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The Effect of Thyroidectomy on Lactation in the Bovine¹

Dairy Division, University of Minnesota

ABSTRACT

1. Thyroidectomy performed on cows preceding gestation, during pregnancy, and during lactation caused a complete cessation of lactation in about 180 days.
   
2. Total milk and fat yield were reduced about 75 per cent.
   
3. Incomplete removal of thyroid gland produced a temporary decline in milk secretion followed by a gradual return to former levels.
   
4. Composition of the milk as determined by fat, lactose, nitrogen, and specific gravity analyses was not affected.
   
5. Milk and fat yields were restored to former levels by oral administration of fresh thyroid. Decreasing response was observed as the lactation period progressed.
   
6. It is concluded that the reduction of lactation after thyroidectomy is due mainly to thyroid deficiency.
   

¹ Taken from data presented in a thesis to the Graduate Faculty of the University of Minnesota by A. A. Spielman in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Scientific Journal Series Paper No. 2126. Minnesota Agricultural Experiment Station.

^* Now Assistant Dairy Husbandman, Washington Agricultural Experiment Station.