Effects of tetracycline injection on blood calcium and ruminal activity in sheep

Tetracycline is widely used in the treatment of the foot rot in ruminants. It chelates with Ca 2+ ions causing a depression of levels of ionised calcium. The objective of the study was to assess effects of tetracycline admin istration on serum calcium concentrations and the frequency of ruminal contractions. Rumen contractions were monitored by auscultation in 23 sheep prior to administration of oxytetracycline and recorded every 12 hours for 84 hours after intramuscular injection of the antibiotic. Blood for calcium analyses was collected by venepunc-ture of the jugular vein before and 24, 48, 72, and 96 hours after administration of oxytetracycline. The serum calcium concentrations were determined by atomic absorption spectrophotometry. Analysis of variance (ANOVA) was used to analyse the time effect of tetracycline treatment on the rumen contractions and serum calcium con -centrations. There was a significant decrease (P<0.01) in ruminal contractions following application of oxytetracycline, with a maximum decrease at 24 hours following oxytetracycline application and a return to the initial rumen contraction frequency by 60–72 hours following oxytetracycline application. The oxytetracycline administration resulted in serum calcium decrease from 2.42 mmol/l to 2.26 mmol/l 24 hours after the administration (P<0.01). In conclusion, as found in our study the administration of tetracycline in sheep can be associated with a decline in ruminal motility potentially causing production losses, particularly in lactating ewes.