Detection of growth hormones in the plasma of cows treated with recombinant bovine growth hormone

The levels of bovine growth hormone (bGH) in the plasma of cows treated with recombinant bGH (r-bGH) were measured in order to discriminate between treated and untreated animals. bGH concentrations were detected with an enzyme immunoassay (EIA) that uses polyclonal antibodies raised against pituitary bGH. The method can detect levels of bGH as low as 0.25 ng ml-1. The r-bGH used for the animal treatment showed, in EIA, a cross-reactivity with the pituitary bGH of 77.23%. The animals were injected monthly with 640 mg of r-bGH in slow-release form, with a total of four injections. The experimental procedure showed, in the pattern of bGH concentrations of the treated cows, a peak on the seventh day after each injection. The increase was statistically significant in comparison with the basal level (56% increase; P < 0.01). The control animals did not show any significant variation in the plasma concentration of bGH throughout the experiment. The results indicate the usefulness of the EIA in discriminating r-bGH-treated from untreated animals.