Freezability genetics in rabbit semen

[EN] The aim of this study was to estimate the heritability of semen freezability and to estimate the genetic correlation between frozen-thawed sperm traits and the growth rate in a paternal rabbit line. Estimated heritabilities showed that frozen-thawed semen traits are heritable (ranged between 0.08 and 0.15). In the case of Live-FT (percentage of viable sperm after freezing), the estimated heritability is the highest one, and suggests the possibility of effective selection. After the study of genetic correlations it seems that daily weight gain (DG) was negatively correlated with sperm freezability, but no further conclusions could be drawn due to the high HPD95%. More data should be included in order to obtain better accuracy for the estimates of these genetic correlations. If the results obtained at present study were confirmed, it would imply that selection for DG could alter sperm cell membranes or seminal plasma composition, both components related to sperm cryoresistance. (C) 2017 Elsevier Inc. All rights reserved.This work was supported by the Generalitat Valenciana research program (Prometeo II 2014/036). Lavara R. acknowledges the partial support received from Generalitat Valenciana under VALid program (APOST/2014/034) and from Ministry of Economy and Competitiveness under subprogramme "Formation posdoctoral" (FPDI-2013-16707).Lavara García, R.; Moce Cervera, ET.; Baselga Izquierdo, M.; Vicente Antón, JS. (2017). Freezability genetics in rabbit semen. Theriogenology. 102:54-58. https://doi.org/10.1016/j.theriogenology.2017.07.013S545810

Effect of the refrigeration system on in vitro quality and in vivo fertility of goat buck sperm

Cooling goat sperm insemination doses to 4 °C causes a delay in their delivery. However, chilling these doses during the transportation period could expedite their delivery and the insemination process. In this study, an economical and simple apparatus for chilling goat semen doses in itinere was developed, and the in vitro quality and in vivo fertility of these doses were compared with those chilled by means of a programmable water bath in the laboratory at a rate of −0.18 °C/min. Of the tested prototypes, the one that provided an optimal combination of the chilling rate (average of −0.09 °C/min) and time required to reach 4 °C (3 h 45 min) was selected for further testing. Immediately after chilling and 24 h later, the doses chilled in the prototype were determined to be of higher quality than the samples chilled in the programmable water bath. Finally, the kidding rate was similar between the doses chilled in the programmable water bath (61.7% ± 7.1%) and in the prototype (56.1% ± 5.9%). In conclusion, successful chilling of goat sperm doses during transport is possible, thereby accelerating the delivery of insemination doses

Selection for ovulation rate in rabbits: Direct and correlated responses estimated with a cryopreserved control population1

The aim of this work was to evaluate the response in 10 generations of selection for ovulation rate in rabbits using a cryopreserved control population. Selection was based on the phenotypic value of ovulation rate estimated at d 12 of second gestation by laparoscopy. To produce the control population, embryos from 50 donor females and 18 males, belonging to the base generation of the line selected for ovulation rate, were recovered. A total of 467 embryos (72-h embryos) were vitrifi ed and stored in liquid N2 for 10 generations. The size of both populations was approximately 10 males and 50 females. The number of records used to analyze the different traits ranged from 99 to 340. Data were analyzed using Bayesian methodology. A difference between the selected and the control populations of 2.1 ova (highest posterior density interval (HPD95%) [1.3, 2.9]) was observed in ovulation rate (OR), but it was not accompanied by a correlated response in litter size (LS; −0.3; HPD95% [−1.1, 0.5]). The number of implanted embryos (IE) increased with selection in 1.0 embryo (HPD95% [−0.6, 2.0]), but this increase was not relevant. Prenatal survival, embryonic survival, and fetal survival (FS) were calculated as LS/OR, IE/OR, and LS/IE, respectively. Prenatal survival was reduced with selection (−0.12; HPD95% [−0.20, −0.04]), basically because of a decrease in FS (−0.12; HPD95% [−0.19, −0.06]). Embryonic survival could have slightly decreased (−0.05; HPD95% [−0.12, 0.02]). In summary, comparison with a control population showed that ovulation rate in rabbits increased with selection without any correlated response in litter size, basically because of a decrease in fetal survival.This study was supported by the Comision Interministerial de Ciencia y Tecnologia CICYT-AGL2005-07624-C03-01 and by funds from the Generalitat Valenciana research program (Prometeo 2009/125). The authors are grateful to Wagdy Mekkawy for letting us use his programs.Laborda Vidal, P.; Santacreu Jerez, MA.; Blasco Mateu, A.; Mocé Cervera, ML. (2015). Selection for ovulation rate in rabbits: Direct and correlated responses estimated with a cryopreserved control population1. Journal of Animal Science. 90(10):3392-3397. https://doi.org/10.2527/jas.2011-4837S33923397901

Long-term and transgenerational effects of cryopreservation on rabbit embryos

The short-term effects of cryopreservation and embryo transfer are well documented (reduced embryo viability, changes in pattern expression), but little is known about their long-term effects. We examined the possibility that embryo vitrification and transfer in rabbit could have an impact on the long-term reproductive physiology of the offspring and whether these phenotypes could be transferred to the progeny. Vitrified rabbit embryos were warmed and transferred to recipient females (F0). The offspring of the F0 generation were the F1 generation (cryopreserved animals). Females from F1 generation offspring were bred to F1 males to generate an F2 generation. In addition, two counterpart groups of noncryopreserved animals were bred and housed simultaneously to F1 and F2 generations (CF1 and CF2, respectively). The reproductive traits studied in all studied groups were litter size (LS), number born alive at birth (BA), and postnatal survival at Day 28 (number of weaned/number born alive expressed as percentage). The reproductive traits were analyzed using Bayesian methodology. Features of the estimated marginal posterior distributions of the differences between F1 and their counterparts (F1 - CF1) and between F2 and their counterparts (F2 - CF2) in reproductive characters found that vitrification and transfer procedures cause a consistent increase in LS and BA between F1 and CF1 females (more than 1.4 kits in LS and more than 1.3 BA) and also between F2 and CF2 females (0.96 kits in LS and 0.94 BA). We concluded that embryo cryopreservation and transfer procedures have long-term effects on derived female reproduction (F1 females) and transgenerational effects on female F1 offspring (F2 females).Lavara García, R.; Baselga Izquierdo, M.; Marco Jiménez, F.; Vicente Antón, JS. (2014). Long-term and transgenerational effects of cryopreservation on rabbit embryos. Theriogenology. 81(7):988-992. doi:10.1016/j.theriogenology.2014.01.030S98899281

Estudio del efecto de la época de parto sobre la producción lechera en 8 ganaderías de cabras murciano-granadinas de la región de Murcia

En este trabajo se ha estudiado el efecto de la época de parto (primavera, otoño) sobre la producción lechera de cabras Murciano-Granadinas. Se han utilizado 4546 datos de 790 cabras alojadas en 8 ganaderías situadas en la Región de Murcia y pertenecientes a la Asociación Nacional de Criadores de la Raza Murciano-Granadina (ACRIMUR). Los datos pertenecen al control lechero realizado en el periodo 1997-98, efectuado cada 30-35 días. El mismo día del control lechero se recogía una alícuota de 100 ml de leche para la determinación de materia grasa, proteína y extracto seco con NIR. Se observaron mayores producciones de leche cuando los partos se producían en otoño (1,94 vs 1,70 kg/d). Por meses, se observó que las producciones más bajas correspondían a las cabras que parían en mayo. Los porcentajes de proteína, grasa y extracto seco también fueron mayores para lactaciones cuyo parto se producía en otoño (3.77 vs. 3.31, 5.41 vs. 4.91, 14.60 vs. 13.53 para proteína, grasa y extracto seco, respectivamente)

Litter size components in a full diallel cross of four maternal lines of rabbits

[EN] A crossbreeding experiment between 4 Spanish maternal lines of rabbits was performed to estimate crossbreeding effects on litter size components. The experiment was designed as a complete diallel cross involving 4 lines selected for litter size at weaning (A, V, H, and LP [L]) and their 12 simple crosses. Does from these 16 genetic groups were distributed among 4 Spanish farms, but only V line was present in all farms, allowing connectivity of the data. A total of 2,015 does in the third, fourth, or fifth gestations were subjected to laparoscopy. The recorded traits were ovulation rate (OR), number of implanted embryos (IE), total born (TB), embryo survival (ES), foetal survival (FS), and prenatal survival (PS). The differences in direct genetic effects, maternal genetic effects, and individual heterosis between the lines were estimated according to Dickerson s model. Line A was significantly inferior to lines V and H, whereas line LP was similar to A line, but for FS and PS, line A showed the best values, followed by line LP. Comparing crossbred groups to line V, significant differences were shown favoring crossbred groups for OR and IE. The crossbred groups presented high implantation rate, but the foetal survival was lower than in V line. Important values for commercial production were presented by some crosses for OR (HV, 1.26 ova), IE (AH, 1.50 embryos; HV, 1.41 embryos), and TB (AH, 0.82 rabbits; HV, 0.78 rabbits). Relevant and significant reciprocal effects were found, especially for OR in all cases except the LV and VL crosses. These differences become nonsignificant in most of the other traits. Regarding direct genetic effects, line A presented lower estimates than the other lines with important values for OR, but the opposite was observed for FS. The maternal effects were significant only for some contrasts in OR and revealed that the LP line was inferior to the others (1.08 ova compared to the A line, 1.23 compared to the H line, and 0.38 compared to the V line). In general, high positive values for heterosis were found in crossbred does for OR and IE. The crosses, where lines A and H were involved, showed significant heterosis. The highest values were obtained by crossing lines A and H (1.18 ova for OR, 1.87 embryos for IE) followed by the cross between lines H and V. Crosses between line LP and the other lines had a negative heterosis for FS and PS.This work was supported by the Spanish project AGL2011-30170 from the Spanish National Research Plan.Mohamed Ragab, M.; Sánchez Serrano, JP.; Mínguez Balaguer, C.; Vicente Antón, JS.; Baselga Izquierdo, M. (2014). Litter size components in a full diallel cross of four maternal lines of rabbits. Journal of Animal Science. 92(8):3231-3236. https://doi.org/10.2527/jas.2013-7286S3231323692

Embryo vitrification in rabbits: Consequences for progeny growth

[EN] The objective of this research is to examine if there are any effects of the rederivation procedures on rabbit growth pattern and on weight of different organ in adults. For this purpose, three experiments were conducted on two different groups of animals (control group and vitrified transferred group) to evaluate the possible effect of embryo manipulation (vitrification and transfer procedures) on future growth traits. The first experiment studies body weight from 1 to 9 weeks of age from the two groups. The second experiment describes the growth curve of progeny from experimental groups and analyzes their Gompertz curve parameters, including the estimation of adult body weight. The third experiment has been developed to study if there are any differences in different organ weight in adult males from the two experimental groups. In general, the results indicate that rederivation procedures had effect on the phenotypic expression of growth traits. The results showed that rabbit produced by vitrification and embryo transfer had higher body weight in the first four weeks of age than control progeny. Results from body weight (a parameter) and b parameter estimated by fitting the Gompertz growth curve did not show any difference between experimental groups. However, differences related with growth velocity (k parameter of the Gompertz curve) were observed among them, showing that the control group had higher growth velocity than the vitrified transferred group. In addition, we found that liver weight at 40th week of age exhibits significant differences between the experimental groups. The liver weight was higher in the control males than in the VF males. Although the present results indicate that vitrification and transfer procedures might affect some traits related with growth in rabbits, further research is needed to assess the mechanisms involved in the appearance of these phenotypes and if these phenotypes could be transferred to the future progeny.This study was supported by the Generalitat Valenciana research program (Prometeo II 2014/036) and Spanish Research Projects (CICYT AGL2011-29831-C03-01; AGL2014-53405-C2-1-P). Lavara R. acknowledges the partial support received from Generalitat Valenciana under VALid+ program (APOST/2014/034) and from Ministry of Economy and Competitiveness under subprogramme "Formacion posdoctoral" (FPDI-2013-16707).Lavara García, R.; Baselga Izquierdo, M.; Marco Jiménez, F.; Vicente Antón, JS. (2015). Embryo vitrification in rabbits: Consequences for progeny growth. Theriogenology. 84(5):674-680. https://doi.org/10.1016/j.theriogenology.2015.04.025S67468084

Breeding programmes to improve male reproductive performance and efficiency of insemination dose production in paternal lines: feasibility and limitations

[EN] This paper aims at reviewing the current genetic knowledge of the issues related to the efficient use of bucks in artificial insemination (AI). Differences between lines have been found relevant in semen production and quality traits not necessarily related to their specialization as maternal or paternal lines. Accurate heritability estimates indicate that genetic selection for increasing semen production by improving male libido and reducing the number of rejected ejaculates may not be effective. However, total sperm produced per ejaculate appears to be as an interesting trait to select for, despite that genetic correlation between ejaculate volume and sperm concentration has not been yet accurately estimated. Semen pH has shown low to medium heritability estimates and a low coefficient of variation, therefore it is not advisable to attempt improvement by direct selection. In general, sperm motility traits have shown low heritabilities but, the rate of motile sperms per ejaculate has been considered as convenient to select for. Morphological characteristics of the spermatozoa have revealed as medium to highly heritable. There are evidences of high genetic correlations between sperm traits before and after freezing-thawing. There are few studies regarding the estimation of heterosis of seminal traits but results indicate important and favorable direct and maternal heterosis in crosses between maternal lines. However, this has not been confirmed in a cross between two paternal lines. Until now, attempts to find parametric or non-parametric functions to predict ejaculate fertility through seminal characteristics recorded in routinely evaluations have been very unsatisfactory. Hence, it may be necessary to find other semen quality markers, or to evaluate some of the currently used ones in a more precise manner or closer to the AI time in order to improve the ability to predict ejaculate fertility. Several seminal characteristics phenotypically correlated to male fertility, could be considered as potential traits to select for in order to genetically improving this trait. However, only the semen pH has been checked for this purpose, and a negative result has been obtained. Other traits can be studied in the future but bearing in mind that the required experiments will need large number of bucks for an accurate estimation of the genetic correlation of the trait with male fertility. This means that these experiments will be expensive and difficult to set up. The most common criterion to select paternal lines, average daily gain, seems not to be genetically correlated to male fertility and seminal traits. Thus, selection for average daily gain has no detrimental consequences on these traits, and a multi-trait selection, including growth rate and seminal traits directly related to an efficient AI semen dose production, is feasible in paternal lines. The male contribution to fertility after natural mating and after AI with semen doses with high concentration is negligible, but it has been found that, under more restrictive conditions of AI, male contributions to fertility and litter size are low but higher in magnitude than the ones obtained after natural mating. The genetic correlation between the female and male contributions to fertility has been found to be moderate to high and positive.This study was supported by the Generalitat Valenciana Research Programme (Prometeo 2009/125) and Spanish Research Projects (INIA RTA2005-00088-CO2; INIA RTA2008-00070-CO2; CICYT AGL2008-03274). Raquel Lavara was supported by a research grant from the Spanish Ministry of Education (MEC, FPU AP2007-03755) and Llibertat Tusell by a research grant from INIA.Piles, M.; Tusell, L.; Lavara García, R.; Baselga Izquierdo, M. (2013). Breeding programmes to improve male reproductive performance and efficiency of insemination dose production in paternal lines: feasibility and limitations. World Rabbit Science. 21(2):61-75. doi:10.4995/wrs.2013.1240SWORD617521

Development of Cheaper Embryo Vitrification Device Using the Minimum Volume Method

[EN] This study was designed to compare the efficiency of the Cryotop and Calibrated plastic inoculation loop (CPIL) devices for vitrification of rabbit embryos on in vitro development and implantation rate, offspring rate at birth and embryonic and fetal losses. CPIL is a simple tool used mainly by microbiologists to retrieve an inoculum from a culture of microorganisms. In experiment 1, embryos were vitrified using a Cryotop device and a CPIL device. There were no significant differences in hatched/hatching blastocyst stage rates after 48 h of culture among the vitrified groups (62±4.7% and 62±4.9%, respectively); however, the rates were significantly lower (P<0.05) than those of the fresh group (95±3.4%). In experiment 2, vitrified embryos were transferred using laparoscopic technique. The number of implanted embryos was estimated by laparoscopy as number of implantation sites at day 14 of gestation. At birth, total offspring were recorded. Embryonic and fetal losses were calculated as the difference between implanted embryos and embryos transferred and total born at birth and implanted embryos, respectively. The rate of implantation and development to term was similar between both vitrification devices (56±7.2% and 50±6.8% for implantation rate and 40±7.1% and 35±6.5% for offspring rate at birth); but significantly lower than in the fresh group (78±6.6% for implantation rate and 70±7.2% for offspring rate at birth, P<0.05). Likewise, embryonic losses were similar between both vitrification devices (44±7.2% and 50±6.8%), but significantly higher than in the fresh group (23±6.6%, P < 0.05). However, fetal losses were similar between groups (10±4.4%, 15±4.8% and 8±4.2%, for vitrified, Cryotop or CPIL and fresh, respectively). These results indicate that the CPIL device is as effective as the Cryotop device for vitrification of rabbit embryos, but at a cost of 0.05 per device.This research was supported by the projects Spanish Research project AGL2014-53405-C2-1-P Comision Interministerial de Ciencia y Tecnologia (FMJ, JSV) and Generalitat Valenciana research program (Prometeo II 2014/036, JSV, FMJ).Marco Jiménez, F.; Jiménez Trigos, ME.; Almela-Miralles, V.; Vicente Antón, JS. (2016). Development of Cheaper Embryo Vitrification Device Using the Minimum Volume Method. PLoS ONE. 11(2):1-9. https://doi.org/10.1371/journal.pone.0148661S1911