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Feed Processing. V. Effect of an Expansion-processed Mixture of Grain and Urea (Starea) on Nitrogen Utilization in Vitro^1,2,

Departments of Dairy and Poultry Science, and Grain Science and Industry, Kansas State University, Manhattan 66502

ABSTRACT

An expansion-processed mixture of grain starch and urea called Starea has been effective in increasing urea utilization by the ruminant. This in vitro study was designed to give a quantitative evaluation of nitrogen utilization by measuring ammonia nitrogen and bacterial protein concentrations following a four-hour fermentation period. Starea supplements markedly reduced the ammonia compared with that from unprocessed corn and urea supplements. The lowered rumen ammonia was, at least in part, the result of more efficient utilization of the ammonia by conversion to microbial protein. Substrates used were: A) 34% crude protein Starea; B) 39% crude protein Starea; C) 44% crude protein Starea; D) 39% crude protein expanded corn + urea; E) 44% crude protein ground corn + urea. Bacterial protein (mg/100 ml) and ammonia N (mg/100 ml) were: A) 64.2 and 117.2; B) 66.3 and 122.5; C) 63.8 and 124.1; D) 59.6 and 126.3; E) 41.9 and 156.0. Similar differences were obtained when all substrates contained 44% crude protein or when all substrates were diluted to 16% crude protein with ground grain. Amino acid analyses were used to evaluate the quality of bacterial protein formed during in vitro fermentation. There were indications that bacterial protein contained more isoleucine, leucine, methionine, tyrosine, and phenylalanine when the substrate was soy-bean meal or Starea rather than ground grain and urea.

¹ Contribution no. 748, Department of Dairy and Poultry Science, and no. 699, Department of Grain Science and Industry, Kansas Agricultural Experiment Station, Manhattan. Data in this paper are in part from a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree in Animal Nutrition at Kansas State University.

² Supported in part by a grant from W. R. Grace and Co., New York.