This study aimed at the identification of genetic variations in the myostatin (MSTN) gene and testing their effects on carcass quality traits. We comparatively sequenced Giant Grey (GG) and New Zealand White (NZW) rabbits that were founders of a cross-bred population. Alignment of our sequence data with the GenBank sequence of the rabbit MSTN gene (Ensembl Gene ID ENSOCUG00000012663) identified three single nucleotide polymorphisms (SNPs). The two novel SNPs (c.-125T>C, c.373+234G>A) and one known SNP (c.747+34C>T) were subsequently analysed for linkage with carcass composition traits in 363 F2 animals of the cross GG × NZW. Significant linkage was found between c.373+234G>A and nine carcass composition traits (P < 0.05). No significant effects were found for c.-125T>C and c.747+34C>T. Because the linked SNP is located in intron 1 and no genetic variation was found in the coding region, further investigations are necessary to understand the functional effect of the c.373+234G>A variant on the variability of the traits.

The study was aimed to determine the effect of reciprocal-crossing rabbits on growth and slaughter traits. The experiment was conducted on 120 New Zealand White (NZW) and Californian (CAL) medium-sized rabbits and their F1 reciprocal crosses (CAL × NZW and NZW × CAL). The rabbits were fed pellets ad libitum, and slaughtered at body weight around 2.5 kg. The following traits were recorded: body weight and average daily gain at birth to slaughter, average feed consumption from weaning to slaughter, slaughter age, carcass weight, meat, bone and fat content of carcass, prime cuts weight (fore part, loin and hind part), and dressing percentage. The results indicated that reciprocal crossbred CAL × NZW and NZW × CAL rabbits were heavier than purebred animals. NZW × CAL crosses attained the slaughter body weight earlier, and had lower feed consumption. The dressing percentage in NZW × CAL crosses was highest, while the lowest in NZW rabbits. For other slaughter traits, except the fat content of carcass, effects of crossing rabbits were small. The magnitude of the crossbreeding effects depended on the direction of crossbreeding. Maximum effects in crosses for slaughter age, body weight, feed consumption and dressing percentage were obtained when the Californian breed was used as a maternal component. Keywords

Genetic parameters for lactose percentage in the milk of Polish Holstein-Friesian cows were estimated using 48,859 test day records from six lactations of 8,418 cows and the Gibbs sampling method. The multiple-trait random regression model was applied for data from the first and subsequent (up to the sixth) lactations treated as two traits. Variance components and heritabilities changed in a similar way through the first and subsequent lactations, reaching the highest values at peripheries and relatively stable values in the middle of lactations. All estimates were smaller in the first than in the later parities. Heritabilities of daily lactose percentage ranged from 0.17 to 0.31 with a mean of 0.24 (SD=0.034), and from 0.23 to 0.36 with a mean of 0.28 (SD=0.026) in first and subsequent lactations. Genetic correlations for lactose percentage between the same days of the first and subsequent parities were less than 0.30, with the average equal to 0.26 (SD=0.047) and the minimum (less than 0.15) occurring in the first days after calving.

BackgroundGenomic resources for the rabbit are still limited compared to many other livestock species. The genomic sequence as well as linkage maps have gaps that hamper their use in rabbit genome research. Therefore, the aims of this study were the improvement of existing linkage maps and the mapping of quantitative trait loci (QTL) for carcass and meat quality traits. The study was performed in a F2 population of an initial cross between Giant Grey (GG) and New Zealand White (NZW) rabbits. The population consisted of 363 F2 animals derived from 9 F1 bucks and 33 F1 does. 186 microsatellite and three SNP markers were informative for mapping.ResultsOut of 189 markers, which could be assigned to linkage groups, 110 markers were genetically mapped for the first time. The average marker distance was 7.8 cM. The map across all autosomes reached a total length of 1419 cM. The maternal linkage map was 1.4 times longer than the paternal. All linkage groups could be anchored to chromosomes. On the basis of the generated genetic map, we identified a highly significant QTL (genome-wide significance p < 0.01) for different carcass weights on chromosome 7 with a peak position at 91 cM (157 Mb), a significant QTL (p < 0.05) for bone mass on chromosome 9 at 61 cM (65 Mb), and another one for drip loss on chromosome 12 at 94 cM (128 Mb). Additional suggestive QTL were found on almost all chromosomes. Several genomic loci affecting the fore, intermediate and hind parts of the carcass were identified. The identified QTL explain between 2.5 to 14.6% of the phenotypic variance in the F2 population.ConclusionsThe results present the most comprehensive genetic map and the first genome-wide QTL mapping study for carcass and meat quality traits in rabbits. The identified QTL, in particular the major QTL on chromosome 7, provide starting points for fine mapping and candidate gene search. The data contribute to linking physical and genetic information in the rabbit genome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0168-1) contains supplementary material, which is available to authorized users.

Leptin is a hormone synthesized and secreted primarily in adipose cells that help to regulate energy balance. This study examined the associations of single nucleotide polymorphisms in the rabbit leptin gene with growth traits, slaughter traits and physicochemical parameters of New Zealand White (NZW) and Belgian Giant Grey (BGG) crossbreed rabbits. In total, 320 crossbreed animals were genotyped for polymorphisms within exon 2-g.16081633T>C, intron 1_2-g.16081420C>T, and within UTR-g.16079636C>G for association analysis. Identified polymorphisms within rabbits leptin gene showed significant differences for dissectible fat percentage in carcass and dissectible fat weight in intermediate part (g.16081633T>C). Moreover, meat traits like protein content (g.16081633T>C; g.16079636C>G), intramuscular fat content (g.16081633T>C; g.16079636C>G, g.16081420C>T), dry matter (g.16081420C>T), ash (g.16081420C>T), water (g.16081420C>T), and cohesiveness (g.16081420C>T, g.16079636C>G) were affected by polymorphisms in leptin gene. We conclude that polymorphism in the rabbit leptin gene influences important carcass and meat traits of NZW × BGG crossbreeds. Therefore, polymorphisms identified in this study may be used in selection as a meat trait markers.