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Influence of Added Roughage and Chlortetracycline to All-Concentrate Rations for Fattening Steers^{1, 2, 3, 4,}

North Carolina State University, Raleigh

Abstract

Two experiments involving four trials were conducted over a 2-year period to determine the influence of added roughages in various physical forms and chlortetracycline on performance, rumen characteristics and liver abscesses of steers fed a ration based largely on ground shelled corn. A 2x4 factorial arrangement of treatments was used to compare the basal all-concentrate ration with rations containing limited roughage (ground rice hulls, whole rice hulls, and long hay) fed with and without chlortetracycline. Feedlot performance and carcass data were not significantly influenced by roughage or antibiotic treatment.

Steers fed long hay had a significantly higher percent of rumen acetic acid with a correspondingly lower percent of propionic acid than steers fed other feeding treatments. Adding fiber in the form of ground rice hulls and hay resulted in significantly (P<.05) higher percentages of butyric acid (Experiment I) when compared to the basal ration. Altering the physical form of the rice hulls or antibiotic treatment had no consistent effect on rumen VFAs. Rumen fluid of steers fed hay had considerable higher pH values than steers fed no hay. Ruminal pH of steers fed either the basal or rice hull rations was similar.

Severe rumen parakeratosis was observed in steers fed no roughage or ground roughage. Coarse roughage in limited amounts (either 5% whole rice hulls or 1.36 kg. long hay) significantly improved health of the rumen epithelium. Steers fed the basal or basal plus ground rice hulls exhibited severe clumping and sloughing of papillae with considerable hair accumulation in the rumen mucosa. Chlortetracycline appeared to be ineffective in improving health of the rumen epithelium.

Twenty-three of 128 steers involved in this study had abscessed livers. Sixteen of the 23 were found in steers fed the basal or ground rice hull rations. Five of the abscessed livers were found in steers fed whole rice hulls and two in steers fed hay. A marked reduction in abscessed livers was achieved by the inclusion of 75 to 85 mg. of chlortetracycline per head daily (33 vs. 3%).

¹ Paper number 2475 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh.

² This paper is part of a thesis submitted by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

³ Acknowledgment is made to the American Cyanamid Co.,Princeton, New Jersey, for supplying the chlortetracycline and for partial financial support of this study.

⁴ Acknowledgment is made to the Arkansas Rice Growers Coop. Association, Stuttgart, Arkansas for supplying the rice hulls.

⁵ Animal Science Department.

⁶ Food Science Department.

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