By Adri Mertens - phenotyping specialist
As a breeding company, we are continuously looking for new methods to improve the quality of our measurements. It is well known that we put a lot of selection pressure on breeding for the highest amount of 1st quality eggs per hen housed. More 1st quality eggs will generate higher revenues and we should not forget that most of the consumers only encounter the egg itself, hardly ever with the hens that produce this amazing superfood. It has already been a few years since we introduced our first Eggxaminator, and since its first introduction, loads of data have been collected and analyzed.
Short wrap up: The Eggxaminator was created in collaboration with Hendrix Genetics Innovations and one of our tech partners from the Brainport Eindhoven region (home to companies such as Philips, ASML, and VDL). The Eggxaminator uses Robotics and Machine Vision technology to examine and collect data on exterior egg phenotypes with large accuracy and consistency.
With the Eggxaminator we focus on 10 different traits, all related to the exterior quality of the egg, with the finest detail. The Eggxaminator takes more than 15 different pictures of one egg, and via automated image analyses, output values are given for each trait. One of the traits that the Eggxaminator can measure is egg mottling. Egg mottling occurs when there is a deviation in calcite columns of the eggshell. Due to these deviations in calcite columns of the eggshell, moisture can accumulate in the spaces between the columns. This moisture appears as translucent spots on the egg (Talbot and Tyler, 1973). Examples of variation in egg mottling is shown in the pictures below.
Photo 1: Value 16
Photo 2: Value 42
Photo 3: Value 91
Another goal when breeding laying hens is to select hens that produce nice and smooth eggshells. A trait that can be sometimes observed when looking to the eggshell are so called sandpaper shells (rough areas that are located on the top/bottom of the egg). Both the top and bottom of the egg are area’s that are graded in much detail by the Eggxaminator. Values are given for the number of irregularities on these sides of the egg. Examples are given below.
Photo 1: Value 0,05
Photo 2: Value 3,47
Photo 3: Value 12,02
Not only appearance of the shell, and shell quality are of interest, also the shape of the egg. It is well known that the shape of the egg plays an important role in overall shell strength. Already used for many years, but now automated in the eggxaminator, is the shape-index. The shape index is an objective way to express the shape of an egg. Egg shape-index is calculated by measuring and dividing the width of the egg by its length. A shape index <0.72 indicates a long egg (often pointy). If the shape index is >0.76 the egg is too round (Piet Simons, 2017). Clear examples of eggs with different shape-index values are shown below.
Photo 1: Shape index 0,695
Photo 2: Shape index 0,742
Photo 3: Shape index 0,814
With all this egg quality data being generated by the eggxaminator, our geneticists have been able to calculate heritabilities. A heritability measures how much of the variation of a trait within a group of animals is caused by genetic variation. As an example, when the heritability of a specific trait is 0.40, it means that 40% of the variation that is observed on that trait is caused by genetic variation among that specific group of animals. As a rule of thumb, the higher the value of a heritability estimation, the faster genetic progress can be achieved.
Please note, when only selecting on 1 specific trait, faster genetic progress can be made, but it will be no surprise that breeding laying hens requires a balanced breeding approach, all traits of interest should go in the desired direction when selecting. But what is all that data telling us? Let’s have a look at 1 of our pure line white egg layers in more detail. We examined and analyzed the eggs during a 2-year period (spring 2019 - spring 2021) with the Eggxaminator. The eggs were collected and analyzed at four different periods: 20-40 weeks of age, 40-60 weeks of age, 60-80 week of age
and 80-100 weeks of age. We have given heritabilities for the traits that we have described earlier, egg mottling, sand index, shape index and on top of that egg weight.
0.40 ± 0.062
0.48 ± 0.058
0.43 ± 0.059
0.38 ± 0.049
0.46 ± 0.065
0.38 ± 0.055
0.37 ± 0.057
0.34 ± 0.045
0.38 ± 0.063
0.33 ± 0.050
0.32 ± 0.055
0.44 ± 0.050
0.57 ± 0.070
0.48 ± 0.059
0.46 ± 0.054
Table 1: Heritably estimations different traits based on Eggxaminator data.
The results from table 1. clearly show the relevance of accurate phenotyping and high-quality data collection. Moderate (0,30-0,50) to high (>0,50) heritabilities, with low and stable standard errors, have been calculated and will help us to keep on improving overall eggshell quality in all our breeds. Accurate data collection is at the core of our breeding program. With the implementation of the Eggxaminator we have been able to further improve our genetic progress on eggshell quality. As a result, our customers will benefit that their laying hen flocks are able to produce more 1st quality eggs per hen housed with every new generation, clearly setting the standard for sustainable breeding.
