Selective breeding has produced crops and animals with higher yields, more milk or meat, and resistance to disease, and it needs no special equipment. But it is slow, because it takes many generations. It also reduces genetic variation, so the population is more at risk from a new disease, and inbreeding can bring harmful inherited problems. Some animals have been bred for features that harm their welfare, which raises an ethical objection.
Genetic engineering is faster and more precise because it can add a single gene. In agriculture, crops that resist pests can mean less pesticide is used and the yield is higher. In medicine, bacteria make insulin for people with diabetes. The risks include unknown long-term effects on human health from eating GM food, and pollen from GM crops could carry the transferred gene to wild plants.
There are practical concerns, such as the high cost of GM seed, which farmers must buy from companies. There are also ethical concerns. Some people object to changing the genome of living things, and some worry about the welfare of genetically modified animals. To evaluate, weigh the benefits for food supply and health against the risks to the environment, to people and to animals.