Culling
For livestock and wildlife, culling often refers to killing removed animals based on their characteristics, such as their sex or species membership, or as a means of preventing infectious disease transmission.
The process of culling starts with examination of the conformation standard of the animal and will often include additional qualities such as health, robustness, temperament, color preference, etc.
[2] With the tandem method, a minimum level of quality is set for important characteristics that the breeder wishes to remain constant.
The breeder will raise the threshold for selection on this trait with each successive generation of progeny, thus ensuring improvement in this single characteristic of his breeding program.
Independent levels is a method where any animal who falls below a given standard in any single characteristic is not used in a breeding program.
Should progeny fall below the desired quality in any one characteristic being measured, it will not be used in the breeding program regardless of the level of excellence of other traits.
The breeder will determine what the minimum acceptable quality for each of these traits will be for progeny to be folded back into their breeding program.
The breeder determines the lowest acceptable total score for an animal to be folded back into their breeding program.
In a domestic or farming situation, the culling process involves the selection and selling of surplus stock.
In order to increase the frequency of preferred phenotypes, agricultural practices typically involve using the most productive animals as breeding stock.
[3] With dairy cattle, culling may be practised by inseminating cows—considered to be inferior—with beef breed semen and by selling the produced offspring for meat production.
These individuals have little use in an industrial egg-producing facility as they do not lay eggs, so the majority of male chicks are killed shortly after hatching.
[9] Populations of game animals such as elk may be informally culled if they begin to excessively eat winter food set out for domestic cattle herds.
In such instances the rancher will inform hunters that they may hunt on their property in order to thin the wild herd to controllable levels.
[11] Culling for population control is common in wildlife management, particularly on African game farms and Australian national parks.
Cormorants are culled in many countries due to their impact on commercial and recreational fisheries and habitat modification for nesting and guano deposition.
Another example is the culling of silver gulls in order to protect the chicks of the vulnerable banded stilt at ephemeral inland salt lake breeding sites in South Australia.
[16] In the Australian states of Tasmania and South Australia, Cape Barren geese are culled to limit damage to crops and the fouling of waterholes.
[18] In South Australia, the recovery of the state's native population of New Zealand fur seals (Arctocephalus forsteri) after severe depletion by sealers in the 1800s has brought them into conflict with the fishing industry.
[28] Baited hooks known as drum lines were to be set over several consecutive summers to catch and kill otherwise protected great white sharks.
Thousands of people protested against its implementation, claiming that it was indiscriminate, inhumane and worked against scientific advice the government had previously received.
[30] White-tailed deer (Odocoileus virginianus) have been becoming an issue in suburbs across the United States due to large population increases.
[35] Those in favor of the culls argue that they can be used to combat the selection pressure that is imposed by hunting that creates smaller antler and body sizes in deer.
[38] Many zoos participate in an international breeding program to maintain a genetically viable population and prevent inbreeding.
By using such methods population numbers might be reduced more gradually and in a potentially more humane fashion than by directly lethal culling actions.
Currently, wildlife contraceptives are largely in the experimental phase and include such products as Gonacon, an adjuvant vaccine which delivers a high dosage of a competitor ligand of the hormone GnRH to female mammals (e.g. whitetail deer).
[49] Though the endocrinology behind Gonacon is sound, the need for multiple lifetime doses for full efficacy make it a less-guaranteed and less-permanent solution for wildlife than lethal culls.
