Rumen degradability In sacco of physically and chemically treated oat and barley grain

The effects on rumen degradation of chemical and physical treatment of oats and barley were investigated by use of the in-sacco technique. Whole oats (75% DM) were treated with 0, 30 and 50 g NaOH, 30 g NH₃ or urea per kg DM. Three different strengths of NaOH (11, 22.5 and 45% w/v) were tested at the 30 g kg^?1 DM level. Oat hulls and crushed, shelled-crushed and shelled-whole oats were also tested, with or without addition of NaOH. Whole barley was subjected to a pearling treatment, removing 7, 11 and 18% of the DM, mainly hulls. A part of the pearled barley was also steeped in cold water for 8 h. All pearled samples were reconstituted before in-sacco incubations. Barley was also ‘clipped’ into pieces or crushed manually, using a hammer. All samples were incubated for variable amounts of time up to 24 h (48 h for oat hulls). Oat samples were analysed for DM, NDF, ADF and lignin and barley samples for DM, NDF and starch. To compare the effects on rumen pH and ammonia-N, two rumen fistulated cows were fed 50% hay and either 50% whole NaOH-treated oats (30 g NaOH kg^?1 DM) or crushed oats. In-sacco results showed that whole oats treated with 3 or 5% NaOH had 24 h DM degradation of 61% and 68%, respectively, compared with 7% for the untreated oats. Extra water additions with the NaOH had no significant effect. Shelled oats were degraded more (85%) at 24 h than whole oats treated with NaOH (max 68%). NH₃ (30%) or urea (22%). Alkali treatment had no additional effect on the shelled oats. Crushing gave the most rapid degradation for both whole and shelled oats. However, treatment with NaOH after crushing reduced degradation. Only 10% DM of the hulls were degraded at 48 h, but treatment with 5% NaOH increased this value to 55%. In the rumen study, mean rumen pH was similar for both diets, but pH variation was smaller and ammonia level consistently higher after feeding NaOH-treated oats. Increasing the pearling intensity of the barley improved starch disappearance at 24 h from 45% to 83%. Steeping further enhanced disappearance by an average of 10 percentage units. Clipping gave a degradation very similar to the highest pearling intensity.