Analysis of reproductive performances during the formation of a synthetic rabbit strain

[EN] In 1995, a synthetic rabbit strain ('2666') was formed at INRA for commercial meat purposesby crossing the INRA '2066' strain and the 'V' strain from the Polytechnical University of Valencia (Spain).The development of some reproductive traits and body weight at palpation of the '2666' does was studiedfrom the F1 (first generation cross) to the F4 generation in comparison with the 'V' does. This developmentwas quantified in terms of Dickerson's crossbreeding parameters. The base strains did not differ significantlyfor any of the studied traits, either overall or in their direct and maternal genetic value. F1 does exhibitedsignificant individual heterosis for body weight (5.5% of the parental average), pregnancy rate (13.3%),total born (18.3%), born alive (24.4%) and weaned (21.0%) per litter born. Concerning body weight, asignificant crossbred superiority over the 'V' line was retained in the F2 but not thereafter. The rate ofpregnancy showed no crossbred advantage from the F2 on. Concerning litter size traits, the benefit ofcrossbreeding was maintained until the F4, but at a lower magnitude than in the F1. Body weight andpregnancy rate exhibited maternal heterosis, while litter size did not. Direct epistatic losses were significantfor body weight, tended towards significance for pregnancy rate, but did not affect litter size. Overall, thecomparison between the synthetic strain and the founders was favourable to the synthetics.Brun, J.; Baselga, M. (2005). Analysis of reproductive performances during the formation of a synthetic rabbit strain. World Rabbit Science. 13. doi:10.4995/wrs.2005.514SWORD1

Performance, digestive disorders and the intestinal microbiota in weaning rabbits are affected by a herbal feed additive

[EN] A herbal feed additive (Digestarom(R), containing a mixture of onion, garlic, caraway, fennel, gentian, melissa, peppermint, anise, oak bark and clove) was fed to rabbit does and kits to study its impact on performance, post-weaning digestive disorders and intestinal microbiota. Two groups of 9 doe rabbits and their offspring, after weaning, were fed a standard diet without or with the addition of 300 mg Digestarom(R)/kg diet. Forty kits from each group were weaned at 28 d of age weighing 0.614±0.005 kg. They were caged in groups of four rabbits (10 cages/treatment) and fed the same diet as their mothers for 13 d. Weight gain and feed intake of the kits fed Digestarom(R) was 18 and 14% higher, respectively, than those fed control diet (P<0.001), with no differences in the feed conversion. Rabbits were killed 13 d after weaning and 10 healthy animals from the Digestarom(R) group and 10 healthy and 10 diseased animals from the control group were dissected. Healthy rabbits fed control diet and those fed Digestarom(R) showed closer intestinal digesta dry matter, pH and volatile fatty acid (VFA) profi les, compared to diseased animals. VFA concentration in the small intestine was higher (P=0.030) in the diseased animals of the control group compared with the healthy and Digestarom(R) fed rabbits. However, no differences were observed in VFA concentration in stomach or caecum contents. The fermentation profi le of diseased animals was characterised by a higher proportion of propionic, i- and n-valeric acids in the caecal contents (P<0.001), and an increased i-butyric acid concentration in the stomach and caecum contents (P=0.014), whereas n-butyric acid was reduced (P<0.033) compared with the healthy or Digestarom(R) fed rabbits. Denaturing gradient gel electrophoresis indicated a higher caecal bacterial diversity in the control rabbits compared with kits fed Digestarom(R) (P=0.008). The reduced evenness factor (P<0.010) also indicated that the bacterial composition included more dominant species in the Digestarom(R) group. Under our experimental conditions, the tested herbal feed additive Digestarom(R) had protective effects in rabbit kits after weaning, making it an interesting alternative for establishing nutritional strategies.Krieg, R.; Vahjen, W.; Awad, W.; Sysel, M.; Kroeger, S.; Zocher, E.; Hulan, H.... (2009). Performance, digestive disorders and the intestinal microbiota in weaning rabbits are affected by a herbal feed additive. World Rabbit Science. 17(2):87-95. doi:10.4995/wrs.2009.662879517

Abstracts of the XXXIV Symposium de cunicultura de ASESCU. Sevilla, Spain. 4-5 Jun, 2009

[EN] The annual Congress of the Spanish Association of Cuniculture (ASESCU) was held in Calahorra (La Rioja) on 30-31st October of 2008. The 33th edition was devoted to study different strategies to enhance the farm profitability. The high increment in the feeding and the low price of the meat has been the main responsible of the decrease in the profitability in the last 2 years. Different possibilities to reduce the feed conversion ratio (FCR) both in fatteners and females were discussed in two sessions. Furthermore, a total of 15 communications were presented in 5 working sessions: Meat quality in commercial or wild rabbits, Genetic and Reproduction, with a focus on new selection criteria and semen quality, Management and economy, with a study of the costs, Nutrition, with strategies to reduce mortality and Pathology, with references to different pathologies.52(2010). Abstracts of the XXXIV Symposium de cunicultura de ASESCU. Sevilla, Spain. 4-5 Jun, 2009. World Rabbit Science. 18(1). doi:10.4995/wrs.2010.18.074318

EFFECT OF FEED RESTRICTION IN A RABBIT LINE SELECTED FOR GROWTH RATE ON REPRODUCTIVE PERFORMANCE: OVULATION INDUCTION, OOCYTE QUALITY, EMBRYONARY AND FETAL LOSSES

Tesis por compendio[EN] The general aim of this thesis was to reproductively characterize females from a rabbit line selected for growth rate and to evaluate the effect of different nutritional strategies (ad libitum and restricted), in order to improve the reproductive performance. In chapter 1, the influence of maternal and embryonic genotype on prenatal survival and fetal growth was evaluated and contrasted with a maternal line. Prenatal survival, fetal weight and fetal placenta weight were affected by both embryonic and maternal genotype. Nevertheless, no differences were detected either at transcriptomic level in fetal placenta or in progesterone and IGF-I plasma levels in these females. It may be concluded that in rabbit females from paternal lines both embryonic and maternal genotypes are key factors in the reproductive performance of these females. The aim of chapter 2 was to explore the causes of ovulation failures in these rabbit females. Results showed that non-ovulated females presented lower LH plasma concentration as well as higher body weight and leptin and BOHB plasma levels than ovulated females. Thus, ovulation failures in females from line R could be attributed to decreased LH plasma concentrations in these females which may be related with their higher body weight and leptin levels. The following three chapters were focused on improvement of the reproductive performance of these females through a different nutritional strategy: a feed-to-appetite diet of these females after the rearing period and prior to insemination. The initial hypothesis was that the females are submitted to a restricted nutritional regimen which is not enough to cope with their needs during reproduction, causing long-term disturbances of energy balance which leads to the subsequent reproductive problems. Chapter 3 aimed to determine if a feed-to-appetite nutritional strategy would affect the hypothalamus-hypophysis axis and the quality of the produced oocytes, by transcriptomic analysis. While no differences were found in the microarray analysis of the hypothalamus-hypophysis, small differences were detected in the transcript expression analysis in oocytes of a group of genes selected. MSY2 was found to be downregulated in oocytes from restricted females. As a key regulator of maternal RNA transcription and translation, changes in this essential gene could explain some of the reproductive problems of these females. Whether the differences found at oocyte level were inherent at embryonic level and so involved in the drop of fertility was studied in Chapter 4. Although no significant differences were revealed in ovulation, embryo recovery, and implantation rate, higher fetal and gestational losses were found in restricted females, as well as lower fetal growth. Thus, we concluded that the nutritional strategy employed may have an impact on the oocyte (Chapter 3), but we also demonstrated that these changes were inherited by the embryo, and result in disturbances in gestational losses and fetal growth. The final chapter of this thesis was conducted to determine whether these effects on reproductive and metabolic elements were also evident in females following the common semi-intensive farm production system. Although the results obtained showed small variances in NEFAs and BOHB plasma levels, and also in body weight, no differences were detected in global reproductive performance in terms of fertility, prolificacy and productivity. The results obtained established that although differences are found at oocyte level and inherited by embryo and fetus, no improvements are reached with the proposed nutritional strategy in terms of reproductive performance when females selected for growth rate lead a normal semi-intensive production system.[ES] El objetivo general fue la caracterización reproductiva de las hembras de una línea de conejo seleccionada por velocidad de crecimiento y el efecto de distintas estrategias nutricionales (ad libitum y restringidas), con la finalidad de mejorar el rendimiento reproductivo. En el capítulo 1 se evaluó la influencia de los genotipos materno y embrionario en la supervivencia prenatal y crecimiento fetal, entre las hembras de esta línea y una línea maternal. La supervivencia prenatal, peso fetal y el peso de la placenta resultaron afectados por los genotipos tanto embrionario como materno, pero no se detectaron diferencias sobre la placenta fetal a nivel del transcriptoma ni en los niveles de progesterona e IGF-I. Por lo tanto, se puede concluir que en éstas tanto el genotipo embrionario como el materno son factores clave en su rendimiento reproductivo. El objetivo del capítulo 2 fue explorar las causas de los fallos reproductivos en estas hembras. Los resultados mostraron que las hembras que no ovularon presentaban menores niveles de LH, un mayor peso corporal y mayor concentración en sangre de leptinas y BOHB, que aquellas que había ovulado. Por ello, los fallos en ovulación detectados en estas hembras podrían estar relacionados con una reducción en los niveles de LH, consecuencia del mayor peso de estas hembras y de los incrementados niveles de leptinas. Los siguientes capítulos se enfocaron a la mejora del rendimiento reproductivo de estas hembras empleando una estrategia nutricional distinta: la ingesta ad libitum de alimento tras el periodo de crianza hasta el momento del comienzo de su vida reproductiva. La hipótesis de partida fue que estas hembras son sometidas a un régimen nutricional restringido que no es suficiente para satisfacer sus necesidades energéticas durante la reproducción, lo que causa alteraciones en su balance energético que se manifestarían en los problemas reproductivos observados. El capítulo 3 trató de determinar a través de un análisis trasncriptómico si la estrategia nutricional planteada afectaría el eje hipotalámico-hipofisario y la calidad de los ovocitos. Aunque no se encontraron diferencias en el análisis de un micrarray realizado sobre el hipotálamo-hipófisis, sí que se detectaron en la expresión génica de los ovocitos. El transcrito MSY2 mostró una menor expresión en los ovocitos de las hembras restringidas. Este gen es un regulador clave en la maduración ovocitaria, por lo tanto, cambios en la expresión de este gen podrían explicar algunos de los problemas reproductivos de estas hembras. En el capítulo 4 se estudió si las diferencias a nivel ovocitario eran heredadas por el embrión pudiendo causar la baja fertilidad de estas hembras. Aunque no se encontraron diferencias en las tasas de ovulación, recuperación embrionaria e implantación, sí que aparecieron diferencias en las pérdidas fetales y gestacionales, así como un menor crecimiento fetal en los embriones procedentes de hembras con restricción alimentaria. Por ello, concluimos que la estrategia nutricional empleada tiene unas consecuencias en el ovocito (Capítulo 3), y demostramos que estos cambios parecen continuar en el embrión, resultando en alteraciones en pérdidas gestacionales y crecimiento fetal. El capítulo final fue desarrollado para evidenciar si los efectos reproductivos y metabólicos observados en los capítulos previos se manifestaban en las hembras que se encuentran en un sistema de producción tradicional en granja. A pesar de que los resultados mostraron variaciones en los niveles circulantes de NEFAs y BOHB y de peso corporal, no se encontraron diferencias en el rendimiento reproductivo global a nivel de fertilidad, prolificidad y productividad. Los resultados obtenidos parecen indicar que a pesar de las diferencias encontradas a nivel ovocitario, embrionario y fetal, con el régimen nutricional propuesto no se logra alcanzar mejoras en la eficiencia reproductivo de las h[CA] L'objectiu general va ser la caracterització reproductiva de les femelles d'una línia de conill seleccionada per velocitat de creixement i l'efecte de diferents estratègies nutricionals (ad libitum i restringides), amb la finalitat de millorar el rendiment reproductiu. En el capítol 1 s'avaluà la influència dels genotipus matern i embrionari en la supervivència prenatal i el creixement fetal, entre les femelles d'aquesta línia i les de una altra línia maternal. La supervivència prenatal, el pes fetal i el pes de la placenta resultaren afectats pels genotipus embrionari i matern, però no es detectaren diferències en la placenta fetal a nivell de trascriptoma ni en els nivells de progesterona i IGF-I. Per tant, en les femelles de conill seleccionades per velocitat de creixement, tant el genotipus embrionari com el matern són factors clau en el seu rendiment reproductiu. L'objectiu del capítol 2 va ser explorar les causes de les fallades reproductives en aquestes femelles. Les femelles que no ovularen presentaren menor nivells de LH, major pes corporal i major concentració de leptines i BOHB que aquelles que sí que hi havia ovulat. Per això, les fallades d'ovulació detectades en aquestes femelles podrien estar relacionades amb la reducció en els nivells de LH, com a conseqüència del major pes d'aquestes femelles i dels incrementats nivells de leptines. Els capítols següents s'enfocaren a la millora del rendiment reproductiu d'aquestes femelles mitjançant una estratègia nutricional distinta: la ingesta ad libitum d'aliment després del període de criança i fins al moment de l'inici de la vida reproductiva. La hipòtesi de partida fiu que aquestes femelles són sotmeses a un règim nutricional restringit que no és suficient per a satisfer les seves necessitats energètiques durant la reproducció, la qual cosa provoca alteracions en el balanç energètic que podrien manifestar-se en els problemes reproductius observats. El capítol 3 tractà de determinar mitjançant un anàlisi trasncritòmic si la estratègia nutricional plantejada podria afectar l'eix hipotalàmic-hipofisiari i la qualitat dels ovòcits. Metre que no es detectaren diferències en el anàlisi del microarray realitzat en el hipotàlem-hipòfisi, sí que es detectaren en l'expressió gènica del ovòcits. El transcrit MSY2 mostrà una menor expressió en els ovòcits de les femelles restringides. Aquest gen es un regulador clau en la maduració ovocitària, per aquest motiu, canvis en la seva expressió gen podrien explicar alguns dels problemes reproductius de les femelles. En el capítol 4 s'estudià si aquestes diferències a nivell ovocitari eren heretades per l'embrió i podrien causar la baixa fertilitat d'aquestes femelles. Encara que no se trobaren diferències en les taxes d'ovulació, recuperació embrionària i implantació, sí que es trobaren diferències en les pèrdues fetals i gestacionals, així com un menor creixement fetal en els embrions de les femelles provinents d'un règim alimentari restringit. Per això concloíem que l'estratègia nutricional emprada té conseqüències en el ovòcit (Capítol 3), i demostrarem que aquest canvis pareixen continuar en l'embrió, resultant en alteracions en pèrdues gestacionals i creixement fetal. El capítol final fou desenvolupat per evidenciar si els efectes reproductius i metabòlics observats en els capítols previs eren manifestats en les femelles que es troben en un sistema productiu tradicional de granja. Tot i que el resultats mostraren variacions en els nivells circulants de NEFAs i BOHB i pes corporal, no es trobaren diferències en el rendiment reproductiu global, en termes de fertilitat, prolificitat i productivitat. Els resultats obtinguts pareixen indicar que tot i que les diferències trobades a nivell ovocitari i embrionari amb un efecte significatiu en el desenvolupament i creixement fetal, amb el règim nutricional proposat no s'aconsegueix assolir millores enNaturil Alfonso, C. (2016). EFFECT OF FEED RESTRICTION IN A RABBIT LINE SELECTED FOR GROWTH RATE ON REPRODUCTIVE PERFORMANCE: OVULATION INDUCTION, OOCYTE QUALITY, EMBRYONARY AND FETAL LOSSES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/73065TESISCompendi

Effect of restricted feeding under rearing on reproduction, body condition and blood metabolites of rabbit does selected for growth rate

[EN] Young rabbit females selected for growth rate can have nutritional needs which may not be met by the common practice of feed restriction during rearing in commercial rabbit production. The aim of this study was to analyse the effect of two different feeding programmes: restricted and ad libitum feeding, applied in young rabbit females for one month at the end of rearing, on reproductive performance, body condition and circulating metabolic hormones and metabolites in a rabbit line selected by growth rate in 3 consecutive reproductive cycles. Thus, twenty-four 16-week-old does were randomly assigned to a group in which the daily recommended nutrient intakes were satisfied (fed restricted: 130 g/day, n=13) or a group fed to satiety (ad libitum: 235.5 g/day, n=11) during one month. Then, all does were inseminated in 3 consecutive cycles using a 42-day reproductive cycle. Measurements of does’ body weight, perirenal fat thickness and plasma leptin, non-esterified-fatty-acids (NEFA), beta-hydroxybutyrate (BOHB) and fructosamine were performed at artificial insemination (AI), parturition and weaning time in 3 consecutive cycles. Reproductive performance of does was evaluated based on fertility, litter size at parturition, prolificacy and productivity. Differences in body weight were found only in the 1st cycle, ad libitum fed females being heavier than restricted ones. Nevertheless, body weight variances disappeared in later cycles. No differences were found in perirenal fat thickness. Finally, in ad libitum fed females slight differences were found in plasma levels of NEFAs (452 vs. 258 μekv/L and 527 vs. 306 μekv/L for 1st and 2nd cycles) and BOHB (0.26 vs. 0.03 mM for 2nd cycle), but disappeared in the 3rd reproductive cycle. Fertility, prolificacy and productivity was not significantly affected by the feeding programme. Nevertheless, total litter size showed to be higher in ad libitum fed females at second parturition (8.7 vs. 5.9 kits). Therefore, the evaluated feeding programmes until first AI in females selected by growth rate had no effect on their reproductive outcomes, as the global reproductive performance was not affected.This work was supported by the Spanish Research Project AGL2014- 53405-C2-1-P (CICYT). Carmen Naturil was supported by a research grant from the Education Ministry of the Valencian Regional Government (programme VALi+d. ACIF ⁄ 2013 ⁄ 296). English text version revised by N. Macowan English Language Service.Naturil-Alfonso, C.; Marco-Jiménez, F.; Pascual, J.; Vicente, J. (2017). Effect of restricted feeding under rearing on reproduction, body condition and blood metabolites of rabbit does selected for growth rate. World Rabbit Science. 25(4):303-312. https://doi.org/10.4995/wrs.2017.6848SWORD30331225

Rearing programmes for breeding rabbits. Effect of early development and feeding on future reproductive performance of rabbit females and males

Tesis por compendio[ES] Cualquier mejora en el conocimiento de la nutrición y el manejo de los futuros conejos reproductores debe considerarse como prioritario en la producción cunícola. Sin embargo, los principales esfuerzos en investigación se han centrado en estos animales durante la fase de reproducción propiamente dicha. La hipótesis inicial de esta tesis fue que alcanzar un desarrollo temprano adecuado durante la gestación, lactancia, engorde y recría, con la ayuda de programas ajustados de alimentación en algunos de estos períodos, mejoraría el rendimiento reproductivo y la vida útil de los futuros conejos reproductores. Para evaluar esta hipótesis, se llevaron a cabo dos tipos de ensayos, tanto en conejos hembra de líneas maternas como en machos de líneas seleccionadas por velocidad de crecimiento y destinadas a la inseminación artificial. El primero de estos ensayos se centró en los diferentes patrones de crecimiento, desde el nacimiento hasta el final de la fase de recría, y su influencia en la carrera reproductiva y la vida útil del conejo. En el segundo tipo de pruebas, se evaluó el efecto del uso de diferentes dietas o programas de alimentación durante el período de recría en la productividad a corto y medio plazo. Los resultados muestran dos fases importantes en el desarrollo temprano, de acuerdo con sus efectos sobre el rendimiento reproductivo y la vida útil. Mostrar un mayor desarrollo corporal desde el nacimiento hasta los 63 días de vida parece tener una influencia positiva en el grado de madurez y la productividad al comienzo de su vida reproductiva, además de poder mejorar su supervivencia a corto plazo, pero con posibles efectos negativos en la esperanza de vida a largo plazo. Sin embargo, el desarrollo durante el período de recría (desde los 63 días de vida hasta el comienzo de la carrera reproductiva) parece tener un mayor impacto en la productividad y la esperanza de vida de nuestros futuros conejos reproductores. Las hembras más engrasadas en la primera inseminación tuvieron tamaños de camada más pequeños y un mayor riesgo de ser sacrificadas que las magras (P<0.05). Además, los machos que mostraron una mayor ganancia media diaria durante el período de recría tuvieron un número y porcentaje de eyaculados viables más bajos a lo largo de su vida productiva y mayor riesgo de muerte o sacrificio. Estos resultados podrían indicar que la clave para llevar a cabo un desarrollo adecuado durante el período de recría debería basarse tanto en conseguir que los conejos alcancen un grado de madurez apropiado, tanto fisiológica como reproductivamente, así como evitar un excesivo engrasamiento al inicio de su vida productiva. En los ensayos destinados a evaluar los programas de alimentación durante la recría, el uso de una restricción alimentaria en hembras, y especialmente el uso de dietas fibrosas (de 8.5 a 10 MJ ED/kg MS) permiten un desarrollo corporal gradual y adecuado a la edad de cubrición, con suficientes reservas corporales para afrontar el comienzo de la vida reproductiva y mejorando tanto su rendimiento reproductivo como su vida útil. El éxito de estos programas de alimentación de recría depende del momento y la duración de la aplicación de estos, mejorándose con la aplicación de un cambio a un pienso enriquecido energéticamente alrededor del primer apareamiento. En los machos, se observó que un programa de alimentación durante la recría adecuado debería adaptarse a la capacidad de ingesta de estos y a sus necesidades nutricionales en períodos concretos de la recría, consiguiendo así mejoras en algunos parámetros del semen al inicio de su vida reproductiva. En conclusión, tanto un desarrollo temprano adecuado desde la gestación hasta el comienzo de su vida reproductiva, como el uso de programas adecuados de alimentación durante la recría podrían mejorar significativamente el rendimiento reproductivo futuro, así como la esperanza de vida, tanto en conejos he[CA] Qualsevol millora en el coneixement tant de la nutrició com del maneig dels futurs conills de criança ha de considerar-se com a prioritari en la producció de conills. No obstant açò, els principals esforços en investigació s'han centrat en aquests animals durant la fase de reproducció pròpiament dita. La hipòtesi inicial d'aquesta tesi va ser que aconseguir un desenvolupament primerenc adequat durant la gestació, lactància, engreix i criança, amb l'ajuda de programes ajustats d'alimentació en alguns d'aquests períodes, milloraria el rendiment reproductiu i la vida útil dels futurs conills reproductors. Per a avaluar aquesta hipòtesi, es van dur a terme dos tipus d'assajos, tant en conills femella de línies maternes, com en mascles de línies seleccionades per a la velocitat de creixement i destinades a la inseminació artificial. El primer d'aquests assajos es va centrar en els diferents patrons de creixement, des del naixement fins al final de la fase de criança, i la seua influència en la carrera reproductiva i la vida útil del conill. En el segon tipus de proves, es va avaluar l'efecte de l'ús de diferents dietes o programes d'alimentació durant el període de criança, en la productivitat a curt i mig termini. Els resultats obtinguts semblen indicar que podríem diferenciar dues fases en el desenvolupament primerenc, d'acord amb els seus efectes sobre el rendiment reproductiu i la vida útil. Mostrar un major desenvolupament corporal des del naixement fins als 63 dies de vida sembla tenir una influència positiva en el grau de maduresa i la productivitat al començament de la seua vida reproductiva, a més de poder millorar la seua supervivència a curt termini, però amb possibles efectes negatius en l'esperança de vida a llarg termini. No obstant açò, el desenvolupament durant el període de sembla tenir un major impacte en la productivitat i l'esperança de vida dels nostres futurs conills reproductors. Les femelles més greixades en la primera inseminació van tenir grandàries de ventrada més xicotets (tant nascuts com deslletats) i un major risc de ser sacrificades que les magres (P<0.05). A més, els mascles que van mostrar un major guany mitjà diari durant el període de criança van tenir un nombre i percentatge d'ejaculats viables més baixos al llarg de la seua vida productiva i major risc de mort o sacrifici. Aquests resultats podrien indicar que la clau per a dur a terme un desenvolupament adequat durant el període de criança hauria de basar-se tant a aconseguir que els conills aconseguisquen un grau de maduresa apropiat, per a afrontar els futurs desafiaments productius, com evitar un excessiu greixatge a l'inici de la seua vida productiva. En els assajos destinats a avaluar els programes d'alimentació durant la criança, l'ús d'una restricció alimentària en femelles, i especialment l'ús de dietes fibroses (de 8.5 a 10 MJ ED/kg MS) permeten un desenvolupament corporal gradual i adequat a l'edat de cobriment, amb suficients reserves corporals per a afrontar el començament de la vida reproductiva i millorant tant el seu rendiment reproductiu com la seua vida útil. L'èxit d'aquests programes d'alimentació de criança depèn del moment i la durada de l'aplicació d'aquests, millorant-se amb l'aplicació d'un canvi a un pinso enriquit energèticament al voltant del primer cobriment. En els mascles, es va observar que un programa d'alimentació durant la criança adequat hauria d'adaptar-se a la capacitat d'ingesta d'aquests i a les seues necessitats nutricionals en períodes concrets de la criança, aconseguint així millores en alguns paràmetres del semen a l'inici de la seua vida reproductiva. En conclusió, tant un desenvolupament primerenc adequat des de la gestació fins al començament de la seua vida reproductiva, com l'ús de programes adequats d'alimentació durant la criança podrien millorar significativament el rendiment reproductiu futur, així com l'esperança[EN] Any improvement on the knowledge of both nutrition and management of the future rabbit breeders should be considered as crucial. However, main research efforts have been focused on animals during reproduction phase. The initial hypothesis of this thesis was that achieving an adequate early development during young rabbits' gestation, lactation, fattening and rearing, with the help of fitted feeding programmes in some of these periods, would be improved reproductive performance and lifespan of the future breeding rabbits. To evaluate this hypothesis, two types of trials, both in rabbit females from maternal lines selected for litter size at weaning and males from paternal lines selected for growth rate and intended on artificial insemination, were carried out. The first of these trials were mainly focused on the different growth patterns, from birth to the end of the rearing age, and their influence on rabbit's reproductive career and lifespan. In a second type of trials, the effect of the use of different diets or feeding programs during the rearing period in the performance in the short- medium-term was evaluated. The results obtained from the evaluation of the different growth patterns trials seem to indicate that, we could differentiate two parts on the early development according to their effects on reproductive performance and lifespan. To show a greater body development from birth to 63 days of life seems to have a positive influence on the maturity degree and productivity at the beginning of their reproductive life, as well as being able to improve their survival in the short-term, but it could be even negative for long-term lifespan. However, the development during the rearing period (from 63 days of life to the beginning of reproduction career) seems to have a higher impact on the productivity and lifespan of our rabbit breeders. Fatter rabbit females at first insemination had smaller litter sizes (born and weaned) and a higher risk of being culled (+13% per positive change in mm of perirenal fat) than lean ones (P<0.05). Also, rabbit males that showed a greater average daily gain during rearing period had a lower number and percentage of profitable ejaculates through it productive life (-10.1 and -4.9% per each 10 g of daily gain increase, respectively; P<0.05) and higher risk of death or culling (+16.2% per each increase in one standard deviation unit on live weight; P<0.05). These results could indicate that the key to carrying out an adequate development during the rearing period should allow the rabbits to reach an appropriate degree of physiological and reproductive maturity to face the future productive challenges, avoiding an excessive fatness at the beginning of their productive life. The use of a feeding restriction in rabbit females, and especially the use of fibrous diets (from 8.5 to 10 MJ DE/ kg DM) lead a gradual and adequate body development at mating, with enough body reserves to face the beginning of reproduction life and improving their whole reproductive performance and lifespan. The success of these rearing feeding programs depends in the moment and duration of application of them and improved with the application of a nutritional flushing around first mating. In rabbit males, it was observed that an adequate rearing feeding program should adapt it to the male's intake capacity and their nutritional requirements rearing period, especially to their high DP needs at the beginning of rearing period or when their requirements were close to maintenance, to improve some semen parameters at the beginning of their reproduction life. In conclusion, both the adequate early development of future rabbit breeders, from their own gestation to the beginning of their reproductive life, and the use of appropriate rearing feeding programs could significantly improve their future reproductive performance, as well as their life expectancy, both in rabbit females and males.Martínez Paredes, EM. (2019). Rearing programmes for breeding rabbits. Effect of early development and feeding on future reproductive performance of rabbit females and males [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124969TESISCompendi

Flushing or doe relocation as biostimulation methods for improvement of sexual behaviour and performance of multiparous rabbit doe after a summer resting period

[EN] A study was conducted to clarify the influence of flushing or doe relocation as biostimulation methods on oestrus response and subsequent performance on thirty NZW multiparous 10-11-month-old rabbit does after a two-month resting period in summer. After weaning of their last litter in June, the does were not re-mated and were fed a 100 g daily ration till September, the end of resting period. Then the does were randomly allocated to three groups (10 does/group): a control group (C) in which does remated without oestrus synchronisation, a relocated group (R) and a flushed group (F). Relocation consisted of moving does to another room in cages similar to their initial cages 48 h before the intended mating. F does returned to ad libitum feeding one week before mating. After mating, all females were fed and housed under the same conditions. The following parameters were measured: oestrogen level at end of rest period and at mating time, oestrus response parameters, fertility rate, nest quality traits, milk production, litter and kit traits at birth and weaning, and doe weight at mating and kindling. Results obtained revealed that, under the condition of this experiment, flushing was superior to relocation as a biostimulation method, since does of F group responded by significantly higher oestrogen level at mating, improved receptivity and fertility rates, higher milk production, and their litters were heavier at birth and weaning. No significant differences were recorded between the different groups for the nest quality traits. On the other hand, doe relocation did not exert any significant effect on oestrus response and subsequent performance of the rabbit does. In conclusion, a short flushing period of one week could be good biostimulation method for oestrus synchronisation and improvement of receptivity in multiparous restricted fed rabbit does after a long rest period.Manal, AF. (2010). Flushing or doe relocation as biostimulation methods for improvement of sexual behaviour and performance of multiparous rabbit doe after a summer resting period. World Rabbit Science. 18(3). doi:10.4995/wrs.2010.774418

Early development and reproductive lifespan of rabbit females: implications of growth rate, rearing diet and body condition at first mating

[EN] Factors influencing early development such as birth weight, nest competition, and the diet received during rearing have been proposed as elements conditioning the future reproductive performance of European rabbit (Oryctolagus cuniculus) females. To evaluate their effects, we followed the life of 1513 females from birth to time of death, culling or censoring (animals alive at a fixed date). Between 0 and 63 days of age 353 females died. From the remaining 1160 females, 864 were chosen based on their birth weight to be transferred from the selection to the production farm. At this farm, 431 females received the control diet (184g of CP, 381 g of NDF and 11.8 MJ of DE per kg DM), while the other 433 received the fibrous diet (134 g of CP, 436g of NDF and 10.0 MJ of DE per kg DM). Throughout the rearing period, we checked for the individual live weight and body condition (perirenal fat thickness) at first artificial insemination. Reproductive lifespan was defined as the number of days between the first parturition and the time of death, culling or censoring. Birth weight affected the survival of newborn females during lactation and the presence of a milk spot at birth (related to nest competition) increased the survivability of newborns weighing <45g (P <0.001). Rearing diet altered the growth curve of females and their body condition at first insemination. The diet also altered the relative risk of death during the rearing period, which was lower among females fed on the fibrous diet (-12.5%; P < 0.001). Therefore, a higher number of females fed with this diet reached their reproductive life, directly affecting the productivity measured per housed female. Fatter females at first insemination had smaller litter sizes and a higher risk of being culled than lean ones (P < 0.05). In general, the fibrous diet reduced the risk of leaving the herd at early rearing, and both birth weight and perirenal fat thickness affected female's reproductive lifespan. An excess of fat (positive change in one unit of perirenal fat) at their first insemination represented an increased the risk of death or elimination of 13%.The authors acknowledge Cesar Villalba (Fabara, Spain), Luis Eroles (Valderrobres, Spain) for the technical support in managing the animals and for kindly providing a space to conduct our study. They also thank the Commission for Science and Technology (CICYT) of the Spanish Government (AGL2014-53405-C2-1-P) for the economic support to carry out this study.Martinez-Paredes, E.; Ródenas Martínez, L.; Pascual Amorós, JJ.; Savietto, D. (2018). Early development and reproductive lifespan of rabbit females: implications of growth rate, rearing diet and body condition at first mating. animal. 12(11):2347-2355. https://doi.org/10.1017/S1751731118000162S23472355121

Descriptive characterization of a Nigerian heterogeneous rabbit population - factors affecting litter traits

[EN] This study evaluated the effect of female body weight at conception (FWC), season of mating (SM), type of mating (TM) and litter size at birth (LSB) on the litter performance in a heterogeneous Nigerian population of rabbits. Data on 116 litters from 10 bucks and 48 does across three parities were analysed. Reproductive traits evaluated included LSB, number born alive (NBA), litter sizes and weights at 7, 14 and 21 d post-kindling, pre-weaning survival rate (SR) and daily weight gain of kits from kindling to weaning (DWG). A fi xed linear model that included FWC (light and heavy does), TM (homospermic and heterospermic matings), LSB classes (low, medium and large) and SM (rainy or dry) was used. Results showed that heavier does at concenption showed higher performance for LSB and NBA (P<0.05) than lighter does. Average weight of kits at kindling and at 28 d, as well as kit SR and DWG, were signifi cantly higher in low-sized litters, when compared with intermediate- and large-sized litters (P<0.05). LSB, NBA and litter size at weaning were higher in litters produced by heterospermically mated does compared with homospermically mated does. Season of mating affected LSB and NBA (P<0.05), being signifi cantly larger the litters in the rainy season.The authors gratefully acknowledge the International Foundation for Science (IFS) of Sweden for its financial support (through grant B3871-1). The efforts and assistance of Jimi Talabi and Nike Olabode in data collection are appreciated.Oseni, S.; Ajayi, B. (2010). Descriptive characterization of a Nigerian heterogeneous rabbit population - factors affecting litter traits. World Rabbit Science. 18(2). doi:10.4995/WRS.2010.18.1418