between CDC Nasser and CDC Austenson barley on total digestible nutrients (TDN1x), net energy for lactation (NEL) and intestinal digestibility of bypass CP (dBCP). In study 2, heat processing (steam-flaking and pelleting) increased EE (P<0.01) and tended to decrease uNDF (P=0.09). Steam-flaking increased (P=0.04) the total digestible nutrients (TDN1x), ME, and NEL and increased (P<0.01) rumen bypass CP (%BCP). Rolled barley showed the lowest (P=0.03) metabolizable protein (MP) and degradable protein balance (DPB) (P<0.01) among the studied treatments. Processing methods did not significantly change the protein molecular structure of the oat treatments, making the protein related structures hard to separate using PCA or HCLA. In the third study, cows fed dry-rolled oat had the lowest DMI, while increased (P<0.01) milk production compared to all other treatments. Milk fat percentage was also higher (P<0.01) for rolled-oat when compared to pelleted oat and rolled barley. Acetate concentration in the rumen was lower (P<0.01) for cows fed pelleted oat (-3.95 mM). Digestibility of starch was higher for oat grain (P=0.05). Based on the data presented by this research, oat grain can be suitable as an energy concentrate for lactating dairy cows in total mixed rations.