Seasonal variation in semen characteristics of
Chios and Friesian rams in Greece
A. Karagiannidis
a,*, S. Varsakeli
b, C. Alexopoulos
a, I. Amarantidis
a aClinic of Obstetrics and AI, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, 54006 Thessaloniki, GreecebNAGREF/Institute of Reproduction and AI of Thessaloniki, Ionia Thessaloniki, Greece
Accepted 17 November 1999
Abstract
Five Chios and ®ve Friesian rams were used to study the effect of season on semen production. Semen samples were collected with an arti®cial vagina. In spite of the large variation of most of the semen characteristics among rams of the two breeds, seasonal variation in semen quantity (volume, concentration and total number of spermatozoa per ejaculate) and quality (percentage of motile spermatozoa, sperm progressive motility and percentage of abnormal spermatozoa) were signi®cant (P< 0.05). The best semen was produced mainly during autumn and the worst during spring (semen volume: 1.47 ml in Chios and 1.48 ml in Friesian rams versus 1.24 ml in Chios and 1.07 ml in Friesian rams; percentage of abnormal sperm: 5.66% in Chios and 5.42% in Friesian rams versus 8.22% in Chios and 7.75% in Friesian rams; total sperm/ejaculate (109): 7.05 in Chios and 6.74 in Friesian rams versus 4.09 in Chios and 4.05 in Friesian rams). The magnitude of these seasonal effects was not suf®cient to prevent rams from being used for breeding throughout the year. However, the existence of differences among rams within each breed in semen quality and quantity makes it necessary to perform a semen evaluation on individual basis in order to select the best males before they are used for breeding.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Ram; Semen; Seasonal variation
1. Introduction
Semen production of rams is in¯uenced by many factors, such as breed, age, environment (daylight length, climatic temperature and humidity) and man-agement, which result in great variations of semen characteristics (Folch, 1983). Since the application of arti®cial insemination in animals, there has been a
growing interest and necessity for more knowledge concerning variation of semen characteristics, espe-cially in seasonally polyestrous animals. On the other hand, under the climatic conditions of Western Eur-ope, semen production of dairy type rams is satisfac-tory during the breeding season (mid summer to winter), but a signi®cant number of ewes are insemi-nated in the non-breeding season, when semen pro-duction is signi®cantly reduced (Colas et al., 1988; Colas et al., 1990).
Although information is available on semen characteristics of rams (Mohamed, 1978; Haynes *Corresponding author. Tel.:30-31-994464;
fax:30-31-994474.
E-mail address: [email protected] (A. Karagiannidis)
and Schanbacher, 1983; Nowakowski and Cwikla, 1994; Ibrahim, 1997), little is known on the semen of dairy breeds in Mediterranean countries. It is well known that there is a signi®cant seasonal varia-tion in semen quality of small ruminants living at high or mid altitudes (Mohamed, 1978; Ibrahim, 1997). However, there is again little information on the effects of season and/or day length on semen characteristics of small ruminants in Mediterranean areas.
The aim of this study was to evaluate the effect of seasonal climatic variations on the semen quality of Chios and Friesian rams in Greece.
2. Materials and methods
The present study was carried out at the Institute of Reproduction and AI of Thessaloniki, Greece at 408370
N, 228580
E, and an altitude of 32 m. Clima-tological information for this location during the experimental year is summarized in Table 1.
2.1. Animals
Five Chios and ®ve Friesian, 2±4 year-old rams were used. They were housed in a cover shelter with an open-air run, allowed to walk freely. Throughout this study, the nutrition of rams remained uniform and constant. Each ram was fed 1 kg alfalfa hay (crude protein content: 182 g/kg DM and energy content: 8.3 MJ ME/kg DM), supplemented with 1 kg com-mercial concentrate (crude protein content: 120 g/kg DM and energy content: 10.4 MJ ME/kg DM) daily and had free access to water. A general management schedule for deworming, disease prevention, and hoof trimming was followed.
2.2. Semen collection
Semen was collected from each ram twice a week using an arti®cial vagina (418C) into a pre-warmed tube at 308C and was maintained at this temperature until processed. An ovariectomized ewe was used for mounting by the rams. Occasionally, the rams failed to mount or to ejaculate and so some ejaculates were not available. One to two ejaculates per ram per month were missed. The tubes with the freshly collected semen were immediately transferred to the laboratory and immersed in a water bath at 308C.
2.3. Semen evaluation
The ejaculated semen volume was recorded imme-diately after collection using a glass graduated tube. Sperm concentration was measured by haemocyto-metric counts of diluted semen with 0.05% formal saline (1 : 400). The overall number of spermatozoa per ejaculate was then calculated (volumedensity). The percentage of motile spermatozoa and the sperm progressive motility were assessed by diluting a drop of semen with 0.1 M sodium citrate, pH 6.7±6.9, transferring it to a warm slide (378C), mounting it with a cover slip and examining it under a microscope at high magni®cation (40 objective). The assess-ment of the sperm progressive motility was made on the basis of an arbitrary scale from 0 to 5 (0no motility, 5100% motility). For sperm morphology and sperm live/dead ratio, semen was stained with eosin-nigrosin stain and examined microscopically (400). Results are presented as seasons: spring (22/3±21/6), summer (22/6±21/9), autumn (22/9±21/12) and winter (22/12±21/3). Late summer and autumn are considered as breeding season and winter and spring as non-breeding season for sheep in Greece.
Table 1
Climatological data for the experimental year from the Meteorological Laboratory of the Aristotelian University of Thessalonikia
Season Air temperature (8C) Relative humidity (%) Average Mean Minimum Maximum Minimum Maximum Day length (h) Summer 24.60 19.12 30.62 41.47 62.14 13.58 Autumn 13.58 9.67 18.34 53.05 75.51 10.36
Winter 6.22 1.96 11.17 47.51 73.57 10.34
Spring 17.69 12.90 22.96 46.58 66.18 13.59
2.4. Statistical analysis
Data were subjected to one-way analysis of var-iance (one-way ANOVA) by using the `exclude cases analysis by analysis' for missing values. Duncan's multiple range was used to detect signi®cant differ-ences between means. When distributions were deviated from normality, data were transformed to logarithms. Correlation coef®cient between various semen charac-teristics was calculated (Steel and Torrie, 1980).
3. Results
Semen characteristics of the Chios and Friesian rams collected throughout the year are presented in Table 2. Signi®cant differences among rams within each breed (P< 0.001) were found in most seminal characteristics examined. However, no signi®cant dif-ferences were found between the two breeds in any trait. Table 2 also gives the effect of the seasonal variations on semen characteristics. Season affected
Table 2
Seasonal variations in semen characteristics (meanSEM) of Chios and Friesian rams
Semen characteristics Season Chios breedb Friesian breed
Volume (ml) Springa 1.24y0.05 1.07y0.06
Summer 1.45x0.07 1.49x0.08
Autumn 1.58x0.08 1.55x0.07
Winter 1.47x0.08 1.48x0.05
Mean 1.430.04 1.400.04
Motile sperm (%) Spring 70.83xy1.84 70.76yz1.04
Summer 69.35x1.171 69.21z1.78
Autumn 75.00y1.54 75.29x48
Winter 73.77xy1.53 74.29xy1.42
Mean 72.170.84 72.360.75
Sperm progressive motility (1±5) Spring 4.18xy0.06 4.25y0.04
Summer 4.08xy0.06 4.06x0.06
Autumn 4.34y0.06 4.32y0.03
Winter 4.31y0.06 4.30y0.04
Mean 4.220.03 4.230.02
Abnormal sperm (%) Spring 8.22x0.45 7.75x0.29
Summer 7.40xy0.40 7.17xy0.44
Autumn 5.66z0.32 5.42z0.25
Winter 6.73yz0.39 6.42y 0.36
Mean 7.010.20 6.680.18
Sperm concentration (109mlÿ1) Springa 3.33z0.12 3.74z0.12
Summer 3.96y0.10 3.90yz0.10
Autumn 4.44x0.12 4.37x0.11
Winter 4.28x0.10 4.14xy0.11
Mean 4.010.06 4.040.17
Total sperm/ejaculate (109) Spring 4.09z0.23 4.05y0.24
Summer 5.74y0.38 5.96x0.40
Autumn 7.05x0.42 6.74x0.36
Winter 6.28xy0.25 6.17x0.26
Mean 5.800.18 5.750.17
aBreed differences were signi®cant (P< 0.05).
b,x,y,zMeans in the column of each parameter with different superscripts differ signi®cantly (
quantity, as well as quality of semen. Semen volume was lower (P< 0.05) during spring in both Chios and Friesian rams, compared to summer, autumn and winter. Friesian rams showed lower semen volume during spring compared to Chios rams.
Percentage of motile spermatozoa was lower (P< 0.05) during summer compared to fall, winter and spring in Chios rams, while, although it was also lower (P< 0.05) during summer in Friesian rams, a gradual increase was observed with the highest values during autumn. The spring and winter seasons were a transitional period.
Sperm progressive motility was lower (P< 0.05) during summer compared to the other three seasons. In Chios rams, spring was a transitional period.
Percentage of abnormal spermatozoa varied greatly among rams. It was obvious that the condition of the rams at the time of collection had an in¯uence on the percentage of abnormal spermatozoa. The types of abnormality were also variable but were present in the semen of all rams studied. In spite of these facts, semen quality from the viewpoint of sperm normality improved signi®cantly during autumn. Percentage of abnormal spermatozoa was higher (P< 0.05) during spring and summer, while winter was a transitional period.
Sperm concentration was higher (P< 0.05) during autumn and winter in both breeds, compared to the other two seasons. In Chios rams, the lowest sperm concentration was observed during spring, while sum-mer was a transitional period. In Friesian rams, the reduction of sperm concentration from autumn to spring and the increase from spring to autumn was more gradual.
Total sperm per ejaculate was higher (P< 0.05) during autumn and winter in Chios rams then deceased signi®cantly during spring to its lowest values. Sum-mer was a transitional period. In Friesian rams total sperm per ejaculate was higher (P< 0.05) during summer, autumn and winter, compared to spring.
Correlation coef®cients between various semen characteristics are shown in Table 3. Percentage of abnormal spermatozoa apparently affects percentage of motile spermatozoa as shown by the negative correlation of ÿ874. All correlations were highly signi®cant, except those between semen volume and each of sperm concentration and percentage of abnor-mal sperm.
4. Discussion
It is well known that the ejaculate of the ram is small in volume (0.7±2 ml) with a high sperm concentration (2±5109), percentage of motile spermatozoa ran-ging from 70±90% and percentage of abnormal sper-matozoa from 5±15% (Mann and Lutwac-Mann, 1981). In this study, most of the mean values for the semen characteristics of Chios and Friesian rams in Northern Greece (408370
N, 228 580
and altitude 32 m above sea level) were generally higher than those reported by Ibrahim (1997) for Chios crosses in the United Arab Emirates, as well as for Texel, Suffolk and Ile-de-France rams evaluated under similar tem-perate regions (Mandiki et al., 1998).
Regarding semen production, it was found that season affected almost uniformly Chios and Friesian rams. Semen characteristics were generally better during summer (onset of improvement) and autumn (peak of improvement) than during winter (onset of decline) and spring (lowest quality). Considering that summer and autumn are seasons with decreasing day length (breeding season) and winter and spring are seasons with increasing day length (non-breeding season), it is obvious that Chios and Friesian rams are sensitive to photoperiodism. The increase in quan-tity and improvement in quality of ram semen during the breeding season is consistent with previous reports (Folch and Colas, 1979; Dacheux et al., 1981; Folch and Roca, 1981; Colas et al., 1986; 1988; 1990; Baril et al., 1993; Mandiki et al., 1998). However, Ibrahim (1997) in a similar study with Chios crossberd rams raised in the United Arab Emirates found that semen characteristics were improved mainly during winter. The variation of quantitative and qualitative sperm
Table 3
Correlation between various semen characteristics of the rams Semen characteristics Correlation
coefficienta
Volumesperm concentration 0.005 Volumetotal sperm/ejaculate 0.855** Sperm concentrationtotal sperm/ejaculate 0.527** Sperm concentrationabnormal sperm (%) ÿ0.190* Motile spermabnormal sperm (%) ÿ0.874**
Volumeabnormal sperm (%) 0.021
production, as well as the time of the year in which the unfavorable effect of photoperiodism occurs varies between several latitudes and between breeds. Breeds used for industrial crossing seem to be more sensitive to photoperiodism than the hardy breeds (Folch, 1983). On the other hand, some breeds like Romanov, are less in¯uenced by season than that of Mediterra-nean breeds, at least compared to Ile-de-France and Prealpes rams (Dacheux et al., 1981), Sarda and Frisian X Sarda (Cappai et al., 1981), as well as with Chios breed according to the ®ndings of the present study.
Contrary to the general consideration that semen quality is better during the breeding season, in our work, it was found that the sperm progressive motility was lower during summer compared to the other three seasons of the year. According to Mandiki et al. (1998), semen motility do not vary greatly over sea-sons, while a sporadic decrease was observed during spring. However, Colas (1980) suggested that photo-period has any effect on the sperm motility. The low sperm motility observed in our study during summer lead us to speculate that this result could be probably due to the high ambient temperatures that were recorded at that time.
In conclusion, the semen characteristics of Chios and Friesian rams in Northern Greece showed a sig-ni®cant seasonal variation in semen quantity and quality. The best semen is produced during late sum-mer and autumn (breeding season). Nevertheless, the magnitude of these seasonal effects should not prevent the rams from being used for breeding throughout the year. However, the existence of differences among rams in semen characteristics makes it necessary to perform a semen evaluation on an individual basis for every male used for breeding in order to select the best males before joining with females.
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