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University of Florida, Gainesville, Florida 32601 and Centro Investigaciones Agronomicas, Maracay, Venezuela
Abstract
Three experiments were conducted with 63 yearling wethers to investigate the influence of supplemental nitrogen in the form of natural proteins (soybean and cottonseed meal) or as urea and biuret combined with an energy source on voluntary intake, digestibility of nutrients and nitrogen balance when sheep were fed low quality (2.57 and 4.63% crude protein) pangolagrass hay. In general, the supplements were consumed at levels of 130 to 150 g per sheep daily which provided 8.0 to 9.5% total dietary crude protein. Supplements containing either 6.32 or 7.12% urea were not consumed completely and resulted in a lower total dietary crude protein than occurred with natural protein or biuret supplements. In each of the 3 experiments, the addition of supplemental nitrogen with an energy source increased (P<.01) hay intake and improved (P<.01) the apparent digestibility of nitrogen. All sheep receiving supplemental nitrogen were in positive nitrogen balance while those consuming hay alone or hay plus a low-protein (5.84%) energy source were in negative balance. In general, organic matter digestibility increased due to the addition of supplements containing organic matter of greater digestibility. Cellulose digestibility was not influenced significantly by treatment but was numerically greater in each experiment when nitrogen was added. Biuret plus an energy source gave a response similar to that obtained with either soybean or cotton-seed meal and in the experiment, where compared, urea and biuret responded similarly.
1 Florida Agricultural Experiment Stations, Journal Series No. 4069.
2 Department of Animal Science, University of Florida.
3 Graduate Fellow, Sponsored by Fondo Nacional Investigaciones Agropecuarias de Venezuela, Caracas, Venezuela. Present address: Facultad Ciencias Veterinarias, University Central de Venezuela, Maracay.
4 Beef Cattle Research Station, Brooksville, Florida.
5 Seccion Zootecnia, Centro Investigaciones Agronomicas, Maracay, Venezuela.
6 The authors wish to acknowledge Dow Chemical Company, Midland, Michigan and the Center for Tropical Agriculture, University of Florida, for funds in support of this study; Pfizer, Inc., Terre Haute, Ind. for supplying vitamins A and D; and American Cyanamid Company, Princeton, N. J. for supplying urea.
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