Breeding programs in meat rabbits are characterised by the development of specialized lines in selection nucleus farms. A three‑line crossbreeding system in widely used by commercial rabbit producers. Two lines are selected for litter size to obtain crossbed females. Another line is selected for growth rate, a trait very related with feed efficiency.
Genetic response for litter size is between 0.04 and 0.15 young weaned rabbits by litter per year. Two alternative ways to improve litter size are developed. Firstly, the application of a high intensity of selection over a large population, in order to create a new line (hyperprolific scheme). Secondly, selection for uterine efficiency. Uterine efficiency is the maximun number of fetuses that a female can be support to birth when ovulation rate is not a limiting factor.
The annual genetic response in lines selected for growth rate is aproximately 0,8 g/day during the growth period. The improvement of growth rate seems to lead to an increase of adult weight and a lower degree of maturity of the rabbit at slaughter.
Crossbreeding of two maternal lines is performed due to the advantage from heterosis of crossbred dams. These crossbred does are mated with a male of a third line. Dams have a good reproduction ability and their offspring have a high growth rate transmitted by the sire line.
Universidad Politécnica de Valencia and Institut de Recerca i Tecnología Agroalimentaries (IRTA) have created selection nucleus farm and helped rabbit association in developping their own selection programs. Average size of the farms and reproductive characteristics of rabbits make possible that farmers can developed the multiplication step in their own farm. This has economic, logistic and sanitary advantages.