Influence of ammoniation on the nutritive value, N retention and intake of straw

Abstract

Studies have been conducted to compare the increases in dry matter digestibility (DMD) in vitro and in vivo and to determine the metabolisable energy (ME) value of straw ammoniated at ambient temperature. Stacks of straw sealed with polyethylene were allowed to react with 3% (w/w) of anhydrous NH₃ for 30 and 56 days respectively. Both DMD in vitro and total nitrogen (N) tests were carried out over an 8-week period subsequent to opening the stacks. Digestibility in vivo was measured with twelve wether lambs. Separate digestibility studies involving six wether lambs were conducted to measure N retention from ammoniated straw. There was a mean increases of 15 and 14.2 percentageunits in the DMD in vitro and in vivo content respectively of the ammoniated straw irrespective of whether it was treated for 30 or 56 days. The crude protein (CP) equivalent content of the straw was increased from 3.1 to 7.6%. The increase in DMD in vitro of the ammoniated and N content was maintained in all cases throughout the 8-week sampling period. Approximately 58% of the anhydrous NH₃ added to the straw appeared irreversibly “bound”

The N retention studies resulted in a slight increase in N retention as a result of straw ammoniation. The mean values for the control and ammoniated straw DM were—0.586 g N and—0.345 g N/100 g straw per day respectively. The ME values for ammoniated straw averaged 7.14 MJ/kg on a DM basis. Straw ammoniation resulted in a marked increase in intake with sheep.