Why was bovine insulin used as the source of insulin?

Bovine insulin was used as a source of insulin because it is structurally similar to human insulin, differing by only a few amino acids. This similarity allowed it to effectively regulate blood sugar levels in diabetic patients. Additionally, cows were readily available as a livestock source, making bovine insulin an accessible option for medical use before the advent of recombinant DNA technology, which enabled the production of human insulin.