Lactation Studies. I. Effects upon Milk Ejection in the Bovine of Various Injection Treatments Using Oxytocin and Relaxin

A cow became unable, in most instances, to eject milk normally. Oxytoein was administered to this cow intravenously, to study milk ejection. Six hundredths I. U. oxytocin was the least amount that caused partial milk ejection, whereas 0.12 to 0.25 I. U. caused normal ejection. Amounts up to ten units were increasingly more effective. Small amounts of oxytocin were more effective in ejecting milk when injected rapidly rather than slowly. However, there was little difference resulting from two 0.25 I. U. injections within a few minutes, and one 0.5 I. U. Complementary milk increased after a second injection of oxytocin, but decreased in per cent of total milk, and the fat per cent was unchanged as the time between injections increased from one to two milking intervals. Milk from the cistern of the udder increased in volume before milk ejection at milkings subsequent to oxytoein treatment, and decreased in fat as the time extended from one to two mflkings and as the amount of oxytociu decreased. More complementary milk, higher in fat, was collected from certain amounts of oxytocin, divided into two injections given at one milking, if the most effective injection was given last. Relaxin was tested for milk ejection properties, and from 750 to 1,800 G.P.U. injected intravenously into three cows on two occasions did not cause noticeable milk ejection.