Abstract
In a previous study, times from parturition to the first ovulation were followed in 55 Finnhorse mares on the basis of milk progesterone determinations. Ninety-six per cent of mares had ovulated by day 20 post-partum. If intervals of more than 19 days are excluded from the data, the time from parturition to 1 st ovulation was 117 days. However, in cases of foaling before and after the beginning of June the times were 13.0 days and 8.8 days, respectively (p < 0.001). Long intervals (over 16 days) occurred mainly before 1st May (in 6 out of 7 cases).
In a 2nd study, 25 post-partum Finnhorse mares were examined by rectal palpation and ultrasonic scanning. Five and 7 days post partum, but not 2 days post partum there was a statistically significant difference between ovulatory ovaries and non-ovulatory ovaries regarding size of whole ovary and the largest follicle. Six to 8 days before the first post-partum ovulation, the size of the preovulatory follicle was greater in mares which had foaled before the middle of May (32 mm) than in those which had foaled after the middle of May (20 mm) (p < 0.05). Within 2 days before ovulation there was no statistical difference between the sizes (43 mm and 42 mm, respectively). The growth rate was therefore slower in cases of early foaling (1.8 mm/day) than in cases of late foaling (3.7 mm/day).
Keywords: anoestrus, follicle, foal heat, ovulation, progesterone determination, horses, ultrasonography
Sammanfattning
I den första delen av undersökningen uppföljdes tiden melian fölning och den första Ovulationen postpartum hos 55 finnhästston genom mätning av progesteronhalten i mjölk. Nittiosex procent av stona hade ovulerat senast 20 dygn postpartum. Om man utesluter de fall där Ovulationen skedde senare än 19 dagar postpartum, var genomsnittstiden till den första Ovulationen 11.7 dygn. Det förelåg en signifikant skillnad i detta intervall mellan de ston som fölade före den 1. juni jämfört med dem som fölade senare (13.0 vs. 8.8 dygn, p < 0.001). Intervall på mer än 16 dygn påträffades främst bland de ston som fölade före den 1 maj (6 av 7).
I den andra delen av studien undersöktes 25 finnhästston postpartum genom rektal palpering och sonografi. Fem och 7 dygn postpartum var det ovulerande ovariet signifikant större an det ickeovulerande ovariet, vilket också gällde storleken av den största follikeln; denna skillnad kunde inte påvisas 2 dygn postpartum. Sex till 8 dygn före den första postpartum Ovulationen var storleken av den preovulatoriska follikeln större hos de ston som hade fölat före mitten av maj (32 mm) jämfört med dem som hade fölat senare (20 mm); skillnaden var statistisk signifikant (p < 0.05). Däremot förelåg ingen skillnad i detta avseende om follikelstorleken mättes 2 dygn före Ovulationen (43 mm respektive 42 mm). Follikeltillväxten var sålunda långsammare hos tidigt fölande ston (1.8 mm per dygn) än hos ston som fölade sent (3.7 mm per dygn).
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