Is “natural cover” ethical? - Veterinary Practice
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Is “natural cover” ethical?

Modern horse breeding systems often reduce the ability for horses to express normal behaviours, but which system has the greatest welfare benefits?

One of the requirements for good welfare under the Five Freedoms framework (Webster, 1994) is that animals should be able to express normal behaviours. The importance of this welfare need was emphasised in the Five Domains model developed by Mellor and co-workers (Mellor and Beausoleil, 2015), and is nowadays well recognised.

This piece argues that modern methods of horse breeding, whether artificial or “natural cover” systems, deny horses the ability to express the normal behaviours associated with reproductive activity. However, the loss of such behavioural freedoms may be justified by a benefit in terms of reduced risk of injury during breeding. Artificial insemination systems offer positive welfare effects associated with reduced risk of transport-associated stress and disease.

Artificial insemination systems offer positive welfare effects associated with reduced risk of transport-associated stress and disease

Normal breeding behaviours of horses

In the wild, the breeding behaviours of horses centre around social interactions which occur within a group consisting of a dominant stallion and his “harem”. Though horses are seasonal breeders, the stallion and “his” mares interact year-round (McDonnell, 2000). When a mare is in oestrus, the stallion will typically engage in prolonged “teasing” behaviours to test her sexual receptivity, before venturing to mount the mare (often initially with his penis still withdrawn, or sideways, until he is confident that the mare is not going to kick him), and subsequently to engage in coitus. The mare frequently initiates contact with the stallion when she is in oestrus, and positions herself in such a way as to facilitate copulation (McDonnell, 2000).

Modern horse breeding systems

The organisation of the equine breeding industry differs hugely from the naturally occurring situation. Whereas feral horses exist in established hierarchical herds and harems, human-controlled horse breeding frequently involves the mating of horses which are unknown to each other. Though some breeders do still allow stallions to socialise and mate with mares at pasture without human interference (“pasture breeding”), the majority of breeders nowadays use either “natural cover” (less confusingly referred to as “hand breeding”) or artificial insemination systems. The main drivers for the adoption of such systems have been the desire to reduce risk of injury to stallions and mares unfamiliar with each other (for both systems), and to abolish the need for stallion and mare to be in the same location (artificial insemination systems).

Hand breeding systems typically involve the mare being held by a handler and immobilised, often using hobbles and/or nose twitch. The mare may have boots on her hind legs (to reduce the risk of her injuring the stallion by kicking), and her neck may be protected with a leather cover against the stallion biting her. The stallion is led towards the mare, and often expected to mount her swiftly, with minimal teasing/interaction between stallion and mare being allowed.

In artificial insemination systems, semen is normally collected using an artificial vagina, using either a “dummy mare” or a mare in oestrus for the stallion to mount. Where a real mare is used, she is likely to be immobilised in the same ways as for a hand breeding system. The mare being bred is subsequently restrained (usually in stocks) and inseminated using semen (freshly collected, chilled or frozen) which is placed in the uterus via a catheter.

Negative welfare effects associated with modern breeding systems

Clearly, artificial insemination systems radically reduce or completely abolish the opportunities for stallions and mares to express normal breeding behaviours, since there is no need for the mare and stallion to even catch sight of each other for the breeding process to be completed. The interaction between the mare and stallion in hand breeding systems is normally deliberately minimised in an effort to reduce the risk of injury. While often undertaken enthusiastically, the process of semen collection is essentially an unnatural process for the stallion, as is the process of hand breeding with minimal preceding interaction with the oestrus mare – something which can be reflected in both systems in low libido when compared to stallions breeding in a harem situation (McDonnell, 2000).

An additional consideration is the welfare of any foal at foot – in artificial insemination systems foals can typically remain alongside their mothers, either in or adjacent to the stocks in which the mare is restrained. When hand breeding is being used, foals are normally separated from the mare to reduce the risk of injury, which can be stressful for both mare and foal.

In “natural cover” systems, the stallion is led towards the mare, usually with minimal teasing or interaction allowed

Positive welfare effects associated with modern breeding systems

Many of the restrictions on normal reproductive behaviours imposed upon mares and stallions in modern breeding systems are undertaken with the aim of reducing the risk of injury (and thus safeguarding welfare). Thus, using a dummy mare rather than a real mare to collect semen from a stallion reduces the risk of injury not only to the stallion and the mare, but also to personnel. Similarly, immobilising the mare and allowing minimal interaction between stallion and mare during hand breeding is aimed at reducing the chances both of the mare kicking the stallion, and of the stallion biting or striking out at the mare.

There are additional positive welfare effects associated with the use of artificial insemination systems. Hand breeding necessarily requires the mare and stallion to be in the same place. Often, this involves mares and their foals being transported significant distances (sometimes internationally), which can be stressful, and can expose them – either during transportation or upon arrival at the premises with many, often transient, animals – to unfamiliar pathogens.

These stresses can be avoided by keeping the mare and foal at home and having semen delivered (though it should never be forgotten that all venereal diseases which can be spread by coitus can also be spread in artificially inseminated semen). Finally, when a popular stallion is being used in a hand breeding system, he may be required to breed three or four mares a day, which can be physiologically stressful (Allen, 2015). Where semen is collected artificially, the ejaculate can be divided, typically between four to seven mares, which significantly reduces the number of breeding efforts required by the stallion each day.


Both hand breeding and artificial breeding systems reduce the ability for horses to express normal behaviours when compared to pasture breeding or feral situations. However, in a harm:benefit (utilitarian) ethical analysis, such reductions in the ability to express normal behaviours could be traded for protection against injury. One should aim to maximise the benefits and to minimise the harms.

Though artificial insemination systems are not devoid of risk of injury, it is lower than that associated with hand breeding systems, at least where a dummy mare is used for semen collection. Collecting and dividing ejaculates reduces physical demands upon the stallion compared to hand breeding systems. Artificial insemination of mares at home also reduces the risk of contact with infectious (non-venereal) disease, and of stress due to transportation and/or to separation of mare and foal, compared to hand breeding systems. For these reasons, while neither system allows the expression of normal breeding behaviours, artificial semen collection and insemination is ethically preferable to hand breeding (so-called “natural cover”).


Allen, W. R.


AAF IETS Equine Reproduction Symposium. IETS, Paris. Pp. 28-29.

McDonnell, S. M.


Animal Reproduction Science, 60, 211-219.

Mellor, D. J. and Beausoleil, N. J.


Animal Welfare, 24, 241–253.

Webster, J.


Animal Welfare: A Cool Eye Towards Eden. Blackwell Science, Oxford. Pp. 10-14.

Madeleine Campbell

Madeleine Campbell, BVetMed, MA (Oxon), MA (Keele), Phd, DipECAR, DipECAWBM, MRCVS, is a RCVS and European Recognised Specialist in Equine Reproduction. She is the sole partner at Hobgoblins Equine Reproduction Centre, and has active research interests in clinical equine reproduction, and in the ethics of using assisted reproductive technologies in animals.

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