Predicting the fertilising ability of avian semen: comparison of a simple colourimetric test with other methods for predicting the fertilising ability of fowl semen

Sperm subpopulations in avian species: a comparative study between the rooster (Gallus domesticus) and Guinea fowl (Numida meleagris)

The main aims of this research were to study possible differences in objective morphometric sperm characteristics, establish normative sperm morphometry standards, and evaluate the presumed different subpopulation distribution of avian spermatozoa from the rooster (Gallus domesticus) and Guinea fowl (Numida meleagris) as model avian species. Seventy-two ejaculates (36 per species studied) were obtained manually, following a training period involving gently combined dorso-abdominal and lumbo-sacral massage of the birds. Ejaculates were processed for volume, sperm concentration, viability, motility, and morphology. Moreover, samples were submitted for sperm morphometric assessment using objective Computer-Assisted Semen Analysis for Morphometry (CASA-Morph) methods, with sperm morphometric descriptors evaluated by Principal Component Analysis (PCA) and multivariate clustering analyses. There were several differences observed between the avian species in values obtained for ejaculate volume and sperm concentration (P < 0.001). Irrespective of species, PCA revealed two Principal Components (PCs) explaining more than 80% of the variance. In addition, the number of subpopulations differed with species (three and five subpopulations for rooster and Guinea fowl, respectively). Moreover, the distribution of the sperm subpopulations was found to be structurally different between species. In conclusion, our findings from using CASA-Morph methods indicate pronounced sperm morphometric variation between these two avian species. Because of the strong differences observed in morphometric parameter values and their subpopulation distribution, these results suggest that application of objective analytical methods such as CASA-Morph could substantially improve the reliability of comparative studies and help establish valid normative sperm morphological values for avian species.

Semen characteristics, cryopreservation, and successful artificial insemination in the Blue rock pigeon (Columba livia)

The present study was undertaken in the Blue rock pigeon (Columba livia) to evaluate the annual semen characteristics, to identify a suitable extender for semen short-term storage, to determine a protocol for cryopreservation of semen and finally to check whether intracloacal insemination would lead to the birth of a chick. Semen characteristics such as semen volume, sperm concentration, sperm motility, and percentage of normal spermatozoa were maximum during the monsoon season. TALP was observed to be the most suitable semen extender and the sperm survived best at 37 degrees C at a dilution of 1:100 in TALP. Further, cryopreservation studies on pigeon semen indicated that 8% DMSO with or without egg yolk (20%) proved to be a better cryoprotectant compared to glycerol and polyethylene glycol. In addition, the slow freezing protocol was better than the fast-freezing protocol and about 40% of the cryopreserved spermatozoa were motile following thawing. Computer-aided semen analysis indicated that pigeon spermatozoa were extremely active immediately after dilution in TALP and exhibited linear trajectories persisting up to 9h. But, with time there was a time-dependent decrease in the velocity parameters (VAP, VSL, and VCL). Cryopreserved spermatozoa following thawing also exhibited linear trajectories but had reduced velocity as evident from the significant decrease in VAP, VSL, and VCL. Further, artificial inseminations using fresh semen resulted in 45% fertilization and birth of a live chick.

Application of an MTT reduction assay for assessing sperm quality and predicting fertilising ability of domestic fowl semen

1. The ability of domestic fowl spermatozoa to reduce MTT tetrazolium to its coloured formazan was compared with other tests of sperm quality and fertilising ability. 2. MTT reduction was highly correlated with sperm ATP content (r2 = 0.85); sperm mobility (r2 = 0.62.); sperm:perivitelline layer interaction (r2 = 0.80) and fertilizing ability (r2 = 0.83). 3. The simple, robust, MTT-reduction assay may therefore be used to select male chickens on the basis of their sperm quality and thus potential fertilising ability.

Assay of sperm quality in the domestic fowl by MTT reduction

1. An assay which measures the capacity of spermatozoa from the domestic fowl to reduce the colourless tetrazolium dye MTT to its highly coloured purple formazan pigment has been developed and characterised. 2. The assay has several advantages over a previous tetrazolium-based sperm quality assay: it functions without the unstable phenazine methosulphate and toxic cyanide reagents and, following the reductive reaction, the sperm suspension is solubilised to produce optically clear solutions without centrifugation. 3. For samples of semen from individual males, MTT-reduction is strongly correlated with INT-reduction, which has been previously shown to be a useful predictor of sperm fertilising ability.

Storage of poultry semen

Methods of semen collection and artificial insemination (AI) in poultry, requirement for diluents, methods of liquid and frozen storage of avian semen and evaluation of spermatozoa after storage for fertilizing ability are reviewed. Frozen storage of semen from non-domestic birds is also briefly discussed.

Assessment of fresh and stored duck spermatozoa quality via in vitro sperm-egg interaction assay

An in vitro sperm-egg interaction assay was used to measue the quality of duck spermatozoa in fresh and stored semen. The inner perivitelline layer (IPVL), which had been separated from laid duck eggs, was incubated with spermatozoa in vitro. The number of points of sperm hydrolysis in the IPVL in vitro was logarithmically correlated with the fertility of the eggs laid by inseminated females, for both fresh semen (r = 0.85, P < 0.001) and stored semen at 5 degrees C for 24 h (r = 0.84, P < 0.001). After semen storage, the ability of spermatozoa to hydrolyze the IPVL decreased by 67.4% compared with the values for fresh semen, whereas egg fertility and sperm motility decreased by 47.8% and 15.2%, respectively. These results suggest that the in vitro sperm-egg interaction assay accurately reflects the fertilizing ability of fresh and stored duck spermatozoa and detects spermatozoal damage due to semen storage more sensitively than motility or fertility tests.

Lessons for the poultry industry gleaned from experiences with other commodity species

Do breeders really know how well or poorly they are managing reproduction? Poultry breeders could benefit from application of proven concepts of reproductive management used to exploit elite mammalian males, via selection for reproductive traits and extensive use of AI. Use of elite males could dramatically increase the impact of genes of economic importance transferred to the producer level. Testes weight has up to a 35-fold range among males within most lines of poultry, as does number of sperm that can be harvested from a male. These observations should not be ignored. Males with small testes will provide few sperm and they should be culled. Similarly, identification and elimination of males whose sperm are likely to have low fertilizing potential should be beneficial. Approaches to maximize harvest of those sperm produced by an elite male and minimize wastage of these valuable cells are emphasized. To this end, semen should be extended to allow insemination of a minimal volume containing just sufficient sperm consistent with the breeder's goal. Presumably, the goal should be obtaining the maximum number of offspring from a unique male or great-grandparent family, while minimizing cost of producing each chick. This goal might not require maximizing "fertility". A 10-fold increase in dissemination of DNA from elite males to the next generation is realistic. Over three generations, this increase equals a 1,000-fold increase in the number of birds with the desirable traits! Appropriate biotechnology is available. Will decision makers evaluate new (to them) approaches and progress into the next millennium using modern technology, when cost-effective, or will they continue to manage reproduction with methods more than 50 yr old? Those who choose the latter path may risk extinction.

Evaluation of semen from individual male domestic fowl by assessment of sperm: perivitelline interaction in vitro and in vivo

1. Spermatozoa in semen samples from 8 individual male domestic fowls were shown to have a differential and characteristic ability to hydrolyse holes in the inner perivitelline layer from laid eggs in an in vitro assay. 2. The number of holes produced by samples of spermatozoa per unit area of inner perivitelline layer in vitro was linearly correlated with sperm ATP content (r = 0.85) and motility (r = 0.76). 3. The number of holes formed in the inner perivitelline layer in vitro was also linearly correlated with the numbers of holes formed in the inner perivitelline layer of eggs fertilised in vivo, in inseminated hens (r = 0.90); and was correlated logarithmically with the proportion of fertile eggs laid by these hens.

Synergistic effect of gramicidin and EDTA in inhibiting sperm motility and cervical mucus penetration in vitro

Gramicidin, a linear polypeptide with antiviral and antimicrobial properties, was compared in vitro with a commonly used spermicidal detergent-nonoxynol-9 (N9). The inhibition of sperm functions was evaluated by computer-assisted semen analysis (CASA) for sperm motility, in cervical mucus penetration assay, and by colorimetric tetrazolium salt and lactate dehydrogenase release assays routinely employed for testing the toxicity of drugs. The effective 100% inhibitory concentration (IC100) of gramicidin in a 2-min sperm immobilization assay by CASA was equal to 4 micrograms/ml, whereas IC100 of N9 was equal to 200 micrograms/ml. The presence of 0.1% of chelating agent, EDTA, reduced IC100 of gramicidin to 10 ng/ml, while less than a twofold enhancement in N9 activity was observed upon combination with EDTA. Likewise, the gramicidin/EDTA combination was 100,000 times more potent than N9/EDTA in the sperm penetration assay. Quantitative toxicity tests confirmed that gramicidin is a potent spermostatic rather than spermicidal agent. Further development of a gramicidin/EDTA formulation is warranted as a nontoxic topical contraceptive with activity against viral and microbial sexually transmitted diseases (STDs).

Analysis of poultry fertility data. 3. Analysis of the duration of fertility in naturally mating Japanese quail

The purpose of the present study was to test the appropriateness of iterative least squares regression for the evaluation of fertility data in naturally mating quail. In each of four trials, 20 male and 200 female randombred Japanese quail were housed in stacked breeder cages. Paired females were exposed to their assigned male for a single 48-h period. Eggs were collected for 2 wk following removal of the male, incubated, and fertility determined by visual inspection at egg breakout. In Trials 1 and 3, sexually experienced males were placed with experienced and inexperienced females, respectively. In Trials 2 and 4, inexperienced males were placed with experienced and inexperienced females, respectively. Duration of fertility, by male, was analyzed by iterative least squares, using the model y(x) = gamma/(1 + e beta(tau - x)). Overall fertility was analyzed with a log odds model following transformation to logits. Iterative least squares provided estimates of fertility duration of 3.75 to 9.18 d, with significant (P < 0.05) differences in the duration of fertility observed between individual males as well as between the trials. Differences (P < 0.05) in overall fertility (17.7 to 58.3%) were also observed, with inexperienced males paired with experienced females exhibiting the lowest overall means. Taken together, these results suggest that iterative least squares may be used to evaluate fertility in naturally mating populations and that reproductive experience can have a profound effect on the interpretation of fertility in naturally mating quail.

Analysis of subfertility associated with homozygosity of the rose comb allele in the male domestic fowl

Sperm metabolism and duration of fertility were compared between roosters homozygous (RR) and heterozygous (Rr) for the rose comb allele. In the absence or presence of Ca+2, a motility agonist, the metabolic rate of spermatozoa from RR males was 76 to 77% of that of spermatozoa from Rr males. In the presence of caffeine, the metabolic rate of spermatozoa from RR males was increased significantly (P < .05) to 86% of that of spermatozoa from Rr males. Although intramagnal insemination of ejaculated spermatozoa reduced the disparity in duration of fertility between RR and Rr males, the duration of fertility of RR males was still less than that of Rr males. No difference in duration of fertility was observed following intramagnal insemination of testicular spermatozoa. Subfertility associated with RR males seems to stem from an aberrant activation or regulation of spermatozoal metabolism and not a reduction in absolute metabolic capacity per se.

Analysis of the combined effect of the spermatozoal degeneration allele (Sd) and homozygosity of the rose comb allele (R) on the duration of fertility of roosters (Gallus domesticus)

Roosters homozygous for the rose comb allele (R/R) are subfertile. Likewise, roosters bearing the dominant spermatozoal degeneration allele (Sd) are subfertile. The objective of the present research was to see whether these effects were cumulative. Domestic fowl were bred in order to obtain males representing the following genotypes: R/r+ sd+/sd+, R/r+ Sd/sd+, R/R sd+/sd+, and R/R Sd/sd+. Duplicate fertility trials were conducted with Single Comb White Leghorn hens. In each trial, ejaculates were pooled according to genotype. The insemination dose was 1 x 10(8) viable spermatozoa per hen, and eggs were collected over a 21-day interval following a single intravaginal insemination. Fertility over the 21-day period was 53 +/- 2.1 (SEM), 36 +/- 1.6, 21 +/- 2.1, and 11 +/- 1.2%, respectively. Therefore, the effect of homozygosity for the R allele and the presence of the Sd allele were cumulative in the depression of fertility.

Physiological changes in fowl and turkey spermatozoa during in vitro storage

1. Although early work on semen storage has been rather empirical in approach, only basic research can provide a framework of biological mechanisms from which improvements in the techniques of cryopreservation and liquid semen storage can progress logically. 2. A major drawback in this work has been the lack of adequate tests for quantitating and differentiating aspects of 'fertility'. 3. Basic research has now provided techniques for assessing: sperm fertilising ability in terms of numbers of fertile eggs; the efficiency of hens' oviducts at accepting and retaining spermatozoa, and sperm 'quality' as motility, metabolism and plasma membrane patency. 4. These techniques may be used for a more critical assessment of the effects of both cryopreservation and liquid semen storage on sperm function, although the integrity of sperm surface proteins may be a more sensitive variable which has yet to be measured. 5. Further improvements in sperm cryopreservation technology are best approached through an understanding of the fundamental cellular and molecular changes which take place during freezing; thus far little is known of such changes in avian spermatozoa. 6. The ideal milieu for maintaining spermatozoa in liquid semen storage should mimic the environment of the oviducal sperm storage tubules; elucidation of the factors involved in progressing steadily.