Effects of Temporary Hormonal Suppression of Lactation on Milk Constituents, Clinical Mastitis, Colostrum, and the Estrous Cycle

Abstract

Estradiol-testosterone injection had similar lactation suppressing effects in sheep, goats and cattle. The depression in milk production was generally in proportion to the dose, although the extent and duration was influenced by individual animal characteristics. Cows and goats responded within three days, whereas, sheep required eight days for maximum depression. The net synthesis of fat, protein and solids-not-fat following injection was reduced. As expected, when milk production decreased, solids-not-fat and generally per cent protein increased, whereas, fat was somewhat more erratic and generally depressed. A stimulatory effect of the hormone on milk synthesis following the initial depression was evident. In subsequent lactations, there was no altered production. In addition, the milk was colostrum-like following smaller injections and was markedly altered (watery, clotted, etc.) following larger injections. The physical appearance was accompanied by relative increases in all whey proteins derived from blood (two times for albumin, and 20 times for immune and β2-globulins). Those synthesized in the mammary gland decreased to one-third for α-lactalbumin and to one-half for β-lactoglobulin. Possible effects of estrogen on suppressed lactation and altered composition during pregnancy were considered. Visible changes in the appearance of milk suggested that normal variations in endogenous hormone levels, especially during the estrous cycle, may influence milk leucocytes to a great extent. © 1968, American Dairy Science Association. All rights reserved.