Introduction
“Stress” is responsible for many things, including subfertility. Many agricultural advisers and veterinarians are very familiar with those intangible factors that reduce fertility on farms but often they are unable to pinpoint precise contributory causes — and hence blame “stress”.
This, in itself, provides a definition of “stress”, that is, the inability of an animal to cope with its environment, a phenomenon that is revealed by a failure to achieve genetic potential, e.g. for growth rate, milk yield, disease resistance, or fertility.