Traits Of Rabbits Research Articles

Assessing the Genetic Response of Crossing on Post-Weaning Growth Traits in Rabbits

Assessing the Genetic Response of Crossing on Post-Weaning Growth Traits in Rabbits

Association of single nucleotide polymorphisms in Neuropeptide Y (NPY) and Phosphoglycerate Mutase 2 (PGAM2) genes with growth traits in rabbits

Genetic improvement of local rabbit breeds using modern approaches such as marker-assisted selection requires accurate and precise information about marker‒trait associations in animals with different genetic backgrounds. Therefore, this study was designed to estimate the association between two mutations located in the Neuropeptide Y (NPY, g.1778G > C) and Phosphoglycerate Mutase 2 (PGAM2, c.195 C > T) genes in New Zealand White (NZW), Baladi (BR), and V-line rabbits. The first mutation was genotyped using high-resolution melting, and the second mutation was genotyped using the PCR-RFLP method. The results revealed significant associations between the NPY mutation and body weight at 10 (V-line) and 12 weeks of age (NZW, BR, and V-line), body weight gain (BWG) from 10 to 12 weeks of age (BR), BWG from 6 to 12 weeks of age (NZW, BR, and V-line), average daily gain (NZW, BR, and V-line, and BR), growth rate (GR) from 8 to10 weeks (V-line), 10 to 12 weeks (BR), and GR from 6 to 12 weeks of age (BR, and V-line). The PGAM2 mutation was associated with body weight at 10 (V-line) and 12 (NZW, and V-line) weeks of age, with significant positive additive effects at 12 weeks of age in all breeds, and was associated with BWG from 8 to 10 and 10 to 12 in BR, and BWG from 6 to 12 weeks of age (NZW, and BR), and average daily gain (NZW, and BR), and was associated with GR form 8 to 10 weeks (BR), from10 to 12 weeks (BR, and V-line) and from 6 to 12 weeks (BR). The results highlighted the importance of the two mutations in growth development, and the possibility of considering them as candidate genes for late growth in rabbits.

Meat quality and sensory traits in rabbits fed with two different percentages of bovine colostrum

The nutritional, antimicrobial, and antioxidant properties of bovine colostrum (BC) have encouraged its use in animal nutrition as a functional food in recent years. Nonetheless, the potential implications of BC supplementation on meat quality remain to be thoroughly assessed. To address this, thirty-nine New Zealand White rabbits (n = 13/group) were fed different dietary regimens until slaughter.: commercial standard diet for the control group (C) and C with 2.5% and 5% w/w of BC for BC-2.5 and BC-5 groups, respectively. Rabbits were slaughtered at 91 days of age and meat quality, and sensory characteristics were evaluated at days 2 (48 h after slaughter), 5, and 10 of refrigerated storage at 4 °C.The addition of colostrum in the diet resulted in a reduction of the total viable count, albeit only at the highest concentration and at the final detection, whereas for Lactobacillus spp. and Pseudomonas spp., there was little or no effect. The colour coordinates showed no differences between the groups, but they varied over time according to diet. Some differences between groups emerged in the definition of sensory attributes but did not affect the overall liking and overall scores of individual descriptors. These results indicate that the use of colostrum in rabbit feeding does not significantly impart meat quality and sensory attributes, but the potential of this valuable by-product for the food industry needs further investigation.

Influence of polymorphisms in candidate genes on carcass and meat quality traits in rabbits.

Candidate gene is a powerful approach to study gene-trait association and offers valuable information for genetic improvement using marker-assisted selection. The current work aimed to study the polymorphisms of four single nucleotide polymorphism (SNPs) at located growth hormone (GH), insulin-like growth factor-II (IGF-II), fat mass and obesity-associated (FTO), and insulin receptor substrate-1 (IRS-1) genes, and their association with the carcass, and meat quality traits in rabbits. The SNPs were genotyped using RFLP-PCR in New Zealand White and local Baladi rabbits. The results revealed that the heterozygous genotype was the most frequent in all cases, except for the FTO SNP in LB rabbits. There was a significant effect for GH genotypes on meat lightness after slaughter and hind-part weight. While, IGF-II mutation significantly affected slaughter, hot carcass, commercial carcass, and hind-part weights. The FTO SNP was associated with cooking loss and intramuscular fat weight, and the IRS-1 SNP was significantly associated with drip loss and intramuscular fat. Specific-breed effects were obtained for IGF-II SNP on cooking loss, and for the intramuscular fat. Although the results suggested that these mutations are useful candidate genes for selection, more research for detecting more variants associated with carcass and meat quality traits in rabbits are recommended.

Genome wide association study of growth and feed efficiency traits in rabbits

Feed efficiency is a major production trait in animal genetic breeding schemes. To further investigate the genetic control of feed efficiency in rabbits, we performed a genome-wide association study (GWAS) for growth and feed efficiency on 679 rabbits genotyped with the Affimetrix Axiom Rabbit 200K Genotyping Array. After quality control, 127 847 single-nucleotide polymorphisms (SNP) were retained for association analyses. The GWAS were performed using GEMMA software, applying a mixed univariate animal model with a linear regression on each SNP allele. The traits analysed were weight at weaning and at 63 days of age, average daily gain, total individual feed intake, feed conversion ratio and residual feed intake. No significant SNP was found for growth traits or feed intake. Fifteen genome-wide significant SNPs were detected for feed conversion ratio on OCU7, spanning from 124.8 Mbp to 126.3 Mbp, plus two isolated SNP on OCU2 (77.3 Mbp) and OCU8 (16.5 Mbp). For residual feed intake, a region on OCU18 (46.1-53.0 Mbp) was detected, which contained a putative functional candidate gene, GOT1.

Efficiency of leptin gene polymorphisms in the evaluation of the growth performance and carcass measurements of v-line and Baladi black rabbits

This study investigated the association between both polymorphisms and metabolic marker changes of the leptin gene, and body weight, weight gain, carcass traits, feed intake, and feed conversion ratio. Blood samples were collected from 60 V-line and 60 Baladi Black rabbits for DNA extraction and biochemical analysis. DNA sequencing of leptin (202-bp) revealed four non-synonymous single nucleotide polymorphism (SNPs) that characterized a number of V-line rabbits. Statistical analysis revealed that the identified SNPs were associated with rabbit growth and carcass measurements (p < 0.05). A discriminant analysis model showed a high classification percentage for the identified SNPs within and between breeds using body weight at 5-14 weeks of age (91.7%), slaughter traits (91.6%), feed intake, daily feed intake, and feed conversion ratio (76.7%). This study reveals that leptin gene could be a candidate for growth traits in rabbits enabling the development of marker-assisted selection (MAS) in different rabbit breeds.

Influence of dietary corn distillers' dried grains with solubles on nutrient digestibility, growth performance, and carcass traits in rabbits.

Two experiments were performed to evaluate the digestibility and growth performance of New Zealand White rabbits fed corn distillers' dried grains with solubles (DDGS). For the digestibility trial, 20 rabbits were housed in metabolic cages. The animals were distributed in two treatments, T1 (control diet without inclusion of DDGS) and T2 (control diet + 300gkg-1 DDGS). For the growth performance trial, 100 rabbits (50 males and 50 females) were assigned in a factorial design 2 × 5 (2 gender × 5 inclusions of DDGS) and five replicates. The treatments were composed of diets with inclusions of 0, 60, 120, 180, and 240gkg-1 of DDGS. The rabbits were housed at 35days old, and the experiment lasted 35days. The DDGS showed high digestibility for protein (74.10%) and lipids (81.51%) and a high content of digestible energy (2979kcalkg-1). In the second trial, growth performance and carcass yield and organ relative weights were evaluated. There were no interactions between gender and DDGS inclusions (P > 0.05). A linear decrease was observed for feed intake (FI) for the period from days 35 to 50 (FI, P = 0.001) and FI and FCR from days 35 to 70 (FI, P = 0.004; FCR, P = 0.001) with the increasing levels of DDGS. Rabbits supplemented with 240gkg-1 had lower (P < 0.05) whole carcass yield (WCY) and carcass without head yield compared with the control rabbits. DDGS is highly digestible in rabbits, and when supplemented up to 240gkg-1 in diets, it improved FCR but reduced FI and WCY.

Genotype by heat conditions interaction effects on growth and litter traits in rabbits.

Heat stress has severe impacts on rabbit performance because they have difficulty getting rid of excess heat. The interaction between genetic and environmental factors plays a vital role in the adaptation process. The current study aimed to evaluate the effects of interaction between the genotype and heat conditions (G×H) on litter size and growth traits. Two rabbit lines were used in the current study, Egyptian maternal line (APRI) and New Zealand White (NZW). The rabbits were raised under normal (22°C) or heat stress (35°C) conditions. The does were raised in individual cages, and their kits were reared under the same conditions. Negative effects of heat conditions were noted for litter traits, as heat stress had significantly reduced the number of born alive, total born, and marketed number rabbits by about 16, 11, and 25%, respectively. Moreover, growth traits were reduced under heat stress conditions compared to normal temperature conditions. Significant differences between genotypes were observed, APRI rabbits were higher than NWZ rabbits in the total born, number of born alive, number weaned, and the number of marketed rabbits by 10, 8, 11, and 10%, respectively. Genotype by heat conditions interaction effects were observed, APRI litters under normal conditions showed significantly higher litter traits than NWZ litters, whereas relevant reductions in litter traits of APRI line than NZW litters when reared in heat conditions. For growth traits, the differences between the two lines under normal conditions were reduced when animals of the two lines were raised under heat stress, for BW28, BW42, BW63, ADG28-42, and DF28-42 while these differences were increased for ADG42-63, DF28-42 and feed conversion during the whole fattening period. Based on the observed G × H interactions, it is important to select the animals under the same production conditions to raise rabbits that can cope with the expected global warming conditions.

Cost-effectively dissecting the genetic architecture of complex wool traits in rabbits by low-coverage sequencing

BackgroundRabbit wool traits are important in fiber production and for model organism research on hair growth, but their genetic architecture remains obscure. In this study, we focused on wool characteristics in Angora rabbits, a breed well-known for the quality of its wool. Considering the cost to generate population-scale sequence data and the biased detection of variants using chip data, developing an effective genotyping strategy using low-coverage whole-genome sequencing (LCS) data is necessary to conduct genetic analyses.ResultsDifferent genotype imputation strategies (BaseVar + STITCH, Bcftools + Beagle4, and GATK + Beagle5), sequencing coverages (0.1X, 0.5X, 1.0X, 1.5X, and 2.0X), and sample sizes (100, 200, 300, 400, 500, and 600) were compared. Our results showed that using BaseVar + STITCH at a sequencing depth of 1.0X with a sample size larger than 300 resulted in the highest genotyping accuracy, with a genotype concordance higher than 98.8% and genotype accuracy higher than 0.97. We performed multivariate genome-wide association studies (GWAS), followed by conditional GWAS and estimation of the confidence intervals of quantitative trait loci (QTL) to investigate the genetic architecture of wool traits. Six QTL were detected, which explained 0.4 to 7.5% of the phenotypic variation. Gene-level mapping identified the fibroblast growth factor 10 (FGF10) gene as associated with fiber growth and diameter, which agrees with previous results from functional data analyses on the FGF gene family in other species, and is relevant for wool rabbit breeding.ConclusionsWe suggest that LCS followed by imputation can be a cost-effective alternative to array and high-depth sequencing for assessing common variants. GWAS combined with LCS can identify new QTL and candidate genes that are associated with quantitative traits. This study provides a cost-effective and powerful method for investigating the genetic architecture of complex traits, which will be useful for genomic breeding applications.

A Single Nucleotide Polymorphism in the WIF1 Promoter Region Regulates the Wool Length in Rabbits

Wool length is an important trait in the rabbit wool industry. Wnt inhibitory factor 1 (WIF1), a key gene, regulates hair follicle growth and development. This study explores the WIF1 gene relationship with wool production traits in three different rabbit breeds, Rex rabbit, New Zealand rabbit, and Angora rabbit. The rabbit WIF1 gene sequence was obtained from GenBank, and PCR and Sanger sequencing were applied to screen SNP (single nucleotide polymorphism) from the gene exons and promoter regions. Sequencing results found no SNP in the PCR products of 10 exons from the rabbit WIF1 gene, indicating that the WIF1 gene was not polymorphic. Thus, the gene was conserved in all three rabbit breeds. Only one SNP was found in the WIF1 promoter region, associated with wool-producing traits in rabbits. Luciferase activity assays showed that the AA genotype had higher transcriptional activities than the AG or GG genotype (p &lt; 0.01). In addition, WIF1 was significantly upregulated in the Rex rabbit compared to the New Zealand rabbit and Angora rabbit (p &lt; 0.01). In summary, a key SNP in the WIF1 promoter region was found to be associated with rabbit fiber length trait.

Consequences of Selection for Post-weaning Growth Performance Traits on Fat Partition Traits in Rabbits

Genetic and phenotypic parameters, using multi-trait animal model, for weaning weight (WW), slaughter weight (SW) and daily gain (DG) from weaning to slaughter were applied on 218 New Zealand White rabbits to improve post-weaning growth traits using selection indices. The specific objective was to improve profitability of rabbit producers through increasing body weight at slaughter and daily gain from weaning to slaughter. Expected impacts of selection for post-weaning growth traits on fat partition traits were also investigated. The fat partition traits included weights of subcutaneous fat (SF) and intermuscular fat (IF) as carcass components and heart fat (HF), kidneys fat (KF), mesenteric fat (MF) and caul fat (CF) as offal components. Growth traits showed low to moderate heritability estimates (h2,0.03 to 0.37), while fat partition traits had higher h2 estimates (0.72 to 0.93), except for SF (h2=0.27). Application of the reduced index considering WW and DG was as efficient as full index in terms of accuracy of selection (rTI=0.66); it provided higher improvement in aggregate genotype represented in SW (+170.72gm) and DG (+2.41gm/day) for each round of selection. This improvement in post-weaning traits was accompanied by unfavorable expected impact in fat traits SF, HF, MF and CF (+45.32, +12.77, +56.50 and +12.25%, respectively) and favorable expected impact on IF and KF (-32.16 and -59.47gm, respectively). The single trait selection index (I6) with SW was found to be useful for rabbit meat consumers, as it decreased the undesirable fat gain in fat depots compared to the other indices, with some reduction in accuracy. In conclusion, it is possible to improve the post-weaning growth traits through selection programs, taking into consideration the undesirable changes in fat partition traits of New Zealand White rabbits.

Association between IRS-1, PPAR-γ and LEP genes polymorphisms and growth traits in rabbits

Single nucleotide polymorphisms are commonly associated with changes in quantitative traits, and have been considered useful markers for improving different traits in livestock. The current study aimed to explore the effect of three SNPs located in Insulin receptor substrate (IRS-1), Peroxisome proliferator-activated receptor γ (PPAR-γ), and Leptin (LEP) genes on the growth traits of rabbits. Individuals from three rabbit breeds were genotyped using RFLP-PCR. The IRS-1 variant (c.189T > G) was associated with post-weaning body weight, and body weight gains, However, the effect on growth rates was insignificant in Baladi Red and V-line rabbits. The PPAR-γ variant (c.207A > C) was significantly associated with 8-wk body weights in V-line rabbits, 10-wk body weights, and growth rates from 8 to 10 weeks of age in New Zealand rabbits. However, the differences between genotypes were insignificant for body weight gains and average daily gain. The LEP gene mutation (g.16079636C > G) had significant effects on body weights at 6 and 8 weeks of age in New Zealand White rabbits and 8 weeks of age in Baladi Red rabbits were associated with the presence of the C allele. Concludingly, the results stressed the importance of the IRS-1 gene in post-weaning growth and suggested the existence of breed-specific effects for PPAR-γ and LEP.

Growth performance, nutrient utilization and carcass characteristics of rabbits on probiotic supplementation

An experiment was conducted to study the effects of probiotic supplementation on growth, nutrient utilization and carcass traits in rabbits. Atotal of 60 weaner (28 days-old) Soviet Chinchilla rabbits were divided in four groups of 15 each. Pellet feed was supplemented with live microbial cultures of Lactobacillus plantarum (LP), Saccharomyces cerevisiae (SC) and combination of both L. plantarum + S. cerevisiae (LP+SC), whereas control group was supplemented with equal amount of culture medium. The rabbits were fed ad libitum pellet feed up to 84 days of age. The microbial population in feed pellets was 106 Cfu/g pellet feed. Body weight gain (28 to 84 days) was significantly (p<0.05) higher in LP+SC (1837 g) than control (1751 g), LP (1751 g) and SC (1774 g) groups. Higher digestibility of acid detergent fibre and cellulose was also recorded in LP+SC (14.6 and 22.4%) than LP (11.6 and 19.7%) and SC (11.3 and 18.8%). Carcass characteristics were not influenced in all the four treatment groups. The study suggested that supplementation of SC in feed pellets improved body weight gain in rabbits.

Мінливість показників продуктивності та ступінь фенотипового домінування у кролів при схрещуванні різних порід

Goal. To investigate the level of variability of productivity indicators and the degree of phenotypic dominance in rabbits when crossing breeds of different directions of productivity. Methods. The study was conducted based on the rabbit farm of the Cherkasy Research Station of Bioresources of NAAS on the population of rabbits of the breed Poltavske sriblo with the use of breeders of Radianska chinchilla, Novozelandska bila, and their descendants. Results. The degree of variability of selection traits in rabbits at a combination of breeds of a different direction of productivity is determined. A probable predominance was inserted by the length of the body in young rabbits obtained by crossing rabbits of Radianska chinchilla and Poltavske sriblo breeds (by 7 cm, P>0.999). According to the rest of the indicators (breast circumference, live weight at different ages, lumbar width), animals obtained as a result of crossing males of Novozelandska bila breed and females of Poltavske sriblo (P0.99). The color of the fur in both crosses had a wild form of “agouti”. The presence of a high degree of inheritance by selection traits in the offspring: body length (h2=0.46–0.70, P>0.999), lumbar width (h2=0.48–0.56, P>0.999) and for young animals rabbits meat productivity, live weight at the age of 120 days (h2=0.62, P>0.999). The share of the influence of the breed on the manifestation of the trait in the offspring varied in the range of 0.01–0.49, the probable influence of the breeder was determined by the length of the body and the hardness index (ηx2=0.32 and 0.49, P>0.999), which indicates dominance on this basis of the breed of meat direction of productivity. Conclusions. At crossing breeds of rabbits of the combined and meat directions of selection the maximum level of heredity of traits is revealed on an indicator of the length of a body: at breeds of the combined direction the phenotypic correlation between traits of mothers and descendants is positive, and at crossing with breeders of a meat direction of productivity — negative, i.e. this indicator decreased. There is also a high degree of inheritance of live weight in the descendants for the combination of rabbits Poltavske sriblo with breeders of Nevozelandska bila breed. In both variants of crossing, the descendants lose the characteristic fur color of the parent forms, which indicates the recessive nature of this trait. The maximum influence of the male breed was on the indicator of body length and the hardness index of the descendants.

Genome-Wide Association Studies for Growth Curves in Meat Rabbits Through the Single-Step Nonlinear Mixed Model.

Growth is a complex trait with moderate to high heritability in livestock and must be described by the longitudinal data measured over multiple time points. Therefore, the used phenotype in genome-wide association studies (GWAS) of growth traits could be either the measures at the preselected time point or the fitted parameters of whole growth trajectory. A promising alternative approach was recently proposed that combined the fitting of growth curves and estimation of single-nucleotide polymorphism (SNP) effects into single-step nonlinear mixed model (NMM). In this study, we collected the body weights at 35, 42, 49, 56, 63, 70, and 84 days of age for 401 animals in a crossbred population of meat rabbits and compared five fitting models of growth curves (Logistic, Gompertz, Brody, Von Bertalanffy, and Richards). The logistic model was preferably selected and subjected to GWAS using the approach of single-step NMM, which was based on 87,704 genome-wide SNPs. A total of 45 significant SNPs distributed on five chromosomes were found to simultaneously affect the two growth parameters of mature weight (A) and maturity rate (K). However, no SNP was found to be independently associated with either A or K. Seven positional genes, including KCNIP4, GBA3, PPARGC1A, LDB2, SHISA3, GNA13, and FGF10, were suggested to be candidates affecting growth performances in meat rabbits. To the best of our knowledge, this is the first report of GWAS based on single-step NMM for longitudinal traits in rabbits, which also revealed the genetic architecture of growth traits that are helpful in implementing genome selection.

Effects of Genotype and Weaning Age Interaction on Growth Traits in Rabbits

Weaning age is an important factor that affects the growth and health of weaned animals. Therefore, the current experiment was conducted to study genotype (G) and weaning age (WA) interaction (G×WA) effects on growth traits of the animals belonged to two lines of rabbits (APRI and V line) reared under Egyptian conditions. Multiparous doe rabbits were serviced to obtain 225 litters with 1800 young rabbits at weaning. The weaning ages ranged from 26 to 43 days where the young rabbits were weaned at different ages (≥28 days, WA1; 28 &lt; Treatment ≥ 35 days, WA2; 35 &lt; Treatment ≥ 40 day, WA3 and 40&lt; Treatment, WA4). Body weight (BW) from 4 to 16 weeks of age and corresponding average daily gain (ADGt1-t2) were measured. The BW significantly increased in APRI rabbits, compared to those in V line at the different ages where at the end of the fattening period, the difference was 105 g per animal with higher ADG. Regarding the weaning age effects, positive effects were observed where the highest BW was observed at the fattening period. The ADG of rabbits weaned in late weaning was higher than in early weaning with significant differences. The observed results suggest the existence of relevant G×WA interaction for the investigated traits. Therefore, the weaning age of 29-35 days is recommended for young APRI rabbits while it is suggested to wean the V rabbits after 35 days. The study confirmed that early weaning is not preferable for the rabbit under Egyptian conditions and it is better to wean young rabbits at the minimum age of 30 days to achieve the best BW and growth rate.

Using Linear Discriminant Analysis to Characterize Novel Single Nucleotide Polymorphisms and Expression Profile Changes in Genes of Three Breeds of Rabbit (Oryctolagus cuniculus).

The objectives of this study were to investigate polymorphisms and changes in expression patterns of the genes FGF5, PGAM2, TLR2 and IL10 in V-line, Baladi Black and Baladi Red rabbits. Blood samples were collected from 180 healthy rabbits (n = 60 for each breed) for DNA extraction and DNA sequencing. At 3 mo of age, 20 randomly selected females from each breed were euthanized for gene expression quantification in muscle and spleen samples. PCR-DNA sequencing revealed single nucleotide polymorphisms (SNPs) among the 3 breeds that provided a monomorphic pattern for 3 of the 4 genes analyzed. Linear discriminant analysis (LDA) was used to classify the SNPs of these genes in the 3 breeds. The overall percentage of correctly classified cases for the model was 75%, with percentages of 100% for FGF5, 63% for IL10, and 100% for TLR2. Breed was a significant predictor for gene classification with estimation (1.00). Expression profiles of the genes were higher in V-line as compared with Baladi Black or Baladi Red. The LDA discriminated the 3 breeds using results of the gene expression profile as predictors for classification. Overall, 73% of the cases were correctly classified by gene expression. The identified SNPs, along with changes in mRNA levels of FGF5, PGAM2, TLR2, and IL10, could provide a biomarker for efficient characterization of rabbit breeds and could thus help develop marker assisted selection for growth and immune traits in rabbits.

Association of GH gene polymorphism with growth and semen traits in rabbits

&lt;p&gt;Although growth hormone (&lt;em&gt;GH&lt;/em&gt;) gene mutations are described in several species, the studies concerning their variabilities and associations with economic traits in rabbits are scarce, particularly associations with semen traits. A total of 149 rabbit bucks from five populations (V-line=36, Moshtohor line=28, APRI line=42, cross ½A½M=23, and Gabali=20) were used in the present study to identify polymorphism of c.-78 C&amp;gt;T single nucleotide polymorphism (SNP) of &lt;em&gt;GH&lt;/em&gt; gene among these populations and to investigate the association of &lt;em&gt;GH&lt;/em&gt; gene polymorphism with body weight (BW), daily weight gain (DG) and semen traits. DNA was extracted from blood samples for genotyping of c.-78 C&amp;gt;T SNP of &lt;em&gt;GH&lt;/em&gt; gene based on polymerase chain reaction with the restriction fragment length polymorphism (PCR-RFLP) technique. The genetic diversity of SNP C&amp;gt;T of &lt;em&gt;GH&lt;/em&gt; gene was assessed in terms of genotypic and allelic frequencies, effective number of alleles (Ne), observed (Ho) and expected (He) heterozygosity, Hardy-Weinberg equilibrium (HWE), reduction in heterozygosity due to inbreeding (F&lt;sub&gt;IS&lt;/sub&gt;) and polymorphism information content (PIC). Three genotypes of TT, CC and TC of PCR product of 231 bp of &lt;em&gt;GH&lt;/em&gt; gene were detected and all the populations were in HWE in terms of &lt;em&gt;GH&lt;/em&gt; gene. The highest Ne was obtained for the Moshtohor line (1.978), while the lowest allelic numbers were obtained for V-line (1.715) and Gabali breed (1.800). The highest genotype frequency of &lt;em&gt;GH&lt;/em&gt; gene was 0.48 in TT genotype of V-line, 0.21 in CC genotype of Moshtohor line, 0.67 and 0.56 in TC genotype of ½A½M and Gabali rabbits (&lt;em&gt;P&lt;/em&gt;&amp;lt;0.05). The highest frequency for C allele was recorded by Moshtohor line (0.45) and the lowest frequency by Gabali (0.32). The genetic diversity scores for &lt;em&gt;GH&lt;/em&gt; gene were intermediate (Ho=0.551, He=0.471, PIC=0.358). The values of Ho ranged from 0.444 in V-line to 0.667 in ½A½M cross, while the values of He were 0.425 in V-line and 0.508 in Moshtohor line. The values of PIC were moderate and ranged from 0.332 in V-line to 0.375 in M-line. The highest F&lt;sub&gt;IS&lt;/sub&gt; was observed in Moshtohor line (0.042) and the lowest value was observed in ½A½M cross (–0.413). The CT genotype of &lt;em&gt;GH&lt;/em&gt; gene showed the highest and significant values for body weights at 4, 8, 10 and 12 wk (542, 1131, 1465 and 1861 g) and daily gains at intervals of 4-6 and 8-10 wk (23.1 and 26.5 g). Additionally, the CT genotype recorded the highest and significant values for volume of ejaculate (1.1 mL), sperm motility (57.6%), live sperm (85.6%), normal sperm (93.1%) and sperm concentration in semen (611×106/mL), along with the lowest and significant values for dead sperms (14.4%) and abnormal sperms (6.9%).&lt;/p&gt;

Phenotypic relationships between gestation length and preweaning litter traits in rabbits.

A total of 135 kittens from 22 kindlings were used to determine the relationship between gestation length (GL) and some preweaning litter traits alongside the weight of their 12 dams. Average daily gain at 21 days (ADG21), average litter weight at birth (ALWB), kindling to weaning viability (KWV), litter size at birth{L.SB), litter size at 21 days (LS21), litter weight at 21 days(LW21), litter weight at birth (LWAB), and still birth number (SBN) when subjected to multiple regression analysis revealed non-significant t-test value with GL. However, Average litter weight at 21 days (ALW21) was highly significant (P&lt;0.01) suggesting that such can be used to predict GL. Weight of doe (WOD) was highly significant (P&lt;0.01) showing that such parameter is important for predicting GL. A high R2 value was obtained indicating that the variability in GL is explained by the linearity of the preweaning litter traits and WOD. However the correlation coefficient R, (0.89) revealed a high degree of association between the preweaning litter traits in the rabbits and the weight of doe in a linear form. The F-value was significant at P&lt;0.05 indicating that WOD and the preweaning litter traits in rabbits have significant contribution to the variation in GL. The correlations among traits were positive and significant for majority of the traits, which include live birth number (LBN), ADG21, ALW21, KWV, LS21, and LW21. However SBN had negative correlation with other traits.

Genetic parameters of resistance to pasteurellosis using novel response traits in rabbits

BackgroundPasteurellosis (Pasteurella infection) is one of the most common bacterial infections in rabbits on commercial farms and in laboratory facilities. Curative treatments using antibiotics are only partly efficient, with frequent relapses. Breeding rabbits for improved genetic resistance to pasteurellosis is a sustainable alternative approach. In this study, we infected 964 crossbred rabbits from six sire lines experimentally with Pasteurella multocida. After post-mortem examination and bacteriological analyses, abscess, bacteria, and resistance scores were derived for each rabbit based on the extent of lesions and bacterial dissemination in the body. This is the first study to use such an experimental design and response traits to measure resistance to pasteurellosis in a rabbit population. We investigated the genetic variation of these traits in order to identify potential selection criteria. We also estimated genetic correlations of resistance to pasteurellosis in the experimental population with traits that are under selection in the breeding populations (number of kits born alive and weaning weight).ResultsHeritability estimates for the novel response traits, abscess, bacteria, and resistance scores, ranged from 0.08 (± 0.05) to 0.16 (± 0.06). The resistance score showed very strong negative genetic correlation estimates with abscess (− 0.99 ± 0.05) and bacteria scores (− 0.98 ± 0.07). A very high positive genetic correlation of 0.99 ± 0.16 was estimated between abscess and bacteria scores. Estimates of genetic correlations of the resistance score with average daily gain traits for the first and second week after inoculation were 0.98 (± 0.06) and 0.70 (± 0.14), respectively. Estimates of genetic correlations of the disease-related traits with average daily gain pre-inoculation were favorable but with high standard errors. Estimates of genetic and phenotypic correlations of the disease-related traits with commercial selection traits were not significantly different from zero.ConclusionsDisease response traits are heritable and are highly correlated with each other, but do not show any significant genetic correlations with commercial selection traits. Thus, the prevalence of pasteurellosis could be decreased by selecting more resistant rabbits on any one of the disease response traits with a limited impact on the selection traits, which would allow implementation of a breeding program to improve resistance to pasteurellosis in rabbits.