Date of Award:

5-1969

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Zoology

Committee Chair(s)

Datus Hammond

Committee

Datus Hammond

Committee

Thomas Bahler

Committee

Merthyr Miner

Abstract

One hundred Hereford calves were used in 2 experiments, with each experiment lasting approximately 3 months. In the first experiment, 40 yearling heifers were each inoculated with approximately 50,000 E. bovis oocysts daily for 10 days (500,000 oocysts, mixed with water, were poured over the morning dry feed allotment for each pen of 10 animals). Amprolium was given in the feed at 25 mg/kg of body weight daily for 30 days to 20 of the calves; the remaining 20 were not treated. Treatment was started one day before inoculation. The untreated calves had some diarrhea, discharged moderate numbers of oocysts with peak numbers usually occurring 20 to 22 days after inoculation, and had a slightly lower weight gain per calf than did the treated calves. In the treated calves, few or no oocysts were discharged during the period from 5 days after the beginning of treatment until 7 days after treatment was stopped; no discernible discharge peak occurred in the treated animals. Differences significant at the .01 level occurred between the treated and the untreated calves with respect to total oocyst discharge, day of peak oocyst discharge, number of days oocysts were discharged (patent period), and days of diarrhea; the difference with respect to peak discharge was significant at the .05 level. Differenced in weight gain and days of bloody feces were not significant.

In the second experiment, 60 Hereford steers about 6 months in age were inoculated as in Experiment 1, with approximately 100,000 E. bovis oocysts each for 3 days. One group of 20 calves was given amprolium for 21 days at 5 mg/kg of body weight starting one day before inoculation, 20 were treated for 5 days at 10 mg/kg starting 13 days after inoculation, and 20 were untreated. Diarrhea occurred in one calf treated for 5 days at 10 mg/kg and in 6 untreated calves; bloody feces were discharged by 2 calves treated for 5 days at 10 mg/kg and in 12 untreated calves; in the calves treated for 5 days, the oocyst discharge peak occurred later and was lower than that in the untreated calves; the peak was also delayed in the 21-day treated calves. The calves treated for 21 days had no diarrhea or bloody feces, and discharged lower total numbers of oocysts than did the other two groups. The calves treated for 21 days had the best mean weight gain per calf; those treated for 5 days were intermediate in weight gain and the untreated calves gained least. Evidently, the inoculation levels used in these experiments were not high enough to produce severe infections in calves of these ages. Treatment with amprolium at the dosage levels used appeared to result in lower levels of infection than in the untreated calves. Differences between treated and untreated calves with respect to peak oocyst discharge, total oocyst discharge, and days of bloody feces were significant at the .01 level as were differences between the 5 mg/kg treated and the untreated calves with respect to day of peak and days of oocyst discharge (patent period). Differences between the 10 mg/kg treated and the untreated calves in the number of days of oocyst discharge (patent period) were significant at the .05 level. No significant difference was found between any of the groups in weight gain or days of diarrhea, between the two groups of treated animals with respect to any of the characteristics examined, or between the 10 mg/kg treated and untreated animals in the day of peak discharge.

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