Saturday 24 January 2015

Rare breed Ixworths 88% fertile

Infertile "clear" egg
The Ixworth hatching eggs are 88% fertile. This is based on a small sample, only six eggs, but it seems to indicate that crossing the two distinct lines of Ixworths has resulted in greater fertility and may have overcome the inbreeding problems that results from having a very small population and a narrow genetic base.

The eggs that were set last week were weighed and candled today, the Bresse Gauloise eggs in the same incubator were only 67% fertile, not bad but they should have been at least 75% so I cannot sell any yet. Fertility should improve as the days lengthen and we have warmer Spring days.

Incubation takes 21 days but, by day 19 the embryo is more or less fully developed and as it emerges from the egg it needs the air held in the air sac in the blunt end of the egg. In order to have enough air the egg must lose about 13% per cent of its moisture in days 1 - 19, this is replaced by air.

Target and actual egg weights

Relative humidity in the incubator is as important as
Fertile egg
temperature so that moisture is lost at a steady rate, approximately 13% of the egg's initial weight over 19 days. To achieve this target weight loss the Rh should e from 40 - 45 %. You can see from the graph that humidity as been too high and weight loss has been less than required during days 1 - 8 so humidity will have to be decreased to bring it back to target on day 19.

In 2013 we visited the Cotswold Farm Park to have a look at their rare breeds. They had a few Ixworths, they were a bit on the small side and not really up to standard for the breed. I offered to send some fertile eggs so perhaps they will want some this year when their incubator is set . 

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