Both male and female animals which are finely bred or which have particularly commendable points from a breeding point of view, may be overused for breeding purposes, giving rise to inferior progeny or infertility. Females of certain species may be mated consecutively when it may be better for them to have a resting period between pregnancies. Males may be overused for financial reasons, or for their prowess or virility, or because of their fine breeding or special qualities. Males may be used too often with the same herd or the same individual animals. They may be overused for artificial insemination purposes, where demand for the services of sires of high merit is extensive, and where one ejaculation may be extended to 100 or more services, almost on the level of mass production.
Inbreeding of domestic animals is a common practice to improve stock and to preserve qualities found in one or two exceptionally fine animals. However, the effect of inbreeding also serves to increase the proportion of defective, weak, slow-growing animals, and unless the method is used very selectively, especially with species that are normally cross-fertilizing and outbred, these characteristics will predominate. Reasons for excessive inbreeding include lack of due care, general inexperience, overzealousness, and financial rewards.