Department of Genetics and Animal Breeding, Wrocław University of Environmental and Life Sciences
Katedra Genetyki i Ogólnej Hodowli Zwierząt, Uniwersytet Przyrodniczy we Wrocławiu the study included 21 mares of Małopolski horse, and 18 mares of Polish warmblood horse aged from 3 to 18 years. the mares were used for breeding in years 1999–2004 in a stud situated in south-west part of Poland. In total, 222 reproduction seasons were analysed. the results of an as-sessment of the follicular stage of mare ovaries conducted by ultrasonografic method with use of the Echosond USG apparatus, and palpable method (per rectum) in a scale from F0 to F4 were used in the study. the obtained results concerning the frequency of particular phases on mares ovaries were divided according to: month of the reproductive season, age, family and age of mares. Si-gnificance of differences between the parameters analysed was verified using Chi2 test. Significant differentiation in ovaries activity in particular months of the reproductive season were noted. the highest activity measured by F3 and F4 phases frequency corresponded to the highest breeding effectiveness. No influence of genetic factors (breed and family) and the age on the level of ovaries activity was observed. Higher activity measured by F2, F3, F4 phases frequency was observed on the left ovary.
KEY WOrDS: horse, reproduction, ovaries activity
iNTROdUCTiON
One of the most important factors determining horse breeding effect is the proper repro-duction. Choosing the right time for mating or insemination constitutes the key element of reproduction. In the case of seasonally bred mares it is connected with physiologi-For citation – Do cytowania: Kruszyński W., Maliszewska M., Wilk K., 2011. the analysis of mare ovaries activity depending on month of reproductive season, breed and age.Zesz. Nauk. UP Wroc., Biol. Hod. Zwierz., LXIII, 583: 169–174.
cal condition of ovaries examination. the mare examination should be conducted before the reproduction season in order to establish the health status, probability of foaling and proper pregnancy termination. Particular attention should be paid to ultrasonographic examination which enables a thorough diagnostics in seeking infertility reasons in mares (Gastal et al. 1998). the intense studies aimed at the explanation of ovaries growth mech-anism and ways of they control and regulation have been conducted concurrently (Gastal et al. 1997, Ginther et al. 2004).
the frequently diagnosed mares infertility may result from hypoovarianism, ovarian follicles persistency, ovarian haematoma, cysts and tumours, as well as the previous season course (Nagy et al. 1998) or nutrition (van Niekerk and van Heerden 1972). the-refore the proper attention, observation and regular examination before breeding season should be highly significant to the breeder.
the aim of the study was to investigate the differentiation in ovaries activity depen-ding on an influence of reproduction season month, breed and age.
mATERiAl ANd mEThOd
the study included 21 mares of Małopolski horse and 18 mares of Polish warmblood horse aged from 3 to 18 years. the mares were used for breeding in years 1999–2004 in a stud situated in south-west part of Poland. In total, 222 reproduction seasons were analysed (108 mares of Małopolski horse, and 114 mares of Polish warmblood horse). the results of an assessment of the follicular stage of mare ovaries conducted by ultra-sonografic method with use of the Echosond USG apparatus, and palpable method (per rectum) were used in the study. the control study of ovaries started depending on mare physiological status. the pregnant mares were examined for the first time at 7th day after foaling, while axenic mares or those starting reproduction performance were examined at the beginning of the season, i.e. on the turn of January and February. the examinations were conducted every 21 days, with exception of the situation when the revolutionary blister was observed, and then the second examination was conducted after 72 hours. the examinations were conducted during the whole reproductive season, until the mares foal-ing was obtained. the assessment of the size of blister, its consistency and state of ovary tension was carried out according to Żywotkow division (Bielański 1972) in a scale from F0 to F4. According to that scale: F0 – follicle rest state, F1 – follicle of 10 mm diameter, F2 – follicle of 20 mm diameter, F3 – follicle of 30 mm diameter, F4 – follicle of 40 mm diameter. the rest of the information was obtained from animal breeding records. the results of mare ovaries state were divided according to following criteria:
month of the reproductive season (since January to July) –
breed (Malopolski horse and Polish warmblood horse) –
family (the families with at least 6 mares were selected for the analysis) –
mare’s age (three groups were distinguished: up to 5 years, 6-10 years, above 15 –
years).
the information obtained were used to estimate the frequency of particular ovaries stages in subsequent months of reproductive season, breeds and age groups. the signifi-cance of differences between the parameters analysed was verified using Chi2 test.
RESUlTS ANd diSCUSSiON
the analysis of reproductive season month influence (tab. 1) on ovaries activity mea-sured with frequency of various follicular stages occurrence demonstrates that the blisters observed most often were in phase F0. During the analysed period of time they were observed the most often in January (61.0% left and 76.4% right ovary) as well as in July (83.7% on right ovary), and the most seldom in March (50.7% left ovary and 60.1% right ovary). Phase F1 was the most often observed in March on the left and right ovary (9.2 and 9.0%, respectively) and the most seldom in January on the left ovary (3.7%) and in July (2.3% right ovary). the frequency of phase F2, F3 and F4 in analysed months of reproductive season demonstrated the similar course. the distinct growth of frequency is observed since January till March, when the values close to maximum were noted on the right ovary (19.2% F2, 17.9% F3 and 8.7% F4) and the left one (13.5% F2, 12% F3 6.5% F4). the decrease in the frequency of phases F2, F3 and F4 on both ovaries is observed in April. this tendency is maintained in May for phase F2 on the left ovary, and than the frequency of this phase occurrence increases. Phases F3 and F4 after the April frequency decrease, begin to increase their occurrence frequency. this phenomenon is subject to suppression in July – the last of analysed months of reproductive season. Similar results were obtained by Okólski (1981), in the study on Malapolski mares he observed the larg-est number of mare’s with active ovaries in May and June. the results obtained demon-strate a strict relationship between the horses reproductive season and increased activity of ovaries manifesting, among others, in an increased frequency of blisters occurrence in phases F3 and F4. Also the study by Wesson and Ginther (1981) demonstrate the relation-ship between ovaries activity and reproductive season month, however the results are not unequivocal.
table 1 tabela 1 Frequency (%) of follicles occurrence on ovaries (left ovary – l.o and right ovary – r.o)
in particular stages (F0-F4) in analysed months of the reproductive season
Częstość (w %) występowania pęcherzyków na jajnikach (lewy jajnik – l.o. i prawy jajnik – r.o) w poszczególnych fazach (F0-F4) w analizowanych miesiącach sezonu reprodukcyjnego (P=0,023)
Month
Miesiąc l.o.F0 r.o. l.o.F1 r.o. l.o. F2r.o. l.o. F3r.o. l.o. F4r.o. January – Styczeń 61.7 76.4 3.7 6.7 8.5 12.4 19.5 1.1 7.3 3.4 February – Luty 51.2 63.1 8.0 8.3 14.2 13.5 17.9 9.8 8.7 5.3 March – Marzec 50.7 60.5 9.3 9.0 19.2 11.3 14.3 12.0 6.5 6.2 April – Kwiecień 62.2 67.2 6.8 7.8 14.4 9.2 10.7 11.5 5.9 4.3 May – Maj 64.0 64.7 6.5 3.1 6.8 13.6 14.9 13.3 7.8 5.3 June – Czerwiec 62.5 65.3 4.9 7.5 14.7 12.2 12.2 8.0 5.7 7.0 July – Lipiec 48.9 83.7 6.7 2.3 22.2 4.7 13.3 7.0 8.9 2.3
the effectiveness of breeding depending on mating month in the reproductive season was the highest in March (26%) and in May (24%). the lowering of breeding index (21% in April) was observed between these months. the lowest breeding frequencies were
noted in January and in July (1.8% each). the highest effectiveness of breeding was obse-rved after mating conducted after detection of revolutionary blister in phase F4 (43.03%), however mating after F3 blister detection gave just a little lower results (40.6%).
the results obtained demonstrate that the effectiveness of breeding is clearly connec-ted with the presence of phase F3 and F4 on ovaries. the two peaks of these phases in March and May are related with the highest effectiveness of breeding noted then.
the analysis of the functioning of particular ovaries of the mares examined shows clearly higher activity of the left ovary. the frequency of phases F3 and F4 observation on this ovary is definitely higher than those observed on the right ovary (F3 21.2% and F4 28.5%, respectively). Okólski (1981) also observed higher activity of mare’s left ovary (54%) as compared to right one measured with effectiveness of breeding. Davis Morel and O’Sullivan (2001) also noted higher activity of the left ovary (50.5% ovulations) than right one (49.5%). Wesson and Ginther (1981) in turn observed higher activity of the right ovary (52.4%) as compared to the left one (47.6%). the phenomenon of larger activity of one from the gonads is also well-known in different species like for example in cattle.
No influence of mares breed on ovaries activity was observed in the present study (tab. 2). the average values of follicular phase in both analysed breeds were similar. Other results were obtained by Górecka et al. (2005) who observed higher mean surface of follicles at the ovulation day in thoroughbred mares as compared to mares of Konik breed. However, no differences in activity of ovaries between the families in analysed breeds were noted.
table 2 tabela 2 Frequency (%)of follicles occurrence on ovaries (left ovary – l.o and right ovary – r.o)
in particular stages (F0-F4) of analysed breeds (P=0.0912) and age groups (P=0,527) Częstość (%) występowania pęcherzyków na jajnikach (lewy jajnik – l.o. i prawy jajnik – r.o) w poszczególnych fazach (F0-F4) analizowanych ras (P=0,0912) i grup wiekowych (P=0,527)
F0 F1 F2 F3 F4
l.o. r.o. l.o. r.o. l.o. r.o. l.o. r.o. l.o. r.o. Breeds Małopolski horse (n=108) 58.4 66.9 5.6 6.5 13.3 11.5 17.0 10.3 5.7 3.8 Polish warmblood horse (n=114) 59.3 63.8 8.3 7.1 13.9 11.9 10.7 11.2 7.8 6.0 Age (years) Wiek (lata) 3–5 (n=53) 58.9 62.5 7.4 7.8 15.6 13.4 11.5 11.8 6.6 4.5 6–9 (n=56) 50.4 67.4 8.6 5.7 14.6 12.6 18.1 9.4 8.4 5.1 above 10 (n=115) 62.3 67.5 5.7 7.5 12.9 8.3 12.5 10.4 6.3 6.3 the influence of mare’s age was analysed in the three age classes (tab. 2). the distri-bution of frequency of subsequent follicular phases occurrence in particular age classes was differentiated, however not significant statistically. the highest frequency of F4 and F3 phase on the left ovary (18.1 and 8.4%, respectively) in the group of mares aged from 6 to 10 years, deserves an attention. In the case of the youngest (up to 5 years) and the
ol-dest (above 10 years) mares that phases were observed the most seldom. Also the highest contribution of F0 phase on both ovaries in the group of the oldest mares should be em-phasized (62.3% left and 67.5% right ovary). Ginther et al. (2009) analysing an influence of the age on ovaries activity also observed the lowest, however insignificant statistically, rate of follices growth to F4 phase in the group of the oldest mares.
CONClUSiONS
1. Significant differentiation in ovaries activity in subsequent months of the repro-ductive season was noted. the highest activity measured by F3 and F4 phases frequency corresponded to the highest breeding effectiveness.
2. No significant influence of genetic factors (breed and family) and the age on the level of ovaries activity was observed.
3. Higher activity measured by F2, F3, F4 phases frequency was observed on the left ovary.
REfERENCES
Bielański W., 1972. rozród zwierząt. PWriL, Warszawa.
Davis Morel M.C., O’Sullivan J.A., 2001. Ovulation rate and distribution in the thoroughbred mare, as determined by ultrasonic scanning: the effect of age. Anim. reprod. Sci., 66: 59–70. Gastal E.L., Gastal M.O., Ginther O.J., 1998. the suitability of echotexture characteristics of the
follicular wall for identifying the optimal breeding day in mares. theriogenology, 50: 1025– 1038.
Gastal E.L., Gastal M.O., Bergelt D.r., Ginther O.J., 1997. role of diameter differences among follicle in selection of future dominant follicle in mares. Biol. reprod. 57: 1320–1327. Ginther O.J., Gastel E.L., Gastel M.O., Beg M.A., 2004. Seasonal influence on equine follicle
dynamics. Anim. reprod. Sci., 1: 31−44.
Ginther O.J., Gastel M.O., Gastel E.L., Jacob J.C., Beg M. A., 2009. Age-related dynamics of follices and hormones during an induced ovulatory follicular wave in mares. theriogenology, 71: 780−788.
Górecka A., Jezierski t., Słoniewski K., 2005. relationships between sexual behavior, dominant follicle area, uterus ultrasonic image and pregnancy rate in mares of two breeds differing in reproductive efficiency. Anim. reprod. Sci., 87: 283−293.
Nagy P., Huszenicza G., Juhasz J., Kulcsar M., Solti L., reiczigel J., Abavary K., 1998. Factors influencing ovarian activity and sexual behavior of postpartum mares under farm conditions. theriogenology, 50: 1109−1119.
Okólski A., 1981. Sezonowa czynność jajników i zatrzymywanie niezapłodnionych komórek ja-jowych w jajowodach klaczy. rozprawa habilitacyjna nr 84, Ar Kraków.
van Niekerk C.H., van Heerden J.S., 1972. Nutrition and ovarian activity of mares early in the breeding season. J.S. Afr. vet. Med. Assoc., 4: 351−360.
Wesson J.A., Ginther O.J., 1981. Influence o season and age on reproductive actvity in pony mares on the bais of a slaughtehouse survey. J.Anim.Sci., 52 (1): 119–129.
ANALIZA AKTYWNOŚCI JAJNIKÓW KLACZY W ZALEŻNOŚCI OD MIESIĄCA SEZONU REPRODUKCYJNEGO, RASY I WIEKU
S t r e s z c z e n i e
Badaniami objęto 21 klaczy rasy małopolskiej i 18 klaczy rasy polski koń szlachetnej półkrwi w wieku od 3 do 18 lat użytkowanych rozpłodowo w latach 1999–2004 w stadninie koni położonej w Polsce południowo-zachodniej. Łącznie przeanalizowano 222 sezony reprodukcyjne. Do badań wykorzystano wyniki oceny stadium pęcherzykowego jajników klaczy wykonywanego metodą ul-trasonograficzną oraz metodą palpacyjną w skali od F0 do F4. Uzyskane częstości występowania poszczególnych faz na jajnikach klaczy podzielono według: miesiąca sezonu reprodukcyjnego, rasy, rodziny, wieku klaczy. Istotność różnic pomiędzy analizowanymi parametrami weryfikowa-no za pomocą testu Chi2. Odnotowano istotne zróżnicowanie aktywności jajników w kolejnych miesiącach sezonu reprodukcyjnego. Najwyższa aktywność mierzona częstością faz F3 i F4 ko-respondowała z najwyższą skutecznością zaźrebień. Nie zaobserwowano wpływu czynników ge-netycznych (rasy i rodziny) i wieku klaczy na poziom aktywności jajników. Stwierdzono wyższą aktywność jajnika lewego pod względem częstości faz F2, F3, F4.
UNIWERSYTETU PRZYRODNICZEGO WE WROCŁAWIU 2011 BIOLOGIA I HODOWLA ZWIERZĄT LXIII NR 583
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