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Colorado Agricultural Experiment Station, Fort Collins 80521
Abstract
The effects of mastication, salivary contamination and leaching on the chemical composition of forages fed to esophageally fistulated steers were examined in two replicated trials in 1970 and 1971. Significant (P<.01) increases in ash (37 to 51%) and phosphorus (43 to 210%) of extrusa samples were observed, highest increases being obtained with blue grama and crested wheat-grass hay forages. Esophageal fistula effects on crude protein were confined to the 1970 trials, which showed increases of up to 133% in blue grama samples but decreases of 2.5% in alfalfa samples. Esophageal fistula effects on acid detergent fiber, acid insoluble lignin and in vitro dry matter digestibility of forages were variable and influenced by drying methods, steers and replications. Alteration of forage chemical composition was due to the esophageal fistula effects per se and not to the time for which extrusa samples were exposed to ambient temperatures prior to initiation of drying. It was concluded that with the exception of minerals and possibly crude protein the chemical composition of extrusa obtained via the esophageal fistula gave a reasonable estimate of the chemical composition of the grazed forage. Little additional accuracy was obtained by processing extrusa samples immediately following collection.
Oven drying at 55 C resulted in increased (P< .05) crude protein (5.7%), ADF (4.1%) and in vitro dry matter digestibility (2.7%) compared with freeze drying, although differences were variable and not consistent between experiments. Oven dried extrusa samples were higher in AIL than corresponding freeze dried samples (P< .01) with increases of 23 to 30% in alfalfa and 36% in blue grama, although increases in blue grama did not always occur. Forage mineral composition was unaffected by drying methods (P>.05). With the exception of AIL in alfalfa extrusa samples the low biological significance of many of the drying method differences indicate that oven drying at less than 55 C may be used with relative confidence for both extrusa and forage samples.
1 Supported by the Colorado State University Experiment Station and published as Scientific Series Paper No. 1849.
2 Present address: Tara Hills High Country Research Station, Kurow, New Zealand.
3 Streeter Ranch, Buffalo Gap, South Dakota.
4 Eastern Colorado Range Station, Akron.
5 Department of Animal Sciences, Colorado State University, Fort Collins.
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