INFLUENCE OF THERMO-AMMONIATION ON FORAGE QUALITY AND UTILIZATION OF WARM-SEASON GRASS HAY (DIGESTIBILITY, INTAKE, PARTICLE SIZE, STATISTICAL MOMENTS, IMAGE ANALYSIS)

Warm-season grass hay is an important source of winter feed for cattle production in the Northern Great Plains. Frequently, these forages are harvested at mature stages. Chemical treatment offers a management tool to improve the value of this resource. This study evaluated the use of thermo-ammoniation to improve forage quality of warm-season grass hay. Immature switchgrass, Panicum virgatum L., (Swi-I), mature switchgrass (Swi-M) and mature indiangrass, Sorghastrum nutans (L.) Nash, (Ind-M) were fed without treatment (CTR) or thermo-ammoniated with 3% anhydrous ammonia for 23 h at 85 C (NH3) to mature steers. Two 6 x 6 latin square trials, at ad libitum or equalized intakes, were used to examine effects of thermo-ammoniation on voluntary intake, digestibility, rates of overall disappearance, rates of passage and NDF digestion, and particle size distribution of rumen digesta. Thermo-ammoniation increased digestibility, intake, rate of disappearance and rate of NDF digestion. Increases were greater with either of the mature hays than with Swi-I. Thermo-ammoniation did not affect rate of passage of undigested residues, determined from the excretion of chromium-mordanted fiber. Thermo-ammoniation improved the feeding value of mature, warm-season prairie hay; primarily by increasing digestibility and promoting increased voluntary intake. Assumptions of a log normal distribution were invalid for weight-size frequency data resulting from wet sieving of rumen digesta. Statistical moments were calculated to describe these data. Moment analysis was appropriate, and did not suffer from the assumption of a log normal distribution necessary for published regression techniques. Moments provided more definitive evidence of treatment effects on central tendency and dispersion of rumen digesta particle size distributions. Skewness and kurtosis could also be evaluated using moments. A greater proportion of rumen digesta had smaller particle sizes with Swi-M CTR or Ind-M CTR than with other hays. An inexpensive, microcomputer-based, low-resolution imaging system was developed to evaluate photomicrograph slides of forage material. Machine language programming stored an image scanned by a television camera interfaced to the computer. Application programs estimated total area of a projected image or diagonal dimension of objects within the image