487 Rumen degradation, N-To-Energy Synchronization, and Intestinal digestion Study in dairy cows: Effect of oat varieties and types (feed type vs. milling type)

Abstract This study aimed to determine the impact of four oat varieties and types (feed type vs. milling type) on the rumen degradation kinetics of nutrients, intestinal digestion of nutrients, and N to energy synchronization. Twelve samples [4 varieties (Arborg, Haymaker, Nasser, Summit) × 3 harvested years (2018, 2019, 2020)] were used for in situ rumen incubation analysis, three-step in vitro analysis, and available N to energy synchronization evaluations. The experiment design was RCBD design (oat varieties as a fixed effect and harvested year as a random block effect). Statistical analysis was performed by MIXED procedure model of SAS 9.4, and significance was declared at P < 0.05 and tendency at 0.05 ≤ P < 0.10. Results showed that Haymaker and Arborg oat had higher rate of degradation of degradable fractions (Kd) of dry matter (DM), crude protein (CP), and starch than that of Nasser oat (P < 0.05). Nasser oat had greatest rumen bypass dry matter (BDM, g/kg DM), and rumen bypass feed starch (BST, g/kg DM) in these four varieties (P < 0.05) while the effective degradability of dry matter (EDDM, g/kg DM), effective degradability of feed crude protein (EDCP, g/kg DM), and effective degradability of feed starch (EDST, g/kg DM) of Nasser oat were least among varieties (P < 0.05). There were significant differences in BDM, EDDM, %BST, and EDST between milling oat and feed oat. For the intestinal nutrient digestibility, Summit oat had greatest intestinal digestibility of rumen bypass dry matter (%dBDM) among four varieties (P < 0.05), and the value of intestinal digestible rumen bypass dry matter (IDBDM, g/kg DM) of Summit was greatest in these varieties, which has greater IDBDM (g/kg DM) content than that of Nasser oat (P < 0.05). Nasser oat also had the least total digestible dry matter (TDDM, g/kg DM) in these varieties (P < 0.05). Summit oat had similar intestinal digestibility of rumen bypass protein (%dBCP) with Haymaker and Nasser oat but had greater %dBCP content than that of Arborg oat (P < 0.05). Nasser oat had greater intestinal digestible rumen bypass protein (%IDBCP, % of CP) in these four varieties (P < 0.05), while its value of total digestible protein (TDCP, g/kg DM) was the smallest and the TDCP content of Nasser oat was less than Haymaker oat (P < 0.05). Summit and Arborg oat had greater total digestible feed starch (TDST) than that of Nasser oat (P < 0.05). Significant differences were found on %dBDM, IDBDM, TDDM, and TDST between the feed type and milling type oat (P < 0.05). Haymaker oat had similar ratio of N to organic matter (OM) of the oat (N/OM) with Nasser oat but had greater N/OM content than that of Arborg and Summit oat (P < 0.05).