BSTH AND IGF-I LEVELS IN BLOOD AND MILK OF BLACK-AND-WHITE DAIRY-COWS BEFORE AND AFTER APPLICATION OF RECOMBINANTLY DERIVED BOVINE SOMATOTROPIN

In an 8 week trial period six black and white dairy cows were injected with Optiflex®, a slow release formulation of recombinantly derived bovine somatotropin (BST). Three cows each were injected at two‐weeks (BST‐14) or four weeks (BST‐28) intervals. The dosage was 640 mg BST per injection. Average milk yield increased by 18. 3% and 13. 8% in groups BST‐14 and BST‐28 respectively. Blood plasma levels of bSTH and IGF‐I increased till day 10 post‐injection; thereafter they declined, except IGF‐I levels in group BST‐14 which persisted continuously elevated with minor variations. No bSTH above detection level could be assayed in the milk of treated animals. The IGF‐I level in milk was slightly elevated after BST‐application but stayed within the normal range. © 1990 Blackwell Verlag GmbH