Few numbers of new lines were synthesized in our Arabian hot climate countries using different criteria and methods of selection and crossbreeding particularly in Egypt and Saudi Arabia. In this concept, Saudi 2 and APRI rabbits (as maternal lines) and Alexandria and Saudi 3 (as paternal lines) and Moshtohor (as multipurpose line) were being formed to be convenient in hot climate. The most common selection criteria used in selection programs to develop new maternal lines were related with litter size at birth or at weaning and milk production, while in paternal lines, post-weaning daily gain or marketing weight are commonly selected individually. Spanish V-line rabbits genetically selected for more than 35 generations were introduced in various developing countries (as alive animals or as frozen embryos) and by using recent bio-techniques and applying selection and /or crossbreeding programs with local lines, this line was widely distributed in some hot countries of the world like Egypt and Saudi Arabia. Direct selection had little or moderate effects on litter and lactation traits, while it had considerable effects on post weaning growth and feed conversion. Direct heterotic effects were evidenced for litter size, litter weight, and milk yield. Crossbred does and dams gave favourable heterotic effects on litter traits, milk yields and components and milk conversion ratio. Direct heterosis for body weights raised in hot countries were mainly positive and ranging from 1.3 to 14.5 %, but the estimates for maternal heterosis were mainly low and ranging from 0.2 to 5.3 %. Crossbred dams gave moderate maternal heterotic effects ranging from 4.8 to 18.7%. Neither individual heterosis, nor maternal heterosis were evidenced for meat quality traits. Crossbred bucks were associated with an existence of heterotic effects in ejaculate volume (11.6%), sperm concentration (10.5 %), percentages of motile (9.8%) and living sperms, along with a reduction in percentages of abnormal (-10.8%) and dead sperms (-23.5%). Crossbred dams gave maternal heterotic effects on some semen parameters in their progeny of crossbred bucks. The recent molecular technologies were used only in developing countries to detect the associations between phenotypic traits and genetic markers and three markers were detected for litter and milk traits and body weights. |
