Selection of Young Broiler Breeders for Semen Quality Improves Hatchability in an Industry Field Trial 1

Transcription

1 2002 Poultry Science Association, Inc. Selection of Young Broiler Breeders for Semen Quality Improves Hatchability in an Industry Field Trial 1 H. M. Parker and C. D. McDaniel 2 Poultry Science Department, Mississippi State University, Mississippi State, Mississippi Primary Audience: Broiler Breeder Supervisors, Primary Breeding Companies, Researchers SUMMARY Previous laboratory research has shown that the sperm quality index (SQI) is predictive of broiler breeder fertility. The SQI is a tool to estimate overall semen quality by monitoring the number of times that sperm movement causes deflections within a light path. An industry field trial was undertaken to determine if life of flock hatchability could be improved by selecting young males for house placement based on the SQI. The SQI was used to select males at 26 wk of age. Males with an SQI in approximately the top 80% of the population were moved into two hen houses, whereas the lower 20% of the SQI population was culled. Two control houses received males selected solely on physical appearance. Life of flock hatchability was improved by 1.1% in the SQI-selected houses over that of males selected for house placement based on physical characteristics alone. The males selected for the SQI numerically outperformed the control males in 64% of the hatches with the greatest difference in hatch occurring during postpeak production. This increase in hatch resulted in 21,000 more chicks being produced in the two houses containing SQI-selected males. In conclusion, the SQI is a useful tool for accurately identifying the reproductive ability of broiler breeder roosters throughout a complete laying cycle. Key words: broiler breeder, fertility, hatchability, semen, sperm quality index 2002 J. Appl. Poult. Res. 11: DESCRIPTION OF PROBLEM In the poultry industry, there are no breeding soundness evaluations per se. At hen-house placement, roosters are selected based on physical characteristics associated with a reproductively mature male. Such characteristics are comb and wattle size and color as well as over- all body size and shank length [1]. Males that are underweight or that have bad legs are culled and not used. However, Wilson and colleagues [1] showed that physical characteristics are not strongly predictive of male fertility (r < 0.5). Prior to or during hen-house placement, semen characteristics of broiler breeders can be evaluated. According to Donoghue [2], semen 1 This is Journal Article No. J9946 from the Mississippi Agriculture and Forestry Experiment Station supported by MIS Use of trade names in this publication does not imply endorsement by the Mississippi Agricultural and Forestry Experiment Station of the products or of similar ones not mentioned. 2 To whom correspondence should be addressed: cmcdaniel@poultry.msstate.edu.

2 PARKER AND MCDANIEL: SEMEN SELECTION IMPROVES HATCH 251 evaluation tests can be a valuable tool in the management of roosters or toms. The main objective of evaluating semen quality should be to predict the fertility of an individual male [3]. However, Donoghue [2] stated that semen quality tests currently available to the poultry industry are time-consuming, labor intensive, and unreliable predictors of fertility and semen quality. If a quick and accurate semen quality test was available to predict fertility, males could be chosen for hen-house placement based on semen quality and not physical characteristics alone. By testing roosters for semen quality, fertility and, ultimately, hatchability could be improved. One method of semen analysis that is quick and has been correlated to sperm concentration, viability, and motility in rooster [4] and mammalian semen [5, 6, 7, 8] is the sperm quality index (SQI). The SQI is generated by the OptiBreed sperm quality analyzer (SQA) in 20 s. The analyzer has a photocell that monitors the number of times sperm movement disrupts a path of light. In a laboratory trial using artificial insemination, Parker and colleagues [9] selected males based on the SQI. They demonstrated that by removing males whose semen quality ranked in the lowest 22% of the SQI population, fertility was increased by as much as 4% over an unselected population. In a different artificial insemination study, Parker and colleagues [10] found that semen from males in the lowest 25% of the SQI population fertilized approximately 20% fewer eggs when compared to semen from males in the upper 75% of the SQI population. As a result of previous mammalian and avian research using the SQI, it was reasoned that this method of semen evaluation could be used to select roosters within the poultry industry for improved reproductive performance. Therefore, this research was undertaken to determine if selection of young males for the SQI would improve life of flock hatchability in an industry field trial. MATERIALS AND METHODS The males and females utilized in this field trial were hatch mates and reared on the same pullet farm. All males (Avian) used in this study were reared in one cockerel house. The pullets (Avian) were reared in two pullet houses. At 22 wk of age, 36,000 pullets were divided into four hen houses equally, on a single hen farm. Each hen house contained approximately 9,000 pullets. Also, at 22 wk of age, 1,800 males were divided and placed into two of the four hen houses (controls). Each of these two control houses received 900 males that were chosen for house placement based solely on general physical appearance. The integrator was unwilling to move the males that were to be selected for the SQI in with the hens at the same time as the control males. The integrator did not want to risk disrupting egg production in the SQI-selected houses by penning roosters in the hen house for semen collection and SQI testing. As a result, the males utilized for SQI testing remained in the cockerel house until they were 26 wk of age, and only the control birds were moved in with the hens at 22 wk of age. Also, by keeping the males in the cockerel house, mating activity with hens was eliminated, therefore semen volume was increased. To establish a preliminary assessment of semen quality for the males remaining in the cockerel house, approximately 9% of the males were individually tested for the SQI at 25 wk of age. This initial testing was performed to obtain a preliminary distribution of the SQI population and to establish an approximate SQI value that would be utilized for culling males with SQI values in approximately the lowest 20% of the population. The SQI of each male was determined by diluting the semen 10-fold with 0.85% saline [9, 10, 11]. Beginning at 26 wk of age, all males remaining in the cockerel house were individually tested for the SQI. An assembly line was created so that two semen diluters and two SQA operators could be utilized at the same time. One person collected semen for this assembly line. The minimum semen volume desired for each test was 50 µl. Each male was numbered 1 through 6 on the wattle, using a black marker, and placed into a cage with a corresponding number. Individual males were held in these cages until an SQI reading was obtained and it was determined what SQI holding pen the male should be placed. Pens held

3 252 JAPR: Research Report FIGURE 1. Weekly percentage of males relative to females. Each point represents the mean percentage of males each week for the sperm quality index-selected males (open symbols) and control males (closed symbols) (P > 0.84). males with SQI values of < 350, 350 to 400, or > 400. The SQI values for these holding pens were established utilizing approximate SQI culling values from the preliminary distribution obtained at Week 25. For each male, it took approximately 1 minute to complete semen collection, SQI determination, and pen placement. Three days were required to test and select males based on the SQI. The males with an SQI in approximately the bottom 20% of the SQI population were culled. The culled males were not used in this study. After SQI selection, the males were moved into the two treated hen houses to yield the same male to female ratio as was present in the two control hen houses at that time (9:100). In all houses, both treated and control, hens and roosters were feed restricted according to FIGURE 2. Weekly egg production. Each point represents the mean egg production for houses containing the sperm quality index-selected males (open symbols) and control males (closed symbols) (P > 0.16).

4 PARKER AND MCDANIEL: SEMEN SELECTION IMPROVES HATCH 253 FIGURE 3. Weekly body weights of males. Each point represents the mean body weight each week for the sperm quality index-selected males (open symbols) and control males (closed symbols) (P > 0.98). primary breeder recommendations. Approximately 5% of the males in each house were weighed by the integrator weekly from hen house placement to 40 wk of age and monthly thereafter. The birds received 14 h of light at placement, 15 h at 5% egg production, and 16 h at 25% egg production. The males remaining in the cockerel house received the same lighting protocol as the control houses. From the time the birds were 29 to 51 wk of age, hatchability data for each house were obtained weekly from the local company hatchery. The birds in all houses utilized in this trial contracted Mycoplasma synoviae and were destroyed at 51 wk of age. Therefore the data collected for 22 wk of hatches were analyzed using ANOVA [12] with a split plot in time. Each hen house was an experimental unit. RESULTS AND DISCUSSION Because it was thought that SQI testing may interrupt egg production, company management required that this procedure be performed prior to hen house placement of males. Therefore, SQI-tested cockerels were moved 4 wk after controls. Cumulative male mortality from 22 to 26 wk of age was higher for the males maintained in the cockerel house versus the males that were placed in the hen house (10% and 5% respectively, SEM = 0.35, P < 0.05). According to Craig [13], when birds are provided excessive floor space, agonistic behavioral levels increase. Therefore, increased aggression may have resulted in increased mortality in the cockerel house. During this period, control males were allowed to mate with hens, while the males maintained in the cockerel house were not. After selecting males for the SQI and moving them to the hen house, the percentage of males relative to females remained the same for the two treatment groups, due to similar mortality, throughout the trial (Figure 1). In addition, there were no significant differences in egg production of the hens (Figure 2) or body weight of the males (Figure 3) between the control and treated houses throughout this trial. The preliminary SQI population distribution at 25 wk of age (approximately 9% of the population) is represented in Figure 4. The majority of the males tested had an SQI that ranged from 441 to 520 U. The mean for the preliminary population was 451 U. The preliminary population distribution revealed that the 20% cull point for this sample population was an SQI 400 U (Figure 5). Therefore, the top 80% of the population had an SQI 401 U and higher as predicted by this sample population. When the males were tested at 26 wk of age, the overall population distribution (Figure

5 254 JAPR: Research Report FIGURE 4. Distribution of the sperm quality index (SQI) in a 25-wk-old male population used to establish the preliminary SQI selection value for culling the lowest 20% of the population. Each bar represents the number of males grouped by every 40 U of SQI (n = 183). 6) differed slightly from the preliminary distribution that had been established the prior week. Most of the males (n = 622) had SQI values between 450 to 499, and the mean for the total population tested was 404 U. The overall SQI population, therefore, was skewed to the right (w = 0.86). This skewed SQI population is similar to that reported by Parker and colleagues [9]. However, they reported a lower overall population mean than in the present trial. This difference in means could be due to the utilization of a different strain of bird. It is possible that semen characteristics and age of sexual maturity varies among broiler breeder strains [14]. The cumulative percentage distribution of SQI in the 26 wk old population with the final cull point is represented in Figure 7. All birds with an SQI lower than 350 were culled, so that approximately 77% of the original population was kept. By culling the bottom 23% of the SQI population, the mean SQI for the population was raised from 404 to 446 U. The mean (404 U) and cull point (350 U) utilized for this trial was approximately 50 U lower than the mean and cull points (451 and 400 U, respectively) established the previous week for the preliminary distribution. To obtain the preliminary distribution, approximately 9% of the population was tested. This discrepancy in population means and cull points could be due to inadequate numbers of males tested when establishing the preliminary SQI distribution the previous week. Another possibility is that semen quality of the males may not have stabilized by 25 wk of age, because males were still maturing sexually after that time [14]. More recently it was found that for one strain of

6 PARKER AND MCDANIEL: SEMEN SELECTION IMPROVES HATCH 255 FIGURE 5. Cumulative percentage distribution of the sperm quality index (SQI) in a 25-wk-old male population. Each bar represents the number of males grouped by every 40 U of SQI (n = 183). broiler breeder males semen quality did not stabilize until 29 wk of age [10, 11]. However, once males reach sexual maturity, their SQI rank in the population does not appear to change substantially with age [9, 11]. Similar results were reported by Holsberger and colleagues for sperm mobility of turkey toms [15]. They revealed that toms grouped by sperm mobility phenotype maintained their rank in the population over 5 months of semen production. There was a significant interaction between treatment and age (P < ) for hatchability of eggs set as represented in Figure 8. Hatchability of the males selected for the SQI was significantly greater than that of the control males at Weeks 32, 36, 37, 41, 47, 49, and 50. Table 1 further breaks down hatchability by treatment and production period. When comparing prepeak hatchability (Weeks 29 to 35) for each treatment, the birds in the SQI-selected houses and control houses had similar hatchabilities (88.6 and 88.0, respectively). This occurred despite the fact that the SQIselected males were placed with the hens 4 wk after the control roosters. In fact, hatchability for the first full hatch obtained from these birds at 29 wk of age was similar for both the control and SQI-selected males. Apparently, the SQIselected males either did not require a lengthy period to adjust to socialization in the hen house, or semen quality was better for these males so that fewer matings were required. The SQI-selected males significantly outperformed the control males during the postpeak period (Weeks 36 to 51). In addition, life of flock hatchability for the SQI-selected males was 1.1% higher than that of the control males (Table 1). It is possible that if the SQI-selected roosters had been placed with the hens at the same time as the control males, there could have been even a greater increase in life of flock and postpeak hatchability due to SQI selection of roosters. Research has shown that body weight is negatively correlated with fertility [1]. However, body weight was similar for the control and SQI-selected males throughout the trial. It also has been suggested that libido declines as the rooster ages [16]. Even though libido might be decreasing with age, semen quality could be superior for the

7 256 JAPR: Research Report FIGURE 6. Distribution of the sperm quality index (SQI) in the total 26-wk-old male population. Each bar represents the number of males grouped by every 40 U of SQI (n = 1,945). The population of males was skewed to the right (w = 0.86, skewness 1.47, kurtosis 2.6). SQI-selected males. Another possibility for this difference in postpeak hatchability is that semen quality in the control males was declining at a faster rate than the SQI-selected males. Overall, the SQI-selected males had numerically higher hatchabilities than the control males in 64% of the hatches (14 of 22 hatches). Data are needed after 51 wk of age to see if this improvement in hatchability for the SQIselected males would continue. In order for an egg to hatch, it must first be fertilized, and flocks with high fertility have the best potential for excellent hatchability [17]. The hatchability results of this trial are similar to the fertility results that Parker and colleagues [9] found when utilizing artificial insemination. They found that, by culling the lowest 22% of the SQI population, they were able to improve fertility. Unfortunately, the hatchery utilized in the current trial was not able to furnish fertility data. However, it is quite possible that fertility of the flocks containing SQI-selected males was improved in this trial because life of flock hatchability improved 1.1 percentage points by culling the lowest 23% of the SQI population. This increase in hatchability resulted in approximately 21,000 more chicks being produced in the SQI treated houses. According to Pollock [18], if an integrator producing 15 million eggs per week could improve hatchability by just 1%, weekly profits would be increased by $30,000. This increase in hatch due to the use of the SQI could be achieved by all integrators, whether they are broiler or turkey producers or even primary breeders. For example, turkey producers utilize artificial insemination and collect semen from each tom individually. Neuman and colleagues [19, 20] have already

8 PARKER AND MCDANIEL: SEMEN SELECTION IMPROVES HATCH 257 FIGURE 7. Cumulative percent distribution of the sperm quality index (SQI) in the 26-wk-old male population. Each bar represents the number of males grouped by every 40 U of SQI (n = 1,945). The black arrow represents the cull point utilized in this field trial. shown that the SQI is indicative of turkey semen quality. Prior to movement into the tom houses, each male could be semen tested to obtain a more accurate assessment of fertilizing potential. By doing so, subfertile toms could be culled, allowing the integrator to utilize toms with superior semen quality. The semen from superior toms could be extended more than that of inferior toms, which would increase the number of poults produced [2] per tom housed. It has been revealed that artificial insemination doses could be reduced in half without negatively affecting fertility, if roosters are used based on their SQI [11]. According FIGURE 8. Weekly hatchability of eggs set data. Each point represents the mean hatchability for the sperm quality index (SQI)-selected males (open symbols) and control males (closed symbols). *Significant difference between control and SQI-selected males for a given week of age (treatment by age interaction; P < ).

9 258 JAPR: Research Report TABLE 1. Comparison of prepeak, postpeak, and life of flock hatchability of eggs set Prepeak, Postpeak, Life of flock, Weeks Weeks Weeks SQI selected Control (difference) P < to Amman [21], 0.1 ml of rooster semen at the great-grandparent level is worth approximately $125. The SQI would allow a primary breeder to extend the semen of an elite male over more females, maximizing his genetic potential. Many factors affect fertility in poultry, and because of the small number of males in a house relative to hens, the rooster is responsible for a greater percentage of flock fertility than the hen [1]. Because the male is so responsible for flock fertility, monitoring semen qual- ity throughout the reproductive life of a flock with the SQI could be beneficial to hatchability and integrator profits. For example, if a flock is experiencing low hatchability due to environmental or management problems, the SQI could be obtained for a sample of males in the flock. Thus, poultry managers would then know if a hatchability problem was due to poor semen quality. As a result, an informed decision could be made as how to best alter the environment surrounding the male so as to improve his reproductive potential. CONCLUSIONS AND APPLICATIONS 1. Selection of young broiler breeder males by the SQI prior to hen house placement, improved hatchability over selection of males based on traditional physical characteristics alone. 2. Use of the SQI could also benefit primary chicken breeders by allowing them to select males with superior semen quality. REFERENCES AND NOTES 1. Wilson, H. R., N. P. Piesco, E. R. Miller, and W. G. Nesbeth Prediction of the fertility potential of broiler breeder males. World s Poult. Sci. J. 35: Donoghue, A. M Prospective approaches to avoid flock fertility: Predictive assessment of sperm function traits in poultry. Poult. Sci. 78: Hammerstedt, R. H Evaluation of sperm quality: Identification of the subfertile male and courses of action. Anim. Reprod. Sci. 42: McDaniel, C. D., J. L. Hannah, H. M. Parker, T. W. Smith, C. D. Schultz, and C. D. Zumwalt Use of a sperm analyzer for evaluating broiler breeder males. 1. Effects of altering sperm quality and quantity on the sperm motility index. Poult. Sci. 77: Bartoov, B., J. Ben-Barak, A. Mayevsky, M. Sneider, L. Yogev, and A. Lightman Sperm motility index: a new parameter for human sperm evaluation. Fertil. Steril. 56: Johnston, R. C., G. N. Clarke, D. Y. Liu, and H. W. G. Baker Assessment of the sperm quality analyzer. Fertil. Steril. 63: Matilsky, M., M. Ben-Ami, V. Eyali, Y. Geslevieh, Y. Ben-Barak, and E. Shalev Correlation between sperm motility index as measured by the sperm quality analyzer and the outcome of intrauterine inseminations. Human Reprod. 8 (Suppl. 1):98. (Abstr.) 8. Zavos, P. M., J. R. Correa, and P. N. Zarmakoupis-Zavos Measurement of the sperm motility index via the sperm quality analyzer and its relationship to other qualitative sperm parameters. Theriogenology 46: Parker, H. M., J. B. Yeatman, C. D. Schultz, C. D. Zumwalt, and C. D. McDaniel. Use of a sperm analyzer for evaluating broiler breeder males. 2. Selection of young broiler breeder roosters for the sperm quality index increases fertile egg production. Poult. Sci. 79: Parker, H. M., A. G. Karaca, J. B. Yeatman, and C. D. McDaniel Fertility following selection for the OptiBreed Sperm Quality Index when hens are inseminated with a constant number of sperm. Poult. Sci. 80(Suppl. 1):45. (Abstr.) 11. Parker, H. M., A. G. Karaca, J. B. Yeatman, L. R. Frank, and C. D. McDaniel Fertility of broiler breeders following categorization by the OptiBreed Sperm Quality Index when hens are inseminated with a constant number of sperm. Poult. Sci. 81: SAS Institute The SAS System for Windows, Release SAS Inst. Inc., Cary, NC. 13. Craig, J. V Measuring social behavior in poultry. Poult. Sci. 71: Lake, P. E Factors affecting the fertility level in poultry, with special reference to artificial insemination. World s Poult. Sci. 39:

10 PARKER AND MCDANIEL: SEMEN SELECTION IMPROVES HATCH Holsberger, D. R., A. M. Donoghue, D. P. Froman, and M. A. Ottinger Assessment of ejaculate quality and sperm characteristics in turkeys: sperm mobility phenotype is independent of time. Poult. Sci. 77: Mauldin, J. M Applications of behavior to poultry management. Poult. Sci. 71: Eslick, M. L., and G. R. McDaniel Interrelationships between fertility and hatchability of eggs from broiler breeder hens. J. Appl. Poult. Res.1: Pollock, D. L Geneticist s perspective from within a broiler primary breeder company. Poult. Sci. 78: Neuman, S. L., C. M. Braun, and P. Y. Hester Utilization of a sperm quality analyzer to assess traits in male turkey breeders. Poult. Sci. 79(Suppl. 1):49. (Abstr.) 20. Neuman, S. L., C. D. McDaniel, J. Radu, L. Frank, and P. Y. Hester Use of the OptiBreed sperm quality analyzer for evaluating semen quality of turkey breeders. Poult. Sci. 80(Suppl. 1):172. (Abstr.) 21. Amann, R. P Lessons for the poultry industry gleaned from experiences with other commodity species. Poult. Sci. 78: