This paper reviews the current knowledge on the genetics of growth, carcass and meat traits in rabbits. There is a great variety in size of rabbit breeds, from which commercial production uses medium size breeds for does and large breeds as terminal sires. Selection experiments for growth and feed efficiency have been successful. Selection for residual feed intake did not modify growth rate, acting on reducing the appetite. Selection for growth rate increased adult weight and led to poorer carcass yield when comparing selected and unselected animals at the same commercial weight, but not at the same age, near the same maturity stage. The results on meat/bone ratio do not show a clear pattern. Negative effects on intramuscular fat and some sensorial traits have been found in lines selected for growth rate, but meat quality in general does not seem to be affected.

To test for the presence of purging in populations, the classical pedigree-based inbreeding coefficient (F) can be decomposed into Kalinowski’s ancestral (F_ANC) and new (F_NEW) inbreeding coefficients. The F_ANC and F_NEW can be calculated by a stochastic approach known as gene dropping. However, the only publicly available algorithm for the calculation of F_ANC and F_NEW, implemented in GRain v 2.1 (and also incorporated in the PEDIG software package), has produced biased estimates. The F_ANC was systematically underestimated and consequently, F_NEW was overestimated. To illustrate this bias, we calculated F_ANC and F_NEW by hand for simple example pedigrees. We revised the GRain program so that it now provides unbiased estimates. Correlations between the biased and unbiased estimates of F_ANC and F_NEW, obtained for example data sets of Hungarian Pannon White rabbits (22,781 individuals) and Dutch Holstein Friesian cattle (37,061 individuals), were high, i.e., >0.96. Although the magnitude of bias appeared to be small, results from studies based on biased estimates should be interpreted with caution. The revised GRain program (v 2.2) is now available online and can be used to calculate unbiased estimates of F_ANC and F_NEW.

Effect of dietary supplementation of spirulina (Arthrospira platensis) and thyme (Thymus vulgaris) on apparent digestibility and productive performance of growing rabbits

Demographic history, current status, and efficiency of the mating strategy were analyzed using the pedigree of Pannon White (PW) rabbits born between 1992 and 2007. Potential accumulation of detrimental effects and loss of genetic diversity were also considered. Calculations and estimates were done most often for rabbits born in 2007, whereas other reference populations (REFPOPXXXX) were specified explicitly. The pedigree contained 4,749 individuals and 580 founders, and its completeness was 82.1% up to 10 and 94.5% up to 5 generations, respectively. Generation intervals through different pathways averaged 1.2 yr. When adjusted to the pedigree completeness, the amount of inbreeding (F_i) of rabbits was comparable (5.54%) with that of other livestock populations, whereas the 10 (30) founders contributing the most to inbreeding explained a large part of the population inbreeding [i.e., 42.24% (73.18%)]. The ancestral inbreeding coefficient of REFPOP2004 (10.67%) was one-half that of REFPOP2007 (20.66%), showing its strong dependence on pedigree length. Family variance, inbreeding, and realized effective population size were 84.18 (REFPOP2006; this variable could not be calculated for the last year examined), 37.19, and 91.08, respectively. The effective numbers of ancestors, founders, and founder genomes were 48, 26, and 7.33, respectively. Although the circular mating scheme applied was generally effective, the large accumulated reduction in genetic variability indicates the need to revise and improve the current breeding strategy. Copyright © 2010. American Society of Animal Science .