a compatible , biodegradable microcapsule delivery system for active ingredients , including hormonally active peptides , proteins , or other bioactive molecules , and a method of making the same . the ingredients are encapsulated in biodegradable copolymer excipients of varying mole ratios and the blend of the microcapsules are administered to an animal . delivery of the ingredient occurs over a prolonged period of time at a constant rate as a result of the varying break - down rates of the copolymer excipients .