Rederivation by Cryopreservation of a Paternal Line of Rabbits Suggests Exhaustion of Selection for Post-Weaning Daily Weight Gain after 37 Generations.

Rabbit selection programmes have mainly been evaluated using unselected or divergently selected populations, or populations rederived from cryopreserved embryos after a reduced number of generations. Nevertheless, unselected and divergent populations do not avoid genetic drift, while rederived animals seem to influence phenotypic traits such as birth and adult weights or prolificacy. The study aimed to evaluate the effect of a long-term selection for post-weaning average daily weight gain (ADG) over 37 generations with two rederived populations.

Freezability genetics in rabbit semen.

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.

Effects of Female Dietary Restriction in a Rabbit Growth Line During Rearing on Reproductive Performance and Embryo Quality.

Maternal diet prior to mating has an effect on reproductive performance. We analysed the effect of maternal dietary restriction during rearing on reproductive performance, the embryo development and foetal growth. Females were categorized in two groups: (i) does with ad libitum access to feed or (ii) restricted.

Embryo vitrification in rabbits: Consequences for progeny growth.

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.

Role of embryonic and maternal genotype on prenatal survival and foetal growth in rabbit.

The aim of this work was to evaluate the influence of maternal and embryonic genotype on prenatal survival and foetal growth during pregnancy. Embryos were recovered at 48 h of gestation from two different donor lines (R = 46 and A = 40) and transferred to nulliparous recipient does (26 R and 24 A). Each recipient doe received six embryos into one oviduct from line R, and six embryos form line A into the other.

Use of cyclodextrins to increase cytoplasmic cholesterol in rabbit embryos and their impact on live kits derived from vitrified embryos.

Background: Low cryotolerance in oocytes and embryos is frequently associated with lipid accumulation in the cytoplasm.

Objective: This study aimed to evaluate the effect of cyclodextrin used as a cholesterol loader to change cytoplasmic cholesterol content of embryos and raise their tolerance to cryopreservation.

Methods: In the first experiment compact morulae-early blastocysts were exposed to CLC (0.

Generation of live offspring from vitrified embryos with synthetic polymers SuperCool X-1000 and SuperCool Z-1000.

Background: Ice growth and recrystallisation are considered important factors in determining vitrification outcomes. Synthetic polymers inhibit ice formation during cooling or warming of the vitrification process.

Objective: The aim of this study was to assess the effect of adding commercially available synthetic polymers SuperCool X-1000 and SuperCool Z-1000 to vitrification media on in vivo development competence of rabbit embryos.

Direct comparison of the effects of slow freezing and vitrification on late blastocyst gene expression, development, implantation and offspring of rabbit morulae.

This study aimed to assess the effect of different cryopreservation procedures (slow freezing vs vitrification) on the gene expression in pre-implantation embryos and its implication in post-implantation embryo losses in rabbit. For this purpose, rabbit morulae were recovered at Day 3 of development, frozen or vitrified and transferred to recipients. Then, embryos were recovered on Day 3 post-transfer (Day 6 of development) or kept until the end of gestation.

Aminopeptidase activity in seminal plasma and effect of dilution rate on rabbit reproductive performance after insemination with an extender supplemented with buserelin acetate.

Ovulation induction in artificially inseminated rabbits by adding GnRH synthetic analogues in the seminal doses is a welfare-orientated method to induce ovulation in rabbits and could have some advantages in field practice. This study was conducted to determine the effect of male genotype on the aminopeptidase activity in rabbit seminal plasma and the effects of dilution rate of semen on availability and reproductive performance when buserelin acetate is added to the seminal dose. To study the aminopeptidase activity, 12 mature bucks belonging to a paternal line and 12 from a maternal line were used.

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).

Vitrification alters rabbit foetal placenta at transcriptomic and proteomic level.

Although numerous studies have demonstrated that cryopreservation alters gene expression, less is known about those embryos that implanted successfully and continued in gestation. To raise the question of the neutrality of this technique, we examine the effects of vitrification through gestation in rabbit before and after the implantation. We monitored the distribution of losses of 569 vitrified morulae, observing that embryos which reach the last pre-implantatory stage are able to implant.

Effect of freezing extender composition and male line on semen traits and reproductive performance in rabbits.

This study was conducted to elucidate the effect of different freezing extenders on two lines selected for hyperprolificacy and longevity (H and LP, respectively). In extender A, dimethyl sulphoxide (Me2SO) and sucrose were used as cryoprotectants. In extenders B and C, the sucrose was replaced by 20% egg yolk, and in extender C the Me2SO was substituted by acetamide.

Foetal and postnatal exposure to high temperatures alter growth pattern but do not modify reproductive function in male rabbits.

Purpose: The 'foetal origin hypothesis' postulates that a number of organ structures and associated functions undergo programming during embryonic and foetal life and the neonatal period, which determines the set point of physiological and metabolic responses that carry into adulthood. We evaluate the relationship between high environmental temperatures and the reproductive function of male offspring to determine whether pregnant mammals and their infants are potentially vulnerable to the effects of climate change.

Methods: Rabbit pups were exposed to high temperatures during gestation and lactation.

Genetic variation in head morphometry of rabbit sperm.

The aim of this study was to determine the repeatability and heritability of sperm head characteristics: width (W, μm), area (A, μm2), length (L, μm), and perimeter (P, μm), and to explore the relationships between them and with the selection objective in a rabbit paternal line selected for daily weight gain (DG, g/day) between 28 and 63 days of age. Six sets of three-trait analyses were performed involving 12,908 DG records, with 1795 ejaculates corresponding to 283 males and 14,700 animals in pedigree file. The results obtained showed that sperm head dimensions are heritable (ranged between 0.

In vivo development of vitrified rabbit embryos: effects of vitrification device, recipient genotype, and asynchrony.

This study was designed to evaluate the effects of vitrification device, recipient genotype, and recipient asynchrony on implantation rate, offspring rate at birth, and fetal losses of rabbit embryos. Morphologically normal embryos (N = 787) recovered at 72 hours of gestation were kept at room temperature until transfer or vitrification. Vitrified embryos in Cryotop and ministraw devices were transferred into females induced to ovulate 60 hours (asynchrony) or 72 hours (synchrony) before transfer.

Environmental and male variation factors of freezability in rabbit semen.

The aim of this study was to analyze the environmental and male effects that could have an influence on sperm freezability using a recursive model. A total of 853 ejaculates from 217 males belonged to a paternal rabbit line were collected and frozen. Six different traits were evaluated: the sperm concentration (10(6) spermatozoa per mL), the acrosome integrity on fresh (%) and frozen-thawed semen (%), the sperm motility on fresh (%) and frozen-thawed semen (%), and the percentage of viable sperm on frozen-thawed semen (%).

Effect of embryonic and maternal genotype on embryo and foetal survival in rabbit.

The aim of this work was to study the influence of embryonic and maternal genotype of two lines of rabbits selected by growth rate (line R) and litter size at weaning (line A) on prenatal survival. Embryos were recovered at 48 h of gestation from R and A donors (39 and 35 does, respectively) and reciprocally transferred to the oviducts of recipient does to the R (n = 15) and A (n = 14) lines. Each recipient doe received six embryos from line R into one oviduct and six embryos from line A into the other.

Estimation of genetic parameters for semen quality traits and growth rate in a paternal rabbit line.

Variance components of sperm quality traits were estimated in a paternal line of rabbits selected on the basis of daily weight gain (DG, g/day) between 28 and 63 days of age. Features of the marginal posterior distributions for the genetic variance ratios, variance due to non-additive plus environmental permanent male effects, and variance due to litter of birth effects with respect to phenotypic variance are reported. The correlation between sperm quality traits and the selection criteria were also estimated.

Influence of zona pellucida thickness on fertilization, embryo implantation and birth.

Defective sperm-zona pellucida binding and penetration are the main causes of IVF failure. The purpose of this study was to evaluate the effect of zona pellucida thickness in fertilization failure and test the influence of zona pellucida thickness on implantation and birth in rabbits. Embryos and oocytes were collected from 72 females on Day 2 post-insemination.

Gestational losses in a rabbit line selected for growth rate.

Prenatal death can occur due to several genetic and environmental factors which alter normal embryo development, maternal environment to support normal fertilisation, development of embryos, placenta and foetus, or affect the necessary relationship between embryo and endometrium. The aim of this work was to study gestational losses and progesterone, 17 β-estradiol and IGF I serum levels in a rabbit line selected for growth rate (paternal line). In this study, a maternal line well characterised in previous studies was used as a reference line.

Detrimental effect on availability of buserelin acetate administered in seminal doses in rabbits.

The study evaluated a seminal effect on the ability to induce ovulation of a synthetic GnRH analogue, buserelin acetate, administered by vaginal mucosa in rabbit does. In a first experiment, 751 receptive nulliparous and multiparous non-lactating does were randomly assigned to groups of different seminal doses (6, 12, 24, 50, and 100 million total sperm in 0.5 mL).

Does storage time in LN2 influence survival and pregnancy outcome of vitrified rabbit embryos?

Vitrification is one of the most widely used techniques for embryo cryopreservation. The aim of this work was to study the effect of storage time in liquid nitrogen on vitrified rabbit embryos. A total of 1467 vitrified rabbit embryos were transferred into 174 females.

Genetic parameter estimates for semen production traits and growth rate of a paternal rabbit line.

Variance components of sperm production traits (volume in ml, V; concentration in ×10⁶ sperm/ml, CN; sperm production in ×10⁶ sperm, PROD) were estimated in a paternal line of rabbit selected for 25 generations based on daily weight gain (DG, g/day) between 28 and 63 days of age. Features of the marginal posterior distributions for ratios of genetic variance, variance owing to non-additive plus environmental permanent male effects and variance owing to common litter of birth effects with respect to phenotypic variance are reported. The correlations between sperm production traits and the selection criteria were also estimated.

Aneuploidy in rabbit males: semen traits and fertility.

Chromosomal analyses were performed from peripheral blood samples from 20 adult rabbit males from Line R. This line has been selected for growth rate after weaning through 25 generations. Seminal characteristics and reproductive outcomes from these males were also examined.

Poor prediction value of sperm head morphometry for fertility and litter size in rabbit.

This study was conducted to investigate the predictive capacity of fertility and litter size of sperm head morphometric measurements when the ejaculates fulfilled the minimum requirements commonly used in artificial insemination (AI). Semen samples from 11 rabbits (77 ejaculates) were evaluated for sperm motility, abnormal spermatozoa and sperm head morphometry using computer automated sperm analysis system. Morphometric dimensions for length, width, area and perimeter were analysed.