Tags: Candling and transfer | Whitepaper
11 September 2014,
During the incubation process, eggs are candled to determine the number of infertile eggs and eggs with dead embryos, together indicated as ‘clears’. This can be done as early as day 5 - 6 of incubation by an individual candling light, but it is time consuming - and the risk of candling errors (e.g. accidentally removal of an egg with a normal living embryo) is evident.
The risk for candling errors is reduced if candling is performed at day 9 or 10 of incubation. By this time, it is also possible to use a so-called ‘candling table’, whereby the entire setter tray is illuminated from beneath. Using a candling table is less time consuming than using an individual candling light - though at the expense of accuracy. Because when the number of ‘clears’ is high, light escaping through the empty places - or ‘flooding’ - in the setter tray makes it more difficult to identify remaining clears conclusively. In many hatcheries, it is therefore common practice to candle eggs on the day of transfer to the hatcher, as this is most efficient in terms of time and labour productivity. When eggs are checked in this way at the point of transfer, automatic candling equipment that illuminates all eggs before the clears are removed, may be used without the disadvantage of reduced accuracy by light flooding.
There are several reasons for candling
For reasons 1-3, it is sufficient to candle a representative number of eggs set. For reasons 4 and 5, all eggs should be candled and clears removed.
The work of Reis et al (1993) showed improved chick quality as a consequence of clear egg removal during candling, especially with older flocks. Studies by Embrex Inc. (IHP Volume 17 Number 7) also favour the removal of clear eggs during transfer and prior to in ovo vaccination. This trend appears to be stronger in the case of older flocks - a factor also supported by the results of Pas Reform Academy’s work with customers in the field - and by experienced hatchery managers.
Clear eggs transferred to the hatcher create an unstable climate in the hatcher baskets, because they do not produce metabolic heat. When automatic chick separators are used, clear eggs are liable to break, causing ‘painted’ chicks.