István Nagy

Effect of dam and sire genotypes on productive and carcass traits of rabbits

The aim of the experiment was to study the effect of dam and sire genotypes on the production and slaughter performance of growing rabbits. The experiment was carried out at Kaposvár University. Pannon White (PW) and maternal line (M) does were inseminated with the sperm of PW, M, large body line (LB), terminal line of Hycole hybrid (H), or colored line (CL) bucks. The mature body size of the M, PW, and CL genotypes was medium. The mature body size of the LB and H genotypes was large. Only PW and LB rabbits were selected for carcass traits based on computer tomograph (CT) scanning data. The rabbits (n = 320) were weaned at the age of 5 wk and housed in a closed climate-controlled rabbitry in wire cages. Rabbits were fed ad libitum a commercial pellet. Rabbits were slaughtered at 78 d of age. Daily BW gain (5.7%, P < 0.001) and G:F (6.2%, P < 0.001) of the progeny of PW does were better than those of the progeny of the M does. The weight of the chilled carcass and body parts was greater for the progeny of the PW does (P < 0.001). The ratio of the hind part compared with the reference carcass was greater in the PW group (P < 0.001); however, the ratio of the fore part was greater in the M group (P < 0.05). Examining the effect of the genotype of the sires, the BW and daily BW gain were greater in groups H and LB, whereas the progeny of M and CL sires were inferior (P < 0.05). Body weights at 11 wk of age were H: 2,918 g, LB: 2,793 g, PW: 2,678 g, CL: 2,636 g, and M: 2,585 g (P < 0.001). Similar differences were found for daily feed intake (P < 0.05). The G:F differed (P < 0.05) significantly between groups H and CL. The weights of the chilled carcass and of the body parts were the greatest for the progeny of the H sires, and the smallest in the M group. The differences between the dressing out percentages of the groups were not significant. The ratio of the fore part was greater (P < 0.05) in groups LB, H, and CL, but the ratio of the middle part was not different. The ratio of hind part related to the reference carcass was largest in progeny of PW and least in LB and CL groups (P < 0.05). It was concluded that the production of growing rabbits was affected by the adult BW of their sires, but the carcass traits were influenced by their own adult BW and by the CT-based selection.

Genetic diversity and population structure of the synthetic Pannon White rabbit revealed by pedigree analyses

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.

Effect of housing conditions on production, carcass and meat quality traits of growing rabbits

Production, carcass traits and meat quality of rabbits housed in cages or in different pens were compared. Rabbits (n=579) were sorted into 5 groups: C=cage (2 rabbits/cage); pen without platform: P11=9 rabbits/pen; P16=14 rabbits/pen; pen with platform: PW=wire net platform, 14 rabbits/pen; PD=platform with straw-litter, 14 rabbits/pen. Feed intake and average daily gain between 5 and 11 weeks, and body weight at 11 weeks were significantly higher in C rabbits than that of the mean of pen-housed groups, while the PD group had the lowest growth performance. C rabbits had the smallest hind part to reference carcass (P<0.001) and the largest percentage of perirenal and scapular fat (P<0.001). The meat/bone ratio was the largest in group C (P<0.05). Differences were recorded in a* value and lipid content of m. Longissimus dorsi. Rabbits housed in cages generally had the best performance whereas those housed in pens with platform exhibited the worst.

Comparison of performance and welfare of single-caged and group-housed rabbit does

Although rabbit does are generally single housed on rabbit farms worldwide, it has been suggested by some specialists and recommendation of organic rabbit production systems that group housing of does is more comfortable and similar to the living conditions of the European wild rabbits. The aim of this experiment was to compare production of single-caged (S) and group-housed does (G). The S does were housed in commercial rabbit cages (floor area 0.32 m(2) and 0.3 m high). In treatment G, four does and one buck were housed in four pens measuring 7.7 m(2) (half of the floor was deep litter and the other half was plastic slat), with four nest boxes in each pen (n = 16). In treatment S, approximately half of the does (n = 18) were inseminated 2 days after kindling (S-33), whereas in the remaining does (n = 16) AI was done 11 days after kindling (S-42). A single-batch system (all of the does in the group were inseminated on the same day) was used in both S treatments. Kindling rates were 77.6%, 85.2% and 45.6% in treatments S-33, S-42 and G, respectively (P < 0.05). During the experiment, the percentage of does that kindled 0, 1, 2, 3, 4 and 5 times were 17%, 25%, 17%, 25%, 17% and 0% (G); 0%, 0%, 0%, 8%, 69% and 23% (S-33); and 0%, 0%, 17%, 58% and 25% (S-42, in this treatment does had a maximum of four kindlings). There were no significant differences among treatments for litter size. In treatments S-33, S-42 and G, suckling mortality was 14.0%, 15.2% and 38.5%, respectively (P < 0.001); survival of does was 71%, 81% and 50% (P = 0.084); and faecal corticosterone concentrations were 61, 54 and 175 nmol/g (P < 0.001). The high mortality of kits was associated with stress and aggressive behaviour of does, including scratching, biting or killing the kits, which resulted in the high rates of mortality and culling, as well as shorter lifespan of does. Because of high stress, increased mortality and morbidity, and low productivity, group housing of rabbit does resulted in poorer animal welfare and increased production costs, and therefore is not recommended.

Effect of adult weight and CT-based selection on carcass traits of growing rabbits

Abstract The aim of this study was to compare the carcass traits of different genotypes. Maternal line (M; n=31; adult weight/AW/4.0-4.5kg) (selected for number of kits born alive), Pannon White (P; n=32; AW: 4.3-4.8kg), and Large type line (L, n=32; AW: 4.8-5.4kg) (P and L were selected for carcass traits based on CT/Computer tomography/data) rabbits were analysed. Rabbits were slaughtered at 11 wk of age. P rabbits showed the highest dressing out percentage (M=60.2, P=61.3 and L=61.1%, with a significant difference between groups M and P, P<0.05), the lowest ratio of fore part (M=26.0, P=25.7 and L=26.9%, differences were significant between groups M-P and L, P<0.05), and the largest ratio of the hind part (M=37.3, P=38.2 and L=37.2%, differences were significant between groups M-L and P, P<0.05) to the reference carcass. It can be concluded that carcass traits were influenced by CT-based selection.

Effect of adult weight and CT-based selection on the performances of growing rabbits

Abstract The aim of the study was to compare the productive performance of different genotypes. Maternal (M; n=32, adult weight /AW/ 4.0-4.5kg, selected for number of kits born alive), Pannon White (P; n=32, AW: 4.3-4.8kg), and Large body line (L; n=32, AW: 4.8-5.4kg) (P and L were selected for carcass traits based on CT /Computer tomography/data) rabbits were analysed. Average daily gain between 5-11wk of age, body weight at 11wk of age and feed intake were significantly (P<0.001) highest for L rabbits. For M, P and L rabbits, the following values were observed: average daily gain=38.6, 43.1 and 47.4g/d; body weight=2458, 2667 and 2949g; feed intake=115, 121 and 138g/d, respectively. Mortality of growing rabbits was unaffected by genotype. It can be concluded that production traits were mainly affected by the adult weight of the genotypes.

Genetic parameters, genetic trends and inbreeding depression of growth and carcass traits in Pannon terminal line rabbits

Abstract. Genetic parameters, inbreeding depression and genetic trends were estimated for average daily gain between the ages of 5-10 weeks and thigh muscle volume (measured in vivo with computerized tomography) in a group of 22 098 Pannon terminal line rabbits born between 2006 and 2011 and reared in 3 396 litters. The data sets were analysed with bi-variate animal models taking pedigree completeness (complete generation equivalent) into account. By 2011, all rabbits were inbred and the average inbreeding coefficient and complete generation equivalent of the population were 7.69 % and 11.89 %, respectively. Estimated heritability was moderate both for average daily gain (0.23±0.02) and thigh muscle volume (0.25±0.03). Litter effects were low for both traits (0.16±0.00 and 0.09±0.01 respectively). The genetic correlation coefficient estimate between average daily gain and thigh muscle volume was also low (0.02±0.08). Significant inbreeding depression (per 10 % inbreeding) was only detected for average daily gain (0.57 g/d). The estimated annual selection response was substantial both for average daily gain and thigh muscle volume (1.49 g/d and 5.84 cm3, respectively), proving the efficiency of the breeding programme.

Comparison of pens without and with multilevel platforms for growing rabbits

Abstract This experiment compared the productive performance and location of growing rabbits in pens without and with two-level platforms (wire-mesh or plastic-mesh). A total of 174 rabbits of both sexes weaned at 5 weeks of age were randomly divided into three groups (n = 58 rabbits/group, 2 pens/treatment, 29 rabbits/pen). The floor area of pens was 1.0 × 1.83 m, and the floor was made of wire-mesh. Two pens were equipped with wire-mesh (WP) and two pens with plastic-mesh elevated platforms (PP) on two levels, and two pens were without platforms (NoP). Treatment had no effect on the productive performance of growing rabbits. Based on video recordings, animal density (rabbits/m2 in each location) was higher (p < .001) on the floor than on the platforms (in WP: 12.0 vs. 5.2, in PP: 10.2 vs. 7.4 rabbits/m2, respectively). Animal density on the floor was higher (p < .001) in front of the platforms than under the platforms (in WP 15.7 vs. 9.8 rabbits/m2 and in PP 13.3 vs. 8.3 rabbits/m2, respectively). The animal density on platforms was 1.4 times higher in group of PP than in WP (p < .001). The animal density was 1.6 and 2.9 times higher on the second floor than on the first one (p < .001), in group of PP and WP, respectively. The concentration of cortisol metabolites in faeces and the ratio of injured rabbits were similar in the three groups. The rabbits showed higher preference staying on the floor compared to the platform. Pens with platforms were not influencing productive performance.

Light colour preference of growing rabbits

Abstract The objective of the experiment was to evaluate the light colour preference of growing rabbits placed in a free-choice cage. The experiment was carried out on 128 Pannon White growing rabbits weaned at the age of 5 weeks and placed into blocks (2m2) of four cages. The rabbits could move freely among the four cages (0.5m2 each) through swing doors. The cages differed only in the colour of the light applied (white, yellow, green or blue). The lighting schedule was 16L: 8D. From 6 until 10 weeks of age, infrared video recording was performed once a week (24 hours). The number of rabbits in each cage was counted every 15 minutes. Feed consumption was measured weekly. Between 6 and 10 weeks of age the rabbits significantly preferred white light (28.0%). The preference order was the following: yellow (26.3%), blue (23.4%) and green (22.3%) (P<0.001). No significant differences were recorded in the feed consumption among the cages. In conclusion, the cage preference of the rabbits was slightly affected by the light colour.

Heritability and genetic trends of number of kits born alive in a synthetic maternal rabbit line

Abstract Heritability and genetic trends for number of kits born alive in a synthetic maternal rabbit line were estimated in this study. The data were collected from 1999 to 2007 on 5640 kindlings of 1425 does. The total number of animals in the pedigree was 2576. The mean number of kits born alive was 8.42 with a standard deviation of 2.87. Genetic parameters and breeding values were estimated using the VCE-5 and PEST software based on the REML and BLUP methods using a repeatability animal model. For litter size, the first, second and third parities were treated as repeated trait, while the fourth and further parities were pooled and considered as same repetition. The estimated heritability and the repeatability for number of kits born alive were low (0.05 and 0.14). The observed selection response was about 0.04 rabbits/year.