Effects of season and breed on sperm acrosin activity
and semen quality of boars
A. Ciereszko
a,∗, J.S. Ottobre
b, J. Glogowski
aaDepartment of Molecular Andrology, Institute of Animal Reproduction and Food Research,
Polish Academy of Sciences, 10-747 Olsztyn, Poland
bDepartment of Animal Sciences, Ohio State University, Columbus, OH 43210, USA
Received 24 December 1999; received in revised form 27 June 2000; accepted 2 August 2000
Abstract
Acrosin activity and semen quality (sperm concentration, ejaculate volume and number of sper-matozoa) were assessed from March 1997 to March 1998 in semen of Large White, Pietrain and Duroc×Pietrain boars. Semen quality varied with season, including high production of sperma-tozoa in autumn and winter and low production in summer. Semen quality also differed across breeds. Acrosin activity of boar spermatozoa was not affected by breed (range 3.16–3.32 mU/106 spermatozoa), but exhibited distinct seasonal changes. Monthly changes in acrosin activity were parallel to changes in number of sperm in the ejaculate from November to March. On the other hand, dramatic changes in acrosin activity between July and October (range 1.85–4.59 mU/106 spermatozoa) were not paralleled by similar changes in number of ejaculated sperm. These fluctu-ations in acrosin activity may reflect either changes in sperm acrosin production or disturbances to sperm membranes, probably related to effects of high summer temperatures during spermatogene-sis. Results confirmed seasonal and breed-related differences in boar semen quality characteristics. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Pig-male; Breed; Reproduction; Spermatozoa; Semen; Acrosin; Seasonal dynamics
1. Introduction
The use of artificial insemination (AI) in the pig industry is increasing. Although cryopre-served semen is not available, methods for short-term storage (at least 3 days) are acceptable enough to use AI for pig breeding programs. Boars consistently producing high-quality ejac-ulates are crucial in AI programs, due to the limited number of insemination doses that can be obtained from one ejaculate. Unfortunately, sperm production of boars may fluctuate up as much as 25–30% throughout the year, forcing AI centers to keep additional boars
∗Corresponding author. Tel.:+48-89-535-7426; fax:+48-89-535-7421.
E-mail address: acieresz@food.irzbz.pan.olsztyn.pl (A. Ciereszko).
to compensate for these fluctuations (Colenbrander and Kemp, 1990). Therefore, better knowledge of factors influencing both quantity and quality of semen may help to improve the efficiency of AI organizations.
Recently, we have optimized a clinical acrosin assay for boar spermatozoa (Glogowski et al., 1998). This assay was originally developed for human spermatozoa and employed for evaluation of sperm quality (Kennedy et al., 1989). The current study was designed to determine the effects of breed and season on acrosin activity, and semen quality character-istics. Acrosin activity was not affected by breed, but activity exhibited distinct seasonal changes. These changes were especially dramatic from July to November. Semen quality characteristics were affected by both breed and season.
2. Materials and methods
2.1. Source of semen
Semen was collected from March 1997 to March 1998 from adult boars 17–22 months of age. The following breeds were used: Large White (n = 3), Pietrain (n = 3), and Pietrain×Duroc (n = 5). Boars were housed at the Animal Breeding and Insemination Station in Olsztyn and were used in an AI program. Semen was collected five or six times per month and we sampled about three ejaculates per month for analysis. Semen was collected manually into a cup with a filter (enabling us to discard the gel fraction).
2.2. Determination of semen volume, sperm concentration, and acrosin activity
Table 1
Effect of breed on sperm characteristics and acrosin activity of Large White, Pietrain and Pietrain×Duroc boarsa
Sperm feature Large White Pietrain Pietrain×Duroc
N Acrosin activity (mU/106spermatozoa) 3.31±0.93 a 3.16±0.87 a 3.26±0.84 a
aData are expressed as means±S.D. Means followed by different letters within the rows are significantly
different (P <0.001 for sperm concentration and for ejaculate volume andP <0.01 for number of sperm in ejaculate).
of Triton X-100 was 0.005%. These changes were introduced as a result of optimization experiments (Glogowski et al., 1998). Due to a high acrosin activity of boar spermatozoa (about 100 times higher than in human spermatozoa) we expressed this activity as mU/cm3 rather thanmU/cm3. All assays were done in triplicate.
2.3. Statistical analysis
The data for each boar were averaged for each month. Data were subjected to two-way ANOVA. A Tukey’s test was used for post-hoc comparisons. No significant breed-by-season interactions were observed, therefore we were able to make general statements for breed and season. All calculations were performed using the statistical package STATISTICA (StatSoft, Inc., Tulsa, Oklahoma, USA).
3. Results
We found significant differences in semen quality characteristics among breeds (Table 1). Pietrain boars produced semen with lowest volume and number of sperm in ejaculate and highest sperm concentration. The highest semen volume and lowest sperm concentrations were recorded for Large White boars. On the other hand, no differences in acrosin activities were found among breeds.
Fig. 1. Effect of season on sperm acrosin activity and number of spermatozoa in ejaculate of boar semen. Data are presented as mean±S.E.M. Means followed by different superscripts are different (P <0.05).
4. Discussion
Our results indicated that breed affected semen quality characteristics, but not acrosin activity. These results suggested, that selection within swine breeds produced differences in spermatogenic activity and/or efficiency of accessory glands. On the other hand it seems, that selection pressure did not affect amounts of acrosin in spermatozoa. This suggests acrosin may be important for sperm function, since its concentration did not vary among breeds.
Fig. 2. Effect of season on ejaculate volume and sperm concentration of boar semen. Data are presented as mean±S.E.M. Means followed by different superscripts are different (P <0.05).
has been recently seriously challenged, and it is now claimed that acrosomal hydrolases are not crucial for mammalian fertilization (Bedford, 1998). It is also not clear now if BAPNA-hydrolyzing activity of mammalian spermatozoa is exclusively related to acrosin, as it was claimed before (Kennedy et al., 1989). Recent results of Yamagata et al. (1998) suggest that other (non-acrosin) protease(s) are present in mammalian spermatozoa and that these protease(s) may have a basic function in penetration of the zona pellucida.
Sperm quality characteristics exhibited clear seasonal changes. The cause(s) of seasonal fluctuations in semen quality are not fully understood, but likely are mediated by hormonal mechanisms controlled by photoperiod (Claus et al., 1985a,b). Clearly an ancient mecha-nism characteristic for the European wild pig, is still present in modern commercial swine breeds.
The European wild pig is a seasonal breeder and does not mate during the summer and fall months (Mauget and Boissin, 1987). For this reason, the lowest reproductive performance of commercial swine is observed in summer (Xue et al., 1994). Ancient seasonal mechanisms likely still influence semen characteristics of boars, especially semen volume and number of sperm in the ejaculate. These characteristics are highest in the fall and winter (Slaweta and Strzezek, 1984; Cameron, 1985; Trudeau and Sanford, 1986a; Borg et al., 1993). This was also confirmed in the current work. On the other hand, many other factors may modify semen characteristics of the boar, including high ambient temperature leading to heat stress (McNitt and First, 1970), frequency of semen collection (Strzezek et al., 1995) and age (Kennedy and Wilkins, 1984). However in our study, frequency of semen collection and age of boars were within the range of values which do not affect semen quality (Kennedy and Wilkins, 1984; Strzezek et al., 1995) and social environment and nutrition were the same for all boars. For this reason we believe that our data reflect mainly seasonal changes of semen quality characteristics. However, it is difficult to determine if changes in acrosin activity observed in our work are general across years or specific for a particular year, because our experiment was restricted to 13 months. A significant difference in acrosin activity between March 1997 and 1998 suggests that these changes might be specific for the year. To more fully characterize the repeatability of seasonal changes in acrosin activity would require studies such as the current one carried out for multiple years.
Acrosin activity exhibited distinct seasonal changes. These changes however, only par-tially overlapped those of semen quality characteristics. The greatest similarity between changes in activity and number of spermatozoa per ejaculate was from November to March. However, the most striking change in acrosin activity occurred between July and November, when, first a rise in August took place followed by a rapid decline by more than 100% by October and then a rebound by more than 100% occurred in November.
hand, if a decrease in the quality of sperm membranes occurred, extensive washing before the acrosin assay may result in a loss of acrosin. However, significant losses of acrosin are unlikely because the majority of its activity is sperm-bound (De las Heras et al., 1996). The latter authors suggest that alterations in acrosin activity may be related to different ac-cessibility to BAPNA or inhibitors, dissociation of acrosin complexes, and rates of acrosin activation and inactivation. Further studies, including testing of mRNA levels for acrosin, are necessary to clarify a reason for a decrease of acrosin activity in September and October. Recent data of Kokolis et al. (2000) indicate dramatic changes in ram sperm acrosin activity during a short time in response to melatonin. This supports the idea that dramatic changes in acrosin activity can occur over short intervals.
In summary, our results confirm seasonal and breed-related differences in boar semen quality characteristics. Acrosin activity of boar spermatozoa was not affected by breed, but exhibited distinct seasonal changes. These changes were partially parallel to that of number of sperm in ejaculate (from November to March). On the other hand, dramatic changes in acrosin activity were observed between July and October. These changes may reflect either changes in sperm acrosin concentrations or disturbances to sperm membranes.
Acknowledgements
We thank Ms. Halina Karol and Ms. Dorota Kubiak for excellent technical assistance; the personnel of Animal Breeding Station in Olsztyn for providing boar semen.
References
Bedford, J.M., 1998. Mammalian fertilization misread? Sperm penetration of eutherian zona pellucida is unlikely to be lytic event. Biol. Reprod. 59, 1275–1287.
Borg, K.E., Lunstrs, D.D., Christenson, R.K., 1993. Semen characteristics, testicular size, and reproductive hormone concentrations in mature Duroc, Meishan, Fengjing, and Minzhu boars. Biol. Reprod. 49, 515–521. Cameron, R.D.A., 1985. Factors influencing semen characteristics in boars. Aust. Vet. J. 62, 293–297. Claus, R., Schopper, D., Wagner, H.-G., Weiler, U., 1985a. Photoperiodic influences on reproduction of domestic
boars. I. Light influences on testicular steroids in peripheral blood plasma and seminal plasma. Zbl. Vet. Med. A 32, 86–98.
Claus, R., Weiler, U., Wagner, H.-G., 1985b. Photoperiodic influences on reproduction of domestic boars. II. Light influences on semen characteristics and libido. Zbl. Vet. Med. A 32, 99–109.
Colenbrander, B., Kemp, B., 1990. Factors influencing semen quality in pigs. J. Reprod. Fertil. 40 (Suppl.), 105–115.
Crozet, N., 1993. Fertilization in vivo and in vitro. In: Thibault, C., Levasseur, M.-C., Fraser, R.H.F. (Eds.), Reproduction in Mammals and Man. Elipses, Paris, pp. 327–347.
De las Heras, M.A., Valcarcel, A., Furnus, C., Perez, L., Moses, D., Baldassarre, H., 1996. Changes in sperm-bound amidase activity suggest subtle damage to ram sperm acrosomes by freezing/thawing, not detected by light microscopy. Anim. Reprod. Sci. 45, 81–89.
Glogowski, J., Demianowicz, W., Piros, B., Ciereszko, A., 1998. Determination of acrosin activity of boar spermatozoa by the clinical method: optimization of the assay and changes during short-term storage of semen. Theriogenology 50, 861–872.
Heitman, H., Cockrell, J.R., 1984. Cycling ambient temperature effect on boar semen. Anim. Prod. 38, 129–132. Kennedy, B.W., Wilkins, J.N., 1984. Boar, breed and environmental factors influencing semen characteristics of
Kennedy, W.P., Kaminski, J.M., Van der Ven, H.H., Jeyendran, R.S., Reid, D.S., Blackwell, J., Bielfeld, P., Zaneveld, L.J.D., 1989. A simple clinical assay to evaluate the acrosin activity of human spermatozoa. J. Androl. 10, 221–231.
Kokolis, N., Theodosiadou, E., Tsantarliotou, M., Rekkas, C., Goulas, P., Smokovitis, A., 2000. The effect of melatonin implants on blood testosterone and acrosin activity in spermatozoa of the ram. Andrologia 32, 107–114.
Larsson, K., Einarsson, S., 1984. Seminal changes in boars after heat stress. Acta Vet. Scand. 25, 57–66. Mauget, R., Boissin, J., 1987. Seasonal changes in testis weight and testosterone concentration in the European
wild boar (Sus scrofa L.). Anim. Reprod. Sci. 13, 67–74.
McNitt, J.I., First, N.L., 1970. Effects of 72-hour heat stress on semen quality in boars. Int. J. Biometeorol. 14, 373–380.
Slaweta, R., Strzezek, J., 1984. The season of year and biological properties of preserved boar’s semen. Med. Vet. 10, 619–622.
Strzezek, J., Kordan, W., Glogowski, J., Wysocki, P., Borkowski, K., 1995. Influence of semen-collection frequency on sperm quality in boars, with special reference to biochemical markers. Reprod. Domest. Anim. 30, 85–89. Trudeau, V., Sanford, L.M., 1986a. Effect of season and social environment on testis size and semen quality of the
adult Landrace boar. J. Anim. Sci. 63, 1211–1219.
Trudeau, V., Sanford, L.M., 1986b. Season and social environment influence the membrane integrity of ejaculated boar spermatozoa as assessed by oubain sensitivity. Can. J. Physiol. Pharmacol. 64, 1407–1412.
Wetteman, R.P., Bazer, F.W., 1985. Influence of environmental temperature on prolificacy in pigs. J. Reprod. Fertil. 33 (Suppl.), 199–208.
Xue, J.-L., Dial, G.D., Marsh, W.E., Davies, P.R., 1994. Multiple manifestations of season on reproductive performance of commercial swine. J. Am. Vet. Med. Assoc. 204, 1486–1489.
