La significación es irrelevante y los P-valores engañosos. Qué hacer

[EN] The main statistical methods used in agricultural research for treatment comparison and for describing uncertainty about estimated parameters are reviewed. Since wrong interpretations of these methods are common, more informative procedures for presenting results are proposed. The concept of “relevant valor” is discussed and it is assumed as a fundamental concept for designing experiments and results interpretation. Finally, a Bayesian alternative of analyzing data is presented.[ES] En este artículo se revisan los métodos estadísticos más habituales usados en el análisis de datos en agricultura, tanto para comparar tratamientos como para expresar la incertidumbre respecto a un parámetro estimado. Se subraya que son muy frecuentes las interpretaciones erróneas de estos métodos, se indica su interpretación correcta y sus limitaciones, y se propone una metodología más informativa para presentar los resultados. Se discute el concepto de “valor relevante”, que se propone como fundamental para el diseño de experimentos y la interpretación de los resultados. Finalmente se propone una alternativa bayesiana al análisis de datos.Blasco Mateu, A. (2011). La significación es irrelevante y los P-valores engañosos. Qué hacer. ITEA. Información Técnica Económica Agraria. 107:48-58. http://hdl.handle.net/10251/43889S485810

Genetics of growth, carcass and meat quality in rabbits

[EN] 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.Blasco Mateu, A.; Nagy, I.; Hernández, P. (2018). Genetics of growth, carcass and meat quality in rabbits. Meat Science. 145:178-185. https://doi.org/https://doi.org/10.1016/j.meatsci.2018.06.030S17818514

Embryologic changes in rabbit lines selected for litter size variability

[EN] A divergent selection experiment on litter size variability was carried out. Correlated response in early embryo survival, embryonic development, size of embryos, and size of embryonic coats after four generations of selection was estimated. A total of 429 embryos from 51 high-line females and 648 embryos from 80 low-line females were used in the experiment. The traits studied were percentage of normal embryos, embryo diameter, zona pellucida thickness, and mucin coat thickness. Traits were measured at 24, 48, and 72 hours postcoitum (hpc); mucin coat thickness was only measured at 48 and 72 hpc. The embryos were classified as zygotes or two-cell embryos at 24 hpc; 16-cell embryos or early morulae at 48 hpc; and early morulae, compacted morulae, or blastocyst at 72 hpc. At 24 hpc, the percentage of normal embryos in the high line was lower than in the low line (-2.5%), and embryos in the high line showed 10% higher zona pellucida thickness than those of the low line. No differences in percentage of zygotes or two-cell embryos were found. At 48 hpc, the high-line embryos were less developed, with a higher percentage of 16-cell embryos (23.4%) and a lower percentage of early morulae (-23.4%). At 72 hpc, high-line embryos continued to be less developed, showing higher percentages of early morulae and compact morulae and lower percentages of blastocyst (-1.8%). No differences in embryo diameter or mucin coat thickness were found at any time. In conclusion, selection for litter size variability has consequences on early embryonic survival and development, with embryos presenting a lower state of development and a lower percentage of normal embryos in the line selected for higher variability. (C) 2016 Elsevier Inc. All rights reserved.This experiment was supported by projects of National Research Plan AGL2011-29831-C03-02 and GVPRE/2008/145.Garcia, M.; Blasco Mateu, A.; Argente, M. (2016). Embryologic changes in rabbit lines selected for litter size variability. Theriogenology. 86(5):1247-1250. https://doi.org/10.1016/j.theriogenology.2016.04.065S1247125086

Modeling production functions and economic weights in intensive meat production of guinea pigs

[EN] A profit function for a typical commercial farm of intensive guinea pig production was designed. The simulated farm contained 86 cages with a ratio of 7:1 females/males, with continuous mating. Kits were weaned at 15 days of age and slaughtered for meat production at 90 days of age. The absolute (EW) and relative economic weights of the main traits were calculated. The highest EW were kits produced per kindling (US$25), kits weaned per kindling (US$22), kits born alive per kindling (US$20), and the number of kindlings per female and year (US$12). Profit, returns, and costs per female and year were US$15, 68, and 53, respectively. Returns came from the production of young guinea pigs and discarded reproductive adults for meat production, 90 and 10% of the total returns. The highest costs were feeding and labor, 44 and 23% of the total cost. The EW and profit did not substantially change when simulating variations of ±20% in the prices of kilograms of fattening feed and kilograms of live weight of guinea pig, showing their robustness to future variations in market prices or to variations in prices between countries. The results obtained highlight the importance of the feeding costs in the guinea pig meat production.Pascual, M.; Cruz, DJ.; Blasco Mateu, A. (2017). Modeling production functions and economic weights in intensive meat production of guinea pigs. Tropical Animal Health and Production. 49(7):1361-1367. doi:10.1007/s11250-017-1334-4S13611367497Cartuche, L., Pascual, M., Gómez, E. and Blasco, A., 2014. Economic weights in rabbit meat production, World Rabbit Science, 22, 165–177.Chancay, 2015. Venta de cuyes. http://www.ventadecuyes.com . Accessed 20 Jun 2016.Chirinos, O., Muro, K., Álvaro, W., Otiniano, J., Quezada, J. C. and Ríos V., 2008. Crianza y comercialización del cuy para el mercado limeño, (Esan University, Lima, Peru).Chupin, D., 1995. Rearing unconventional livestock species: a flourishing activity, (Food and Agriculture Organization of the United Nations, Rome, Italy).Espinoza, J., Furushio, E. and Rodríguez, A., 2008. Propuesta de un plan de negocio para una empresa dedicada a la crianza tecnificada de cuyes ubicada en Ñaña y su comercialización al mercado local, (MSc thesis, Peruvian University of Applied Science, Lima, Peru).Humberto-Rodriguez, L., Mabel Palomino, T., Victor Hidalgo, L. and Gustavo Gutiérrez R., 2013. Efectos de factores fijos y al azar sobre el peso al nacimiento y al destete en cuyes de la costa central del Perú. Revista de Investigaciones Veterinarias del Peru, 24, 16–24.Instituto de Investigación Agraria, 1991. Proyecto sistemas de producción de cuyes. https://idl-bnc.idrc.ca/dspace/bitstream/10625/35272/4/104403_v2.pdf . Accessed 02 Sep 2016.Jimenez, A., 2005. Determinación de parámetros productivos y reproductivos de cuyes mejorados con sistemas de crianza en jaula y en poza, (BSc Thesis, Polytechnic School of Chimborazo, Roibamba, Ecuador).Ministerio de Agricultura, Ganadería, Acuacultura y Pesca de Ecuador, 2014. Manual de crianza y producción de cuyes con estándares de calidad. http://www.agricultura.gob.ec/wp-content/uploads/downloads/2015/11/Manual-para-la-crianza-del-cuy.pdf . Accessed 17 Jun 2016.Universidad Nacional Agraria la Molina, 2015. Programa de investigación y proyección social en alimentos. http://www.lamolina.edu.pe/cproducciόn/plantaalimentos/ . Accessed 27 Jan 2015

Effect of selection for intramuscular fat on the fatty acid composition of rabbit meat

[EN] Intramuscular fat (IMF) content and composition are relevant for the meat industry due to their effect on human health and meat organoleptic properties. A divergent selection experiment for IMF of Longissimus dorsi (LD) muscle was performed in rabbits during eight generations. The aim of this study is to estimate the correlated responses to selection for IMF on the fatty acid composition of LD. Response to selection for IMF was 0.34 g/100 g of LD, representing 2.4 phenotypic SD of the trait. High-IMF line showed 9.20% more monounsaturated fatty acids (MUFA) and 0.39%, 9.97% and 10.3% less n-3, n-6 and polyunsaturated fatty acids (PUFA), respectively, than low-IMF line. The main MUFA and PUFA individual fatty acids followed a similar pattern, except for C18:3n-3 that was greater in the high-IMF line. We did not observe differences between lines for the percentage of total saturated fatty acids, although high-IMF line showed greater C14:0 and C16:0 and lower C18:0 percentages than low-IMF line. Heritability estimates were generally high for all fatty acids percentages, ranging from 0.43 to 0.59 with a SD around 0.08, showing an important genetic component on these traits. Genetic correlations between IMF and LD fatty acid percentages were strong and positive for C14:0, C16:1, C18:1n-9, and MUFA, ranging from 0.88 to 0.97, and strong and negative for C18:0, C18:2n-6, C20:4n6, n-6 and PUFA, ranging from ¿0.83 to ¿0.91. These correlations were accurately estimated, with SD ranging from 0.02 to 0.06. The genetic correlations between IMF and other fatty acids were estimated with lower accuracy. In general, phenotypic and genetic correlations were of the same order. Our experiment shows that selection for IMF strongly affects the fatty acid composition of meat, due the high heritabilities of fatty acids and their high genetic correlations with IMF.This work was supported by project AGL2014-55921-C2-01-P from the Spanish National Research Plan. M. Martinez-Alvaro acknowledges a FPI grant (BES-2012-052655) from the Economy Ministry of Spain. The authors thank Federico Pardo and Marina Morini for their technical assistance.Martinez Alvaro, M.; Blasco Mateu, A.; Hernández, P. (2018). Effect of selection for intramuscular fat on the fatty acid composition of rabbit meat. animal. 12(10):2002-2008. https://doi.org/10.1017/S1751731117003494S20022008121

Litter Survival Differences between Divergently Selected Lines for Environmental Sensitivity in Rabbits

[EN] Simple Summary Two rabbit lines are divergently selected for increasing or decreasing the variability of litter size at birth. Decreasing the litter size variability produces more resilient females with less sensitivity to diseases, being an indirect selection way to improve environmental sensitivity. The kits' survival rate at weaning was higher in the homogeneous line. Moreover, this line led to a greater uniformity of the kits' weight at weaning, although the weight variability at birth was higher, which could be due to a higher lactation capacity of the homogeneous line. A divergent selection experiment on environmental sensitivity was performed in rabbits. The aim was to estimate the correlated response in kit weight and survival, litter weight, and weight distance from birth to weaning. The weight distance was calculated as the absolute value of the differences between the individual value and the mean value of its litter. The relationship between the probability of survival at 4 d of age, and the weight at birth, was studied. Environmental sensitivity was measured as litter size variability. A total of 2484 kits from 127 does from the low line, and 1916 kits of 114 does from the high line of the 12th generation were weighed. Both of the lines showed similar individual and litter weights at birth and weaning, and a similar survival rate at birth, and at 4 d of age. The survival rate at weaning was higher in the low line (0.67 and 0.62; P = 0.93). The weight distance was higher at birth, but lower at weaning in the low line (47.8 g and 54.1 g; P = 0.98). When the weight at birth was high, the kits had a higher survival rate. In conclusion, selection for environmental sensitivity showed a correlated response in the kits' survival, and in the homogeneity of litter weight at weaning.This study is supported by the Spanish Ministry of Economy and Competitiveness (MINECO) with the Projects AGL2017-86083, C2-1-P and C2-2-P.Agea, I.; Garcia, M.; Blasco Mateu, A.; Argente, M. (2019). Litter Survival Differences between Divergently Selected Lines for Environmental Sensitivity in Rabbits. Animals. 9(9):1-9. https://doi.org/10.3390/ani9090603S1999Garcı́a, M. L., & Baselga, M. (2002). Estimation of genetic response to selection in litter size of rabbits using a cryopreserved control population. Livestock Production Science, 74(1), 45-53. doi:10.1016/s0301-6226(01)00280-9Sánchez, J. P., Theilgaard, P., Mínguez, C., & Baselga, M. (2008). Constitution and evaluation of a long-lived productive rabbit line1. Journal of Animal Science, 86(3), 515-525. doi:10.2527/jas.2007-0217Larzul, C., Ducrocq, V., Tudela, F., Juin, H., & Garreau, H. (2014). The length of productive life can be modified through selection: An experimental demonstration in the rabbit1. Journal of Animal Science, 92(6), 2395-2401. doi:10.2527/jas.2013-7216Rauw, W. ., Kanis, E., Noordhuizen-Stassen, E. ., & Grommers, F. . (1998). Undesirable side effects of selection for high production efficiency in farm animals: a review. Livestock Production Science, 56(1), 15-33. doi:10.1016/s0301-6226(98)00147-xBlasco, A., Martínez-Álvaro, M., García, M.-L., Ibáñez-Escriche, N., & Argente, M.-J. (2017). Selection for environmental variance of litter size in rabbits. Genetics Selection Evolution, 49(1). doi:10.1186/s12711-017-0323-4Argente, M. J., García, M. L., Zbyňovská, K., Petruška, P., Capcarová, M., & Blasco, A. (2019). Correlated response to selection for litter size environmental variability in rabbits’ resilience. animal, 13(10), 2348-2355. doi:10.1017/s1751731119000302Bolet, G., Esparbié, J., & Falières, J. (1996). Relations entre le nombre de fœtus par corne utérine, la taille de portée à la naissance et la croissance pondérale des lapereaux. Annales de Zootechnie, 45(2), 185-200. doi:10.1051/animres:19960207Poigner J., Szendrõ Zs., Lévai A., Radnai I., & Biró-Németh E. (2010). EFFECT OF BIRTH WEIGHT AND LITTER SIZE ON GROWTH AND MORTALITY IN RABBITS. World Rabbit Science, 8(1). doi:10.4995/wrs.2000.413TM Threshold Modelhttp://snp.toulouse.inra.fr/~alegarra/manualtm.pdfPeiró, R., Badawy, A. Y., Blasco, A., & Santacreu, M. A. (2019). Correlated responses on growth traits after two-stage selection for ovulation rate and litter size in rabbits. animal, 13(11), 2457-2462. doi:10.1017/s1751731119001423Pascual, J. J., Savietto, D., Cervera, C., & Baselga, M. (2013). Resources allocation in reproductive rabbit does: a review of feeding and genetic strategies for suitable performance. World Rabbit Science, 21(3). doi:10.4995/wrs.2013.1236Bolet, G., Garreau, H., Joly, T., Theau-Clement, M., Falieres, J., Hurtaud, J., & Bodin, L. (2007). Genetic homogenisation of birth weight in rabbits: Indirect selection response for uterine horn characteristics. Livestock Science, 111(1-2), 28-32. doi:10.1016/j.livsci.2006.11.012Garreau, H., Bolet, G., Larzul, C., Robert-Granié, C., Saleil, G., SanCristobal, M., & Bodin, L. (2008). Results of four generations of a canalising selection for rabbit birth weight. Livestock Science, 119(1-3), 55-62. doi:10.1016/j.livsci.2008.02.009Hamilton, H. H., Lukefahr, S. D., & McNitt, J. I. (1997). Maternal nest quality and its influence on litter survival and weaning performance in commercial rabbits. Journal of Animal Science, 75(4), 926. doi:10.2527/1997.754926xVicente, J., García-Ximénez, F., & Viudes-de-Castro, M. (1995). Neonatal performances in 3 lines of rabbit (litter sizes, litter and individual weights). Annales de Zootechnie, 44(3), 255-261. doi:10.1051/animres:19950305Hull, D., & Segall, M. M. (1965). The contribution of brown adipose tissue to heat production in the new-born rabbit. The Journal of Physiology, 181(3), 449-457. doi:10.1113/jphysiol.1965.sp007773Spencer, S. A., & Hull, D. (1984). The effect of over-feeding newborn rabbits on somatic and visceral growth, body composition and long-term growth potential. British Journal of Nutrition, 51(3), 389-402. doi:10.1079/bjn19840045Venge, O. (1963). The influence of nursing behaviour and milk production on early growth in rabbits. Animal Behaviour, 11(4), 500-506. doi:10.1016/0003-3472(63)90269-0Coureaud, G., Schaal, B., Coudert, P., Rideaud, P., Fortun-Lamothe, L., Hudson, R., & Orgeur, P. (2000). Immediate postnatal sucking in the rabbit: Its influence on pup survival and growth. Reproduction Nutrition Development, 40(1), 19-32. doi:10.1051/rnd:2000117Argente, M. J., Santacreu, M. A., Climent, A., & Blasco, A. (1999). Phenotypic and genetic parameters of birth weight and weaning weight of rabbits born from unilaterally ovariectomized and intact does. Livestock Production Science, 57(2), 159-167. doi:10.1016/s0301-6226(98)00166-3Xiccato, G., Trocino, A., Sartori, A., & Queaque, P. I. (2004). Effect of parity order and litter weaning age on the performance and body energy balance of rabbit does. Livestock Production Science, 85(2-3), 239-251. doi:10.1016/s0301-6226(03)00125-8Rebollar, P. G., Pérez-Cabal, M. A., Pereda, N., Lorenzo, P. L., Arias-Álvarez, M., & García-Rebollar, P. (2009). Effects of parity order and reproductive management on the efficiency of rabbit productive systems. Livestock Science, 121(2-3), 227-233. doi:10.1016/j.livsci.2008.06.01

Correlated response in body condition and energy mobilisation in rabbits selected for litter size variability

[EN] A divergent selection experiment on litter size variability (high and low lines) was performed in rabbits over seven generations. The aim of this study was to evaluate the correlated responses to selection in body condition and fat reserves mobilisation. Litter size variability was estimated as phenotypic variance of litter size within female after correcting for the year-season and the parity-lactation status effects. A total of 226 females were used in this study, of which 158 females were used to measure body condition and energy mobilisation. Body condition was measured as BW and perirenal fat thickness. Females were stimulated with the adrenergic isoproterenol. Mobilisation capacity of fat reserves was measured by the lipolytic potential, defined as the increment in non-esterified fatty acids (NEFA) levels from basal concentration until adrenergic stimulation at mating, delivery and 10 days after delivery of the second reproductive cycle. Females were classified as survivor or non-survivor when they were culled for sanitary reasons or died before the third kindling. Data were analysed using Bayesian methodology. Survivor females presented higher BW than the non-survivor females at delivery (238 g, P=1.00) and 10 days after delivery (276 g, P=1.00). They also showed higher perirenal fat thickness at 10 days after delivery (0.62 mm, P=1.00). At delivery, basal NEFA levels was lower in survivor than non-survivor females (-0.18 mmol/l, P=1.00), but their lipolytic potential ( increment NEFA) was higher (0.08 mmol/l, P=0.94). Body weight was similar between lines in survivor females. Perirenal fat thickness was lower in the high line than in the low line at delivery (-0.23 mm, P=0.90) and 10 days after delivery (-0.28 mm, P=0.92). The high line exhibited higher NEFA (0.10 mmol/l, P=0.93) and lower increment NEFA (-0.08 mmol/l, P=0.92) than the low line at delivery. The low line showed a favourable correlated response to selection on body condition and fat reserves mobilisation. In conclusion, the low line selected for litter size variability seems to adapt better to adverse conditions, as it has a greater capacity to mobilise energy reserves at delivery than the high line. Females that adequately manage their body reserves and perform energy mobilisation correctly have a lower risk of dying or being culled.This study is supported by the Spanish Ministry of Economy and Competitiveness (MINECO), projects AGL2014-55921-C2, P1 and P2.Garcia, M.; Blasco Mateu, A.; Garcia, M.; Argente, M. (2019). Correlated response in body condition and energy mobilisation in rabbits selected for litter size variability. Animal. 13(4):784-789. https://doi.org/10.1017/S1751731118002203S784789134Webster Marketon, J. I., & Glaser, R. (2008). Stress hormones and immune function. Cellular Immunology, 252(1-2), 16-26. doi:10.1016/j.cellimm.2007.09.006Theilgaard, P., Sánchez, J. P., Pascual, J. J., Friggens, N. C., & Baselga, M. (2006). Effect of body fatness and selection for prolificacy on survival of rabbit does assessed using a cryopreserved control population. Livestock Science, 103(1-2), 65-73. doi:10.1016/j.livsci.2006.01.007Theilgaard, P., Baselga, M., Blas, E., Friggens, N. C., Cervera, C., & Pascual, J. J. (2009). Differences in productive robustness in rabbits selected for reproductive longevity or litter size. animal, 3(5), 637-646. doi:10.1017/s1751731109003838Roche, J. R., Friggens, N. C., Kay, J. K., Fisher, M. W., Stafford, K. J., & Berry, D. P. (2009). Invited review: Body condition score and its association with dairy cow productivity, health, and welfare. Journal of Dairy Science, 92(12), 5769-5801. doi:10.3168/jds.2009-2431PILORZ, V., JACKEL, M., KNUDSEN, K., & TRILLMICH, F. (2005). The cost of a specific immune response in young guinea pigs. Physiology & Behavior, 85(2), 205-211. doi:10.1016/j.physbeh.2005.04.008Pascual, J. J., Castella, F., Cervera, C., Blas, E., & Fernández-Carmona, J. (2000). The use of ultrasound measurement of perirenal fat thickness to estimate changes in body condition of young female rabbits. Animal Science, 70(3), 435-442. doi:10.1017/s135772980005178xMartínez-Paredes, E., Ródenas, L., Martínez-Vallespín, B., Cervera, C., Blas, E., Brecchia, G., … Pascual, J. J. (2012). Effects of feeding programme on the performance and energy balance of nulliparous rabbit does. animal, 6(7), 1086-1095. doi:10.1017/s1751731111002643Gellrich, K., Sigl, T., Meyer, H. H. D., & Wiedemann, S. (2015). Cortisol levels in skimmed milk during the first 22 weeks of lactation and response to short-term metabolic stress and lameness in dairy cows. Journal of Animal Science and Biotechnology, 6(1). doi:10.1186/s40104-015-0035-yFortun-Lamothe, L. (2006). Energy balance and reproductive performance in rabbit does. Animal Reproduction Science, 93(1-2), 1-15. doi:10.1016/j.anireprosci.2005.06.009Feugier, A., & Fortun-Lamothe, L. (2006). Extensive reproductive rhythm and early weaning improve body condition and fertility of rabbit does. Animal Research, 55(5), 459-470. doi:10.1051/animres:2006025Blasco, A., Martínez-Álvaro, M., García, M.-L., Ibáñez-Escriche, N., & Argente, M.-J. (2017). Selection for environmental variance of litter size in rabbits. Genetics Selection Evolution, 49(1). doi:10.1186/s12711-017-0323-4Friggens, N. C. (2003). Body lipid reserves and the reproductive cycle: towards a better understanding. Livestock Production Science, 83(2-3), 219-236. doi:10.1016/s0301-6226(03)00111-8Johnson, R. . (1998). Immune and endocrine regulation of food intake in sick animals. Domestic Animal Endocrinology, 15(5), 309-319. doi:10.1016/s0739-7240(98)00031-9Bareille, N., Beaudeau, F., Billon, S., Robert, A., & Faverdin, P. (2003). Effects of health disorders on feed intake and milk production in dairy cows. Livestock Production Science, 83(1), 53-62. doi:10.1016/s0301-6226(03)00040-xBlasco A , Martínez-Álvaro M , Garcia ML , Capcarova M , Zbynovska K , Petruska P , Ibáñez-Escriche N and Argente MJ 2018. Selection for genetic environmental sensitivity of litter size changes resilience in rabbits. In 11th World Congress on Genetics Applied to Livestock Production, 11–16 February 2018, Auckland, New Zealand.Fortun, L., Prunier, A., Étienne, M., & Lebas, F. (1994). Influence of the nutritional deficit of foetal survival and growth and plasma metabolites in rabbit does. Reproduction Nutrition Development, 34(3), 201-211. doi:10.1051/rnd:19940303Rosell, J. M., & de la Fuente, L. F. (2016). Causes of mortality in breeding rabbits. Preventive Veterinary Medicine, 127, 56-63. doi:10.1016/j.prevetmed.2016.03.014Savietto, D., Cervera, C., Blas, E., Baselga, M., Larsen, T., Friggens, N. C., & Pascual, J. J. (2013). Environmental sensitivity differs between rabbit lines selected for reproductive intensity and longevity. animal, 7(12), 1969-1977. doi:10.1017/s175173111300178xGarcía ML , Argente MJ , Muelas R , Birlanga V and Blasco A 2012. Effect of divergent selection for residual variance of litter size on health status and welfare. In Proceedings of the 10th World Rabbit Congress, 3–6 September 2012, Sharm El-Sheikh, Egypt, pp. 103–106.Chilliard, Y. (1993). Dietary Fat and Adipose Tissue Metabolism in Ruminants, Pigs, and Rodents: A Review. Journal of Dairy Science, 76(12), 3897-3931. doi:10.3168/jds.s0022-0302(93)77730-9Blasco, A. (2017). Bayesian Data Analysis for Animal Scientists. doi:10.1007/978-3-319-54274-4Sorensen, D., & Gianola, D. (2002). Likelihood, Bayesian, and MCMC Methods in Quantitative Genetics. Statistics for Biology and Health. doi:10.1007/b98952Rosell, J. M., & de la Fuente, L. F. (2009). Culling and mortality in breeding rabbits. 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Muscle metabolism in two rabbit lines divergently selected for intramuscular fat

[EN] A divergent selection experiment for intramuscular fat (IMF) of Longissismus dorsi muscle at 9 wk of age was performed in rabbits. The objective of this work was to compare the lipid metabolism in muscles and fat tissues of the high-IMF and low-IMF lines. Lipogenic, catabolic and lipolytic activities were studied in two muscles with different oxidative patterns (Longissimus dorsi and Semimembranosus proprius) and in perirenal fat depot at two ages, 9 wk and 13 wk. In addition, adipocytes were characterized in perirenal fat. In the fifth generation, direct response to selection was 0.26 g of IMF/ 100 g of muscle. Lines showed differences in their lipogenic activities of muscles and fat tissues at 13 wk, but not at 9 wk. High-IMF line showed greater glucose-6-P dehydrogenase (G6PDH), malic enzyme (EM) and fatty acid synthase (FAS) activities in Longissimus dorsi than low- IMF line with probabilities P0 = 1.00, 0.93 and 0.90, respectively. Differences between lines were particularly great for G6PDH activity, representing 1.13 SD. High-IMF line also showed greater G6PDH and FAS activities in Semimembranosus proprius (P0 = 0.98 for G6PDH and 0.95 for FAS) and perirenal fat (P0 = 0.91 for G6PDH and 0.96 for FAS). However, in perirenal fat, EM activity was greater in the low-IMF line (P0 = 0.90). No differences between lines were found almost in any catabolic or lipolytic activities of muscles. Regarding adipocyte characteristics, high-IMF line showed larger adipocytes in perirenal fat depot (P0 = 0.97) tissue compared to the low-IMF line, but no differences between lines were observed in the number of adipocytes. This study cast light on the metabolic activities involved in the genetic differentiation on lipid deposition in rabbits. This study shows that lipogenic activities in muscles and fat tissues, in particular G6PDH in Longissimus dorsi, are involved in the lipid accumulation in muscle and adipose tissues.This work was supported by project AGL2014-55921-C2-01-P from the Spanish National Research Plan. M. Martinez-Alvaro acknowledges a FPI grant (BES-2012-052655) from the Economy Ministry of Spain. The authors thank Federico Pardo for his technical assistance.Martínez Álvaro, M.; Agha, SA.; Blasco Mateu, A.; Hernández, P. (2017). Muscle metabolism in two rabbit lines divergently selected for intramuscular fat. Journal of Animal Science. 95(6):2576-2584. https://doi.org/10.2527/jas2017.1371S2576258495

Correlated responses to selection for intramuscular fat in several muscles in rabbits

[EN] The aim of this study was to evaluate the effect of six generations of selection for intramuscular fat (IMF) in muscle Longissimus thoracis et lumborum (LTL) at 9 wk. in IMF and fatty acid (FA) composition of muscles with diverse metabolic profile in rabbits. Direct response to selection was 0.33 g of IMF/ 100 g of LTL, around 0.4 SD per generation. A positive correlated response was observed in IMF of Biceps femoris, Supraspinatus and Semimembranosus proprius muscles at 9 wk., representing around 0.2 SD of the trait per generation. Selection affected similarly the FA composition of all muscles at 9 wk., high-IMF line showing greater monounsaturated but lower polyunsaturated FA percentages than low-IMF line, whereas no differences were observed for saturated FA. Traits were also measured at 13 wk. and correlated responses were in the same direction. Our results suggest a common genetic background for IMF and FA composition in muscles with different metabolic profile in rabbits.This work was supported by project AGL2014-55921-C2-01-P from the Spanish National Research Plan. M. Martinez-Alvaro acknowledges a FPI grant (BES-2012-052655) from the Economy Ministry of Spain.Martinez Alvaro, M.; Hernández, P.; Agha, SA.; Blasco Mateu, A. (2018). Correlated responses to selection for intramuscular fat in several muscles in rabbits. Meat Science. 139:187-191. https://doi.org/10.1016/j.meatsci.2018.01.026S18719113

Correlated response in litter size components in rabbits selected for litter size variability

[EN] A divergent selection experiment for the environmental variability of litter size (Ve) over seven generations was carried out in rabbits at the University Miguel Hernandez of Elche. The Ve was estimated as the phenotypic variance within the female, after correcting for year-season and parity-lactation status. The aim of this study was to analyse the correlated responses to selection in litter size components. The ovulation rate (OR) and number of implanted embryos (IE) in females were measured by laparoscopy at 12 day of the second gestation. At the end of the second gestation, the total number of kits born was measured (TB). Embryonic (ES), foetal (FS) and prenatal (PS) survival were computed as IE/OR, TB/IE and TB/OR, respectively. A total of 405 laparoscopies were performed. Data were analysed using Bayesian methodology. The correlated response to selection for litter size environmental variability in terms of the litter size components was estimated as either genetic trends, estimated by computing the average estimated breeding values for each generation and each line, or the phenotypic differences between lines. The OR was similar in both lines. However, after seven generations of selection, the homogenous line showed more IE (1.09 embryos for genetic means and 1.23 embryos for phenotypic means) and higher ES than the heterogeneous one (0.07 for genetic means and 0.08 for phenotypic means). The probability of the phenotypic differences between lines being higher than zero (p) was 1.00 and .99, respectively. A higher uterine overcrowding of embryos in the homogeneous line did not penalize FS; as a result, this line continued to show a greater TB (1.01 kits for genetic means and 1.30 kits for phenotypic means, p=.99, in the seventh generation). In conclusion, a decrease in litter size variability showed a favourable effect on ES and led to a higher litter size at birth.Spanish Ministry of Economy and Competitiveness (MINECO), Grant/Award Number: AGL2011-29831-C03-02, AGL2014-55921-C2-2-P; Babel project from the Erasmus Mundus programmeArgente, MJ.; Calle, EW.; Garcia, ML.; Blasco Mateu, A. (2017). Correlated response in litter size components in rabbits selected for litter size variability. Journal of Animal Breeding and Genetics. 134(6):505-511. https://doi.org/10.1111/jbg.12283S505511134