Comparison of productive and carcass traits and economic value of lines selected for different criteria, slaughtered at similar weights

[EN] The aim of the experiment was to compare 3 genetic groups, slaughtered at similar weights, to examine their productive and carcass traits and economic value. Three lines of the Pannon Breeding Programme, selected for different criteria, were examined in the experiment. Pannon Ka (PKa, maternal line) does were inseminated with semen of PKa, Pannon White (PWhite) or Pannon Large (PLarge, terminal line) bucks. The kits (PKa×PKa, PWhite×PKa, PLarge×PKa; n=60 in each genetic group) were weaned at 35 d of age and reared until 88, 83 and 79, respectively, when they reached similar body weights for slaughtering (2.8 kg). The weight gain of PLarge×PKa was the largest (51.0 g/d) and that of PKa×PKa was the smallest (47.2 g/d), while PWhite×PKa (41.8 g/d) was intermediate (P<0.001). Difference was found in feed conversion ratio between weaning and the age of slaughter  PKa×PKa: 3.03 respect to PWhite×PKa: 2.75 and PLarge×PKa: 2.66; , P<0.05). Dressing out percentage and ratio of hind part to reference carcass of PWhite×PKa, PLarge×PKa and PKa×PKa were 62.4 and 37.7, 61.8 and 37.5, 61.3 and 36.8%, respectively (P<0.01). Results show that PLarge×PKa rabbits were able to exceed the average economic indicators compared to other groups. It may be concluded that the production performance of growing rabbits was affected by the adult weight, but the carcass traits were influenced by the computer tomography (CT)-based selection.This paper was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, and by the GOP-1.1.1-11-2012-0132 project.Szendrő, K.; Szendrő, Z.; Gerencsér, Z.; Radnai, I.; Horn, P.; Matics, Z. (2016). Comparison of productive and carcass traits and economic value of lines selected for different criteria, slaughtered at similar weights. World Rabbit Science. 24(1):15-23. https://doi.org/10.4995/wrs.2016.3684152324

Effect of hair shearing on live performance and carcass traits of growing rabbits under hot ambient temperature

[EN] The aim of the study was to examine the effect of hair shearing in growing rabbits reared at high ambient temperature. The live performance and carcass traits of growing rabbits reared at 20°C (not sheared, C, n=50) or at 28°C (not sheared, H, n=50, or sheared at 5, 7 and 9 wk, HS, n=50) were compared. The ambient temperature and relative humidity were 20.5±1.1°C and 54±11% in the 20°C room and 28.8±0.2°C and 35±8% in 28°C room, respectively. Feed intake of H and HS groups decreased by 29.0 and 20.4%, respectively, compared to C rabbits (P&lt;0.001). The same data for weight gain were 24.6 and 16.9% (P&lt;0.001), and for body weight at 12 wk were 16.8 and 11.5% (P&lt;0.001). At the same time, the feed conversion ratio improved (C: 3.53, HS: 3.34, H: 3.31; P&lt;0.001). Nevertheless, the mortality rate of rabbits was not affected by the studied treatment and was overall low (0-4%). No differences were observed in dressing out percentages either (ratio of chilled carcass (CC) to the slaughter weight: 61.6-61.9%). The ratio of liver to CC differed among the experimental groups, with the highest value recorded in C group and the lowest in H group; HS rabbits showed intermediate results (C: 4.86%, HS: 4.27%, H: 3.91%; P&lt;0.001). Lower ratios of fat deposits to reference carcass were also observed in rabbits kept at high ambient temperature (perirenal fat: C: 2.59%, HS: 1.82%, H: 1.60%; P&lt;0.001; scapular fat: C: 0.89%, HS: 0.66%, H: 0.51%; P&lt;0.001). It can be concluded that the negative effect of higher ambient temperature (28 vs. 20°C) on production in growing rabbits can be reduced significantly by hair shearing.En este agradecimieento: "The work was supported by the GINOP-2.3.4-15-2016-00005 project. Publication was supported by the EFOP-3.6.3-VEKOP-16–2017–00008 project. The project is co-funded by the European Union and the European Social Fund"Matics, Z.; Kasza, R.; Gerencsér, Z.; Radnai, I.; Dalle Zotte, A.; Cullere, M.; Szendrő, Z. (2020). Effect of hair shearing on live performance and carcass traits of growing rabbits under hot ambient temperature. World Rabbit Science. 28(3):161-167. https://doi.org/10.4995/wrs.2020.13164OJS161167283Balnave D. 1972. The effect of temperature and length of exposure on liver composition and hepatic lipogenic enzyme activity in the immature male chick (Gallus domesticus). Comp. Biochem. Physiol., 438: 999-1007. https://doi.org/10.1016/0305-0491(72)90244-1Blasco A., Ouhayoun J. 1996. Harmonization of criteria and terminology in rabbit meat research. Revised proposal. World Rabbit Sci., 4: 93-99. https://doi.org/10.4995/wrs.1996.278Chiericato G.M., Rizzi C., Rostellato V. 1993. Effect of genotype and environmental temperature on performance of the young meat rabbit. World Rabbit Sci., 1: 119-125. https://doi.org/10.4995/wrs.1993.204Chiericato G.M., Ravarotto L., Rizzi R. 1994. Study of the metabolic profile of rabbits in relation to two different environmental temperatures. World Rabbit Sci., 2: 153-160. https://doi.org/10.4995/wrs.1994.232Chiericato G.M., Rizzi C., Rostellato V. 1996. Growth and slaughtering performance of three rabbit genotypes under different environmental conditions. Ann. Zootech., 45: 311-318. https://doi.org/10.1051/animres:19960403Deltoro J., López A.M. 1986. Development of commercial characteristics of rabbit carcasses during growth. Livest. Prod. Sci., 15: 271-283. https://doi.org/10.1016/0301-6226(86)90034-5EC 2010. Directive 2010/63/EU of the European Parliament and of the Council of 22 September 2010 on the protection of animals used for scientific purposes. Official Journal of the European Union L276: 33-79.Fernández-Carmona J., Cervera C., Sabater C., Blas E. 1995. Effect of diet composition on the production of rabbit breeding does housed in a traditional building and at 30°C. Anim. Feed Sci. Technol., 52: 289-297. https://doi.org/10.1016/0377-8401(94)00715-LFinzi A., Morera P., Kuzminsky G. 1992. Effect of shearing on rabbit bucks performances in hot ambient conditions. J. Appl. Rabbit Res., 15: 489-494.Fuquay J.W. 1981. Heat stress as it affects animal production. J. Anim. Sci., 52: 164-174. https://doi.org/10.2527/jas1981.521164xHermes I.H., Ahmed B.M., Khalil M.H., Salah M.S., Al-Homidan A.A. 1999. Growth performance, nutrients utilization and carcass traits of growing Californian rabbits raised under different ambient temperatures. Egypt. J. Rabbit Sci., 9: 117-138.Jackson R., Rogers A.D, Lukefahr S.D. 2006. Effects of the naked gene on postweaning performance and thermotolerance characters in fryer rabbits: Final results. World Rabbit Sci., 14: 147-155. https://doi.org/10.4995/wrs.2006.559Kovitvadhi A., Chundang P., Thongprajukaew K., Tirawattanawanich C. 2019. Effects of different ambient temperatures on growth performances, digestibility, carcass traits and meat chemical components in fattening rabbits. J. Agriculture, 35: 495-502.Lebas F., Ouhayoun J. 1987. Incidence du niveau protéique de l'aliment, de milieu d'élevage et de la saison sur la croissance et les qualités bouchéres du lapin. Ann. Zootech., 36: 421-432. https://doi.org/10.1051/animres:19870406Lebas F., Coudert P., de Rochambeau H., Thébault R.G. 1997. The rabbit: husbandry, health and production. FAO Anim. Prod. and Health Series No. 21Lukefahr S.D., Ruiz-Feria C.A. 2003. Rabbit growth performance in a subtropical and semi-arid environment: Effects of fur clipping, ear length, and body temperature. Livest. Res. Rural Devel. 15: 2. Available at http://www.cipav.org.co/lrrd/lrrd15/2/luke152.htm Accessed October 2019.Marai I.F.M., Habeeb A.A.M., Gad A.E. 2002. Rabbits' productive, reproductive and physiological performance traits as affected by heat stress: a review. Livest. Prod. Sci., 78: 71-90. https://doi.org/10.1016/S0301-6226(02)00091-XMaya-Soriano M.J., Taberner E., Sabes-Alsina M., Ramon J., Rafel O., Tusell L., Piles M., López-Béjar M. 2015. Daily exposure to summer temperatures affects the motile subpopulation structure of epididymal sperm cells but not male fertility in an in vivo rabbit model. Theriogenology, 84: 384-389. https://doi.org/10.1016/j.theriogenology.2015.03.033Metzger Sz. 2006. Examination on carcass traits and meat quality of rabbit. (in Hung.) Doctoral (Ph.D.) dissertation. pp. 135.NASA https://climate.nasa.gov/Perez J.M., Lebas F., Gidenne T., Maertens L., Xiccato G., Parigi-Bini R., Dalle Zotte A., Cossu M.E., Carazzolo A., Villamide M.J., Carabaño R., Fraga M.J., Ramos M.A., Cervera C., Blas E., Fernández J., Falcão-e-Cunha L., Bengala Freire J. 1995. European reference method for in vivo determination of diet digestibility in rabbits. World Rabbit Sci. 3: 41-43. https://doi.org/10.4995/wrs.1995.239Renaudeau D., Collin A., Yahav S., de Basilio V., Gourdine J.L., Collier R.J. 2012. Adaptation to hot climate and strategies to alleviate heat stress in livestock production. Animal, 6: 707-728. https://doi.org/10.1017/S1751731111002448SAS Version 9.4. 2014. SAS Institute Inc; Cary, NC. Schlolaut W. 1995. Das grosse Buch vom Kaninchen. DLG-Verlag, Frankfurt am Main.Stephan E. 1980. The influence of environmental temperatures on meat rabbits of different breeds. Commercial Rabbit, 8: 12-15.Szendrő Zs., Rashwan R.R., Biró-Németh E., Radnai I., Orova Z. 2007. Effect of shearing of hair in summer on production of rabbit does. Acta Agr. Kapos., 11: 37-42.Szendrő Zs., Papp Z., Kustos K. 2018. Effect of ambient temperature and restricted feeding on the production of rabbit does and their kits. Acta Agr. Kapos., 22: 1-17. https://doi.org/10.31914/aak.2272Verga M., Luzi F., Carenzi C., 2007. Effects of husbandry and management systems on physiology and behaviour of farmed and laboratory rabbits. Horm. Behav., 52, 122-129. https://doi.org/10.1016/j.yhbeh.2007.03.024Zeferino P.C., Moura T.M.A.S.A., Fernandes S., Kanayama S.J., Scapinello C., Sartori R.J. 2011. Genetic group × ambient temperature interaction effects on physiological responses and growth performance of rabbits. Livest. Sci., 140: 177-183. https://doi.org/10.1016/j.livsci.2011.03.02

Divergent selection for fat index in Pannon Ka rabbits: genetic parameters, selection response

[EN] The objective of this study was to estimate the response to selection for total body fat content of rabbits measured by computer tomography (CT). A divergent selection experiment was performed using Pannon Ka rabbits, which were previously selected for number of kits born alive. The so-called zero generation consisted of 351 Pannon Ka rabbits, from which the index, total body fat volume (cm3) divided by the body weight (kg), was measured. Rabbits with low and high fat index values were selected to form the parent groups of the lean and fat lines, respectively. The lines consisted of 55-72 females and 35-47 males, depending on the line and generation. After three generations, the rabbits were evaluated by means of a single trait animal model. The fat index showed a moderate heritability estimate (0.28±0.03). The magnitude of the common litter effect was small (0.10±0.02). The breeding values averaged per generation provided slightly asymmetrical responses. Based on the results, the divergent selection was successful in confirming that CT is a very suitable method for performing selection for body composition traits.EFOP-3.6.3-VEKOP-16-2017-00008 project. The project is co-financed by the European Union and the European Social Fund and the János Bolyai Research Scholarship of the Hungarian Academy of Sciences (BO/00871/19)Kasza, R.; Matics, Z.; Gerencsér, Z.; Donkó, T.; Radnai, I.; Szendrő, Z.; Nagy, I. (2020). Divergent selection for fat index in Pannon Ka rabbits: genetic parameters, selection response. World Rabbit Science. 28(3):129-133. https://doi.org/10.4995/wrs.2020.12733OJS129133283Al-Saef A.M., Khalil M.H., Al-Dobaib S.N., Al-Homidan A.H., García M.L., Baselga M. 2008. Comparing Saudi synthetic lines of rabbits with the founder breeds for carcass, lean composition and meat quality traits. Livest. Res. Rural Dev., 20: 1-12.Donkó T., Czakó B., Kovács Gy., Petneházy Ö., Kasza R., Szendrő Zs., Garamvölgyi R., Matics Zs. 2016. Total body fat content determination by means of computed tomography (CT) in rabbits. In: Proceedings of the 11th World Rabbit Congress, 16-18 June 2016, Qingdao, China, pp. 753-756.Fortun-Lamothe L. 2006. Energy balance and reproductive performance in rabbit does. Anim. Reprod. Sci., 93: 1-15. https://doi.org/10.1016/j.anireprosci.2005.06.009Garreau H., Eady S.J., Hurtaud J., Legarra A. 2008. Genetic parameters of production traits and resistance to digestive disorders in a commercial rabbit population. In: Xiccato G., Trocino A., Lukefahr S. (eds.) In Proc.: 9th World Rabbit Congress. Fondazione Iniziative Zooprofilattiche e Zootechniche, Verona, Italy, pp. 103-108.Falconer D.S., Mackay T.F.C. 1996. Introduction to Quantitative Genetics. 4th Ed. Longman, London, UK. 1-464.Garreau H., Larzul C., Tudela F., Ruesche J., Ducqrocq V., Fortun-Lamothe L. 2017. Energy balance and body reserves in rabbit females selected for longevity. World Rabbit Sci., 25: 205-213. https://doi.org/10.4995/wrs.2017.5216Groeneveld E. 1990. PEST Users' Manual. Institute of Animal Husbandry and Animal Behaviour Federal Research Centre, Neustadt, Germany 1-61.Groeneveld E., Kovac M., Mielenz N. 2008. VCE User's Guide and Reference manual. Version 6.0. Institute of Farm Animal Genetics, Neustadt, Germany, 1-125.Larzul C., de Rochambeau H. 2005. Selection for residual feed consumption in the rabbit. Livest. Prod. Sci., 95: 67-72. https://doi.org/10.1016/j.livprodsci.2004.12.007Larzul C., Gondret F., Combes S., de Rochambeau H. 2005. Divergent selection on 63-day body weight in the rabbit: response on growth, carcass and muscle traits. Genet. Sel. Evol., 37: 105-122. https://doi.org/10.1051/gse:2004038Martínez-Álvaro M., Hernández P., Blasco A. 2016. Divergent selection on intramuscular fat in rabbits: Responses to selection and genetic parameters. J. Anim. Sci., 94: 4993-5003. https://doi.org/10.2527/jas.2016-0590Matics Zs., Nagy I., Gerencsér Zs., Radnai I., Gyovai P., Donkó T., Dalle Zotte A., Curik I., Szendrő Zs. 2014. Pannon breeding program in rabbit at Kaposvár University. World Rabbit Sci., 22: 287-300. https://doi.org/10.4995/wrs.2014.1511Milisits G., Romvári R., Dalle Zotte A., Szendrő Zs. 1999. Non-invasive study of changes in body composition in rabbits during pregnancy using X-ray computerized tomography. Ann. Zootech., 48: 25-34. https://doi.org/10.1051/animres:19990103Nagy I., Ibáñez N., Mekkawy W., Metzger Sz., Horn P., Szendrő Zs. 2006. Genetic parameters of growth and in vivo computerized tomography based carcass traits in Pannon White rabbits. Livest. Sci., 104: 46-52. https://doi.org/10.1016/j.livsci.2006.03.009Romvári R., Milisits G., Szendrő Zs., Sørensen P. 1996. Non invasive method to study the body composition of rabbits by X-ray computerized tomography. World Rabbit Sci., 4: 219-224. https://doi.org/10.4995/wrs.1996.298Rouvier R. 1970. Variabilité génétique du rendement a l'abattage et de la composition anatomique de lapins de trois races. Ann Genet. Sel. Anim., 2: 325-346. https://doi.org/10.1186/1297-9686-2-3-325Shemeis A., Abdallah O.Y. 2000. Possibilities of developing favourable body fat partition via selection indexes - application on rabbits. Arch. Anim. Breed., 43: 193-202. https://doi.org/10.5194/aab-43-193-2000Szendrő Zs., Romvári R., Horn P., Radnai I., Bíró-Németh E., Milisits G. 1996. Two-way selection for carcass traits by computerised tomography. In: Proc. 6th World Rabbit Congress, Toulouse, 2, 371-375.Szendrő Zs., Metzger Sz., Nagy I., Szabó A., Petrási Zs., Donkó T., Horn P. 2012. Effect of divergent selection for the computer tomography measured thigh muscle volume on productive and carcass traits of growing rabbits. Livest. Sci., 149: 167-172. https://doi.org/10.1016/j.livsci.2012.07.011Zomeño C., Hernández P., Blasco A. 2013. Divergent selection for intramuscular fat content in rabbits. 1. Direct response to selection. J. Anim. Sci., 91: 4526-4531. https://doi.org/10.2527/jas.2013-636

EFFECTS OF DIVERGENT SELECTION FOR HIND LEG MUSCLE VOLUME ON ITS LIPID PEROXIDE AND GLUTATHIONE REDOX STATUS, AND FATTY ACID COMPOSITION IN GROWING RABBITS

ABSTRACT: Pannon White bucks were selected divergently using CT method by the volume of the hind leg muscle. Animals showed the highest and lowest muscle volumes were selected as minus and plus-selected variants. The male progenies of the minus and plus-selected parents were slaughtered as fi rst generation which was selected again by CT method and the male progenies of the parents were slaughtered. Results in the fi rst and second generation suggest that selection, as a genetic effect did not affect the rate of lipid peroxidation, as was measured by malondialdehyde content and glutathione redox status, as was measured by the reduced glutathione content and glutathione peroxidase activity of the hind leg muscle. However, there were some differences in the fatty acid composition. Signifi cant (P&lt;0.05) difference was found in palmitoleic acid content which was higher in the minus as compared to the plus variants in the second generation, in eicosadienoic acid which was higher in the fi rst as compared to the second generation of minus variants, and total monounsaturated fatty acids which was higher in the minus as compared to the plus variants in the second generation. It means that selection for higher hind leg volume would not causes marked in changes in the rabbit meat quality as measured by lipid peroxide and glutathione status as well as fatty acid composition

Dietary supplementation of Digestarom® herbal formulation: effect on apparent digestibility, faecal and caecal microbial counts and live performance of growing rabbits

[EN] The experiment aimed to study the effect of Digestarom® dietary inclusion (herbal formulation containing a mixture of essential oils, herbs, spices and extracts) on apparent digestibility and digestive ecosystem of growing rabbits, as well as the effects of its supplementation before and after weaning on growth performance. At kindling, rabbit does and litters were divided into 2 dietary groups (51 does/group) and fed either a control diet (C) or a diet supplemented with 300 mg Digestarom®/kg diet (D) until weaning, which occurred at 35 d (before weaning supplementation). Each group was further divided into 3 dietary groups: CC received the control diet and DD received the D diet from 5 to 12 wk of age, and DC were fed with D (from 5 to 8 wk of age) and C diets (from 8 to 12 wk of age) (after weaning supplementation; 54 kits/group). An in vivo digestibility trial and a faecal microbial count were carried out on growing rabbits that received only the C or D diets during the trial. The C group showed higher DM intake than D group (215 vs. 196 g/d; P<0.05). The faecal digestibility of ether extract (75.9 vs. 59.8%; P<0.001), cellulose (25.9 vs. 20.6%; P<0.05) and gross energy (51.8 vs. 49.1%; P<0.05) was higher for C than for D group, whereas that of starch (98.9 vs. 98.8%; P<0.001) and the digestible protein to digestible energy ratio (13.9 vs. 13.2 g digestible protein/MJ digestible energy; P<0.01) was the highest for rabbits fed D diet. Stomach and caecal pH, caecal and faecal microbial counts were independent of the dietary treatment. The only exception was the stomach pH in 8 wk-old rabbits, which had the lowest value in C rabbits (P<0.05). The D supplementation before weaning improved feed conversion ratio throughout the growing phase (4.3 vs. 4.4 for D and C, respectively; P<0.05), whereas significant differences in daily weight gain, feed conversion ratio and mortality were observed only in the first period after weaning. Based on the results obtained, dietary supplementation with Digestarom® does not seem to confirm the positive results previously reported for growing rabbits.Celia, C.; Cullere, M.; Gerencsér, Z.; Matics, Z.; Giaccone, V.; Kovács, M.; Bónai, A.... (2016). Dietary supplementation of Digestarom® herbal formulation: effect on apparent digestibility, faecal and caecal microbial counts and live performance of growing rabbits. World Rabbit Science. 24(2):129-138. doi:10.4995/wrs.2016.406912913824

Carcass traits and meat quality of growing rabbits in pens with and without different multilevel platforms

[EN] The aim of this trial was to determine the effect of the presence of wire or plastic mesh elevated platforms on carcass traits and meat quality characteristics, with particular attention to the oxidative status of growing rabbits. A total of 174 five-week old rabbits were randomly divided into 3 groups with 2 replications (6 pens; 29 rabbits/pen): pens without platforms (NoP) with a stocking density of 16 rabbits/m2 and pens with wire-mesh platforms (WP) or plastic-mesh platforms (PP) that were placed on 2 levels, with a stocking density of 16 rabbits/m2 on the floor or 9.14 rabbits/m2 when the platform were included. At 84 d rabbits were slaughtered. The slaughter traits and Longissimus lumborum (LL) physical and chemical compositition were not affected by treatments. Rabbits from the PP group showed the highest retinol and γ-tocotrienol content on LL muscle, whereas the NoP ones showed a higher α-tocotrienol and α-tocopherol level. The absence of platforms led to decreased (P<0.001) thiobarbituric acid-reactive substances values and induced an improvement in n-3 polyunsaturated fatty acids. Levels of linoleic, linolenic and docosahexaenoic acids were equal to those of the WP group (23.45, 3.75, 0.64% in NoP and 22.6, 4.14, 0.53% in WP, respectively) but higher than in PP rabbits (20.86, 3.05, 0.45%, respectively). It can be concluded that the pens with elevated platforms provide greater possibilities for movement, which is beneficial from the viewpoint of animal welfare. However, this greater activity influences the oxidative status of the meat, decreasing the antioxidant content and worsening the lipid oxidation of rabbit meat.This research was supported by the GOP-1.3.1-11/B-2011-0045 project and by the János Bolyai Research Scholarship (BO/00373/14/4) of the Hungarian Academy of Sciences.138Martino, M.; Mattioli, S.; Farkas, P.; Szendrő, Z.; Dal Bosco, A.; Ruggeri, S.; Matics, Z.... (2016). Carcass traits and meat quality of growing rabbits in pens with and without different multilevel platforms. World Rabbit Science. 24(2). https://doi.org/10.4995/wrs.2016.392212924

NIRS PREDICTION FOR PROTEIN AND INTRAMUSCULAR FAT CONTENT OF RABBIT HIND LEG MEAT

The goal of this study was to develop calibration equations to predict the chemical composition of raw, homogenized rabbit meat by means of near infrared spectroscopy (NIRS). 44 Pannon White rabbits were housed in groups in three different pen types (16 anim./m2), and were fed the same diet. Another 45 animals were housed in cages (12 anim./m2) and fed by different feeding regimes. Rabbits were slaughtered at the bodyweight of 2.4-2.5 kg. Homogenized fresh and freeze-dried left total hind leg muscles were investigated by NIRS using a NIRSystem 6500 equipment with small ring cup sample holder. The ether extract and protein content of all samples were determined chemically. Samples 44 of housing experiment were applied in producing LOCAL calibration equations tested on the 45 samples from the separate feeding experiment. Coefficients of determination (R2) of the predictions were 0.89 and 0.99 for fat, 0.85 and 0.96 for protein in fresh and freeze-dried samples, respectively. Results are reassuring, because the equations were applicable, however the analyzed samples were from independent housing and feeding systems. Therefore the chemical compositions differed in the two datasets, i.e. 9.46%, and 11.79% for fat, 85.75% and 83.44% for protein content in calibration and prediction datasets, respectively. The average of NIRS predicted values for fat and protein was 11.36%, 83.88% or 11.54%, 83.45% when using fresh or freeze-dried samples, respectively

Resources allocation in reproductive rabbit does: a review of feeding and genetic strategies for suitable performance

[EN] This article reviews how frequent feeding and selection programmes can affect resource allocation in rabbit does during reproduction. The consequences of these programmes and the central role of body condition for suitable female performance are analysed considering genetic level, health and welfare. Future reproductive potential of reproductive rabbit females is decided before first partum. There is enough evidence of a possible threshold for the rabbit female birth weight to reach the beginning of reproductive life in a suitable body condition to maximise their future reproductive potential. The moment of first mating could be identified as the last of the 'pure' data on the animal, a sign of the animal soma that is probably related to its productive potential. An adequate feeding system during rearing and first pregnancy is relevant for the reproductive performance of rabbit females in the short and long term. The body condition of females changes during the reproductive cycle and throughout their reproductive life according to their genetically determined level. The problems arise when the animals are forced to diverge from this appropriate level, increasing susceptibility to disease, other stress factors and eventual failure. Negative energy balances detected during lactation do not seem to have the strength of those observed in late pregnancy. Genetic selection for litter size at weaning has increased prolificacy, but also the ability to obtain resources without compromising the survival of rabbit females. However, it could also have increased the susceptibility of animals to the environment, focusing more on the maternal investment in the future litter rather than on the current one under restricted conditions to maximise their fitness. Rabbit does selected for reproductive longevity have a greater soma, which enables them to better cope with the possible productive challenges. There is also evidence that they have greater plasticity in using their soma, making them more robust to overcome demanding situations. In addition, there is evidence of a possible improvement of immune system modulation in such robust animals.This work was carried out thanks to the research developed in the last decade with the support of different grants from the Spanish Ministry of Science and Innovation (AGL2000-0595-C03-03, AGL 2004-02710, AGL2008-00273 and AGL2011-30170-C02-01).Pascual Amorós, JJ.; Savietto, D.; Cervera Fras, MC.; Baselga Izquierdo, M. (2013). Resources allocation in reproductive rabbit does: a review of feeding and genetic strategies for suitable performance. World Rabbit Science. 21(3):123-144. https://doi.org/10.4995/wrs.2013.1236SWORD12314421

Effect of different weaning age (21, 28 or 35 days) on production, growth and certain parameters of the digestive tract in rabbits

The effect of different weaning ages, that is, 21 (G21), 28 (G28) or 35 (G35) days, on growth and certain parameters of the digestive tract was examined in rabbits to assess the risk of early weaning attributable to the less-developed digestive system. On days 35 and 42, G35 rabbits had 10% to 14% and 10% higher BW, respectively ( P,0.05), than those weaned at days 21 and 28. In the 4th week of life, early weaned animals had 75% higher feed intake than G28 and G35 rabbits ( P,0.05). The relative weight of the liver increased by 62% between 21 and 28 days of age, and thereafter it decreased by 76% between 35 and 42 days of age ( P,0.05), with G21 rabbits having 29% higher weight compared with G35 animals on day 35 ( P,0.05). The relative weight of the whole gastrointestinal (GI) tract increased by 49% and 22% after weaning in G21 and G28 rabbits, respectively ( P,0.05). On day 28, the relative weight of the GI tract was 19% higher in G21 than in G28 rabbits, whereas on day 35 G21 and G28 animals had a 12% heavier GI tract compared with G35 rabbits ( P,0.05). Age influenced the ratio of stomach, small intestine and caecum within the GI tract; however, no effect of different weaning age was demonstrated. The pH value of the stomach and caecum decreased from 5.7 to 1.6 and from 7.1 to 6.3, respectively, whereas that of the small intestine increased from 6.8 to 8.4 ( P,0.05); the differences between groups were not statistically significant. Strictly anaerobic culturable bacteria were present in the caecum in high amounts (108), already at 14 days of age; no significant difference attributable to weaning age was demonstrable. The concentration of total volatile fatty acids (tVFA) was higher in G21 than in G28 and G35 throughout the experimental period ( P,0.05). The proportion of acetic and butyric acid within tVFA increased, whereas that of propionic acid decreased, resulting in a C3 : C4 ratio decreasing with age. Early weaning (G21) resulted in higher butyric acid and lower propionic acid proportions on day 28 ( P,0.05). No interaction between age and treatment was found, except in relative weight of the GI tract and caecal content. In conclusion, early weaning did not cause considerable changes in the digestive physiological parameters measured, but it resulted in 10% lower growth in rabbits

Feeding silkworm (Bombyx mori L.) oil to growing rabbits improves the fatty acid composition of meat, liver and perirenal fat

Silkworm oil was used in a rabbit diet to evaluate its benefit on the fatty acid (FA) profile of different carcass portions. Two experimental diets were prepared: a control diet (commercial diet with 13&nbsp;g/kg sunflower oil) and a silkworm oil diet (SWO) (commercial diet with 13&nbsp;g/kg silkworm oil). Rabbits received the experimental diets the last three weeks before slaughter, which occurred at 10&nbsp;weeks of age. At slaughter, hind leg meat, liver, and perirenal fat were sampled for FA profile analysis. The SWO diet significantly increased the n-3 FA of all three sampling sites and halved the n-6/n-3 ratio of hind leg meat and perirenal fat. Furthermore, the liver of SWO rabbits was also richer in C22:6 n-3 compared to that of control rabbits. In conclusion, this study demonstrated that the total dietary replacement of sunflower oil with silkworm oil in fattening rabbits positively changed the FA profile of the considered carcass tissues