Jean-Michel Brun

The relationship between rabbit semen characteristics and reproductive performance after artificial insemination

The relationships between several rabbit buck semen traits, concerning either the ejaculate or the dose inseminated (volume, mass motility, pH, percentage of motile sperm (PMS), concentration, number of total and motile sperm per ejaculate and per insemination dose) and the reproductive performance of does was investigated in 839 inseminations involving 54 bucks and 111 does. Four genetic types were involved: INRA1601 strain (A), INRA2066 strain (B) and the two reciprocal crossbreds (AB and BA). The mating design was A x A, B x B, (AB or BA) x (AB or BA). Semen was diluted (1:9) and a constant volume of 0.5 ml was inseminated 2-4h after collection. Therefore, the total number of spermatozoa per dose was variable and proportional to the initial concentration. Mass motility significantly influenced the kindling rate. Taken separately, volume, PMS and concentration did not influence the kindling rate but their product, the number of motile sperm per ejaculate, did. Litter size (total born) was significantly influenced by concentration and all variables depending on it, particularly the number of total and motile sperm per dose. However, reproductive performances were predominantly influenced by the physiological status of the does at insemination (lactation stage and receptivity).

Epigenetics and phenotypic variability: some interesting insights from birds

Little is known about epigenetic mechanisms in birds with the exception of the phenomenon of dosage compensation of sex chromosomes, although such mechanisms could be involved in the phenotypic variability of birds, as in several livestock species. This paper reviews the literature on epigenetic mechanisms that could contribute significantly to trait variability in birds, and compares the results to the existing knowledge of epigenetic mechanisms in mammals. The main issues addressed in this paper are: (1) Does genomic imprinting exist in birds? (2) How does the embryonic environment influence the adult phenotype in avian species? (3) Does the embryonic environment have an impact on phenotypic variability across several successive generations? The potential for epigenetic studies to improve the performance of individual animals through the implementation of limited changes in breeding conditions or the addition of new parameters in selection models is still an open question.

Influence of grand-mother diet on offspring performances through the male line in Muscovy duck

BackgroundIn mammals, multigenerational environmental effects have been documented by either epidemiological studies in human or animal experiments in rodents. Whether such phenomena also occur in birds for more than one generation is still an open question. The objective of this study was to investigate if a methionine deficiency experienced by a mother (G0) could affect her grand-offspring phenotypes (G2 hybrid mule ducks and G2 purebred Muscovy ducks), through their Muscovy sons (G1). Muscovy drakes are used for the production of mule ducks, which are sterile offspring of female common duck (Anas platyrhynchos) and Muscovy drakes (Cairina moschata). In France, mule ducks are bred mainly for the production of “foie gras”, which stems from hepatic steatosis under two weeks of force-feeding (FF). Two groups of female Muscovy ducks received either a methionine deficient diet or a control diet. Their sons were mated to Muscovy or to common duck females to produce Muscovy or Mule ducks, respectively. Several traits were measured in the G2 progenies, concerning growth, feed efficiency during FF, body composition after FF, and quality of foie gras and magret.ResultsIn the G2 mule duck progeny, grand-maternal methionine deficiency (GMMD) decreased 4, 8, and 12 week body weights but increased weight gain and feed efficiency during FF, and abdominal fat weight. The plasmatic glucose and triglyceride contents at the end of FF were higher in the methionine deficient group. In the G2 purebred Muscovy progeny, GMMD tended to decrease 4 week body weight in both sexes, and decreased weight gain between the ages of 4 and 12 weeks, 12 week body weight, and body weight at the end of FF in male offspring only. GMMD tended to increase liver weight and increased the carcass proportion of liver in both sexes.ConclusionAltogether, these results show that the mother’s diet is able to affect traits linked to growth and to lipid metabolism in the offspring of her sons, in Muscovy ducks. Whether this transmission through the father of information induced in the grand-mother by the environment is epigenetic remains to be demonstrated.

Duration of fertility and hatchability of the common duck (Anas platyrhynchos) in pure- or crossbreeding with Muscovy drakes (Cairina moschata)

A total of 540 common duck dams were used for a comparison of duration of fertility and hatchability between eggs issued from common dams inseminated with sperm (175 x 10(6) dose(-1)) from either common (pure-breeding or PB) or Muscovy (crossbreeding or CB) drakes. Artificial inseminations (AI) were performed at 3 periods of the reproductive season (27-35, 39-43 and 49-56 weeks) with 2 alternate inseminations/period at 3-week intervals (one with semen from common and the other from Muscovy). Fertility was estimated from egg candling while early embryo mortality (EEM), medium embryo mortality (MEM) and late embryo mortality (LEM) was estimated on Days 0-6 (PB+CB), Days 7-25 (PB) or Day 28 (CB) of incubation, and after, respectively. Overall fertility from Days 2-12 after AI was 61.1% in PB and 42.8% in CB. The maximum duration of fertility (time interval between AI and last fertile egg) was 8.1 days in PB versus 6.4 days in CB (p<0.05). The age of the dam influenced this interval, particularly in PB, with a longer duration at 40 weeks compared to 50 (p<0.05). On average, EEM represented 2.5% of fertile eggs while MEM accounted for 5% of surviving embryos on Day 6 and LEM, for 11.5% of hatched eggs. MEM was significantly higher in CB (6.3%) compared to PB (3.9%; p<0.05). Overall, an increase in EEM and MEM was observed in both types of eggs at and after 50 weeks of age. An increase in EEM (regardless of dams age) and in MEM (only in the oldest females) was observed with sperm storage duration. Sex ratio at hatching (49.2% males in PB vs. 53.0% in CB) was particularly unbalanced on the first fertile day (54.7% and 57.1%, respectively).

Relationships between rabbit semen characteristics and fertilising ability after insemination.

This study aimed to analyse the relationship between rabbit semen characteristics and semen fertilising ability after insemination, which is generally found to be weak. Our hypothesis was that using high semen dilutions (1 : 19), non-oestrus-stimulated does, and homospermic inseminations would make it easier to predict semen fertilising ability. Semen characteristics were evaluated on 275 ejaculates of 128 INRA1001 bucks, distributed into five successive batches. A total of 1970 inseminations were performed. The continuous semen variables were subdivided into three classes of similar size to account for any non-linear relationship between semen characteristics and fertilising ability. Mass motility was divided into two classes according to the presence or absence of waves under microscope observation. Libido, the presence or absence of gel, volume, percentage of progressive sperms, curvilinear velocity, beat frequency of the flagellum, and straightness and linearity of sperm movement did not affect fertility, prolificacy or productivity. It was confirmed that mass motility, estimated by visual observation under the microscope, significantly influenced fertility as well as the percentage of motile and of rapid sperms, and the amplitude of lateral head displacement, estimated by a computer-assisted semen analysis system. To a lesser extent, the percentage of motile cells and of rapid cells significantly influenced prolificacy. Consequently, mass motility and the percentage of motile cells significantly influenced rabbit doe productivity (+1 live births/AI when the semen showed at least a beginning of wave movement, or when the percentage of motile cells was >84%). Interestingly, a gain of 1.5 rabbits was observed when the percentage of rapid cells changed from 64% to 79%, whereas productivity significantly dropped beyond 83% of rapid cells, reflecting a non-linear relationship.

Inheritance of duration of fertility in female common ducks ( Anas platyrhynchos ) inseminated in pure breeding or in inter-generic crossbreeding with Muscovy drakes ( Cairina moschata )

Ducks (common, Muscovy and mule ducks) are the third most important bird species in animal production for human consumption worldwide. Our study aimed to improve the efficiency of mule duck breeding, thus contributing to the efficiency of food production in general. In the common duck, females can be bred either with males of the same species (i.e. in pure breeding (PB) subscript p) or in inter-generic crossbreeding (CB; subscript c) with Muscovy drakes to produce the hybrid mule duck. The aim of the present study was to estimate the genetic parameters of several indicators of duration of fertility, considered to be a trait of the female duck, within and between breeding schemes and, in particular, to estimate the purebred-crossbred genetic correlation (rg pc). These indicators were maximum duration of fertility (MD), that is, the time interval between insemination and the last fertilised egg, the number of fertile eggs (F) and of hatched ducklings (H) after a single artificial insemination (AI), and the fertility rate over days 2 to 12 after AI (F 2,12), taking three sub-periods (F 2,4, F 5,8, F 9,12) into account. A total of 494 females and 2655 inseminations were involved. PB resulted in longer duration of fertility (MD p = 8.1 v. MD c = 6.4 days). Heritability (h 2) was higher for MD p (estimate ± s.e.: 0.27 ± 0.04) than for MD c (0.15 ± 0.04), but both traits were highly correlated with each other (rg pc = 0.85 ± 0.07). F p and F c had similar heritability (h 2 around 0.24) and displayed a high genetic correlation (0.78 ± 0.07). The same was true for H p and H c (h 2 around 0.17 and rg pc = 0.88 ± 0.05). The heritability estimates were 0.24 ± 0.03 for F 2,12p and 0.20 ± 0.04 for F 2,12c, with a 0.80 ± 0.07 genetic correlation between each other. Permanent environmental effects influenced MD p far less than MD c, F p less than F c, but H p and H c to the same extent. The high values for rg pc (>0.78) indicated that the same genes are involved in the duration of fertility for both PB and CB. Unlike CB, initial fertility for PB (F 2,4p) was not correlated to overall fertility rate and to duration of fertility and probably involves different genes, if any. In both breeding schemes, indirect selection on F would be better than direct selection on H to improve H, and easier to implement than selection on MD. Moreover, any gain in one breeding scheme will have its correlated counterpart in the other one, because of the high values of rg pc.