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At least 1,063 records · Page 59Linked to original sources
PubMed2005

Is the yak (Poephagus grunniens L.) really a seasonal breeder?

Yaks are considered to be seasonally polyestrous and breeding occurs from July to November. Here we show that some yaks in peak non-breeding season do exhibit cyclic luteal activity without exhibiting any behavioral signs around expected estrus. A total of eight non-lactating yaks were selected from the Yak Farm belonging to National Research Centre on Yak for various sets of experiments. The animals were maintained as per semi range system of management. They were allowed to graze during daytime and fed concentrate mixture @2 kg/animal/day as per standard farm practices of the center. Blood samples were collected on alternate days for 30 days by jugular venipuncture from the yaks during peak breeding season (July to November) and from the same yaks in non-breeding season (February to March). The plasma samples were analysed for progesterone and estradiol-17beta by RIA and EIA procedures, respectively. During breeding season, the mean plasma progesterone at estrus was basal (<or=0.2 ng/ml) and there after started to increase and reached a peak at days 15-16 of the cycle and then declined rapidly to basal levels at estrus. Mean plasma estradiol-17beta concentrations were high at estrus and then declined to basal level at days 2-3 of the cycle. The mean plasma estradiol-17beta concentrations stayed low for the remaining part of the estrous cycle except for a small elevation, which was exhibited between days 6 and 12 of the cycle. During non-breeding season, in 50% of the animal studied, plasma progesterone and estradiol-17beta levels were at basal level. However, in the remaining animals distinct luteal activity was recorded in terms of plasma progesterone profile. High concentrations of progesterone were maintained in one animal, which suggested existence of cystic corpus luteum. The trend of progesterone and estradiol-17beta profiles in other three animals indicated that they could be cycling although they did not exhibit estrus symptoms. It was concluded from the present study that with improved nutritional support some yaks exhibit estrous cyclicity even during the non-breeding period of the year.

Animals↗
PubMed2006

Influence of protein supplementation on the resistance and resilience on young hair sheep naturally infected with gastrointestinal nematodes during rainy and dry seasons.

Thirty, 4-month-old entire Santa Ines lambs were grazed on an Andropogon gayanus pasture, during a 34-week period (rainy season weeks 0-20 and dry season weeks 21-34) and allocated in two treatment groups (n = 15) each with different protein supplementation: high protein (HP-19% CP) and low protein (LP-11% CP). These were subdivided into those receiving anthelmintic treatment (c) (n = 7) and without anthelmintic treatment (i) (n = 8). The objective was to evaluate the effects of supplementation with protein on resistance and resilience to natural helminth infection of hair breed lambs. Lamb weight, blood collection and faecal egg counts (FEC) were carried out monthly. The lambs were slaughtered after 34 weeks, when worm burdens, worm length and eosinophil cell counts were taken. The sheep on treatments HPc and HPi were heavier in live weight than those from LPi and LPc (P < 0.05) at the end of the rainy period. The HPc group finished heavier (P < 0.05) than the other groups in the dry season, which had no significant differences between them. The predominant species of nematode found was T. colubriformis followed by H. contortus, Trichuris globulosa and Moniezia expansa. Animals on HPi had lower FEC than LPi (P < 0.05). The number of worms was lower for both HP groups (P < 0.05) with worm length shorter in the HPc group (P < 0.05) compared with all other groups. The number of eosinophils was higher in animals in the LPi group, which also showed anaemia and lower plasma urea at the end of the dry season. Diet supplementation with high protein was able to improve resilience and resistance to natural infection by endoparasites during the rainy season. In the dry season there was a decrease in both of these traits, which were intimately linked to the quality of available forage under tropical conditions.

Animal Feed↗
PubMed2005

Seasonal tertiary wastewater treatment in California: an analysis of public health benefits and costs.

A number of communities in the Central Valley of California have requested that seasonally based effluent limits be developed for their wastewater treatment facilities. These seasonal limits would be based on disinfected secondary treatment during the winter and disinfected tertiary treatment during the rest of the year. Such a request for seasonal limits raises a significant water quality policy question with regard to the costs and relative benefits of tertiary treatment during the winter season. A benefit-cost analysis for winter season tertiary wastewater treatment in California's Central Valley is presented here. The assumed societal benefit of winter tertiary treatment is enhanced water quality for recreational purposes, and thus reduced risk to public health. Based on the results of this analysis, between four and sixteen million recreation events would need to occur annually region-wide during the winter to justify the costs of winter tertiary treatment. A similar method and the information described herein could be used by the state water quality regulatory agency to develop a risk-based policy to consider seasonal limits.

California↗
PubMed2006

Assessment of seasonal variations in surface water quality.

Assessment of seasonal changes in surface water quality is an important aspect for evaluating temporal variations of river pollution due to natural or anthropogenic inputs of point and non-point sources. In this study, surface water quality data for 16 physical and chemical parameters collected from 22 monitoring stations in a river during the years from 1998 to 2001 were analyzed. The principal component analysis technique was employed to evaluate the seasonal correlations of water quality parameters, while the principal factor analysis technique was used to extract the parameters that are most important in assessing seasonal variations of river water quality. Analysis shows that a parameter that is most important in contributing to water quality variation for one season may not be important for another season except for DOC and electrical conductance, which were always the most important parameters in contributing to water quality variations for all four seasons.

Carbon↗
PubMedDate not supplied

Seasonal rhythms of menarche in the United States: correlates to menarcheal age, birth age, and birth month.

PURPOSE: To examine the seasonality of menarche in a large sample of women from the United States. METHODS: Retrospective data were collected on month of birth and menarche, age of menarche, and latitude and altitude of residence from a sample of approximately 3,000 U.S. women from the TREMIN Research Program and from a college student population. RESULTS: Monthly analyses using observed (O) to expected (E) ratios indicated a peak frequency of menarche in July (1.45) and January (1.19) and troughs in February (0.75) and May (0.79). Collapsing the data into seasons also revealed summer and winter peaks. Participants from a younger cohort (born after 1970) had an earlier age of menarche than participants from an older cohort (born before 1970). Older cohort participants also had a more pronounced December-January frequency peak and younger cohort participants had a more pronounced July frequency peak. Older cohort participants exhibited more variability in menarcheal age as a function of menarche month and birth month. Late-maturing participants (>14 years) had a larger December peak of menarche frequencies. Spring-born participants exhibited less seasonality to their menarche. Month of birth was not significantly associated with month of menarche; however, fewer cases than expected occurred 3 months after the birth month and more cases than expected occurred 6 months after the birth month. Age of menarche and monthly distribution of menarche did not vary according to latitude or altitude. CONCLUSIONS: Menarche seasonality is suggested to be a multifactor process mediated by the most prominent seasonal time cue. Attention to these cues that have been hypothesized to contribute to menarche seasonality (e.g., stress or the photoperiod) may have practical implications for women's health, given some of the risks associated with early menarche.

Adolescent↗
PubMed2004

Seasonal variation of steroid hormone levels in an intertidal-nesting fish, the vocal plainfin midshipman.

This study characterized the seasonal variation of the steroid hormones testosterone (T), 11-ketotestosterone (11-KT), 17beta-estradiol (E2), and cortisol (F) as they relate to the gonadal development and reproductive behavior of the plainfin midshipman fish, Porichthys notatus. The plainfin midshipman is a deep-water teleost that seasonally migrates into the shallow intertidal zone where type I, or "singing," males build nests, acoustically court and spawn with females. The gonadosomatic index and plasma steroid levels were measured from adult type I males and females collected over four time periods (non-reproductive, pre-nesting, nesting, and post-nesting) that corresponded to seasonal fluctuations in midshipman reproductive biology and behavior. Among type I males, plasma levels of T and 11-KT were low during the winter non-reproductive period, gradually increased during seasonal recrudescence of the testes in the spring pre-nesting period, and then peaked at the beginning of the summer nesting period. In the latter half of the nesting period and during the fall post-nesting period, plasma levels of T and 11-KT were low or non-detectable. Low, detectable levels of E2 were also found in the plasma of 50% or more type I males during every seasonal period except the winter non-reproductive period. Among females, plasma levels of T and E2 were low throughout the year but briefly peaked in April during the spring pre-nesting period when ovaries underwent seasonal recrudescence. Plasma F levels were correlated with collection depth and were lower in males than females when fish were collected deeper than 120 m. The sex-specific peaks of steroid hormone levels in male and female midshipman may serve differential functions related to the physiology, reproductive behavior, and vocal communication of this species.

Animals↗
PubMed2006

Corticosterone responses change seasonally in free-living house sparrows (Passer domesticus).

Avian corticosterone (CORT) concentrations vary seasonally for many species, but most studies examined species from extreme environments or from only a few times of the year. It is unclear how general a phenomenon this is. We examined both baseline and stress-induced CORT from house sparrows (Passer domesticus) in two habitats-Massachusetts, similar to their ancestral habitat; and New Mexico, a semi-arid desert where the house sparrow only thrives as an obligate human commensal. We captured both males and females during four times of the year-Spring (when the male cloacal protuberance indicated birds were in breeding condition), Fall, Winter, and in the late summer when birds were undergoing a prebasic molt. Birds were heaviest and had the longest wing chord lengths in the Fall at both sites and Massachusetts birds were approximately 10% heavier than New Mexico birds. House sparrows also showed a seasonal variation in the amount of fat stores, but the seasonal pattern differed. Massachusetts birds were fatter overall and showed the most fat during Fall and Winter, whereas New Mexico birds showed the most fat in the Spring. Both baseline and stress-induced total CORT did not differ between sexes or sites, with the exceptions of baseline CORT in the Fall and stress-induced CORT in the Spring being elevated in Massachusetts males. There was a distinct seasonal pattern at both sites, however, with total CORT being highest in the Spring and Winter and lowest during Fall and molt. This seasonal pattern was mirrored in corticosterone binding globulin (CBG) capacities, and when free CORT was estimated, the seasonal pattern disappeared. Stress-induced free CORT, however, was higher in Massachusetts males and females during the Fall and Winter, suggesting a potential differential response to stress associated with commensalism.

Animals↗
PubMed2006

Day-to-day and seasonal variability of physical activity during school recess.

OBJECTIVE: Children's physical activity levels are difficult to establish on a day-to-day or season-to-season basis. Most studies have attempted to measure reliability in habitual settings. This study investigated the variability in children's physical activity during recess. METHODS: Fifteen boys and 19 girls (aged 6 to 11 years) from 2 schools in North West England wore heart rate monitors for 5 consecutive days in summer and winter terms to assess day-to-day and seasonal variability during school recess. Data were collected in 2004. Repeated measures ANOVA's and intraclass correlations (ICC) analysed the day-to-day and seasonal variability in children's moderate-to-vigorous (MVPA) and vigorous physical activity (VPA) data. RESULTS: There were no significant differences in children's MVPA and VPA across days and seasons. ICCs for MVPA across 2 days ranged from 0.75 to 0.85 in summer, and from 0.53 to 0.81 in winter. Three-day MVPA ICCs were 0.83 in summer and 0.71 in winter. CONCLUSIONS: The results revealed no significant variation in children's recess physical activity levels across days and seasons. Whilst children were free to choose their recess activities in school, the results suggested that children were relatively consistent in their choices, limiting physical activity variability.

Child↗
PubMed1996

Dietary nutrient profiles of Canadian Baffin Island Inuit differ by food source, season, and age.

OBJECTIVE: To compare the effect of food source (traditional or market), season (six seasons), and age (five age groups) on dietary nutrient patterns of Inuit living in Baffin Island, Canada. DESIGN: Twenty-four-hour recall interviews of all residents who had lived > or = 3 years in this one community in each of six seasons. Foods that were recalled were divided by source. SETTING/SUBJECTS: The study took place in the Inuit community of Qikiqtarjuaq, which harvests the highest quantity of wildlife per capita of all Baffin communities. Three hundred sixty-six residents contributed a total of 1,410 recalls: 401 from nonpregnant, nonlactating adult women, 74 from pregnant women, 301 from adult men, 451 from children aged 3 to 12 years, and 183 from teenagers aged 13 to 19 years. Participation was voluntary and averaged 65% to 75% of residents. MAIN OUTCOME MEASURES: Energy, total dry weight of food, and dietary nutrients (ie, carbohydrate, protein, total fat, saturated fat, polyunsaturated fat, vitamin A, iron, copper, zinc, calcium, phosphorus, magnesium, and sodium) were measured by food source, season, and age. Nutrient density (nutrient per 1,000 kcal) was calculated in traditional and market food sources. Selected nutrients were computed in total diets, and compared with Recommended Dietary Allowances (RDAs). STATISTICAL ANALYSES PERFORMED: Tests for normality of the distribution of nutrient intakes (ie, Shapiro-Wilk statistic) were performed followed by nonparametric analyses (ie, Wilcoxon paired-sample t test, Kruskal-Wallis analysis of variance, and adjustment for Bonferroni inequalities resulting from multiple comparisons). RESULTS: Most nutrient intakes were significantly different by food source (P < .05). Traditional food contributed more protein, phosphorus, iron, zinc, copper, magnesium, and vitamin A for several age groups. Market food contributed greater amounts of dry weight, energy, fat, carbohydrate, calcium, and sodium for most age groups. Seasonal variation (P < .05) existed for nutrients coming from traditional and market food. Of the 10 nutrients assessed for nutrient density, all except calcium and sodium were present in greater amounts in traditional food than in market food (P < .05). Calcium and vitamin A intakes fell below 66.6% of the RDAs for more than 60% of the population. CONCLUSIONS: The comprehensive view of nutrient profiles, food source, and seasonality of Inuit diets will assist health professionals in developing nutrition promotion and education programs for all age groups of this population. Traditional food is an essential source of the total annual dietary nutrient intake of Inuit. Results indicated, however, that calcium and vitamin A intake must be improved.

Adolescent↗
PubMed1997

A controlled evaluation of the efficacy and safety of loteprednol etabonate in the prophylactic treatment of seasonal allergic conjunctivitis. Loteprednol Allergic Conjunctivitis Study Group.

PURPOSE: To evaluate the efficacy and safety of loteprednol etabonate 0.5% as prophylactic treatment for the ocular signs and symptoms of seasonal allergic conjunctivitis. METHODS: In this randomized, double-masked, placebo-controlled, parallel study, 293 adults with history of seasonal allergic conjunctivitis were treated with either loteprednol etabonate or vehicle (placebo) four times daily, beginning before the onset of the allergy season and continuing for 6 weeks. The primary efficacy measure was a primary composite score (sum of itching and bulbar conjunctival injection scores). Supportive efficacy measures were the investigator global assessment and a secondary composite score (sum of tearing, erythema, chemosis, and discomfort scores), all calculated during the 21-day peak pollen season. RESULTS: The proportion of patients who never developed moderate or severe signs and symptoms of allergy during the peak pollen season in the loteprednol etabonate treatment group was greater than that in the placebo group. For the primary composite score, this efficacy criterion was reached by 94% of patients (136/145) in the loteprednol etabonate group and 78% of patients (111/143) in the placebo group (P = .001). The magnitude of effect was similar for the investigator global assessment (86% [118/138] vs 64% [87/137]; P < .001) and, although not statistically significant, the secondary composite score (77% [112/145] vs 68% [97/143]; P = .092). None of the loteprednol etabonate-treated patients had an intraocular pressure increase of 10 mm Hg or more, whereas two placebo patients did. CONCLUSIONS: Loteprednol etabonate is generally effective in prophylaxis of seasonal allergic conjunctivitis and has an acceptable safety profile.

Adolescent↗
PubMedDate not supplied

Seasonal affective symptoms in adults with residual attention-deficit hyperactivity disorder.

There is evidence from clinical, epidemiological, and neuroimaging studies that attention-deficit hyperactivity disorder (ADHD) and seasonal affective disorder (SAD) may have several features in common. To assess seasonal affective symptoms in adults with ADHD, 115 individuals attending an adult ADHD clinic in Toronto, Ontario, Canada were asked to complete the Seasonal Pattern Assessment Questionnaire (SPAQ). From this clinic population of 115, a total of 56 completed SPAQs were returned. Assuming that all individuals failing to complete the SPAQ were nonseasonal and depending on which case-finding criteria were used, the rate of SAD in the overall clinic sample was estimated at either 10.4% (Terman criteria) or 19.1% (criteria of Kasper et al.). These prevalence rates are significantly greater than the rates reported in large population surveys at similar latitudes. There was an apparent relationship between female gender, impulsive-subtype ADHD, and seasonality. Future studies to examine whether core symptoms of ADHD fluctuate across the seasons and to assess the efficacy of light therapy in "seasonal" ADHD patients would be of great theoretical and clinical interest.

Adolescent↗
PubMed2000

Seasonal variability in fertilization and embryo quality rates in women undergoing IVF.

OBJECTIVE: IVF-ET provides unique controlled conditions for the study of seasonal influences on the human reproductive process. This study was designed to evaluate the effects of seasonality on fertilization rate, embryo quality, and conception rates. DESIGN: A retrospective observational cohort study. A chart review of all individuals undergoing IVF-ET from 1988 to 1991 at our institution was performed. SETTING: An assisted reproduction unit at a university-based tertiary medical center. PATIENT(S): 657 women, for a total of 1074 IVF-ET treatment cycles, were evaluated. From this population, we chose 305 women undergoing their first IVF-ET cycle for reasons of pure mechanical infertility. INTERVENTION(S): IVF-ET cycles. MAIN OUTCOME MEASURE(S): Seasonal variability in fertilization rates and quality-A embryo rates, and the correlation with the absolute number of light hours, as well as the influence of temperature, humidity, and other environmental parameters. RESULT(S): A significant seasonal variability in the fertilization rate and the quality-A embryo rate was demonstrated. The highest fertilization and quality-A embryo rates were observed during the spring and the lowest in the autumn. These changes correlated with the absolute number of light hours and its increment over time, but not with the temperature, humidity, or other environmental parameters. CONCLUSION(S): Seasonality seems to have a significant influence on the fertilization process and on the quality of the human embryos that are obtained in vitro, possibly because of the light/dark variations over time. If this finding is confirmed, these seasonal changes should be taken into account when evaluating infertility data and in everyday clinical practice.

Adult↗
PubMed1996

Seasonal onset of systemic-onset juvenile rheumatoid arthritis.

OBJECTIVE: This study was undertaken to investigate the recent finding of a seasonal difference in the onset of systemic-onset juvenile rheumatoid arthritis (SoJRA). We hypothesized that a seasonal onset pattern might implicate on infectious agent as a cause of SoJRA. METHODS: The date of onset was collected from the records of all patients with SoJRA from 1980 to 1992 at presentation to pediatric rheumatology clinics across Canada. The onset pattern of SoJRA was then compared with incidence data on viral infections obtained for the same period. RESULTS: Across Canada the onset of SoJRA was constant across the seasons. However, in the Prairie region there was a statistically significant seasonal pattern, with peaks in autumn and early spring. We could find no evidence that viral incidence correlated with disease incidence either throughout Canada or in the Prairie region. CONCLUSIONS: If a seasonal infectious agent causes SoJRA, then it is likely only one of several causes and may act only in certain regions. Future studies should be carried out in those areas where SoJRA does have a seasonal onset pattern.

Adolescent↗
PubMed1994

Investigation of the diurnal, ontogenetic and seasonal variation in the molluscicidal saponin content of Phytolacca dodecandra aqueous berry extracts.

Daily variation in the content of the saponins of the berries of Phytolacca dodecandra was determined in berries harvested at the full grown green unripe stage of development once every two hours. The saponin content was quantitatively determined by HPLC analysis of the molluscicidal monodesmosidic saponins in the aqueous extract of the crushed berries. No significant daily variations were observed in extracts of berries collected at different times of day (P > 0.05 by ANOVA). But, seasonal variation was apparent in extracts prepared from berries harvested from the same plants once every two weeks. Berries of highest saponin content were those harvested during the dry season and just before the onset of the rainy season. The seasonal variation was attributed to increased water stress during the dry season. Very young racemes had the highest saponin content, while mature berries produced the lowest saponin concentration. There was, however, consistency in the berry saponin composition during the day, season and all stages of berry development.

Carbohydrate Sequence↗
PubMedDate not supplied

The seasonal pattern of dengue in endemic areas: mathematical models of mechanisms.

In dengue-endemic areas such as Thailand, there is clear seasonality in the number of reported cases of dengue virus disease. However, the roles of different entomological and biological variables in determining this pattern have not been ascertained. To investigate this, seasonally-varying parameters were introduced in a step-wise fashion into a mathematical model of the transmission dynamics of dengue viruses. The predicted prevalence of infection was then compared to observed seasonal patterns of disease. The strongest influences on the pattern of infection and its seasonal variation were duration of infectiousness of the host, vector mortality, and biting rate. However, seasonally-varying parameters such as the latent period of infection in the vector had to be incorporated into the model to generate the correct timing of peak infection prevalence. A few limiting variables usually control the prevalence of an infectious disease because small changes in their values can carry the infection beyond the threshold at which its basic reproductive number is one. It was changes in such parameters (vector biting and mortality rate) which caused seasonal prevalence, but the timing of peak prevalence was a result of time delays within the system.

Dengue↗
PubMedDate not supplied

Unstable malaria in Sudan: the influence of the dry season. Plasmodium falciparum population in the unstable malaria area of eastern Sudan is stable and genetically complex.

This paper reviews surveys carried out, over a period of 6 years between 1989 and 1995, to examine Plasmodium falciparum population structure in Asar village in eastern Sudan, an area of unstable malaria, the incidence of which is confined to a few weeks following the short rainy season (June-October). The first phase of the study involved regular cross sectional surveys, between 1989 and 1993 during the seasons of malaria incidence, while the second involved surveys during the malaria-free months of the dry seasons. The parasites were examined for 20 polymorphic loci, including enzyme electrophoretic variants, proteins detected by 2 dimensional polyacrylamide gel electrophoresis, antigens detected by monoclonal antibodies, and in vitro responses to antimalarial drugs. In addition, alleles of the polymorphic genes for merozoite surface proteins 1 and 2 (MSP-1, MSP-2) were examined using the polymerase chain reaction and oligonucleotide probes. Great genetic complexity was observed among the parasites which appeared during the short transmission seasons. A large proportion of the patients who were infected during the transmission season maintained asymptomatic, subpatent parasitaemias throughout the subsequent dry season, often as genetically complex infections.

Adolescent↗
PubMed2000

Fish mercury concentration in the Alto Pantanal, Brazil: influence of season and water parameters.

The tropical flood plain Pantanal is one of the world's largest wetlands and a wildlife sanctuary. Mercury (Hg) emissions from some upstream gold mining areas and recent findings of high natural Hg levels in tropical oxisols motivated studies on the Hg cycle in the Pantanal. A survey was made on total Hg in the most consumed piscivorous fish species from rivers and floodplain lakes in the north (Cáceres and Barão de Melgaço) and in the south part of Alto Pantanal (around the confluence of the Cuiabá and Paraguai rivers). Samples were collected in both the rainy and dry seasons (March and August 1998) and included piranha (Serrasalmus spp.), and catfish (Pseudoplatystoma coruscans, pintado, and Pseudoplatystoma fasciatum, cachara or surubim). There was only a small spatial variation in Hg concentration of the 185 analyzed fish samples from the 200 x 200 km large investigation area, and 90% contained total Hg concentration below the safety limit for regular fish consumption (500 ng g(-1)). Concentration above this limit was found in both Pseudoplatystoma and Serrasalmus samples from the Baia Siá Mariana, the only acid soft-water lake included in this study, during both the rainy and dry seasons. Concentration above this limit was also found in fish outside Baia Siá Mariana during the dry season, especially in Rio Cuiabá in the region of Barão de Melgaço. The seasonal effect may be connected with decreasing water volumes and changing habitat during the dry season. The results indicate that fertile women should restrict their consumption of piscivorous fishes from the Rio Cuiabá basin during the dry season. Measures should be implanted to avoid a further deterioration of fish Hg levels.

Adult↗
PubMed2003

Seasonal changes in semen quality and freezability in the Warmblood stallion.

The objective of this study was to investigate seasonal changes in stallion semen quality and to determine the best time for semen cryopreservation. Experiments were performed using 10 Warmblood stallions from the National Stud Farm in Avenches (Switzerland). Ejaculates were collected and frozen every other week during 1 year from January to December 1999. Volume, concentration, and motility, and the number of morphologically normal sperm and sperm with major defects (abnormal heads, acrosome defects, nuclear vacuoles, proximal droplets, abnormal midpieces) were evaluated. For all frozen-thawed semen samples motility as well as viability (SYBR-14/PI) was tested, and the hypoosmotic swelling test (HOS) was performed. To analyze seasonal differences 4 periods of 3 months each were defined: autumn (September, October, November), winter (December, January, February), spring (March, April, May) and summer (June, July, August). During the 1 year experiment all semen quality parameters showed a clear seasonal pattern. The volume, total sperm count and motility in fresh semen were significantly higher (P<0.05) in summer than in winter, while sperm concentration was significantly lower in summer compared to the other seasons. Regarding morphology, normal sperm was significantly lower (P<0.05) in summer than at any other time of the year and higher values (P<0.05) were found for major defects in summer than in spring and autumn. In frozen-thawed semen motility was significantly (P<0.05) improved in autumn when compared to spring and summer. Viability was lowest in summer and differed significantly (P<0.05) from other seasons. The HOS test revealed significantly more (P<0.05) membrane damaged spermatozoa in winter than in spring, summer and autumn. Our results demonstrate that in our climatic conditions clear seasonal differences occur in semen quality of fresh and frozen-thawed semen and that cryopreservation of stallion semen should preferably be performed in autumn.

Acrosome↗