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Journal of Dairy Science Vol. 54 No. 1 100-105
© 1971 by American Dairy Science Association ®
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Effect of Thymectomy on Growth, Hematology, and Immunological Response of Dairy Calves

A. J. Guidry, R. E. McDowell1, G. L. Coleman2, M. L. Crandall3 and C. A. Kiddy

Animal Science Research Division, ARS, USDA, Beltsville, Maryland 20705

ABSTRACT

Twelve Holstein and seven Brown Swiss were thymeetomized, and 12 Holsteins were sham-operated 24 to 48 hours after birth. All were raised to 18 to 20 weeks of age. In Experiment I (six thymeetomized and six sham-operated Holsteins) lymphocyte counts increased in both groups following injections of whole sheep blood at 13 weeks. Sham-operated calves showed the greatest increase (P < 0.01). Antibody response to sheep blood was lower in the thymeetomized calves (P < 0.01). In Experiment II (six thymeetomized and six sham-operated calves) antibody response was not significantly different between the two groups. In both experiments leucocyte counts were lower in the thymeetomized groups (P < 0.05). Three of the 12 thymeetomized calves and one sham-operated calf showed signs of "wasting disease." Neither experiment showed significant differences in erythrocyte, polymorphonuclear leucocyte, or monocyte counts, hematocrits, body weight gains, nor in the gross or microscopic morphology of lymph nodes and spleens. In Experiment III, seven Brown Swiss were thymeetomized to determine the effect of thymectomy in this breed. One of the seven showed signs of "wasting disease." Necropsy revealed residual thymus in 12 of the 19 thymeetomized calves from the three experiments. However, three of the four thymeetomized calves which showed signs of "wasting disease" had no residual thymus.

FOOTNOTES

1 Department of Animal Science, Cornell University, Ithaca, New York.

2 Chas. Pfizer and Co., Groton, Connecticut.

3 District Veterinarian, Food and Drug Administration, Detroit, Michigan.






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Copyright © 1971 by the American Dairy Science Association ®.