It was written by Olafur R. Dyrmundson and published in Icelandic Agricultural Science in 1994. The summary indicates that a study was undertaken in 1979 of “the attainment of puberty, seasonal sexual activity, gestation length and reproductive efficiency in Icelandic horses kept under free-range conditions.” Of course, my interest is in gestation, which is why I focused on it. This information, found in the summary, is what’s most relevant to us: “The limited information available on the duration of gestation indicated a substantial variation of 315 to 390 days around an average of approximately 350 days.”
The study had three sources. The first was a survey conducted in 1979 by publishing inquiries in the Icelandic equine journals Eiðfaxi and Hesturinn Okkar where horse breeders and owners were asked to provide information on reproductive characteristics such as sexual development, seasonality of breeding, gestation length, and the incidence of twin foal births. Twelve written and several telephone replies were received from horse breeders in various parts of the country, mostly in or soon after 1980.
The second source was the analysis of horse records covering mares born during the period 1936 to 1976 at Lágafell Farm, Austur-Landeyjar Parish, S-Iceland, where the traditional Icelandic free-range management system of horse keeping is practiced, i.e. grazing on natural pastures with or without supplementary feeding in winter. (The stallions were kept with the mares and replacement fillies throughout the year.)
The third source was the monitoring and recording of bits of information reported in journals and newspapers during the period 1980 to 1992 on individual cases of foaling out-of-season (winter) and on twin births in various parts of the country.
Of course, there are a few variables here which in our case differ from the horses in the study. Signy is not free ranging – she lives in a paddock. Her diet also differs – it’s almost exclusively hay. The degree of intervention is greater here than it would be if she resided in a pasture. And in addition, she doesn’t run with a stallion (but she’d like to).
In general, the gestation period of horses (as cited in texts) is 336 days. It sounds to me that in the case of Icelandic horses, this figure is not as close to an absolute as one might think. I now know this – had Signy had her foal a few weeks ago, that it very likely would have been premature, the main sign being that she had not yet produced any milk.
I’m actually a bit cheered by the information that’s included in this study. I have some more intuitively-based reasons to add to the mix – I think that Signy’s waiting for good weather, and for us to be ready. I’m almost there, but probably not quite yet.
Next: 138. 4/25/12: Geese