Editor's note: The following article was featured in the May issue Dairy Herd Management.

Recombinant bovine somatotropin (bST) is most often associated with increased milk production by dairy cows. But recently, a team of researchers set out to evaluate the effects of administering either one or two low doses of slow-release bST on hormone concentrations, embryo development and fertility in dairy cows.

The results were published in the January 2014 Biology of Reproduction journal. The study followed 1,483 cows that were blocked by parity and assigned randomly to receive a single placebo injection at insemination (control), a single injection with 325 milligrams of bST (half the dosage of the commercially available product) at insemination (S-bST), or two injections with 325 milligrams of bST administered on days 0 and 14 (T-bST).

Results show that cows that received T-bST had an earlier rise in the pregnancy-specific protein B in plasma, increased embryo size and enhanced fertility. Cows that received S-bST did not show improvements in embryo development and fertility. In conclusion, the researchers say that supplementation with two low doses of bST enhanced embryo development, reduced embryonic losses and improved fertility in dairy cows.

To access the abstract, visit www.biolreprod.org/content/90/1/10.abstract.