Investigating Hatchery Practice - Routine Quality Control in the Hatchery - 1

In the seventh article in this series, Dr Steve Tullett, consultant for Aviagen specialising in incubation and fertility, describes routine quality control in the hatchery and the recording and analysis of results. The article forms part of a recently published Ross Tech publication, Investigating Hatchery Practice.

29 January 2010

6 minute read

Routine quality control can be a very time-consuming process. For this reason, the precise details of what should be recorded and analysed should be discussed by the Quality Control Team in each hatchery and they should also define how the information collected will to be used. The role of this publication is to provide ideas for discussion.

Some suggestions for the possible ways of classifying the time of death of the embryo are given in Tables 1 and 2.

Table 1. Detailed classification system for the time of embryo death suitable for a diagnostic/research type egg break-out
Developmental time (days)	Classification on recording form	Observations
0	Infertile	No obvious sign of development
1	24h 'Early Dead'	Cream coloured extra-embryonic membranes occupying area up to one cm diameter
2	48h 'Early Dead'	Cream coloured extra-embryonic membranes occupying area up to three cm diameter
2.5-4	'Blood Ring'	Obvious 'blood ring' and the beginning of formation of the sub-embryonic fluid
5-12	'Black Eye'	The black pigmentation of the embryo's eye is obvious. The wings and legs can be seen as well
13-17	'Feathers'	Feathers present. Although the first feathers are seen as early as 11 days, they are often not obvious over the entire body until 13 days of age
18-19	Turned	The embryo is moving from the 'head between thighs' position to the hatching position and the yolk remains outside the body of the embryo
20	Internal Pip	The beak of the embryo has come through the inner cell membrane into the air cell
20	External Pip	The beak of the embryo has broken through the eggshell
0-10	Early Rot	Deep discolouration of the egg contents with emission of rotten odours
11-21	Late Rot	Obvious embryo with deep discolouration of the egg contents and emission of rotten odours

Table 2. Simplified classification system for the time of embryo death suitable for a Quality Control type egg break-out
Developmental time (days)	Classification on recording form	Observations
0	Infertile	No obvious sign of development
0-7	Early Dead	Any death in the first week of incubation. The end of this period is delineated by the appearance of the egg tooth on the end of the beak
8-14	Mid-Dead	Embryos with an egg tooth but feather development is not immediately obvious over the entire body
15-19	Late Dead	Well feathered embryo almost filling the egg. The yolk may be external to the body, or may be retracted
20	External Pip	The beak of the embryo has broken through the eggshell
0-21	Contaminated	Deep discolouration of the egg contents with emission of rotten odours

Tables 3 and 4 give top quartile targets for hatchability losses.

Some ideas for recording forms are given in a forthcoming section, but they should be modified to suit individual needs. The entry of the results into an electronic database and the analysis of trends is highly recommended in order to define working targets.

Table 3. Top quartile targets for hatchability losses when performing detailed diagnostic/ research type egg break-outs (% of total number of eggs set)
	Stage of development of embryo
Flock age	In- fertile	24 hrs	48 hrs	Blood ring	Black eye	Feathers	Turned/ mal- position	Pipped air cell	Pipped shell	Cracked	Con- tam- inated
Young: 25-30 weeks	6.0	1.0	2.0	2.5	1.0	1.0	1.5	1.0	1.0	0.5	0.5
Peak: 31-45 weeks	2.5	0.5	1.0	2.0	0.5	0.5	1.0	1.0	0.5	0.5	0.5
Post Peak: 46-50 weeks	5.0	0.5	1.0	2.5	1.0	0.5	1.0	1.0	0.5	0.5	0.5
Ageing: 51-60 weeks	8.0	0.5	1.0	3.0	1.0	0.5	1.5	1.0	0.5	1.0	1.0

Table 4. Top quartile targets for hatchability losses when performing routine quality control type egg break-outs (% of total number of eggs set)
	Stage of development of embryo
Flock age	Infertile	Early dead	Mid dead	Late dead	External pip	Cracked	Contaminated
Young: 25-30 weeks	6.0	5.5	1.0	3.5	1.0	0.5	0.5
Peak: 31-45 weeks	2.5	3.5	0.5	2.5	0.5	0.5	0.5
Post Peak: 46-50 weeks	5.0	4.0	1.0	2.5	0.5	0.5	0.5
Ageing: 51-60 weeks	8.0	4.5	1.0	3.0	0.5	1.0	1.0

The appearances of chick embryos at different stages of development are well documented, but an embryo which dies at four days of incubation and which then remains in the incubator for a further 17 days will be subject to considerable deterioration. For this reason, the opportunity to open eggs as early as possible by candling at eight to 10 days of incubation is recommended. Thereafter, removal and examination of any dead eggs at transfer and an examination of the hatch debris is recommended.

As a minimum requirement the following are suggested for inclusion into any routine quality control system:

At least three setter trays of eggs should be monitored weekly for each flock in lay; ideally the sample trays should be representative of the whole hatch.
The three setter trays should be weighed empty and the weight recorded.
The trays should then be filled with eggs and the weight of each tray plus eggs recorded.
The trays should be weighed again at the time of transfer to the hatcher. The eggs should then be candled and the 'clear' eggs broken out to enable categorisation and enumeration of infertiles and early deads, mid-term deads and contaminated eggs.
At chick take-off the number of chicks should be counted and recorded from each of the three trays and the chick weight expressed as a percentage of the fresh egg weight or egg weight at setting.
Examination of the hatch debris from the same trays will complete the records.
All data should be recorded to flock age and the setter and hatcher the eggs were incubated in.
The percentage of eggs falling into the different categories should be calculated and compared with the working targets set from historical data. Any large deviations from the working targets should be investigated. Some possible reasons for failures are given in a later section entitled Interpretation of Results. A more comprehensive guide for troubleshooting hatchery problems is H.R. Wilson's Hatchability Problem Analysis published by the University of Florida and available as a free download on the internet.