Inhibitory effect of milk fat on milk secretion in the mouse: a re-examination

Lactating mice were treated I.P. with cow milk, skim milk, milk lipid extract, preparations of milk fat globule membranes and fat globule-enriched milk (cream). Milk, but not skim milk, inhibited litter growth significantly. None of the fractions of milk fat globules had any apparent effect on litter growth. Litter growth was reduced markedly and maternal health adversely affected by cream. It is concluded that previous studies in which milk was injected I.P. cannot be taken to indicate that milk contains a lipid or lipid-soluble inhibitor of milk secretion in addition to the protein inhibitor discovered in milk more recently.