The nutritional value of oat forages for dairy cows

Abstract

Three studies were conducted to evaluate the nutritional value of different oat (Avena sativa) forage cultivars (Assiniboia, Bell and Baler) that were newly emerged cultivars as a result of extensive oat growing conditions in western Canada. A total tract digestibility trial using 24 sheep (n=6) in a completely random design was conducted to assess apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), crude fat (EE), acid detergent fiber (ADF), neutral detergent fiber (NDF), hemicellulose, non-structural carbohydrate, acid detergent lignin (ADL), soluble crude protein (SCP), non-protein nitrogen (NPN) and neutral detergent insoluble crude protein (NDICP) in Assiniboia silage, Bell hay, Baler hay and Rosser (barley- Hordeum vulgare) silage. Rumen in situ degradability characteristics of DM, OM, CP, ADF and NDF were determined on Assiniboia silage, Bell hay, Baler hay and Rosser silage at 96 to 0 h using a Holstein cow fitted with a rumen fistula. A dairy production trial using 8 multiparous Holstein cows at 90±20 DIM averaging 41 kg d⁻¹ milk yield, in a 2 × 3 switch-back design was conducted to compare the production response of the cows fed either 48 percent Assiniboia silage or Rosser silage (DM basis) in total mixed rations with the concentrate portion consisting mainly of rolled barley, canola meal and soy meal. Digestibility of DM, OM, NDF, NPN, NDICP and EE were not different for Assiniboia and Rosser silages. Digestibility of DM, NDF and ADF were similar for Baler hay and Rosser silage. Digestibility of hemicellulose, NSC and ADL were similar for all forages. Sheep voluntary intakes of DM, OM, NDF, ADF and EE, except CP were similar across the forages. Assiniboia silage provided more nutrients to the rumen than the hays due to the higher rumen disappearance and effective degradabilities of DM and CP, and lesser undegradable DM, CP, NDF and ADF (P<0.05). Estimated carbohydrate and protein fractions of Assiniboia and Rosser silages were similar. Assiniboia silage was typically comparable to Rosser silage whereas Baler hay was compatible to Bell hay which in contrast was chemically inferior to Baler hay in NDF and TDN content. An increase (8%, P<0.05) in milk fat percentage was observed in cows fed the Assiniboia diet. Milk protein and lactose percentages, and protein yield were higher (P<0.05) in the cows fed the Rosser diet. However, 3.5% fat corrected milk yields were similar. Milk fatty acids (FA) when Assiniboia diet was fed, showed a remarkable increase (P<0.05) in oleate percentage and yield while the others were not different. The increase in oleate content resulted in an increase (P<0.05) in unsaturated FA to saturated FA ratio. Therefore Assiniboia silage would be useful to increase unsaturated long chain milk fat content. It is concluded that Assiniboia silage could substitute for Rosser silage in dairy rations.