Chemical composition of forage and feces as affected by microwave oven drying

Abstract

Freeze drying, conventional oven drying, and microwave oven drying were compared with respect to their effect on the chemical composition of native range forage and feces from cattle grazing the forage. Forage was collected by hand harvesting and by esophageal-fistulated steers (extrusa) on 10 collection dates from 11 June to 15 Oct. in 1987 and on 6 collection dates from 2 June to 15 Sept. in 1989. Composite fecal samples were obtained from cattle grazing the same pastures the day following forage collections. Drying method had minimal effect on in vitro digestible organic matter (IVDOM), ash, neutral detergent fiber (NDF), nitrogen, and ash insoluble in neutral detergent (AIND) in hand clipped native forage. However, both microwave and conventional oven drying of extrusa resulted in greater NDF than freeze drying. Unexpectedly, IVDOM in microwave oven dried extrusa was equal to or greater than values for freeze dried material. There were no interactions between drying method and sampling date for any components measured in the extrusa. Microwave and conventional oven drying of feces resulted in greater NDF values than freeze drying, with microwave drying resulting in significantly greater NDF than conventional oven drying. There was also more AIND in heat dried feces, but nitrogen and ash levels were not affected by drying method. The data indicate that if nitrogen or ash are to be determined in hand cupped forage, extrusa, or feces, then microwave or conventional oven drying is acceptable; but if fiber levels are to be determined in these materials, then it appears they should be freeze dried for the most accurate results.