In-ovo sexing

In-ovo sexing

There is increasing resistance to the practice of culling male chicks in batches of day-old chicks for the laying sector. And it is financially advantageous to select out male embryos as early as possible. In addition to in-ovo vaccination, in-ovo sexing has also arrived. In-ovo sexing has made great progress in the last few years, and in some countries a ban on culling day-old male chicks is likely within the foreseeable future. The following information represents the situation in 2021. Various factors play a role in the choice of technology: • Invasive or non-invasive: making a tiny hole in the eggshell risks negatively affecting hatchability. So, the non-invasive option is preferable if reliability is comparable. • High reliability: the level of reliability must equal that of the current sexing method, used after hatching. • Timing of gender determination: the earlier, the better. Ideally, before being set in the incubator. • Speed of sexing: the volume of eggs handled at a hatchery is enormous, so a high capacity and throughput rate must be possible. This is important to prevent the eggs from cooling down too much. • Practical and robust technology: a method that works in laboratory conditions must be suitable for practical application at a hatchery.

There are a number of technologies under development: • Spectroscopy: A beam of light is shone through the eggshell, or a tiny hole in the shell. The gender can be determined by the way the light scatters. • Biomarkers: This method requires sampling fluid from the egg (allantoic fluid). These tests usually only work from day 7 or 8. Genetic modification will probably be an option in the future. So, either a marker will be developed that already shows a result on day 1, or the hens would only produce female offspring. The real question is whether this will be ethically acceptable for the consumer. Spectroscopy This non-invasive method has been ready for practical application since mid-2020, and has an accuracy of more than 95%. One machine can test more than 20,000 eggs an hour. No laboratory analysis is required, which makes this technique environmentally friendly (no chemicals required). Currently, the hyperspectral imaging technique only works with brown layer breeds, as of the 13th incubation day. This is actually a form of colour sexing inside the egg based on feather colour (also see page 175).copyright protected

The spectroscopic gender determination unit. Spectroscopic gender determination. The egg is illuminated from below. The gender of the embryo is determined based on the calculated light spectrum. Eggs classified as having female embryos are then incubated normally.

Biomarkers (SELEGGT and PLANTEGG)

These are two systems that work based on biomarkers: • SELEGGT: marker reacts to the female hormone estrone-sulphate. • PLANTEGG: uses the PCR-technique (DNA-analysis). On a carousel, lasers create a fine hole in the eggshell of an 8-10-day incubated egg. Then a minimal amount of allantoic fluid is extracted for analysis. The female hatching eggs are returned to the incubator. The inner membrane reseals on its own.

The carousel for collecting allantois fluid samples. A single laser beam is too weak to cause any damage, but the cross-point between two beams is powerful enough to bore through the eggshell. copyright protected The lasers make a tiny hole of 0.3 mm in diameter. A suction mechanism extracts allantoic fluid through this hole (PLANTEGG and SELEGGT).

Colouring indicates if the fluid contains estrone sulphate (female) or does not (male) contain any (SELEGGT). The laser hole is 0.3 mm in diameter (PLANTEGG and SELEGGT)

The PCR technology provides results within 1 hour (PLANTEGG).

Biomarkers: InOvo

The InOvo system works by indicating a specific metabolite in the allantoic fluid, as a biomarker around day 9. In this system, a tiny opening is pierced in the eggshell. The best location for this hole is determined for each egg. Then some allantoic fluid is extracted by a needle. The hole (< 1 mm) is resealed afterwards. The fluid is analysed very quickly using mass spectrometry. This analysis takes less than a second. The speed of the analysis and the lack of a need for chemical analysis make this concept viable for scaling up.

Mass spectrometry can determine the gender of the embryo based on a small gender specific molecule in the allantoic fluid. After sexing, each egg is stamped with an additional identification code (male or female). The eggs with female embryos are then incubated and the males are removed.

The sampled eggs have a clearly visible seal-layer that closes the hole made during the process. Gender reversal Another option does not involve determining the gender but changing it. Gender is, of course, determined genetically. But suppressing the expression of the gene responsible for male gender will make an embryo develop into a female. An Israeli company is developing a technique based on subsonic sound, with the aim of achieving this. The exact mechanism involved in the influence of sound on embryonic development is still unknown. In early 2021, they achieved 63% females, and 70% in some parts of the incubator. This technique is still in an experimental stage, but the company expects commercially interesting results within a short time.copyright protected