Nicholas Turkey Breeding Farms, Sonoma, California 95476; and #Hybrid Turkeys, Kitchener, Ontario, Canada N2K 352. ABSTRACT Our objectives were to ...
PHYSIOLOGY AND REPRODUCTION Efficacy of Sperm Mobility Assessment in Commercial Flocks and the Relationships of Sperm Mobility and Insemination Dose with Fertility in Turkeys1 L. M. King,* J. D. Kirby,† D. P. Froman,‡ T. S. Sonstegard,§ D. E. Harry,储 J. R. Darden,# P. J. Marini,储 R. M. Walker,# M. L. Rhoads,† and A. M. Donoghue*,2 *Germplasm and Gamete Physiology Laboratory, Agricultural Research Service, USDA, Beltsville, Maryland 20705; †University of Arkansas, Fayetteville, Arkansas 72701; ‡Oregon State University, Corvallis, Oregon 97337; §Gene Evaluation and Mapping Laboratory, Agricultural Research Service, USDA, Beltsville, Maryland 20705; 储Nicholas Turkey Breeding Farms, Sonoma, California 95476; and #Hybrid Turkeys, Kitchener, Ontario, Canada N2K 352 ABSTRACT Our objectives were to evaluate: 1) the efficacy of the Sperm Mobility Test on commercial turkey farms, and 2) the influence of sperm mobility phenotype on fertility when insemination parameters are varied. In research flocks, differences in sperm mobility among toms are predictive of fertility. We wanted to test the efficacy of this sire selection test in practical, real-world situations, evaluating its usefulness in terms of assessing large numbers of toms, different strains of turkeys, and variable management practices. Utilizing field study results, controlled studies were then conducted to improve test parameters. For the field trials, semen from each of 405 breeder toms (11 strains or lines) was evaluated either in duplicate (n = 285) or in triplicate (n = 120). Sperm mobility was normally distributed among all toms tested, except for one strain. Because the sperm mobility indices for toms evaluated in these field trials were higher than those observed in research flocks, the Sperm Mobility
Test was modified to increase the separation between high and low sperm mobility phenotypes by increasing the concentration of Accudenz.威 To determine the effects of sperm mobility and insemination dose on sustained fertility through time, hens from a research flock were inseminated twice before the onset of lay with sperm from toms classified as high-, average-, or low-mobility in concentrations of 25 to 400 million sperm per artificial insemination dose, and egg fertility was evaluated over a 5-wk period. Toms with the high-mobility sperm phenotype maintained higher fertility (P < 0.05) over the 5-wk period at all insemination doses compared with toms with low-mobility sperm. Toms with high-mobility sperm sired equal numbers of poults in a sperm competition study in which numbers favored low-mobility toms by 3:1. These results demonstrate that the Sperm Mobility Test can be used for on-farm evaluation of semen quality of toms in commercial flocks and that sperm mobility influences fertility and sire fitness.
(Key words: turkey, sperm, sperm mobility, fertility) 2000 Poultry Science 79:1797–1802
INTRODUCTION Turkeys are the only agriculturally important species that are produced exclusively by artificial insemination (AI; see review: Brillard, 1995). Although AI mandates the regular collection of semen throughout production, surprisingly little evaluation of semen is performed onfarm, and current management practices could benefit greatly from a semen assessment and sire selection component. Often, methods to evaluate turkey semen have
Received for publication January 31, 2000. Accepted for publication June 30, 2000. 1 This research has been supported in part by the U.S. Egg and Poultry Association, Project No. 340. 2 To whom correspondence should be addressed: donoghue@comp. uark.edu.
not been routinely used by the turkey industry because they are tailored to controlled research settings, they are difficult and time-consuming, and the results correlate poorly with fertility in field trials (Wilson, 1979; Wishart, 1995). Thus, toms with substandard fertility are managed throughout their breeding lifetime, yet could be eliminated if identified early in production. An additional challenge exists, in that for a majority of commercial farms, toms are managed within flocks, and semen from 10 or more toms is pooled for the insemination of multiple hens. It has been assumed that sperm from each tom are equally fecund, but a recent study indicated that a majority of offspring were produced by only a few toms
Abbreviation Key: AI = artificial insemination; CV = coefficient of variation.
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after pooled inseminations (Donoghue et al., 1999a). The DNA fingerprint analysis of turkey poults produced after pooled inseminations showed that paternity was highly skewed among the individual males; in one trial, a single male produced 37 of 70 offspring when semen from 10 males was pooled (Donoghue et al., 1999a). In these studies, there was no significant relationship between proportions of offspring produced by a given tom and semen traits that have been used to characterize or select breeder toms, such as semen volume, sperm concentration, sperm viability, and membrane integrity. In more recent studies, measuring the functional aspects of sperm, mobility, and the ability to penetrate a thick solution has demonstrated a significant correlation with paternity in AI trials using both pooled semen samples and individual males (Donoghue et al., 1998, 1999b; Birkhead et al., 1999). In research trials, the sperm mobility trait is normally distributed, and toms remain consistent within mobility phenotype over a 5-mo period (Holsberger et al., 1998). Additionally, the Sperm Mobility Test has been adapted for use with various instruments and semen concentrations, making the procedure streamlined (King and Donoghue, 1999). Our goal is to develop physiological tests that are related to sperm function and can be measured on-farm. Because most of the development of the Sperm Mobility Test has been carried out in research laboratories under controlled conditions, the objective of the current studies was to evaluate and adapt the Sperm Mobility Test for on-farm use by the turkey industry. The variability of sperm mobility phenotype has not been assessed in field conditions. It has been assumed that culling toms that produce low-quality ejaculates (i.e., semen that is low in concentration or volume, or yellow in color) will eliminate those males not contributing to poult production. Therefore, field tests were planned using commercial flocks that were critically screened for semen quality to evaluate the efficacy of the Sperm Mobility Test. We further sought to demonstrate the effectiveness of this test as a sire selection tool by utilizing sperm from research toms of different mobility phenotypes to evaluate the effects of AI dose and sperm competition on fertility. Fertility in commercial flocks is maintained by inseminating with large numbers of sperm. Our goal was to demonstrate that quality is an important factor in overall fertility. Exploring the impact of the sperm mobility trait as it relates to sire selection, insemination doses and practices, fertility, and sperm competition could improve management efficiency of commercial turkeys.
MATERIALS AND METHODS Animals This project was composed of turkeys housed in commercial conditions (Studies 1 and 2) and those housed in
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Accurate Chemical and Scientific Corporation, Westbury, NY 11590. Model 534B-Mod1, Animal Reproduction Systems, Chino, CA 91710.
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research facilities (Studies 2 through 4). For Studies 1 and 2, semen from 405 toms of 11 different commercial strains or lines was evaluated. Line refers to a pure pedigree population, whereas strain refers to a cross between different genetic lines. For purposes of clarity, in this manuscript the birds are termed breeder birds, and lines and strains are not differentiated due to proprietary genetics. Hens and toms were maintained on commercial farms using standard commercial housing conditions in a closed, environmentally controlled facility, on a 14 h of light:10 h of dark lighting schedule. Semen was collected by the abdominal massage technique (Burrows and Quinn, 1935). Toms had been previously evaluated, and those toms consistently producing ejaculates with low semen volume, yellow color, or low semen concentration were eliminated prior to these trials. Because semen was collected for insemination purposes, small aliquots of semen were immediately removed for semen analysis prior to AI. In general, the same personnel did all of the semen collection for a given strain or line on a given day, at the same time of day, and in the same order. Semen was collected in such a way as to minimize contamination from urates or other foreign matter. The entire insemination process for all strains or lines was completed within 3 to 4 h, with a minimal holding time (less than 5 min) before analysis and insemination. For the second portion of Study 2 and Studies 3 and 4, parent-stock turkeys on a research farm were used. Hens and toms were maintained in environmentally controlled houses on a 14 h of light:10 h of dark photoperiod and housed individually in cages (hens) or in groups of 8 to 10 in pens (toms). Feed and water were provided ad libitum. In this paper, these birds are termed research birds.
The Sperm Mobility Test The Sperm Mobility Test has been used in the evaluation of research flocks as previously described (Froman and McLean, 1996; Donoghue et al., 1998), and the same procedure was used in the following studies unless otherwise stated. This test is designed to measure the directional forward progression of sperm (sperm mobility), as opposed to general movement (sperm motility). Briefly, semen was diluted to 1 × 109 sperm/mL with motility buffer (50 mM N-tris-[hydroxymethyl]methyl-2-aminoethanesulfonic acid buffer, pH 7.4, 120 mM NaCl, 10 mM glucose, 2 mM CaCl2). A 300-µL volume of diluted semen was layered upon 3 mL of 2% (wt/vol) Accudenz威 solution,3 which had been prewarmed to 41 C. The sperm suspension was incubated for 5 min in a disposable cuvette in a 41 C waterbath, and the percentage transmission was measured 1 min after the cuvette was loaded into a Densimeter.4 The Sperm Mobility Index was calculated by: 100 minus percentage transmitted light. Toms were ranked according to their Sperm Mobility Index, with high- and low-mobility toms ranking one standard deviation above or below the average-mobility toms, respectively.
SPERM MOBILITY IN COMMERCIAL FLOCKS
Study 1: Evaluation of the Sperm Mobility Test Using Breeder Toms Semen was collected from 405 individual breeder toms, and semen analysis was performed in the barn or in a room adjacent to the barn at the field site. Semen from these toms was examined in duplicate (n = 285) or in triplicate (n = 120), with samples taken 1 to 4 wk apart. Each ejaculate was evaluated for sperm mobility within 5 min of collection. Semen volumes were measured, and a 100-µL aliquot of semen was removed from the total ejaculate for determination of semen concentration and mobility. The remaining ejaculate was used for AI. Pearson’s correlation coefficients (SAS Institute Inc., 1985) were used to compare sperm mobility with sperm concentration and volume. The Kolmogorov-Smirnov (SAS Institute Inc., 1985) test was used to determine normality of sperm mobility phenotype distribution. A subset of breeder toms (n = 47) from which fertility data were available for individual hens was used to analyze correlation coefficients among semen volume, sperm concentration, sperm mobility and fertility. Semen volume was measured using a calibrated vial, and sperm concentration was measured spectrophotometrically. Semen from these toms was examined only at the onset of the study, with duplicate samples taken 4 d apart, just prior to insemination of hens. Sperm mobility values were assessed with 2% Accudenz,威 and the hatch fertility was determined from 4 to 23 wk of egg production (April through September). Semen from individual toms was distributed between several hens each week; however, sperm concentration and AI dose varied due to variation in ejaculate volume. The same hens were inseminated with semen from the same toms every time. Hens (n = 340) were approximately 30 wk of age at the beginning of production, and five different lines of hens were used. Hens were photostimulated 2 wk before the initiation of egg production and inseminated at 14, 18, and 24 d after lighting, and then weekly for the remainder of production. The GLM procedure (SAS Institute Inc., 1985) was used to determine the relationships among each male’s mean semen volume, sperm concentration, sperm mobility, and fertility using replicate values. Linear correlation coefficients and 95% confidence intervals were calculated using the GraphPad Prism5 program.
Study 2: Effect of Accudenz威 Concentration on Sperm Mobility Part 1. The effect of varying the Accudenz威 concentration within the Sperm Mobility Test was evaluated on a subset of breeder toms (n = 89) under field conditions. Semen from these toms was examined in duplicate, with samples taken 4 d apart. Because sperm mobility indices
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GraphPad, San Diego, CA 92121. Continental Plastics, Delvan, WI 53115.
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were higher in Study 1 than in previous studies with research flocks, 2 and 3% Accudenz威 solutions were compared using the same ejaculates. Part 2. To further optimize the concentration of Accudenz威 for increased applicability of the Sperm Mobility Test, semen from toms that were previously ranked by the Sperm Mobility Test using 2% Accudenz威 was used. This portion of the study was done using a research flock (n = 24), because a large volume of semen was required to evaluate sperm mobility using 2, 3, 4, 5, and 6% Accudenz威 solutions in the Sperm Mobility Test. Semen from toms in the field trials was needed for AI. Normality of the data was determined by the Kolmogorov-Smirnov test. Differences in sperm mobility between phenotypes were determined by two-way ANOVA (SAS Institute Inc., 1985).
Study 3: Effect of Sperm Dose and Mobility on Sustained Fertility in Research Hens To determine whether increasing sperm concentration in the AI dose would affect fertility rank of selected males, semen from five research toms was pooled by mobility phenotype, and research hens (n = 12 per mobility phenotype) were inseminated twice before the onset of lay with high-, average-, or low-mobility sperm in concentrations of 25, 50, 100, 200, or 400 million sperm per AI dose. Semen for each concentration treatment was diluted in Beltsville poultry semen extender,6 and each hen was inseminated with a total volume of 50 µL. Fertility was assessed by dividing the total number of eggs laid by the number of fertile eggs. The iterative least squares method (SAS Institute Inc., 1985) was used to determine the statistical significance of the effects of sperm mobility and insemination dose on sustained fertility through time.
Study 4: Effect of Sperm Dose and Mobility on Paternity in Research Toms We previously demonstrated that toms with the highmobility phenotype produce more offspring when ejaculates are mixed equally with semen from low-mobility toms (Donoghue et al., 1999b). To evaluate alteration of the ratio of sperm numbers to favor low-mobility phenotype toms, this study involved inseminating hens with 25% high-mobility and 75% low-mobility phenotype sperm pooled from a total of ten toms (five per phenotype). Semen from toms in the research flock was diluted to 5 × 109 sperm/mL in Beltsville poultry semen extender. To prepare the 25% high-, 75% low-mobility doses for insemination, 125 and 375 µL of semen from high- and low-phenotype toms, respectively, were placed in a 10mL Erlenmeyer flask and mixed at 150 rpm for 15 min at room temperature (total volume 2.5 mL). Hens (n = 9) on the research farm were inseminated with 25 µL for a total of 125 × 106 sperm per insemination. Genomic DNA was extracted from hen, tom, and poult blood, and genotypes were determined using microsatellite markers as previously described in Donoghue et al. (1999b). Differ-
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FIGURE 1. Mean sperm mobility indexes in breeder toms. Sperm mobility values are shown for toms from each commercial strain tested, with Strain L representing the research toms used routinely in our laboratory. Values are expressed as mean ± SEM. The dotted line is used for comparison with the sperm mobility value for research toms. The n value is shown in the corresponding legend, together with coefficient of variation (CV) and normality. For normality, Y = yes, and N = no.
ences in progeny production by sires were evaluated by chi-square analysis.
FIGURE 2. Sperm mobility frequency distribution in breeder toms. Sperm mobility is shown for one subset of breeder toms (n = 89), determined by the Sperm Mobility Test using 2% Accudenz威 solution (A), or 3% Accudenz威 solution (B). The mean sperm mobility value for each trial is designated by an arrow.
RESULTS Study 1: Evaluation of the Sperm Mobility Test Using Breeder Toms In the commercial setting, the mean sperm mobility values ranged from 56.5 to 67.5, with mean standard deviations of 4.48 to 6.07 between samplings from the same males. Sperm mobility was normally distributed in all toms tested except for one strain (Figure 1, Strain K). However, small sample sizes of certain strains or lines may have affected the statistical determination of normality. Coefficient of variation (CV) indicates the range in mobility values for each strain or line. Sperm from breeder toms in these field trials generally had higher mobility than that of toms from the research flocks tested (Figure 1, Strain L). No significant correlations were found among semen volume, sperm concentration, and sperm mobility in the 830 ejaculates that were tested (data not shown). Similarly, there were no significant correlations between semen volume and fertility (P = 0.70) or sperm concentration and fertility (P = 0.76). However, significant positive correlation coefficients were calculated between sperm mobility and fertility (P = 0.008). The slope of the linear regression coefficient (y = mx + b) was 0.4976 ± 0.1375, which was significanty greater than zero (P = 0.0005).
Study 2: Effect of Accudenz威 Concentration on Sperm Mobility Part 1. Sperm mobility was normally distributed when breeder toms were evaluated with 2 and 3% (wt/vol)
Accudenz威 solution, and the mean sperm mobility for all the toms evaluated shifted from 61.3 (2% Accudenz威) to 52.8 (3% Accudenz威) mobility units (Figure 2). The range of sperm mobility values also increased with the 3% Accudenz威 solution, thus increasing the separation between different mobility phenotypes. Part 2. Differences (P < 0.05) between high- and lowmobility phenotypes were seen with 2 through 5% Accudenz威 solution in research toms, but the most significant (P < 0.01) separation between mobility phenotypes was found when using 6% Accudenz威 (Table 1). Toms consistently stayed within their sperm mobility phenotype ranking, regardless of the concentration of Accudenz威 solution used.
TABLE 1. Effect of Accudenz威 concentration on sperm mobility index values of semen from research toms1 Accudenz威 concentration 2% 3% 4% 5% 6%
Sperm mobility phenotype High 35.00 27.80 21.80 21.20 20.60
Average ± ± ± ± ±
a
4.98 4.73a 5.15a 3.92a 3.39a
24.17 18.40 16.00 11.40 11.17
± ± ± ± ±
Low ab
4.18 5.35ab 4.16ab 3.97ab 1.99b
13.50 8.00 3.40 4.20 3.60
± ± ± ± ±
4.70b 1.38b 1.78b 1.36b 1.21c
a−c Means within a row lacking a common superscript differ significantly (P < 0.05) (n = 4 to 8 per phenotype). 1 Research toms were previously ranked by mobility phenotype using 2% Accudenz威. Sperm Mobility Index is calculated by 100 − percentage transmitted light. Data are expressed as mean ± SEM.
SPERM MOBILITY IN COMMERCIAL FLOCKS
FIGURE 3. Effect of sperm dose and mobility phenotype on fertility in research hens. Semen from 5 research toms of each mobility phenotype was pooled and used to inseminate research hens (n = 12 per mobility phenotype). Fertility after two inseminations was determined over 5 wk of egg production.
Study 3: Effect of Sperm Dose and Mobility on Sustained Fertility in Research Toms Differences (P < 0.05) were found in sustained fertility through time between hens inseminated with high- and low-mobility sperm (Figure 3). Hens inseminated with high-mobility sperm maintained higher fertility at all insemination doses compared with low-mobility sperm (P < 0.05). Average-mobility sperm was not significantly different between groups (P > 0.05).
Study 4: Effect of Sperm Dose and Mobility on Paternity in Research Toms In this study of sperm competition between mobility phenotypes, paternity of poults was determined with 95% confidence. Although sperm numbers favored low-mobility toms by a 3:1 ratio, males from each phenotype produced almost equal numbers of the 47 offspring genotyped; 23 and 24 were sired by low- and high-mobility phenotype toms, respectively. If paternity were based on numbers of sperm inseminated, it would be predicted that 12 (25%) and 35 (75%) poults of the 47 poults would be sired by the high- and low-mobility toms, respectively. High-mobility toms produced more offspring (P < 0.05) than predicted.
DISCUSSION In most of the turkey strains or lines we evaluated, sperm mobility is a normally distributed trait. Toms had been screened previously for semen volume, sperm concentration, and semen color, and those toms considered to be poor semen producers had been removed. Sperm mobility of these flocks was highly variable; the CV of sperm mobility for the breeder strains or lines ranged
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from 7.8 to 18.7%, indicating that in a given flock, it is possible to discriminate between individual toms with different mobility phenotypes. The larger the CV is, the more power the test has to detect variances or differences in the population. It was found that the Sperm Mobility Test could be easily performed on commercial farms without significant disruption to the semen collection and AI schedule. The ease of performance of a sire-selection test is important for the adoption and integration of such a test into existing turkey breeding practices. However, the practice of AI in turkeys is very labor-intensive, and tests to improve overall efficiency must be cost-effective and time efficient, and must produce results that impact overall performance. The toms in these field trials were from flocks that had been strictly screened for ejaculate quality. Only those toms producing ejaculates that were thick (high sperm concentration), white (clean collections with no blood or urates visible), and of adequate volume (>0.2 mL) were selected for breeding stock. We have demonstrated here that even with the strictest selection criteria for semen quality used by industry, differences in the sperm mobility trait can be detected. Because semen is routinely collected from individual toms to be used for AI, small aliquots of semen can be removed for analysis without compromising the production routine. One important aspect of sire selection is the distinguishable differences between potential sires in semen traits. In Study 1, because semen from almost all toms, regardless of strain, penetrated the Accudenz威 quickly, adjustments were needed to separate out phenotype differences between individual toms. This observation had not been made previously in research flocks tested (Donoghue et al., 1998; Holsberger et al., 1998). Increasing the concentration of Accudenz威 results in a denser solution, requiring the sperm to exert more force to penetrate and swim down toward the bottom of the cuvette. By increasing the stringency of the Sperm Mobility Test, the range of sperm mobility values is increased, which helps to distinguish the different subpopulations of toms. Because of data collected in the field trials presented in this paper, methods have been optimized for turkeys by evaluating and increasing the concentration of Accudenz威 solution for the Sperm Mobility Test (King and Donoghue, 1999). For a sire selection test to be deemed effective and advantageous for commercial farms, the results of the test must be predictive of fertility (Barbato et al., 1998; Donoghue, 1999). Semen volume and sperm concentration are common and practical measurements of semen production for poultry, but these traits do not always accurately predict fertility (Wilson, 1979; Wishart, 1995; Holsberger et al., 1998; Donoghue et al., 1999b). In this paper, sperm mobility was significantly correlated with fertility under commercial production conditions in toms previously selected for optimal semen color, concentration, and volume. Sperm mobility has repeatedly been shown to be predictive of fertility under research conditions (Froman and Feltmann, 1998; Rhoads et al., 1998; Froman et al., 1999). Here we demonstrate that when
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applied to field conditions, this measure of sperm function can be observed. Identification of physiological sperm characteristics that influence fertility and sperm storage and that may be used to predict fertility could improve commercial productivity. Because of the nature of large-scale breeding systems for turkeys using AI, we wanted to explore how sire selection could alter production efficiency. Current AI practices use high doses of pooled semen (≥250 million sperm per dose) to ensure high fertility (Christensen, 1995). We wanted to evaluate how sperm quality might impact potential fertility, and whether large numbers of sperm from poor sperm mobility toms would compensate for sperm with improved functional traits. We observed in two separate studies that sperm concentration could not compensate for lower sperm mobility in terms of fertility. When hens were inseminated with semen from toms with high sperm mobility, maximum fertility was achieved with a dose of 100 million sperm/ mL (Study 3). When hens were inseminated with semen from toms with low sperm mobility, at even four times that amount (400 million sperm/mL), the fertility remained significantly lower. Similar studies have described the effect of sperm dose and mobility in chickens (Froman and McLean, 1996; Froman et al., 1997). In Study 4, in which sperm mobility favored low sperm mobility toms by 3:1 over high sperm mobility toms, males from both phenotypes produced similar numbers of poults. Therefore, by selection for a trait such as sperm mobility, fewer toms could be used to produce the same level of fertility as pooled ejaculates from many more toms of varied quality. If selection of higher-quality toms would offset the cost of housing larger numbers of toms and the time and labor involved in semen collection and managing these males, use of the Sperm Mobility Test would be cost-effective. In conclusion, the results presented here demonstrate that the Sperm Mobility Test can be used to standardize and improve sire selection in commercial flocks. Because semen must be collected from individual males for AI purposes, a sire selection test could be easily incorporated into existing management practices. Selection of toms based on potential fecundity would allow for identification and distribution of toms with superior semen quality and provide a legitimate reason to cull toms with poor sperm fertilizing ability.
ACKNOWLEDGMENTS We are grateful for the assistance of Greg Music and John Sharp and staff (Nicholas Turkey Breeding Farms, Sonoma, CA 95476) and Rob Walker and staff (Hybrid Turkeys, Kitchener, Ontario, Canada N2K 3S2) in these studies. We thank Tina Deluca, Sophia Fuentes, and Heath Harley (USDA-ARS, Beltsville, MD 20705) for technical assistance.
REFERENCES Barbato, G. F., P. G. Cramer, and R. H. Hammerstedt, 1998. A practical in vitro sperm-egg binding assay which detects subfertile males. Biol. Reprod. 58:686−699. Birkhead, T. R., J. G. Martinez, T. Burke, and D. P. Froman, 1999. Sperm mobility determines the outcome of sperm competition in the domestic fowl. Proc. R. Soc. Lond. B. Biol. Sci. 266(1430):1759−1764. Brillard, J. P., 1995. Artificial insemination: How many sperm and how often? Pages 176−183 in: Proceedings from the First International Symposium on the Artificial Insemination of Poultry. Poultry Science Association, Savoy, IL. Burrows, W. H., and J. P. Quinn, 1935. The collection of spermatozoa from domestic fowl and turkey. Poultry Sci. 16:19−24. Christensen, V. L., 1997. Semen collection and dilution. Pages 1−5 in: Techniques for Semen Evaluation, Semen Storage, and Fertility Determination. M. R. Bakst and H. C. Cecil, ed. Poultry Science Association, Inc., Savoy, IL. Donoghue, A. M., 1999. Prospective approaches to avoid flock fertility problems: Predictive assessment of sperm function traits in poultry. Poultry Sci. 78:437−443. Donoghue, A. M., M. R. Bakst, P. Drummond, S. Haqque, and E. Smith, 1999a. Paternity efficiency in turkeys differs extensively after heterospermic insemination. J. Appl. Poult. Res. 8:214–221. Donoghue, A. M., D. R. Holsberger, D. P. Evenson, and D. P. Froman, 1998. Semen donor selection by in vitro sperm motility increases fertility and sperm storage in the turkey hen. J. Androl. 19:295−301. Donoghue, A. M., T. S. Sonstegard, L. M. King, E. J. Smith, and D. W. Burt, 1999b. Turkey sperm mobility influences paternity in the context of competitive fertilization. Biol. Reprod. 61:422−427. Froman, D. P., and A. J. Feltmann, 1998. Sperm mobility: A quantitative trait of the domestic fowl (Gallus domesticus). Biol. Reprod. 58:379−384. Froman, D. P., A. J. Feltmann, and D. J. McLean, 1997. Increased fecundity resulting from semen donor selection based upon in vitro sperm motility. Poultry Sci. 76:73−77. Froman, D. P., A. J. Feltmann, M. L. Rhoads, and J. D. Kirby, 1999. Sperm mobility: A primary determinant of fertility in the domestic fowl (Gallus domesticus). Biol. Reprod. 61:400−405. Froman, D. P., and D. J. McLean, 1996. Objective measurement of sperm motility based upon sperm penetration of Accudenz.威 Poultry Sci. 75:776−784. Holsberger, D. R., A. M. Donoghue, D. P. Froman, and M. A. Ottinger, 1998. Assessment of ejaculate quality and sperm characteristics in turkeys: Sperm mobility phenotype is independent of time. Poultry Sci. 77:1711−1718. King, L. M., and A. M. Donoghue, 2000. Adaptation of the sperm mobility test for identification of turkey toms with low fertilizing potential. J. Appl. Poult. Res. 9:66–73. Rhoads, M. L., J. Washington, D. P. Froman, and J. D. Kirby, 1998. Use of the sperm mobility assay to predict sperm fertilizing ability in broiler breeder males. Poultry Sci. 77(Suppl. 1):91. (Abstr.). SAS Institute Inc., 1985. SAS User’s Guide. Version 5 ed. SAS Institute Inc., Cary, NC. Wilson, H. R., N. P. Piesco, E. R. Miller, and W. G. Nesbeth, 1979. Prediction of the fertility potential of broiler breeder males. World’s Poult. Sci. J. 35:95−118. Wishart, G. J., 1995. New approaches to evaluating male and female fertility. Pages 207−223 in: Proceedings from the First International Symposium on the Artificial Insemination of Poultry. Poultry Science Association, Savoy, IL.
