Culling is a term used for separating the good from the bad and discarding the bad with the cull being the rejected items. Culling is used to improve the desired group with specific characteristics to improve the group.
Culling is used for strengthening a livestock herd and the culled animals are destroyed. When breeding pedigree animals, the culled are spayed or neutered. This prevents the undesirable trait of the animal from being bred with other animals. Plant life is also strengthened during the culling process in order to obtain the plants with the highest yield. Culling is seen during various talent contests where those that do not measure up are dropped.
Livestock is usually bred for the by-product of the animal: i.e., meat, milk, or eggs. Ranchers/farmers will maintain their herd by continually using the culling methods to keep the herd strong and productive. Any animal that is not selected, meaning they are culled or considered surplus, are then sold or sent to slaughter.
In the poultry industry, the hatchlings are culled according to gender usually resulting in the demise of the roosters. The widespread outbreak of the H5N1 influenza virus in 2008 prompted the culling of chickens and other fowls with the hopes of containing the virus. This occurred again in 2013 with the H7N9 bird flu virus outbreak in China.
Breeders use the tandem method during the culling process to focus on various traits that are being considered. Some changes may need to be made in one trait or characteristic of the animal while other traits need to remain constant. The culling process continues through the generations, raising the criteria for the next culling process.
Another method used by breeders is the total score method. Each trait or characteristic is measured and given a score according to a weighted table used for evaluation purposes. This process helps the breeder evaluate multiple traits at the same time.
The wildlife is managed with the issuance of hunting licenses. Limitations, such as when to hunt and how many of one species can be hunted, are set to control one gender of a species at any given time. Culling of wildlife is necessary to prevent the overpopulation of wildlife that interferes with domestic herds of the ranchers/farmers. Although culling is used in the wildlife management of national parks and game preserves in the United States it is controversial in African countries and has been banned since 1995.
Fishing licenses are issued in much the same manner as wildlife game hunting licenses are with the need to cull certain species of fish in lakes, rivers, streams, and ponds. Culling during fishing tournaments refers to keeping the largest fish thereby releasing the smallest.
Image Caption: Culled foxes help maintain a safe population of the species within a determined region. Credit: Thinkstock