[Digestibility and utilization of rations containing differently treated straw. 2. Energetic utilization by sheep of rations containing differently treated straw].
A total of 59 complete metabolic periods of adult sheep were used to compare energy balance and energy utilization of rations containing 45, 60 and 99% of straw previously subjected to different treatments. In addition, some indices of rumen physiology were determined. The straw was fed in the following forms: chopped, chopped and treated with 6% sodium hydroxide, pelleted with and without NPN-addition (ammonium bicarbonate and/or urea) during the pelleting process. Notwithstanding pressing temperatures above 90 degrees C during compaction, the addition of NPN-compounds did not result in increased digestibility. The NaOH-treatment of the straw increased the energy digestibility of the ration containing 45% straw by 5 to 6 digestibility units. All experiments revealed a higher energy balance and, consequently, a higher energy utilization than could be expected from calculations on the basis of equations derived from earlier experiments with adult sheep. The variations are discussed under the aspect of energetic feed evaluation and with regard to consequence for the efficient use of straw in rations for ruminants.