Using Bovine Somatotropin (BST)

Limin Kung, Jr., Ph.D
Professor
Ruminant Nutrition & Microbiology Laboratory

            Bovine somatotropin has been commercially available in the U.S. since 1994 to increase milk production and improve the efficiency of milk production.  Sales and use of BST have steadily increased since its introduction.  With increasing use, here are some of the more common questions, with answers, about BST use in dairy cattle.

1) Question:  If I stop administering BST after several weeks or months, is there a positive or negative carry over effect in the next several weeks or the rest of lactation?   

Answer:  No.  Within 1 to 2 weeks, milk production will drop to a normal level.

2) Question:  If I administer BST to a cow for an entire lactation (starting at about 60 days to drying off) will there be a positive or negative residual effect in the next lactation if I choose not to administer BST?   

Answer: No.  Cows will milk normally based on body condition and nutrition. 

3) Question:  When I start using BST can I feed the same diet that cows were being fed?  

Answer:  If cows are started on BST at about 60 days in milk, these animals will probably be being fed an energy and protein rich diet.  Cows may have to remain on this diet for a longer period of time if treated with BST.  If cows are started in later lactation and fed a less nutrient dense diet, they may remain on this diet for a short period of time.  However, over the long run, a more nutrient dense diet will probably have to fed to BST-treated cows or body condition will suffer.  Cows that dry off in poor body condition will not milk as well in the next lactation. 

4) Question:  Can I cheat and start administering BST to cows earlier than what is written on the label?   

Answer:  No.  Follow label restrictions because starting BST treatment at calving has no effect on milk production.  During early lactation, the cows produces enough of her own BST to maximize production.  Administering BST before 50 to 60 days in milk is a waste of money. 

5) Question:  If have been using BST for several years and I don't perceive the large increases in milk production that I saw when I first started using the product.  Why is this?   

Answer:  When producers first start using BST, there is an obvious increase in milk in the bulk tank if enough cows are started on the product.  After time, most herds end up with continual use of BST, which makes it more difficult to perceive a difference. 

6) Question: How do I know BST is still working?   

Answer:  Controlled studies have shown that cows respond similarly to BST even after four lactations.  In a study at the University of Arizona, cows receiving BST for 4 years produced on average 8.1 lbs. more milk per day and gained 114 more lbs. of body weight in a lactation than did untreated cows.  Cows responded the same to BST in the first and fourth year of treatment.