Effects of Sustained Release Bovine Somatotropin(Sometribove) on Animal Health in Commercial Dairy Herds

One of the first potential biotechnology products for animal production is bST. Research in the technology of bST has involved scientists and support from federal agencies, universities, and private industry. As a consequence of this extensive cooperation, more than 1000 bST studies have been conducted, which involved over 20,000 dairy cows, and results have been confirmed by scientists throughout the world. This quantity of published research is unprecedented for a new technology and greater than most dairy technologies in use. In contrast to steroids, bST is a protein hormone. Milk yield and persistency responses to bST have been observed for all dairy breeds examined. Quality of management is the major factor affecting magnitude of milk response to bST. The mechanism of action of bST involves a series of orchestrated changes in the metabolism of body tissues so that more nutrients can be used for milk synthesis. It is these coordinated changes that allow the animal to achieve an increased milk yield while remaining normal and healthy. Bioenergetic studies demonstrated that bST-supplemented animals are not stressed. Similarly, there are no adverse health effects from bST even under poor management conditions. Composition of milk (fat, protein, lactose, cholesterol, minerals, and vitamins) is not substantially altered when bST is used and does not differ in manufacturing characteristics. Public perception is of paramount importance if bST or any new technology is to be effectively implemented. New technology must be understood and perceived as safe and beneficial both by farmers, who would utilize it, and consumers, who would purchase the dairy products. With bST use, a unit of milk is produced with less feed and protein supplement and with a reduction in animal excreta (manure, urine, and methane). Nationally, the use of bST simply reinforces, but does not fundamentally change, dairy industry trends of increased milk yield per cow, reduced number of cows, and declining dairy farm numbers. For individual farms, bST technology is size-neutral. However, poorly managed farms where animals are stressed, underfed, or sick are at an economic disadvantage because they will achieve negligible milk response to bST.

Objectives of the research were to examine the effect of bovine somatotropin (bST) on pregnancy rates to a timed artificial insemination protocol and to test a resynchronization system with two consecutive synchronized services. Lactating Holstein cows (n = 403) were assigned to the following treatments: bST treatment (500 mg) was initiated at 63 +/- 3 d postpartum concomitantly with initiation of the timed artificial insemination protocol or bST treatment was initiated at 105 +/- 3 d postpartum. At 63 +/- 3 d postpartum, all cows received GnRH (100 microg), an injection of PGF2alpha (25 mg) 7 d later, and a GnRH injection at 48 h after PGF2alpha and were inseminated 16 to 20 h later. Cows were reinseminated at detected estrus or resynchronized with a GnRH injection at 20 d after insemination. At 27 d after insemination, cows were examined for pregnancy. Resynchronized cows diagnosed nonpregnant received an injection of PGF2alpha and were inseminated at detected estrus or received an injection of GnRH at 48 h after PGF2alpha and inseminated 16 to 20 h later. Cows pregnant at d 27 were reexamined for pregnancy at 45 d after insemination. First-service pregnancy rates at d 45 were increased in cows not resynchronized that initiated bST treatment at 63 +/- 3 d postpartum, compared with cows initiating bST treatment at 105 +/- 3 d postpartum (37.7 +/- 5.8% and 22.1 +/- 4.2%, respectively), but the effect of bST treatment was not observed when cows were resynchronized (25.6 +/- 4.3% and 25.8 +/- 5.5%, respectively). Thus, bST increased pregnancy rates to a timed artificial insemination protocol.