The evaluation of processed grain screenings for potential use in the ruminant ration

Abstract

The objectives of this research were firstly to determine the nutritive values for beef cattle and sheep of refuse screenings that had undergone various chemical or physical treatments; secondly to quantify the effects of chemical or physical treatments on viability of weed seeds after passage through the digestive tract of the ruminant; and thirdly to assess the potential for use of screenings in a hay based ration. The nutritional value of refuse screenings was determined in feeding trials with ewes and steers, as well as by analytical laboratory procedures. The grain screenings were either steam pelleted, untreated, or chemically treated with three percent ammonia or one percent urea, both in whole or pelleted form. Eight diets were fed, six containing screenings, and two control diets of pelleted or unpelleted hay. The screenings were fed at 60, 40, or 20% of the diet in combination with brome-alfalfa hay. Both in vivo and in vitro digestibilities showed pelleting, chemical treatment with ammonia and, to a lesser degree, the addition of urea improved the nutritive value of refuse screenings for the ruminant animal. Ammoniated and pelleted diets showed higher digestibilities of organic matter (OM) , crude protein (CP), energy, neutral detergent fiber (NDF), acid detergent fiber (ADF) and cellulose than whole unprocessed screenings. Digestibility increased as the level of screenings in the diet decreased. Ammoniation and pelleting were both effective in reducing weed seed viability, according to germination tests. Unpelleted diets containing urea or nonchemically treated diets contained large numbers of seeds which survived passage through the digestive tract and germinated, representing a potential weed contamination problem in manure from animals fed these diets. This study showed that refuse screenings can be used effectively as a component of the ruminant ration. With growing ewes and steers it appeared that a screenings level of approximatly 40% of the diet was optimal. This is economically significant as a large amount of relatively inexpensive screenings are available annually. Since ammoniation appeared effective in decreasing weed seed viability, it potentially could replace pelleting of screenings for livestock rations if proven to be more cost effective than the traditionally used steam pelleting.