Field testing the influence of sperm competition based on sperm mobility in breeder turkey toms

Transcriptomic analysis of mechanism underlying the effect of induced molting on semen quality and reproductive performance in aged Houdan roosters

The reproductive performance of breeder roosters has significant economic importance in the poultry industry. Breeder roosters have severely reduced semen quality with age and will be at risk of culling in the following years. In order to extend the use of breeder roosters, we drew on the induced molting model of hens and selected 35 Houdan roosters aged 50 wk for induced molting. By comparing the body weight, testicular weight, semen quality, and reproductive performance before and after induced molting, we found that induced molting could restore the body weight and testicular weight to the levels before molting (P > 0.05). At the same time, it significantly improved sperm motility (P < 0.05) and also improved reproductive performance such as fertilization rate and hatching rate. To further reveal the mechanism underlying the effects of induced molting on semen quality and reproductive performance in aged Houdan roosters, we collected testes from 3 periods: 1 d before fasting (F0), 15 d after fasting (F15), and 32 d after recovery feeding (R32) for transcriptome sequencing analysis. A total of 5,671 genes were detected in F0, F15, and R32, and trend analysis of the 5,671 differential genes showed 2 significant trends (profile 5 and profile 2). KEGG enrichment analysis of the genes in the 2 profiles, revealed significantly enriched pathway regulation of actin cytoskeleton. In the regulation of actin cytoskeleton pathway, we found a protein kinase gene (SRC) and a senescence gene (ROCK2). SRC was highly expressed at F15, leading to the phosphorylation of key substrates, which in turn disrupted the Sertoli cell spermatid connection and the spermiogenesis process, resulting in no mature spermatozoa produced from F15, SRC expression was inhibited at R32, the expression level was reduced, and mature spermatozoa reappeared. The senescence gene ROCK2 was highly expressed at F15 compared to F0 and R32, which may have been responsible for inducing senescence atrophy in the testes.

Flagellum tapering and midpiece volume in songbird spermatozoa

In contrast to numerous studies on spermatozoa length, relatively little work focuses on the width of spermatozoa, and particularly the width of the midpiece and flagellum. In flagellated spermatozoa, the flagellum provides forward thrust while energy may be provided via mitochondria in the midpiece and/or through glycolysis along the flagellum itself. Longer flagella may be able to provide greater thrust but may also require stronger structural features and more or larger mitochondria to supply sufficient energy. Here, we use scanning electron microscopy to investigate the ultrastructure of spermatozoa from 55 passerine species in 26 taxonomic families in the Passerides infraorder. Our data confirm the qualitative observation that the flagellum tapers along its length, and we show that longer flagella are wider at the neck. This pattern is similar to mammals, and likely reflects the need for longer cells to be stronger against shearing forces. We further estimate the volume of the mitochondrial helix and show that it correlates well with midpiece length, supporting the use of midpiece length as a proxy for mitochondrial volume, at least in between-species studies where midpiece length is highly variable. These results provide important context for understanding the evolutionary correlations among different sperm cell components and dimensions.

Sperm tendency to agglutinate in motile bundles in relation to sperm competition and fertility duration in chickens

A unique sperm behavior was observed in Egyptian chickens. Sperm showed a tendency to agglutinate forming motile thread-like bundles. Sperm agglutination behavior, kinematics, and some morphometric measures were studied in relation to sperm competition and fertility duration in Sharkasi and Dandarawi chickens. Sperm tendency to agglutinate was assessed by examining sperm morphology using scanning electron microscopy, Acridine orange-stained semen smears using fluorescence microscopy, and recording videos of sperm under phase contrast microscope. Sperm velocity and morphometric measures were evaluated using image-J software. To assess sperm competition, Sharkasi and Dandarawi hens were artificially inseminated by semen pools possessing equal number of Sharaksi and Dandarawi sperm. Artificial insemination was repeated ten times. The eggs obtained were incubated, and the hatchlings were discriminated as descending from Sharkasi or Dandarawi fathers according to their phenotype. To assess the fertility duration, Sharkasi and Dandarawi hens were inseminated by semen collected from roosters of the same strain. Eggs were collected for a period of 28 days post-insemination and incubated. Sharkasi spermatozoa showed higher tendency to agglutinate forming longer and thicker motile bundles. No significant differences were observed in sperm curvilinear and straight line velocity and in sperm morphometric measures between Sharkasi and Dandarawi chickens. Sharkasi roosters fathered 81.6% and 67.7% of the hatchlings produced by Sharkasi and Dandarawi mothers, respectively. The fertility period in Sharkasi and Dandarawi was 22 and 14 days, respectively. We suggest that the differences seen in sperm competitiveness and fertility duration can be attributed to sperm agglutination behavior.

Longer Sperm Swim More Slowly in the Canary Islands Chiffchaff

Sperm swimming performance affects male fertilization success, particularly in species with high sperm competition. Understanding how sperm morphology impacts swimming performance is therefore important. Sperm swimming speed is hypothesized to increase with total sperm length, relative flagellum length (with the flagellum generating forward thrust), and relative midpiece length (as the midpiece contains the mitochondria). We tested these hypotheses and tested for divergence in sperm traits in five island populations of Canary Islands chiffchaff (Phylloscopus canariensis). We confirmed incipient mitochondrial DNA differentiation between Gran Canaria and the other islands. Sperm swimming speed correlated negatively with total sperm length, did not correlate with relative flagellum length, and correlated negatively with relative midpiece length (for Gran Canaria only). The proportion of motile cells increased with relative flagellum length on Gran Canaria only. Sperm morphology was similar across islands. We thus add to a growing number of studies on passerine birds that do not support sperm morphology-swimming speed hypotheses. We suggest that the swimming mechanics of passerine sperm are sufficiently different from mammalian sperm that predictions from mammalian hydrodynamic models should no longer be applied for this taxon. While both sperm morphology and sperm swimming speed are likely under selection in passerines, the relationship between them requires further elucidation.

Expression analysis of microRNAs and their target mRNAs of testes with high and low sperm motility in domestic pigeons (Columba livia)

Sperm motility is one of the most important indicators to evaluate poultry fertility. In order to explore key molecular regulation roles related to sperm motility, we employed testicular RNA sequencing of pigeon. A total of 705 known and 385 novel microRNAs were identified. Compared with the low sperm motility group, four upregulated and two downregulated miRNAs in the high sperm motility group were identified. A total of 3567 target mRNAs were predicted and four target mRNAs were selected to validate by qPCR. The miRNA-mRNA interaction network analysis, indicated that mmu-miR-183-5p /FOXO1 and PC-3p-244994_31/CHDH pairs might affect sperm motility. GO and KEGG annotation analysis showed that target genes of differentially expressed miRNAs were related to serine/threonine kinase activity, ATP binding, Wnt and MAPK signaling pathway. The study provided a global miRNAs transcriptome of pigeon and a novel insight into the expression of the miRNAs in testes that associated with sperm motility.

Low-mobility sperm phenotype in the domestic turkey: Impact on sperm morphometry and early embryonic death

The sperm mobility assay measures the ability of sperm to swim through a dense layer of Accudenz^® , and the sperm mobility phenotype has been shown to predict fertility and other sperm performance traits in roosters and turkeys. In this study, we examined turkey sperm morphometry and rates of early embryonic death associated with high- and low-mobility semen. We also assessed whether the hypo-osmotic stress test, which evaluates the structural integrity of the sperm plasma membrane, may be used as a faster and simpler assay for sperm mobility and viability. We confirmed previous work that found that high-mobility sperm are faster and swim more linearly than low-mobility sperm, and that mobility traits were repeatable within males. In contrast to previous studies, we did not find higher rates of fertility, but low-mobility sperm was associated with higher rates of early embryonic death, though this trend was not significant. High-mobility sperm had longer sperm heads, explained by longer nuclei, despite shorter acrosomes. Although these sperm were faster, midpiece length and flagellum length did not differ between high- and low-mobility sperm. Finally, mobility was not found to be associated with sperm performance in the hypo-osmotic stress test.

Production of offspring from cryopreserved chicken testicular tissue

Cryopreservation of avian germplasm provides a means of genetic banking for future needs in biological research and animal production. The sperm of birds can be cryopreserved and used to fertilize eggs. However, the fertility of frozen-thawed avian semen is generally much lower than that of mammalian semen and varies among species or among lines, reducing the value of semen for the preservation of genetic resources. In the present study, a simple freezing protocol was used to cryopreserve testicular tissue of day-old chicks, and after subsequent transplantation, the frozen-thawed testicular tissue developed functional seminiferous tubules that produced sufficient sperm to fertilize eggs, resulting in donor-derived offspring. This study provides an alternative to semen cryopreservation for storage of the male germline in birds.

Avian Genetic Stock Preservation: An Industry Perspective

There are different types of poultry genetic resources including mutants, inbred lines, specialized/selected stocks, standard breeds, and elite commercial pure lines. These resources differ in their degree of value to the poultry industry. There is considerable concern within poultry breeding companies about the continuing losses of these genetic resources, particularly as this loss seems to have escalated over the past decade. Varied genetic stocks can provide fundamental information regarding gene function, genetic interactions, and genetic pathways. This information is important for efficient improvement of commercial poultry performance. Equally important is the role of these genetic resources in teaching and the education of students and future researchers. Currently, the only practical preservation method for birds in the poultry industry involves live bird conservation. Flocks of elite commercial stocks are maintained at multiple locations, providing insurance against disease outbreak and the possibility of quarantine restrictions. The current cryopreservation methods apply only to sperm. Thus, the W chromosome and the mitochondria, which are contributed by the female gamete, cannot be preserved. Cryopreserved semen shows considerable variation in both fertility and hatchability rates, not only among lines, but also among males within lines. The biological basis for this variation is unknown, and there is concern that the use of cryopreserved semen may result in unintended selection and loss of genetic variability. Cryopreservation cannot be applied in the poultry breeding industry until methodologies are developed that produce high viability for both male and female avian preserved gametes. More research is needed in the areas of sources of variation in viability following freeze/thaw, female gamete cryopreservation, and embryo preservation. Because there are currently no appropriate methods of cryopreservation available to the poultry industry, the long-term preservation of commercial elite stocks must continue to rely on live bird conservation. Because of the high costs of this live bird preservation, stocks with no perceived current economic value will not be maintained.

Reproductive success of broiler breeders in natural mating systems: the effect of male-male competition, sperm quality, and morphological characteristics

In natural mating systems in which broiler breeder males compete for females, reproductive behavior plays an important role in male fertility, along with sperm competition and morphological and physiological characteristics. We investigated the effect of male-male competition compared with a noncompetitive situation on fertility, sperm quality, and morphological traits. Six groups of 3 males and 12 females were housed in mixed-sex pens. Their frequency of mating was recorded, and progeny of each male was determined through DNA fingerprinting. Males with the highest and the lowest mating frequencies were later placed into groups of 1 male and 4 females, their behavior was recorded, and their fertility was calculated. We collected data on semen quality (semen volume, sperm concentration, and mobility) and morphometrical characters. Finally, females were artificially inseminated with sperm from highest frequency, lowest frequency, or a mix, paternity and fertility were estimated. Our results indicate that heavier males had higher frequency of matings without cloacal contact, and males with smaller combs had more mating attempts. We also detected that males with high sperm concentration had lower fertility. However, we found an overall lack of association between mating behavior, morphometrical traits, sperm quality, and fertility. This, together with the discrepancy of results in fertility when compared with artificial insemination conditions, suggest a multifactorial nature of the fertility of broiler breeder males in natural mating systems. In addition we observed a high male fertility when housed individually, suggesting that male fertility is a relative parameter that depends upon the reproductive quality of the other male competitors within the group.