Attributes of broiler breeder males characterized by low and high sperm mobility

Physiological impacts of overweight on semen parameters and fertility in male broiler breeders

A negative correlation between growth and reproductive traits has declined fertility in the second half of the flock's reproductive life. Excessive weight gain in males is one of the crucial reasons for the reduction of fertility rate in broiler breeder flocks. Field data from commercial flocks were collected at different ages to determine the excess weight of roosters. Forty-four 17-week-old breeder roosters were weighed individually and divided into two groups (Control and Overweight). With the difference in the amount of feed distribution, a 26 % difference in weight was observed between the two experimental groups after six weeks (23rd week). Sperm and blood samples were collected every four weeks from the age of 24 to 64 weeks to evaluate sperm parameters and testosterone levels. Testis weight and testicular histomorphology were evaluated on weeks 24, 44, and 64; and artificial insemination was performed at the end of the experiment. Results showed that the number of active roosters and semen volume did not differ between the two groups (P > 0.05). Sperm concentration and total sperm motility at 24, 28, 32, and 36 weeks in the overweight group were higher than control group (P < 0.05). In other weeks, there was no significant difference between the two groups for sperm concentration (P > 0.05). Semen lipids oxidation was not significantly different between the two groups at any age (P > 0.05). Testosterone levels in the overweight group up to 32 weeks and in the control group at 40 to 56 weeks of age were high (P < 0.05). The number of seminiferous tubules and Sertoli cells only at 24 weeks in the overweight group showed a higher value than the control group (P < 0.05). Artificial insemination showed no significant difference between the two groups in fertility and hatching rates (P < 0.05). Finally, being overweight during the initial stage of the experiment resulted in early testicular hyperplasia and improved sperm quality, followed by a decline with age. In contrast, the control group showed a pattern of slow increase followed by a decrease.

Transcriptome analysis reveals the genes involved in spermatogenesis in white feather broilers

Semen volume is an important economic trait of broilers and one of the important indices for continuous breeding. The objective of this study was to identify genes related to semen volume through transcriptome analysis of the testis tissue of white feather broilers. The testis samples with the highest semen volume (H group, n = 5) and lowest semen volume (L group, n = 5) were selected from 400-day-old roosters for transcriptome analysis by RNA sequencing. During the screening of differentially expressed genes (DEGs) between the H and L groups, a total of 386 DEGs were identified, among which 348 were upregulated and 38 were downregulated. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the immune response, leukocyte differentiation, cell adhesion molecules and collagen binding played vital roles in spermatogenesis. The results showed that 4 genes related to spermatogenesis, namely, COL1A1, CD74, ARPC1B and APOA1, were significantly expressed in Group H, which was consistent with the phenotype results. Our findings may provide a basis for further research on the genetic mechanism of semen volume in white feather broilers.

What can PIWI-interacting RNA research learn from chickens, and vice versa?

P-element induced wimpy testis (PIWI) interacting RNA (piRNA) are essential for fertility, by protecting the integrity of the germ-line genome via silencing of transposable elements (TE). Because new TE are constantly invading the host genome, piRNA-producing loci are under continuous pressure to undergo rapid evolution. This arms race between TE and piRNA is a prime example of the genome being more plastic than previously thought. Historically, the study of piRNA and TE has benefited from the use of diverse model organisms, including worms, fruit fly, zebrafish, frogs, and mice. In domestic chickens, we recently identified a new mode of piRNA acquisition in which the host hijacks and converts a pre-existing provirus into a piRNA-producing locus to defend against Avian leukosis virus, an adaptive immune strategy similar to the prokaryotic CRISPR–Cas [clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas)] system. This finding reveals a previously unrecognized mechanism of the host piRNA repertoire to rapidly evolve and target TE specifically. In this review, we will focus on both the unique and common features of chicken piRNA, as well as the advantages of using chickens as a model system, to address fundamental questions regarding piRNA acquisition in hosts. We will also comment on the potential application of piRNA for improving poultry health and reproductive efficiency.

Association of mitochondrial function and sperm progressivity in slow- and fast-growing roosters

The objectives of the current study were to investigate the activity of the electron transport chain (ETC) complexes, adenosine triphosphate (ATP), and reactive oxygen species (ROS) in the sperm mitochondria of 2 Iranian slow- and fast-growing chickens, namely native and Aryan strains. In this study, semen of 133 roosters was analyzed by computer-assisted sperm analysis (CASA). The roosters were categorized by sperm progressivity, as a low or high sperm motility phenotype. Mitochondrial complex I (NADH ubiquinone oxidoreductase), II (succinate dehydrogenase), III (ubiquinol cytochrome C reductase), IV (cytochrome C oxidase) activity, ATP, and ROS production in sperm were assayed. As a result, Aryan roosters with high progressive motility levels (HPL) had the greatest progressivity. Progressive motility was significant in in both strains (Aryan and native; P = 0.020) and motility levels (high and low; P = 0.007). The highest activity of complexes I was observed in Aryan with HPL roosters (P = 0.004). Native roosters with HPLs demonstrated higher complex activities I compared with Aryan and native roosters with low progressive motility levels (LPL) (P = 0.004). Significant differences were observed not only in the mitochondrial amounts of ATP of the strains (P = 0.000) but also between HPL and LPL (P = 0.003). The highest mitochondrial amounts of ATP was found in Aryan roosters with HPL (P = 0.021). Native roosters with LPL had the highest concentration of mitochondrial ROS (P = 0.033). The Aryan roosters with HPL, on the other hand, indicated less concentration of the mitochondrial ROS compared with Aryan having LPL and native roosters with HPL and LPL (P = 0.033). A significant difference was observed in the mitochondrial ROS between the strains (P = 0.004) and between HPL and LPL (P = 0.000). There was positive relationship between progressivity and each of mitochondrial complexes and ATP (r = 0.71, 0.62, 0.90 and 0.65 respectively). Based on our results, the sperm progressivity largely depends on the whole energy production originating in the mitochondrial compartment. Therefore, the deficiency in the function of mitochondria in the sperm and energy production could be responsible for low progressive motility.

Evaluation of a semen extender from a bioenergetic perspective

Four premises for sperm preservation were previously outlined. The present work tested 2 of these. The first premise was that sperm mobility phenotype affects procedural efficacy. Random bred roosters were phenotyped with the sperm mobility assay. A normal frequency distribution was observed with 35% (SD = 16.4) mobile sperm. Test subjects had values >51% (high) or between 19 and 35% (below average). Phenotypes were confirmed by repeated measure analysis. Ejaculates were pooled by phenotype. Sperm were washed by centrifugation through 12% (wt/vol) Accudenz. Washed sperm were suspended in Beltsville Poultry Semen Extender (BPSE) at 2 × 10 sperm/mL. Such sperm were stored at 10°C for 24 h. In the case of highly mobile sperm, an exponential decay was observed with a -intercept of 72% and an asymptote of 53%. In contrast, postwash values for below-average males decreased linearly from a -intercept of 31 to 17% after 24 h. A logistic decay was observed when sperm from high phenotype subpopulation males were extended with BPSE rather than washed before storage. Whereas -intercepts were equivalent between experiments, end points were not, that is, 53 vs. 17% mobile sperm. This difference was attributed to the extent of cytotoxic edema. The second premise tested was that the sperm mobility assay can predict the status of sperm cell mitochondria in response to sperm manipulation. Highly mobile sperm were washed and then suspended in either saline or glucose-free extender. Solution pH and osmolality were equivalent. Extender osmolality was controlled by replacing glucose with mannitol. Sperm were stressed by incubation at 2 × 10/mL at 20°C for 8 h. In each case, loss of sperm mobility approximated a logistic function. Whereas -intercepts were equivalent, the time at which loss of function was half maximal was prolonged with the extender ( < 0.01). This difference was attributed to a diminution of the process whereby energy-deprived sperm were rendered immobile by cellular edema. An a posteriori analysis was limited to pretreatment data from males categorized a priori with the high phenotype. Phenotype was independent of time ( = 0.81) during the 14-wk interval in which experiments were performed. In summary, extender efficacy was affected by sperm mobility phenotype as well as the means by which the extender was used. To date, such effects have not been addressed in attempts to preserve chicken sperm in vitro.

Premises for fowl sperm preservation based on applied bioenergetics

The primary goal of this work was to test whether the sperm mobility assay could be used to derive mathematical relationships from which predictions could be made about sperm cell function. A precondition was random sampling from a pool of sperm. This precondition was met by centrifuging mobile sperm through 12% (wt/vol) Accudenz containing the Ca(2+) chelator 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and then holding washed sperm at 20°C within buffered potassium chloride. These 2 conditions rendered washed sperm immobile at 20°C. Resumption of sperm mobility was independent of time (P > 0.8558) when sperm were reactivated at body temperature with 2 mM Ca(2+) in isotonic sodium chloride at pH 7.4. Reactivated sperm mobility was 93% of the prewash control. Subsequent experiments served to define a dose response, predict optimal conditions for in vitro sperm mobility, and show how sperm can recover from an imposed non-physiological condition. Thus, functions were derived from which predictions were made. Whereas the utility of BAPTA treatment was confirmed in a new context, such utility did not address the question of whole-cell Ca(2+) flux during sperm cell manipulation. This issue is pivotal for the application of bioenergetics to fowl sperm preservation. Therefore, the secondary goal of this research was to investigate sperm cell Ca(2+) flux using a simulation of conditions encountered by sperm during centrifugation through 12% (wt/vol) Accudenz. These conditions included a temperature of 30°C, a Ca(2+) sink, and no exogenous substrate. Sperm motion was measured with a Hobson SpermTracker. Data points conformed to parabolic functions when motile concentration and velocity were plotted as functions of time. In each case, maximums were observed, e.g., 26 min for motile concentration. The upswing was attributed to a redistribution of intracellular Ca(2+) whereas the downswing was attributed to sperm cell Ca(2+) depletion. A pronounced isothermal increase was observed for each variable when the Ca(2+) sink was overcome with exogenous Ca(2+). Experimental outcomes supported four testable premises applicable to fowl sperm preservation research: 1) the importance of sperm mobility phenotype, 2) the relationship between mitochondrial Ca(2+) cycling and sperm mobility, 3) the utility of the sperm mobility assay for predicting experimental outcomes, and 4) understanding mitochondrial Ca(2+) cycling in terms of whole-cell Ca(2+) flux.

Sperm motility patterns in Andalusian donkey (Equus asinus) semen: effects of body weight, age, and semen quality

The aims of this study were to (1) identify sperm subpopulations with specific motion characteristics in fresh Andalusian donkey ejaculates; (2) evaluate the effects of individual donkey and ejaculates within the same donkey on the distribution of the subpopulations found; and (3) explore the relationship between the age and the body weight of donkey donors, the sperm quality parameters, and the sperm subpopulations structure. Sixty ejaculates from 12 Andalusian donkeys (five ejaculates per donkey), ranging in age from 4 to 15 years, were collected. Immediately after collection, sperm characteristics (volume, sperm concentration, objective sperm motility, and sperm morphology) were assessed. Donkeys were evaluated for body weight. Significant (P < 0.05) correlations were established between the body weight of the donkeys and the pH (r = -0.52), sperm motility (percentage of motile spermatozoa: r = -0.31; percentage of progressive motile spermatozoa: r = -0.34), and total sperm abnormalities (r = 0.38). The correlations of the age with the measures of semen quality were low and not significant (P > 0.05). A multivariate clustering procedure separated 65,342 motile spermatozoa into four subpopulations: subpopulation 1, consisting of slow and nonprogressive spermatozoa (15.4%), subpopulation 2, consisting of moderately slow but progressive spermatozoa (35.9%), subpopulation 3, consisting of highly active but nonprogressive spermatozoa (18.5%), and subpopulation 4, consisting of highly active and progressive spermatozoa (30.2%). The distribution of these subpopulations varied significantly (P < 0.05) according to several parameters such as the individual donkey, the ejaculate of the same donkey, the total motility, and the overall sperm concentration. Our results show the existence of four well-defined motile sperm subpopulations in Andalusian donkey ejaculates, and suggest a high heterogeneity in the ejaculate structure in donkey. The relationship between the distribution of the sperm subpopulations and individual donkey, total motility, and sperm concentration shows that the spermatozoa of each have different motility patterns. However, the proportions of sperm subpopulations in the ejaculates did not vary with age and body weight. Finally, the study of discrete subpopulations of motile spermatozoa could lead to a substantial increase in information acquired during donkey semen analysis.

A new approach to sperm preservation based on bioenergetic theory

To date, attempts to preserve chicken sperm have been based on a trial-and-error experimental approach. The present work outlines the development of an alternative approach based on empiricism and bioenergetic theory. In previous work, we found fowl sperm motility to be dependent on mitochondrial calcium cycling, phospholipase A(2), and long-chain fatty acids as an endogenous energy source. It is noteworthy that fowl sperm reside within the sperm storage tubules (SST) of the oviduct over an interval of days to weeks after insemination. In this regard, a model for in vivo sperm storage was developed and tested in additional previous research. Sperm penetration of the SST, sperm residence within the SST, and sperm egress from the SST can be explained in terms mitochondrial function. Understanding sperm function and longevity in terms of bioenergetics presented the possibility that sperm could be inactivated by disrupting mitochondrial calcium cycling and could thereby be preserved. However, this possibility also posed a problem: maintenance of the inner membrane potential of the mitochondrion within inactivated sperm. This report describes a series of experiments in which fowl sperm were inactivated by treatment with the calcium chelator tetrasodium 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, and then reactivated by treatment with calcium ions. The effect of tetrasodium 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid on mitochondrial calcium cycling was confirmed by flow cytometry and confocal microscopy. When treated sperm were cooled to 10 degrees C, inactivated sperm could be reactivated throughout a 5-h storage interval. When stored sperm were held for 3 h before reactivation and insemination, fertility was 88% of the control. Storage did not affect hatchability. In summary, short-term storage was realized by manipulating mitochondrial function. We propose that 1) complex V consumes ATP within inactivated sperm and, by doing so, maintains the inner membrane potential of the mitochondrion, 2) ATP is regenerated within inactivated sperm by the action of creatine kinase on phosphocreatine, and 3) necrosis follows depletion of intracellular phosphocreatine. Therefore, future attempts to preserve chicken sperm can be based on a theory that encompasses regulation of energy production, a biological context in which sperm cells are motile, and the consequences of mitochondrial failure.

Effect of artificial selection on female choice among domesticated chickens Gallus gallus f.d

In the wild, females choose males with potential good genes to increase their reproductive success in terms of attractive sons and, in the long run, more descendants. Whether this is true of domesticated species is yet uncertain. Our experiments demonstrate breed-specific mate choice among domesticated chickens. Sexually mature females of a traditional domestic chicken breed, White Crested Polish, were compared with Red Leghorn females in the first year of the experiments, whereas they were compared with Lohmann Selected Leghorn Classic females in the second year. White Crested Polish have a statistically significant preference for males of their own breed when a male of another breed is also presented. These data suggest that female choice exists even under the constraints of domestication. Domestication as seen here is an evolutionary process that integrates the human interests of animal breeding with innate mate choice preferences of the same animals.

Sperm Mobility: Deduction of a Model Explaining Phenotypic Variation in Roosters (Gallus domesticus)1

In previous work, variation in sperm mobility phenotype was attributed to the proportion of ejaculated fowl sperm containing dysfunctional mitochondria. In the present work, latent mitochondrial dysfunction was inferred from patterns of sperm egress from the oviduct's sperm-storage tubules. In addition, experiments were performed to help explain how mitochondrial function could be compromised in viable sperm cells. Confocal microscopy demonstrated that sperm Ca2+ content differed between low and high sperm-mobility phenotypes when sperm were stained with rhod-2 AM, a Ca2+ -specific dye. Fluorescence was associated with the nuclear envelope, a variant of the endoplasmic reticulum, and greater fluorescence was observed in sperm from low sperm-mobility males. Fluorescence was reduced by 50% when motile sperm were rendered immotile by incubation with a Ca2+ chelator. Thus, a relationship was established between a dynamic intracellular Ca2+ pool and sperm motility. Sperm N-methy-D-aspartic acid (NMDA) receptors were inferred by the action of D-homocysteinesulfinic acid, a potent NMDA receptor agonist. Seminal plasma from low sperm mobility males was characterized by an elevated glutamate concentration. Thapsigargin, which inhibits the smooth endoplasmic reticulum Ca2+ pump and thereby promotes Ca2+ efflux, rendered sperm immotile. This effect was blocked by cyclosporin A, which prevents the formation of the mitochondrial permeability transition pore (PTP) in response to elevated mitochondrial Ca2+ content. In summary, we propose that 1) glutamate enables Ca2+ uptake into sperm before ejaculation, 2) excessive Ca2+ uptake triggers formation of the PTP in a subpopulation of sperm, and 3) sperm mobility is decreased in proportion.

Effects of supplemental vitamin E during the mature period on the reproduction performance of Taiwan Native Chicken cockerels

One-day-old Taiwan native male chicks were fed with maize-soybean rearing diets without supplemental vitamin E to 23 weeks of age. From 23 to 52 weeks of age, the cockerels (n = 90) were assigned at random to 5 dietary treatments and fed with maize-soybean diets supplemented with 0, 20, 40, 80 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate). Pullets (225) of the same age were fed with standard diets throughout. They were artificially inseminated with one dose of 0.04 ml/bird intact and 5-fold diluted pooled semen at 31 to 43 weeks of age and at 49 weeks of age, respectively. The criteria evaluated included: semen quality, fertility and maximum and effective duration of fertility, blood characteristics, body and testes weight. Supplemental vitamin E did not affect cockerels' effective duration of fertility and percentage of fertility. However, when pullets were inseminated with diluted semen, supplementing 160 mg/kg vitamin E increased the maximum duration of fertility at 49 weeks of age. Cockerels receiving 40 to 160mg/kg supplements had higher sperm viability and motility after 39 weeks of age and those fed 80 mg/kg had higher sperm concentration at 39 weeks of age. Cockerels receiving supplements of more than 40 mg/kg vitamin E had higher body weight gain. Plasma cholesterol and testosterone were not affected by supplemental vitamin E. However, plasma luteinising hormone (LH) concentration was lower in cockerels fed 160 mg/kg. Lack of supplemental vitamin E over 39 weeks was associated with lower semen quality but did not reduce the proportion of fertile eggs laid by inseminated hens, perhaps because the insemination dose compensated for low sperm quality. We found that the maximum duration of fertility might be improved by supplementing 160 mg/kg vitamin E at 49 weeks of age.

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.

Sperm mobility: phenotype in roosters (Gallus domesticus) determined by mitochondrial function

Previously, inheritance of sperm mobility entailed a maternal additive genetic effect, and sperm ATP content was correlated (r = 0.80) with phenotype. The present study was conducted to determine if mitochondrial function was critical to phenotypic expression. Whereas phenotype was independent of mitochondrial helix length, phenotype was correlated with sperm oxygen consumption (r = 0.83) using random-bred roosters. Aberrant mitochondria characterized immobile sperm, as evidenced by transmission-electron microscopy. Such mitochondria were swollen and contained disorganized cristae. Additional experiments were performed with roosters from lines selected for low or high sperm mobility. A threefold difference in sperm oxygen consumption was observed between lines. Single nucleotide polymorphisms were observed in mitochondrial DNA by sequencing replicate mitochondrial genomes from each line. An A-to-G substitution in the gene encoding tRNA(Arg) was inherited consistently, as evidenced by restriction fragment length polymorphism analysis using two male and two female progeny per family group and 14 family groups per line. Motile concentration in semen from low-line males was half that observed in semen from high-line males, as evidenced by computer-assisted sperm motion analysis. Likewise, 47% of sperm from low-line males contained aberrant mitochondria, compared to 4% for high-line males. In summary, sperm mobility phenotype was dependent on mitochondrial function, which in turn was altered by genetic selection. Fowl deferent duct fluid contains a high concentration of glutamate. We propose that variation in sperm mobility phenotype stems from the extent to which glutamate induces excessive mitochondrial Ca2+ uptake before ejaculation.