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Reproduction in Thyroidectomized and Thyro-Parathyroidectomized Cattle¹

Department of Dairy Science, The University of Arizona, Tucson

ABSTRACT

Eight experimental animals, two lactating cows and six heifers, were either thyroidectomized or thyro-parathyroidectomized to determine the effect of hypothyroidism and hypoparathyroidism on breeding efficiency. Of 15 first services, over two breeding periods 80% resulted in conception. Two of the parathyroidectomized animals were not able to carry their feti to term in either of the two breeding periods. Evident manifestation of severe hypocalcemia resulted in abortion in each situation.

A lack of normal mammary development and milk secretion was observed in the parathyroidectomized heifers.

Results of this study do not support the theory that low breeding efficiency in the bovine during hot weather is the result of depressed thyroid secretion.

¹ This work has been supported by the Regional W-49 funds and in part by a grant from The National Institutes of Health, Arizona Agriculture Experiment Station, Technical Paper no. 1131.