46. Culling
It is necessary to cull (destroy) severely to keep the stock in a loft up to standard. Cull birds which do not meet physical requirements for breeding unless all birds are needed. In addition, destroy those which show a definite lack of intelligence, or which do not perform up to the average. About 30 percent of the young bred in any one season are normally under the physical standard and should be culled to keep the stock from degenerating. In addition to losses sustained through culling, 20 to 30 percent of the remaining stock may be expected to be lost during training flights, as result of disease and injury, or through additional culling because of substandard performance.