Reproductive Performance of Thoroughbred Mares in Sweden

Abstract

During 1997-2001, a total of 430 Thoroughbred mares were mated by one of the two Thoroughbred stallions on a well-managed stud farm in the central part of Sweden. On arrival, a thorough gynaecological examination of all mares was performed. An early pregnancy examination was performed on days 14 and 15 after ovulation. The overall conception rates for the two stallions were 92.2 and 88.8%, and the corresponding live foal rates were 82.6 and 75.2%, respectively. The mean number of served oestrous cycles was 1.60 per mare per conception and 1.86 per live foal. The first and second cycle conception rates are reported for different age groups, mare categories and month of mating. The age of the mares had a significant influence on the live foal rate, being lower for mares >13 years of age. Resorption and abortion occurred in higher percentages among mares >8 years of age. The highest embryonic death occurred among mares with a history of being barren, or with having resorbed or aborted foetuses during the previous season. The month of mating had no significant influence on the first cycle conception rate or the second cycle conception rate. The frequency of twinning was 10.5% and the results of manual crushing of one of the conceptuses was successful in 88.9% of all cases, according to the ultrasound scanning 2 days later.

Statistical analysis of some factors affecting the number of horse births in France

“…This was in contradiction with the supposed negative effect of lactation on fertility [6][7][8]. Instead of lower pregnancy losses [6] and other fertility results [49], maiden mares appeared as significantly lower reproducers (21% less than barren mares).…”

Genetic effects on reproductive traits in Warmblood horses

“…Bruck et al (1993) reported a foaling rate of 69% for Australian Thoroughbreds in the 1980s; higher results were achieved in Sweden (Hemberg et al 2004) and the United Kingdom (Morris and Allen 2002) over the past decades, but worse results can also be found in the literature Á 63% fertility in Brazilian horses (Taveira and da Mota 2007). Foaling rate was stable over the analyzed period with a slight increase since the 1960s (Fig.…”

Faktoren, die den Reproduktionserfolg beim Pferd beeinflussen

“…In 1980's the results improved: the seasonal pregnancy rates ranged from 72 to 89% and the foaling rates from 66 to 77% (Ricketts and Young 1990, Brück 1993, Morris and Allen 2002. In 1990's a further improvement took place: a seasonal pregnancy rate of 92% and a foaling rate of 83% was achieved in 1997-2001 in Sweden (Hemberg et al 2004), and respectively, 95% and 83% in U.K. in 1998 (Morris and Allen 2002).…”

“…The age, when the mare fertility starts to decrease, varies from 10 to 15 years in different publications (Hutton and Meacham 1968, Laing and Leech 1975, Hearn et al 1993, Morris and Allen 2002, Hemberg et al 2004, Langlois and Blouin 2004 also the risk for the pregnancy loss increases at a similar age. The decreasing pregnancy rates and increasing pregnancy loss rates lead to low foaling rates.…”

“…The Thoroughbreds (TB) have been studied much more than the other breeds: mating records of the individual TB farms have been reported since decades (Laing and Leech 1975, Osborne 1975, Sullivan et al 1975, Brück et al 1993, Hearn et al 1993, Hemberg et al 2004), a survey including 22 TB farms (Morris and Allen 2002), and a study on the entire TB population registered with the Jockey Club in 1987-8 (McDowell andPowell 1992). Reports have been published also concerning the pasture bred horses (Hugason et al 1985, Bristol 1987, Davies Morel and Gunnarson 2000, feral horses (Keiper and Houpt 1984), and different horse breeds in USA (Hutton and Meacham 1968) and in Finland (Katila 2003).…”