rbGH

Recombinant bovine growth hormone (rbGH), also known as recombinant bovine somatotropin (rbST), is a hormone produced through recombinant DNA technology. It is a synthetic version of the bovine growth hormone and is manufactured in bacterial cells. In dairy farming, rbGH is injected into lactating cows to increase milk production during a lactation cycle.

The primary effect of rbGH is to raise the amount of milk a cow yields. It works by increasing levels of insulin-like growth factor 1 (IGF-1) in the mammary gland, which stimulates greater milk synthesis. Milk composition—including fat, protein, and lactose—typically shows little or no consistent, large change, though management practices and individual cows can cause variability. Some cows may experience higher incidences of mastitis and related health issues, potentially leading to greater antibiotic use and impacts on welfare and culling decisions.

Regulatory status varies by country. The United States approved rbGH for use in dairy cows in 1993; labeling about rbGH use is not universally required. In the European Union, rbGH use in dairy cattle has been banned since the mid-1990s. Canada and other jurisdictions have different regulatory approaches, often reflecting consumer preferences and welfare considerations. Market adoption has been uneven, with some processors and retailers offering rbGH-free milk in response to consumer demand.

Safety assessments by major regulatory bodies have concluded that milk from rbGH-treated cows is not unsafe for human consumption and is not measurably different in safety or nutrition from milk from untreated cows. Nevertheless, debates on animal welfare, antibiotic use, and consumer choice continue to influence its use and labeling in various markets.