EMTECH HATCH HANDOUT #14 EGGS WHICH FAIL TO HATCH Surveys show that 18.5% of chicken and 30% of turkey eggs fail to produce a 1st quality chick or poult. This wastage is made up as follows: Broilers Turkeys Candling Waste ("clears) 8.0 13.0 Dead in Shell 9.5 10. Culls 1.0 2.0 Total Wastage (%) 18.5 25.0 Overall Hatchability 81.5 75.0 Two categories of wastage - infer lity or embryo death at some stage. The major causes of eggs failing to hatch is as follows: Broilers Turkeys % % Egg Storage 25 20 True Infer lity 20 25 Bacterial and Mould Contamina on 12 8 Egg faults and shell damage 10 5 Incuba on faults 5 10 Breeder nutri on 10 12 Disease 10 15 Gene cs 8 5 100 100 The average numbers of first quality chicks obtained as percentages of total eggs set is as follows: Broiler chicks 81.5% Brown egg laying stocks 80.0% White egg laying stocks 83.0% Turkeys 70.0% BREAKING OUT EGGS About half the loss of hatchability is due to infer lity and the other half due to embryo death during incuba on. For this reason it is important to examine samples of both hatched debris and clear eggs, about 5 dead in shell and 50 clear eggs are usually adequate. The start of any inves ga on involves a study of the background history of the flock in ques on. This is why a completed history sheet with the samples is invaluable.
EXAMINATION OF DEAD IN SHELL The main points to look for during an examina on are as follows: 1. Egg size and shell quality 2. Air space 3. Posi on of embryo within shell 4. Anatomical abnormali es 5. Nutri onal abnormali es 6. Unused albumen 7. Age of embryo EGG SIZE AND SHELL QUALITY Egg size can tell us quite a bit about the flock in ques on. Small eggs may come from a young flock or may be as a result of a nutri onal problem, or there may be a candling error at the flock farm or hatchery. Large eggs do not hatch as well as eggs within the op mum size range for that par cular strain. Shell thickness is important as its rela onship with porosity; this may effect the rate of evapora on from the egg and subsequent hatchability. Look for effect of disease especially Newcastle Disease and Infec ous Bronchi s par cularly whether the eggs have lost pigmenta on and whether they are striated. Record whether the shell is cracked. If so, suspect handling either at the flock farm or at the hatchery. The use of individual plas c se ng trays can reduce egg cracking by something like 2-3% and improve hatchability by a similar amount. Cleanliness of the shell can be a clue to the hygiene standard on the flock farm. AIR SPACE The egg is opened at the air space end and the air cell membrane is examined. We are interested in the size of the air space to give some indica on of humidity condi ons in the incubator and also for the presence of any mould growth on the air cell membrane. Cracked eggs are ideal recipients for spores of aspergillosis and an infected egg that becomes cracked can infect many other eggs. Finally, check to see whether the embryo has pipped the air cell membrane before dying. POSITION OF EMBRYO WITHIN SHELL Having exposed the embryo we note its posi on within the shell. The normal posi on is for the head to be under the right wing with the beak towards the air space and the legs in a trussed posi on. Embryos are some mes found in so-called "malposi ons". The most common of which are: Malposi on II (upside down), Malposi on III (head turned towards le ). Most embryos in Malposi on III will die in the shell but about 50% of those in Malposi on II will hatch. The most usual cause of malposi oning is insufficient turning of the eggs, most common in small hatcheries with incubators fi ed with inadequate turning mechanisms. Other causes of malposi oning include se ng the eggs upside down, high incubator temperatures, egg shape and some mes nutri onal deficiences
ANATOMICAL ABNORMALITIES These are o en caused by gene c factors. There are well over 20 lethal genes described which will cause abnormal embryonic growth. These include beak abnormali es, duplica on of legs, lack of one or both eyes, protrusion of the brain and failure to include the viscera. Many of these features may have a gene c basis but are o en precipitated by poor environmental condi ons. Such condi ons might be:- a. Poor storage on the farm or at the hatchery, involving temperature, humidity and turning. b. Rough handling or transport. c. Inadequate se ling me a er transport and before se ng. d. Improper condi ons in the se ers in the early stages of incuba on. e. Fumiga on at suscep ble stages or over fumiga ng at between 24 and 96 hrs of incuba on. NUTRITIONAL ABNORMALITIES Nutri onal deficiencies usually show up as a mid term peak of mortality between 14 and 17 days of incuba on. We can get reduced hatchability due to deficiencies of vitamins such as A, B, B2 (riboflavin), B12, B6, niacin, folic acid, bio n, pantothenic acid and minerals such as calcium, phosphorus, manganese and zinc. It is more likely that the cause is indirect rather than direct. Such an indirect cause would be breeders diet dilu on through feeding grain, peck order effects, selec ve feeding in automa c feeders, insufficient water, effects of medica on which lower feed intake, or outbreaks of or long-term effects of Coccidiosis or worm infesta on. These causes may give symptoms in the dead in shell embryo of apparent nutrient deficiency. Examples of nutri onal abnormali es o en seen are as follows:- 1. Chondrodystrophy 2. Perosis 3. Clubbed down 4. Curled toes 5. Dwarfing 6. Parrot beak 7. Atrophy of legs 8. Subcutaneous haemorrhage 9. Subcutaneous oedema 10. Fluid blebs UNUSED ALBUMEN All albumen should have disappeared by the 17th to 18th day of incuba on. Its presence may indicate a delay in development due to prolonged pre-incuba on storage or to storage under poor condi ons, or low incubator temperature, or some mes it occurs along with nutri onal symptoms. AGE OF EMBRYO (for turkeys increase chicken figures by 1/3rd) Finally es mate the age of embryo when death occurred. This is important as there are cri cal periods of development, ie 3 to 4 days of incuba on and the end of incuba on when most of the mortality occurs.
EXAMINATION OF 'CLEARS The purpose of examining 'clears' is to check on: a. The adequacy of candling at 18 or 24 days, and b. Whether the clear eggs are true infer les or early dead germs. Candling at 8 days (Turkey) 3 groups: (a) blood ring 4-5 days or more (b) no blood or signs of development (c) some development to 1-3 days, no blood. Main causes: egg storage, bacterial contamina on and failure to correctly inseminate. Candling at 18/19 days (Chicken) 24-25 days (Turkey) 3 groups - chicken (a) blood ring 3-4 days or more (b) no blood or signs of development (c) some obvious development with embryos dying at any stage up to 18 days. Main causes: (a) egg storage, bacterial contamina on. (b) infer lity - cockerel or behaviour problem (c) bacterial contamina on, incuba on faults, nutri onal deficiencies. The early mortality is due to a failure to form basic organ systems ie blood system; most embryos die during so called "cri cal periods" of development. About 1/3rd of mortality occurs during this early period (1st week of incuba on). Candling at 24/25 days (turkey) (a) embryos dying 8-24 days Main causes: Nutri onal deficiencies, egg contamina on, incuba on faults and gene c effects. Second mortality peak around full terms, at hatching, associated with poten al changes to the "hatching posi on", u lisa on of remaining albumen; withdrawal of yolk sac, and change of respira on through the C-A membrane to the lungs. Two-thirds of the total mortality occurs here.
FULL TERM MORTALITY Pipped - failed to hatch and alive late transfer low humidity in hatcher old eggs Pipped and died Residual albumen Malposi ons Hatching early young eggs Disease respiratory disease. insufficient turning during 1st 2 weeks old eggs low temperatures high humidity insufficient turning insufficient oxygen set upside down due to faulty egg shape inadequate turning high temperatures Hatching late So chicks old eggs low temperatures High humidity low temperature CULLS Broilers 3/4-1% Turkeys 3-9% Reason for culls BROILERS 1. Old eggs increased malforma ons 2. Machine faults - late hatch - weak chicks 3. Inadequate nutri on - poor chicks
TURKEYS 1. Unhealed navels - egg age and incuba on condi ons. 2. Splay legs, deformi es, leg weakness, distended albumen or small poults. It is important to emphasise the necessity of maintaining a good standard of hygiene when eggs are handled. Our ini al examina on of the shell can give us a good idea of the standard of management on the flock farm, ie whether the shell is clean or otherwise. Bacterial and mould contamina on are major causes of loss in the hatchery and in most cases contamina on originates on the flock farm. This is where a high standard of management on the flock farm and a good standard of hygiene both on the flock farm and at the hatchery is of paramount importance. Having recorded all the evidence from the dead in shell and clear egg findings and taking into account the field informa on we should be able to indicate possible cause of poor hatchability, for example: a. A high incidence of early dead germs together with full formed embryos with much unused albumen o en indicates prolonged storage. b. High embryonic mortality at hatching can indicate disease ie mycoplasmosis or nutri onal (ie pantothenic acid deficiency). c. Many cracked eggs in the sample together with a high propor on of head abnormali es will suggest the handling procedures both at the flock farm, in transit and at the hatchery. d. Many thin shells, cracked eggs, together with a large air space can indicate respiratory disease infec on at the flock farm. Updated and reproduced with the kind permission of BRIAN HODGETTS BH Consul ng and formally ADAS, Ministry of Agriculture, Embryologist Disclaimer: Although the author has made every effort to ensure that the information in this Hatchery Handout is correct at the time of publication, the author and EmTech Hatchery Systems do not assume and hereby disclaim any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from negligence, accident, or any other cause.