Effect of prepartum blockade of microtubule formation on milk production and biochemical differentiation of the mammary epithelium in holstein heifers.

1. Prepartum intramammary infusions of colchicine markedly reduced subsequent milk production compared with untreated mammary glands in the same animal. 2. After the first week postpartum, milk composition was similar in control and treated mammary glands. 3. Rates of fatty acid synthesis, CO2 production and protein synthesis at either 5 or 21 days postpartum were lower in mammary tissue slices taken from mammary glands treated prepartum with colchicine. 4. We conclude that an intact microtubule system is necessary for initiation of milk synthesis and secretion at parturition.