Comparative study onsemen quality of one- and two-year-old ganders during the entire reproductive season
Ewa Lukaszewiczl, Hiroki Furuta1, Yong-Mei Xi2, Noboru Fujihara1
Poultry Breeding Department, Agricultural University, 51-631 Wroclaw, Poland
1Animal Resource Science Section, Division of Bioresource and Bioenvironmental Sciences, Graduate School Kyushu University, Fukuoka 812-8581, Japan
2Captive Feeding and Breeding Center for Crested Ibis, Yangxian, Shaanxi 723300, China
Asian J Androl2000Jun; 2: 139-142
Keywords:gander; age difference; reproductive season; semen; spermatozoa
Abstract
Aim:To evaluate the characteristics of semen produced by one- and two-years old White Italian ganders during the entire reproductive season, in order to clarify whether the young ganders are responsible for a low fertility rate in young geese.Methods:Males were kept individually in cages under natural light.Semen was collected by dorso-abdominal massage three times a week and routine examination was performed. Results:The mean ejaculate volume (2.1 and 1.6 mL, respectively) and sperm concentration (323 and 281106/mL, respectively) in one-year-old ganders were higher than those of two-year-old ones. The percentages viable spermatozoa of one- and two-year-old ganders were similar (91.4 and 92.3%, respectively), but the percentage of normally formed viable spermatozoa was significantly higher in the older ganders than in the younger (47.8 and 42.9%, respectively,P<0.05). Conclusion:The semen from one- or two-year-old Ganders were similar in regard to volume, sperm density and spermmotility, but the percentage of normally formed viable spermatozoa, which is critical for fertilization, was significantly higher in the older ganders. It appears that the ganders are responsible for the low fertility rate in young geese.
1Introduction
In contrary to most domestic birds, geese have a short seasonal reproductive cycle, but they can be used as the breeding flock for up to 4-6 years of age without evident decrease in fertility potency[1-4]. Although it has been indicated that even 14 years old ganders are still able to produce semen and females to laid eggs (Lukaszewicz, 1997, unpublished data), for economic reasons, it is generally accepted to keep the breeding geese for 3-4 years.
It is well documented that the fertility rate is lower in one-year-old geesethan in 2- or 3-year-old ones either mated naturally or artificially inseminated, despite of the fact that during the reproductive seasons (usually from January to May), the egg production rates are similar for these age groups. Then one may ask: is it the young ganders that are responsible for the lower fertility rate of young geese? The present work was a comparative study on the semen quality in one- and two-year-old ganders in order to answer the above question.
2Materials and methods
2.1 Animals
Two groups of 9 White Italian (Anseranser) ganders each were used. The One-Year Group consisted of ganders of 9 months old and the Two-Year Group, ganders of 2 year-old. Semen was collected three times a week by the dorso-abdominal massage method at the same time (9:30-10:00 AM) and by the same three technicians. Animals were placed in individual cages for the whole reproductive season. The reproductive season of the 2-year-old animals starts at the end of December to the second decade of June next year; the younger animals start a littlelater. The caged ganders had visual and acoustic contact with the females, and were housed under natural light and fed with the commercial food for breeding geese, 400-500 g per day per bird.
2.2 Semen examination
Routine semen examination, including semen volume, color, and consistency, sperm motility, concentration and morphology, and blood or fecal contamination, was performed with the freshly collected semen.
Sperm concentration was estimated with a hemocytometer, motility, by visual scoring on microscope slides, and morphology, on smears stained with nigrosin-eosin and examined under oil immersion objective (1250). Dead spermatozoa are stained with the dye, but not the viable ones. In each smear, 300 spermatozoa were counted and classified into the following categories:
0 - Viable spermatozoa in total (including forms 1-6).
1 - Viable spermatozoa with normal morphology (typical spindle-shaped head and well-marked acrosome, and each part of the spermatozoa blends into the other, from head to tail).
2 - Bulb-head spermatozoa.
3 - Crocked-necked spermatozoa (with broken head-midpiece junction).
4 - Spermatozoa with changed midpiece (lack of mitochondrial sheath, with swollen or slightly pinkish midpiece).
5-Immature spermatozoa.
6 - Spermatozoa with other deformities.
7 - Dead spermatozoa (completely or partially stained spermatozoa).
2.3 Statistical analysis
The data were expressed inmeans, if applicable. The student'st-test was employed to analyze the significance of differences with the use of MS Excel 97 software andP<0.05 was considered significant.
3 Results
Taking into consideration the whole reproductive season, the semen volume and sperm concentration were higher in the one-year ganders than in the two-year ganders. From the second half of the reproductive season towards its end, a gradual drop of ejaculate volume was observed in both groups, while the sperm concentration remained unchanged (Table 1 andFigures 1and2). The percentage of total viable spermatozoa (Form 0) in the semen of the two groups was similar, while the percentage of the Form 1 was significantly higher in the 2-years ganders than in the 1-year (Figure 3and Table 1). Similar to the semen volume, a drop in the percentage of Form 1 spermatozoa at the second half of the breeding season (Figure 3) was also observed. The percentage of spermatozoa with abnormal morphology (Forms 2-6, Table 1) was higher in the younger than in the older ganders, though statistically insignificant.
Table 1. Semen data of one and two year-old ganders.n=9. means.bP<0.05,cP<0.01vsthe 2-years group.
Age(year) / Volume(mL) / Sperm Conc.(106/mL) / Sperm classification
0 / 1 / 2 / 3 / 4 / 5 / 6 / 7
1 / 2.10.6c / 32393 / 91.44.4 / 42.911.0b / 26.510.1 / 10.33.2 / 6.22.3 / 4.42.1 / 1.10.8 / 8.64.4
2 / 1.60.6 / 291157 / 92.34.6 / 47.813.4 / 24.711.0 / 9.33.2 / 6.02.5 / 3.81.4 / 0.80.9 / 7.74.6
Figure 1. Semen volume during the entire reproductive season.
Figure 2.Sperm concentration during the entire reproductive season.
Figure 3.Percentage of Form 0 and Form 1 viable sperm.
The sperm motility in both groups was rather poor and only 50-60% of spermatozoa demonstrated positive movement, which is rather typical for geese of these age groups.
4 Conclusions
Proper selection and training of ganders for semen collection procedure prior to the onset of experiment was essential for obtaining good quality and clean semen during the observation period. However, due to the specific structure of the copulatory organ in the ganders, ejaculates contaminated with feces and urine were occasionally encountered. The present data suggest that spermatogenesis in young gander may not be fully matured with the production of low quality semen. However, for the documentation of this observation further investigation is required. The lower quality semen produced by younger ganders may be to some extent compensated by a higher ejaculate volume and higher sperm concentration.
Since at the first half of the reproductive season, ganders of both groups produce semen of higher quality and quantity, more frequent semen collection (say every other day) for artificial insemination may be practiced. At the second half of the reproductive season semen collection should be reduced to twice a week.
As a conclusion, the authors believe that one-year ganders may be responsible for the lower fertility rate of the younger geese, as at this time the concentration of the normal formed viable spermatozoa critical for fertilization, islower.
References
[1] Bielinski K. The age and reproductive performances of White Italian geese (in Polish). Drobiarstwo 1982; 6: 2-5.
[2] Borys H, Stasiak K, Bielinska K.Investigations on quality and quantity of gander semen (in Polish). RoczNauk Zoot 1978; 5: 55-61.
[3] Rosinski A, Bielinski K, Bielinska K.The results of geese reproduction in the same flock during subsequent three years (in Polish). RoczNauk Zoot 1986;13: 127-32.
[4]Toth S.Investigation on sperm production of ganders during successive production periods. Bull UnivAgricSciGodollo 1988; 1: 65-9.