Effect of Growth Hormone on Milk Production and Feed Utilization in Dairy Cows

Highly purified bovine growth hormone was prepared relatively free of thyrotrophin and prolactin contamination. In three short experiments, milk production 4 to 6 days pretreatment was compared to production for 4 to 10 days following the start of injection with bovine growth hormone or saline with four or five cows per treatment. In a fourth experiment, cows were injected three times weekly with bovine growth hormone for 10 wk. In one experiment, injection of the hormone daily for 10 days resulted in a continued rise in milk production with a net increase in milk production of 18% and a reduction in feed per kg of milk of 29%. Injection of bovine growth hormone every third day improved milk production as much as the same total dose given daily. When the hormone was injected over 10 wk, milk production was stimulated for the entire period and there was no measurable development of antibodies to it.