Effects of oxytocin administered in the dry period on subsequent lactation in cows

The need for a dry period in dairy cows has been established for more than a century, but the optimum length of the period and reason for the benefit derived from the pause in lactation has been studied only recently. On the basis of survey studies a dry period of 60-90 days has been shown to result in maximum production. Until a few years ago the stimulus of a dry period to lactation was thought to be due solely to a rebuilding of the nutrient stores in the animal. More recently the involvement of hormonal factors such as an interaction of oxytocin with hormones necessary for maximum lactation has been postulated. Injections of oxytocin during the dry period could simulate the response to milking without evacuation of the gland or loss of nutrients due to lactation. Such treatment would be expected to delay mammary "involution" and might produce an effect in "dry" cows similar to those which were not dried off between lactations.