Effects of lesions of the pituitary stalk on lactation in the rabbit

The daily milk yields and the yields of fat, lactose and protein in milk were studied in New Zealand White rabbits in which the pituitary stalk and its portal vessels had been interrupted by a radiofrequency lesion placed during the second or third weeks of lactation. In comparison with yields from control rabbits i.e. animals in which the lesion did not completely interrupt the stalk, the yields of milk anf of milk constituents were depressed after interruption of the stalk on day 11 or day 15 of lactation. When the lesion was placed on day 19 of lactation the molk yield was depressed whether or not the stalk was completely disrupted; the decline in yield exaggerated the normal decline of yield that occurs at this stage of lactation. After interruption of the pituitary stalk changes in milk composition were associated with changes in milk production, not evidence being obtained to support anearlier suggestion that section of the pituitary stalk in the rabbit alters the milk compostion whilst leaving milk output unaffected.