Natural Bovine Somatotropin
Bovine somatotropin is naturally produced in the cow’s pituitary gland at the base of the brain. BST is a hormone. That means that it works as a chemical messenger in the body to communicate between cells and organs. The term “hormone” has a negative connotation for many people because of its misuse in athletics. It must be remembered, however, that hormones are beneficial when used properly. For example, Vitamin D, which is supplemented in milk, is a hormone. BST is a protein hormone rather than a steroid (non-protein) hormone. It is made of 191 amino acids.
BST changes the way a cow allocates her nutrient supply so that more nutrients are used for milk production. Genetically superior cows naturally produce more BST than poor cows. BST helps to coordinate all of the activities that need to occur to make milk, not only in the udder but also in the entire body. In the udder, BST increases nutrient uptake, secretory cell activity, the number of secretory cells, and overall blood flow. In the body, BST has many effects including, increasing glucose production from propionate, decreasing body fat production, and increasing intestinal absorption of minerals needed to make milk.
The amino acid sequence of BST is much different than that of human somatotropin. When BST was experimentally injected into humans, it had no effect. This is because the hormone must bind to a specific receptor on body cells in order to have its effect. Because of the difference in amino acid sequence, BST cannot bind with human cells. Or, to put it another way, the key cannot fit into the lock.
Commercially Available Bovine Somatotropin
Bovine somatotropin is also known as bovine growth hormone (BGH or GH), somatotrophin (ST or BST) and Posilac®. Posilac®, sold by the Monsanto Company, has been used for dairy cows in the U.S. since 1994. In some countries, it has not been approved for use in dairy cows.
Posilac® is made by recombinant DNA technology. Since Posilac® is a protein, it would be digested just like any other feed protein if it were fed to the cow. Therefore, it must be injected. It is sold in 2 ml syringes with a 16-Gauge, 5/8” needle. Each syringe contains 500 mg of prolonged-release Posilac® to give 36 mg per day when it is injected every 14 days. It is recommended that supplementation begin when cows are 63 days in milk. It is injected under the skin either at the tail head or behind either shoulder of the cow.
Since every cow requires a similar amount of nutrients for maintenance functions (walking, eating, breathing, etc), increasing milk production per cow dilutes out that maintenance requirement. Posilac® increases milk production per cow, making it economically beneficial for many dairy producers.
Responses to Supplemental Bovine Somatotropin
Many studies have been conducted to quantify the response of cows supplemented with Posilac® under different conditions. Responses have been observed when cows have been fed a variety of diets. The nutrient requirements for a Posilac® supplemented cow are no different than those of a high-producing cow.
The response of cows to Posilac® supplementation is directly proportional to the level of nutrition and management on the farm. Those cows under poor management with inadequate nutrition will not respond. Those with excellent nutrition and management will respond the best. A study was conducted with cows fed only pasture. In the spring, when the pasture was lush, BST response was greatest (18%). During the summer drought, there was no response. In the fall, when the pasture improved, the response improved again. Many studies have shown that cows supplemented with BST but having poor management and nutrition, do not “burn out” and have health problems. They simply do not respond.
If a cow is putting on weight (positive energy balance) when she is injected with Posilac®, she will divert those extra nutrients to milk production rather than fat production. If a cow is loosing weight when she is injected with Posilac®, body fat will be used for milk production. But, dry matter intake will increase by about 7% within 4-6 weeks because of the Posilac®. This will help the cow to eventually put on weight or at least not lose more weight while supplemented with Posilac®. Thus, it is critical that cows have adequate access to their ration so that they can increase their dry matter intake while on Posilac®. The range in dry matter intake response is from 4 to 16%.
On average, cows treated with Posilac® respond by producing 13% more milk (or 9 pounds (4 kg)/cow/day). But, milk production response ranges from 9 to 30%. Milk composition is not changed. Efficiency of nutrient usage increases by about 10% but nutrient digestibility is not affected. Peak milk response to Posilac® occurs about 6 days after injection.
References:
Bauman, D.E. 1989. Biology of bovine somatotropin in dairy cattle. In: Proceedings of Advanced Technologies Facing the Dairy Industry: bST. November 10 &11, 1989, Rochester, NY
Bauman, D.E. and M.A. McGuire. 1994. Paradox of BST: Why Cows Don’t Burn Out. 1994 Minnesota Dairy Health Conference, University of Minnesota, St. Paul, MN
Chase, L.E. 1989. Feeding strategies for using bST. In: Proceedings of Advanced Technologies Facing the Dairy Industry: bST. November 10 &11, 1989, Rochester, NY
Smith, R.M. 1994. Production management concerns with bovine somatotropin. Blue Seal Feeds.
Related Links:
Paradox of BST: Why Cows Don’t Get Burn Out
D.E. Bauman and M.A. McGuire, Cornell University
Adoption of Agricultural Technologies and the Economics of BST
John Fetrow, University of Minnesota
Feeding the Bovine Somatotropin (BST) Treated Dairy Cow
Rick Grant and Jeff Keown, University of Nebraska – Lincoln
Can You Afford to Use Bovine Somatotropin (Bovine Growth Hormone)?
Jeff Keown, University of Nebraska - Lincoln
Feeding and Managing the High Producing Cow
Brian Perkins, Ph.D., DairyTech Management Services, Inc.
Dairy Research and Bovine Somatotropin
B.A.Crooker et al., University of Minnesota
Information about bST and the dairy industry
Penn State Bulletin
Bovine Somatotropin
National Institute of Health Assessment
Should Dairy Rations Change When Beginning the Use of POSILAC® Bovine Somatotropin?
Monsanto
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