CC BY
18
Maria Kulisa, Boguslawa DIugosz, Katarzyna Makiela, Regina Koziara ©
Departament of Horses Breeding, Agricultural University 30-059 Krakow, al. Mickiewicza 24/28, Poland, e-mail: bdlugosz@ar.krakow.pl
CHOSEN FACTORS AFFECTING THE GESTATION LENGTH OF THOROUGHBRED MARES
The aim of the research was to analyse the influence of the factors, such as: sex of a newborn foal, racing career of the mare, foaling season, age of the mare, unsuccessful breeding attempts and a stud-horse, on the gestation length of thoroughbred mares. The research data was gathered in July 2005 in one of the oldest thoroughbred stud in Poland. The collected data concerns 21 mares and 118 pregnancy. In the described research it was observed that alive foals were born after gestation periods lasting 314 - 368 days, where the average gestation period was 335 days. Gestations resulting in bringing colts were longer than those resulting in bringing fillies. The mare's racing career had no effect on the gestation length. It was found out that the gestations where the foal was born between January and March were shorter than those with the parturition between April and June. The youngest mares had the shortest gestation lengths whereas the longest lengths were noted in 11- and 14-year-old mares. The average gestation length in the mares with earlier successful breeding attempts in the period of use did not differ from the gestation length in the mares where breeding attempts were unsuccessful. The stud-horse had no statistically significant effect on the gestation length.
Key words: Thoroughbred mares, length of gestation
Introduction. Thoroughbred horses originated in England are the fastest and extremely precious representatives of world-wide breeds. The very racing and breeding industry developed immensely thanks to this breed. The thoroughbred mares are less fertile than other breeds. They foal with a bit of a difficulty and they miscarry more often. One of the factors taken into consideration as the reason of smaller reproductive efficiency is too close relation within the bloodstock (Budzynski 2000). According to literature (Bielanski 1979, Brzeski et al. 1996, Zwolinski 1976) the mare's gestation is said to oscillate between 322 and 345 days, depending on the breed. The shortest gestation period resulting in the parturition of an alive foal lasted 305 days, and the longest 368 days (Janiszewska et al. 1992). A great influence on the gestation length in mares have environmental and feeding conditions. It can be assumed that malnutrition causes the lengthening of the gestation period, whereas intensive nutrition shortens it. Shortening of the gestation period compared to the average can result in sugar rise in colostrum and milk as well as the fall of mineral components, especially calcium, which has a negative effect on the development of a foal. The shorter gestation period, the bigger chance the foal will not survive. (Zwolinski 1976, Kulisa et al. 2005).
© Maria Kulisa, Boguslawa Dlugosz, Katarzyna Makiela, Regina Koziara, 2009
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Task, the aim of the article. The aim of the research was to analyse the influence of the factors, such as: sex of a newborn foal, racing career of the mare, foaling season, age of the mare, unsuccessful breeding attempts and stud-horse, on the gestation length of thoroughbred mares.
Material and methods. The research data was gathered in July 2005 in one of the oldest thoroughbred stud in Poland. The collected data concerns 21 mares and 118 pregnancy. The research was carried out on the basis of the analysis of 15 breeding seasons from 1991 to 2005. The collected data concerned: sex of a newborn foal, racing career of the mare, foaling season, age of the mare, gestation length after unsuccessful breeding attempts, order of gestations and used stud-horse. For each mare the length of the gestation period was calculated where the last day of the mare's mating was assumed as the first day of the gestation, and the last day of gestation was the day preceding the delivery (Chrzanowski 1974). The results was elaborated statistically by means of the SAS package.
Results of researches. The analysis of the collected data allowed to establish the length of the shortest and the longest gestation periods in the observed mares. The longest was 368 days, the shortest, with a live delivery, 314 days. For the given group the average length varied from 328 to 344,3 days. The values were within the range of 322 and 345 days, which in literature is regarded as physiological (Brzeski et al. 1996, Janiszewska et al. 1992, Zwolinski 1961). According to McKinnon et al. (1993) the normal gestation lasts 335 - 442 days, the cases of 305 - 400-day-long gestations are rather rare. Lipowicz (2000) claims that foals born after 300 - 320 days of gestation are born prematurely, and those born before the 300th day of the gestation as miscarriages. Wisniewski et al. (1996) consider the foals born after 300 - 325 days of gestation as prematurely born and delivery date is regarded as proper when it is after 336 - 340 days of gestation whereas gestation lasting 345 - 365 days is recognized as postmature.
Table 1 shows the figures presenting how the sex of a newborn foal affects the average length of the gestation period.
Tabela 1
sex number of gestation maximum [days] minimum [days] average [days] SD
53 348,0 326,0 336,68 8,61
? 65 368,0 314,0 335,12 5,57
In 118 gestations 65 were fillies and 53 - colts. The maximum length of the gestation resulting in bringing a colt lasted 348 days, and a filly - 368 days. The shortest gestation bringing a colt lasted 326 days, a filly - 314 days. The average gestation length bringing males was higher than the one bringing females and lasted, respectively: 336,7 days (colts) and 335,1 days (fillies). These differences were statistically insignificant. Bek-Kaczkowska (2004) and Zwolinski (1961) also say that
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male gestations are a bit longer than female ones. Fedorski (2004) indicated that it also happens in donkeys: male gestations are 2-3 days longer.
The mares under the research were divided into two groups: those which ran races and those which are not trained. Table 2 shows the data on 17 racing mares and 4 not competing in races, and the length of their gestation periods.
Table 2
? number number of maximum minimum average SD
of mares gestation [days] [days] [days]
racing 17 89 368,0 314,0 336,53 13,52
non-racing 4 29 349,0 322,0 335,59 12,21
The racing mares had the gestation period lasting maximum 368 days and minimum 314 days, whereas non-racing mares, respectively, 349 and 322 days. The average gestation length of a racing mare was a bit longer than a non-racing one, but the difference was not statistically significant. Ciszewska et al. (1988) and Oleksiak (1993) in their research either did not find any influence of the races on breeding capacity of mares.
In table 3 are shown the results referring to the gestation length in relation to foaling season. The described mares were divided into two groups, the first group included the mares foaling between January and March (I-III) and the second one -between April and June (IV-VI).
Table 3
foaling season number of gestation maximum [days] minimum [days] average [days] SD
I - III 52 349,0 332,0 335,32 5,32
IV - VI 66 368,0 314,0 337,23 13,21
In season I-III the gestation period lasted maximum 349 days, and minimum 332 days. In season IV-VI the gestation period lasted maximum 368 days, and minimum 314 days. The average calculated length in the first season was 335,3 days, in the second - 337,2 days. No significant differences between these two were observed. The collected data differ a bit from the data demonstrated in literature. Lipowicz (2000) pointed out that the season had a great influence on the gestation length in horses. Gestation in mares which delivered early (January, February, March) was on average 10 days longer than in those which delivered in April, May or June. He assumes that longer days, higher temperature and availability of grass can probably hasten the foaling, whereas low temperature can delay it.
The analysis of the influence that the age of a mare has on the gestation length has been shown in table 4.
The youngest mares foaled for the first time at the age of 4, the oldest at the age of 18. The longest gestation period of 368 days was noted in an 8-year-old mare, the shortest - 314 days - in a 7-year-old mare. The collected data differ from the research outcome obtained by Chmiel et al. (2000). They present that the gestation periods in the younger mares were longer (342 days and more) and the older mares
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Науковий вгсник ЛНУВМБТ шен1 С.З. Гжицького Том 11 № 2(41) Частина 3, 2009
were in foal on average less than 323 days, Kulisa et al obtained similar outcome (2005) in their research. They maintain that the older a mare, the shorter her gestation period. Similar to the above conclusions were findings described by Lipowicz (2000). He claims that the older mares carry longer that the younger ones. He also points out that mares in foal for the first time usually carry longer than other mares. Chrzanowski (1972) in his observations of mares of Malopolska breed, did not confirm that the age had influence on the gestation period.
Table 4
Age $ [year] number of mares maximum [days] minimum [days] average [days] SD
4 3 338,0 324,0 330,33 7,09
5 10 340,0 322,0 331,70 6,66
6 16 347,0 328,0 336,94 5,97
7 17 344,0 314,0 332,06 7,33
8 14 368,0 329,0 338,57 10,64
9 14 344,0 327,0 336,50 4,36
10 9 348,0 327,0 336,78 6,53
11 9 348,0 326,0 334,89 7,45
12 7 349,0 333,0 340,57 6,16
13 6 346,0 316,0 335,00 10,52
14 3 340,0 328,0 333,67 6,02
15 2 345,0 343,0 344,00 1,41
16 2 341,0 339,0 340,00 1,41
17 3 345,0 332,0 340,00 7,00
18 3 338,0 331,0 334,67 3,51
Table 5 compares the data of 118 gestations, 24 of which took place right after an unsuccessful breeding attempt, and 94 without such attempts in the previous and following breeding seasons.
Table 5
kind of gestation number of gestation maximum [days] minimum [days] average [days] SD
right after an unsuccessful breeding attempt 24 335,79 316,0 335,79 8,17
without such attempts in the previous and following breeding seasons 94 335,83 314,0 335,83 7,25
It appeared that the gestation periods were almost identical in both observed groups, and the minute differences occurred in the shortest gestation periods. The average gestation periods in both groups were similar, too. In the research conducted by Janiszewska et al. (1992) greater differences in gestation period length were observed
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in mares which 2-3 years were not in foal, in comparison to those which were put in foal every breeding season.
The gestation period length was also analysed with regard to the 33 studhorses used, but no statistically significant differences were noted. Bielanski (1979) explains differences in gestation period lengths by means of different sperm's survival rate in a mare's reproductive organ for particular stud horses.
Conclusions. In the described research it was seen that alive foals were born after gestations lasting 314 - 368 days, where the average gestation period was 335 days. Gestations brining colts were longer that the ones bringing fillies. The mares racing career had no effect on the gestation length later in the stud use. It was found out than the gestations with delivery in the season from January to March were shorter than those with delivery from April to June. The youngest mares had the shortest gestation lengths whereas 11-and 14-year-old mares had the longest gestation periods. The average gestation length of the mares which did not have unsuccessful breeding attempts during breeding use was not different from those which did. The stud-horse had no statistically significant influence on the gestation length.
Reference
1. Bek-Kaczkowska I., 2004, Rozrod koni - cz. 2, Konski Targ, 11, 12-14
2. Bielanski W., 1979, Rozrod zwierz^t, PWRiL, Warszawa
3. Brzeski E., Morstein J., 1996, Obserwacje nad dlugosci^. trwania ci^zy u klaczy, Zesz. Probl. Post. Nauk Rol. (67), 103-109
4. Budzynski M., 2000, Ocena powi^zan wskaznikow reprodukcyjnych z inbredem klaczy pelnej krwi angielskiej w stadninie Rzeczna, Ann. UMCS, Vol. XVIII, 18
5. Chmiel K., Sobczuk D., Gajewska A., 2000, Wpfyw wieku klaczy czystej krwi arabskiej na dlugosc rui i ci^zy, Ann. UMCS, Vol. XVIII, 19
6. Chrzanowski Sz., 1974, Ocena wynikow hodowlanych stadnin malopolskich i stadniny huculskiej za okres 1958 - 70, Kon Polski, nr 4, 12-15
7. Ciszewska M., Sobczak Z., 1988, Wplyw kariery wyscigowej klaczy polkrwi na ich pozniejsz^. uzytkowosc rozplodow^, Zesz. Probl. Podstaw Nauk. Rol., 345,133-142
8. Fedorski J., 2004, Osly ale te prawdziwe, Konski Targ, 12, 14-15
9. Janiszewska J., Smugala M., 1992, Analiza zdrowotnosci i rozrodczosci koni ardenskich w stadninach panstwowych, Zesz. Nauk AR w Szczecinie, nr 151
10. Kulisa M., Bec K., Dlugosz B., 2005, Wplyw wieku klaczy na wyniki hodowlane, Konski Targ, 8, 8-11
11. Lipowicz Z., 2000, Ci^za i krycie klaczy, Kon Polski, nr 1, 42-45
12. McKinnon A., Voss J., 1993, Equine Reproduction, Lea&Febiger, Philadelphia, London
13. Oleksiak S., 1993, The evaluation of reproduction indices obtained AT the Polish stud farms of Thoroughbred Horses in the years 1958-1987 and a trial
281
at estimating their heritability, Ann. Warsaw Agricult. Univ. - SGGW, Anim. Sci., 29
14. Wisniewski E., D^browska J., 1996, Wczesna obumieralnosc zarodków, ronienia i przedwczesne porody u klaczy, Zycie Wet., nr 2, 41-46
15. Zwolinski J., 1961, Badania nad niektórymi czynnikami wpfywaj^cymi na dlugosC ci^zy u klaczy. Poz. Tow. Przyj. Nauk, Wydz. Nauk Rol. i Les., t. IX, 4, 1
16. Zwolinski J., 1976, Hodowla koni, PWRiL, Warszawa
Summary
Celem badan bylo przeanalizowanie wplywu czynników takich jak: plec urodzonego zrebi^cia, kariera wyscigowa klaczy, sezon wyzrebienia, wiek matki, jalowienia i ogier na dlugosc ciqzy u klaczy pelnej krwi angielskiej. Material do pracy zebrano w lipcu 2005 w jednej z najstarszych polskich stadnin koni pelnej krwi angielskiej. Zebrane dane dotyczyly 21 klaczy i 118 ciqz. W omawianych badaniach zaobserwowano, ze zywe zrebi^ta rodzily si% po ciqzach trwajqcych 314 - 368 dni, przy czym srednia dlugosc ciqzy wynosila 335 dni. Ciqze, w wyniku których rodzily si% ogierki byly dluzsze do ciqz zakonczonych urodzeniem klaczek. Uczestnictwo klaczy matek w gonitwach na torach wyscigowych nie mialo wplywu na dlugosc ciqz w pózniejszym uzytkowaniu hodowlanym. Stwierdzono, ze ciqze zakonczone urodzeniem zrebi^cia w okresie od stycznia do marca byly krótsze do ciqz zakonczonych w okresie od kwietnia do czerwca. U klaczy najmlodszych wykazano najkrótsze ciqze, zas najdluzsze zanotowano u klaczy 11 i 14-letnich. Srednia dlugosc trwania ciqzy u klaczy, które nie jalowily w okresie uzytkowania hodowlanego, nie róznila si% od tych, które jalowily. Ogier, którym kryto klacz nie wplywal w sposób statystycznie istotny na dlugosc trwania ciqzy.
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