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Effects of Capreomycin Disulfate and Oxamycin on Ruminal pH, Lactate and Volatile Fatty Acid Concentrations in Sheep Experiencing Induced Acidosis^{1 ,2 ,3,}

University of Nebraska⁵, Lincoln 68583

Abstract

Experiments were conducted to determine the effects of two antibiotics, capreomycin disulfate (Experiment I) and oxamycin (Experiment II), on ruminal pH and lactate and volatile fatty acid concentrations in sheep experiencing induced acidosis. Acidosis was experimentally induced by engorging the sheep with 34.5 g ground wheat per kilogram body weight. The animals were assigned to antibiotic treatment dosages of 0 (control), 77 (low) and 770 (high) mg antibiotic/kg wheat. Ruminal pH and acid concentrations were monitored hourly for 8 hours.

Administration of capreomycin disulfate had a quadratic effect on ruminal pH (P<.05). Low dosage treatment maintained ruminal pH above controls across sampling hours. There was an antibiotic treatment dosage effect on ruminal lactate concentrations (P<.05). The low dosage level reduced lactate concentration by about 69% compared to controls. The A:P ratio was decreased by capreomycin disulfate. Data from Experiment I suggest enhanced utilization of lactate yielding propionate.

Ruminal pH increased linearly with increased dosage levels of oxamycin (P<.05). The low dosage effectively reduced lactate concentrations compared to controls at all sampling hours. Oxamycin shifted the molar proportions of volatile fatty acids. Compared to controls either dosage level of oxamycin decreased the molar proportion of propionate and increased that of acetate and butyrate. The observed shifts resulted in a linear increase in the A:P ratio with increasing oxamycin dosage levels. Total volatile fatty acid concentrations were not altered by oxamycin treatment (P>.05); however, concentrations tended to be higher in later hours with higher treatment dosages.

¹ Published with the approval of the Director as Paper No. 5205 Journal Series, Nebraska Agricultural Experiment Station.

² Research reported was supported in part by technical assistance of Eli Lilly and Company, Greenfield, IN 46104.

³ The authors wish to express their appreciation to Dr. M. K. Nielsen for statistical advice and computer analysis of the data.

⁴ Present address: Department of Animal Science, University of Kentucky, Lexington 40506.

⁵ Department of Animal Science.