Gestation length in Carthusian Spanishbred mares

Genetic study of gestation length in andalusian and arabian mares

“…In our sample, no gestation lasted over 360 days in the AB breed and only 5 did in the SPB breed (<1%). This value was slightly lower than that found by Pérez et al (2003) in this same breed, but in the Carthusian lineage, that pointed to 1.10% of prolonged gestations. GL, gestation length; i, selection intensity; r AP (precision of valuation method) = 0.458; R, expected response to selection; G1 mean, mean gestation length expected on the next generation; σ P , phenotypic standard deviation expected on the next generation.…”

“…A number of studies have confirmed wide variations in gestation length for different breeds of horses (Salerno and Montemurro, 1965b;Pérez et al, 2003). Hence, even though the mean gestation found in literature for different breeds is generally between 335 and 345 days (see Pérez et al, 2003, for a review), an equine gestation length between 320 and 360 days can be considered normal (Laing and Leech, 1975;Rossdale et al, 1984;Rossdale, 1993;Immegart, 1997).…”

“…Hence, even though the mean gestation found in literature for different breeds is generally between 335 and 345 days (see Pérez et al, 2003, for a review), an equine gestation length between 320 and 360 days can be considered normal (Laing and Leech, 1975;Rossdale et al, 1984;Rossdale, 1993;Immegart, 1997). Gestations of less than 320 days are generally considered short and resulting foals may present, among other characteristics covered by the term 'prematurity', predisposition to illness, low birth weight and inability to stand.…”

“…In horses, the range of variability of the gestation length is larger than in other domestic species (Bos and Van Der Mey, 1980), probably due to the fact that their long gestation period is influenced by physiological factors that do not influence the gestation lengths of other species (for instance, embryonic diapause, reported by Lofstedt, 1992). A number of studies have confirmed these wide variations in gestation length for various breeds of horses (Pérez et al, 2003).…”

“…4 shows the gestation length evolution according to the breeding season and month of conception. The greatest number of conceptions occurs between the months of February and May (84% in SPB and 88% in AB), the natural breeding season in Spain (Pérez et al, 2003), corresponding to births from January to April. Transitional period conceptions (from September to January) were only 13 and 9% for SPB and AB mares, respectively.…”