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Discussion on Research Summary: Sex determination of foals during breeding
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Moderator:
DrO
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Posted on Monday, Apr 23, 2007 - 9:37 am:
Those of you looking to breed a male or female horse look at this! I consider the results a bit suspect but if it works better than my idea of standing the mare into the sun during breeding for boys and away from the sun for girls. You could cut out the mares concentrate or put her on a poor quality hay a month before breeding to produce stallions and conversely increase the feed a month before for producing mares. Let me know if it works for you!
DrO
Biol Lett. 2007 Apr 17;
Extreme sex ratio variation in relation to change in condition around conception.
Cameron EZ, Linklater WL.
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. Studies investigating sex ratio variation in mammals have produced notoriously inconsistent results, although recent studies suggest more consistency if sex ratio variation is related to maternal condition at conception, potentially mediated by changes in circulating glucose level. Consequently, we hypothesized that change in condition might better predict sex ratio variation than condition per se. Here, we investigate sex ratio variation in feral horses (Equus caballus), where sex ratio variation was previously shown to be related to maternal condition at conception. We used condition measures before and after conception to measure the change in condition around conception in individual mothers. The relationship with sex ratio was substantially more extreme than previously reported: 3% of females losing condition gave birth to a son, whereas 80% of those females that were gaining condition gave birth to a son. Change in condition is more predictive of sex ratio than actual condition, supporting previous studies, and shows the most extreme variation in mammals ever reported.
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