The most apparent sign of infertility is the repeated inability to achieve pregnancy or impregnate a partner despite regular and appropriate breeding attempts.

Female pets typically have regular oestrous cycles (heat cycles) during which they are receptive to mating. If a female pet exhibits irregular or absent oestrous cycles, it can be an indication of infertility.

Unusual behaviour during mating attempts can be a sign of infertility. For example, male pets may show disinterest or lack of libido, or they may have difficulty mounting or achieving successful mating

Structural abnormalities in the reproductive organs can contribute to infertility. In males, this can include undescended testicles, testicular abnormalities, or blockages in the reproductive tract. In females, it can involve abnormalities in the uterus, ovaries, or fallopian tubes.

Hormonal disorders can disrupt the reproductive cycle and lead to infertility. Signs may include irregular heat cycles, changes in behaviour, or physical manifestations such as abnormal hair growth or weight gain.

If a pet has a history of previous reproductive issues such as miscarriages, stillbirths, or difficulties in delivering live, healthy offspring, it may indicate underlying infertility.