In chickens, there are negative correlations between laying performance and fattening performance. Therefore, selection centers focus on either selection of egg-type chickens or selection of meat-type chickens. As a result, one-day old male layer chicks are considered as defects in production. This is because, they have a slow growth rate, low feed conversion, and their meat is not tender at maturity. The culling of day-old male chicks in layer production raises animal welfare, environmental, economic and ethical issues. Therefore, researchers are looking for alternative methods to avoid the routine killing of male layer chicks. Currently, three different methods are in focus: raising male eggs for meat production, using dual-purpose breeds, and sex identification in hatching eggs (i.e. »in ovo« sexing). The main disadvantages of rearing male laying hens are the long fattening period, the high feed consumption and the resulting high feed costs. Dual purpose breeds that would allow economically viable production of meat and eggs are not available. The best alternative at present would be to use in ovo spectroscopy for sex determination in the hatching egg on the fourth day of incubation, before the chick embryo develops its sensory nervous system. As a result, the male hatching eggs are removed early and do not hatch. This saves energy costs and the removed male hatching eggs could then be processed into a high quality feed. Some concerns regarding these technologies are the accuracy of sexing, cost effectiveness, and producing rates fast enough for the industry. This thesis describes the mechanisms of sex determination in birds and possible solutions to the problem of male layer chicks being discarded.
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