Definitions

• This invention is directed to a method for the incubation and hatching of premature eggs, in particular premature eggs removed in their shell from a bird prior to transfer of the premature egg to the cloaca of a bird.
• European Patent application no. 01650109 is directed to a method for rearing a bird of germ-free status comprising housing a parent bird, removing a premature egg in its shell from the parent bird prior to transfer of the premature egg to the cloaca and incubating the premature egg in its shell and hatching the premature egg to produce a laying bird.
• Ventilation, temperature control and humidity are very important during the incubation and hatching process.
• the eggshell in particular its pores and cuticle, modulate respiratory gas exchange and hydration of the developing embryo.
• the eggshell is a breathable membrane and whilst the embryo is developing the eggshell allows carbon dioxide and water to escape from the egg and oxygen to enter the egg. As the embryo grows, it requires an increased supply of oxygen. Furthermore, care must be taken to maintain the appropriate humidity levels during the hatching period.
• the conditions required for successful incubation and hatching of a normal, naturally laid egg are well known. These conditions vary between species. For example, for domestic fowl such as chickens, the entire process takes from 20 to 22 days, generally 21 days, with incubation conditions applying from Day 0 to Day 18 and hatching conditions applying from Day 18 to 21. During incubation eggs should be positioned so that the domed end, which contains the air cell, is uppermost. Typical incubator conditions are air temperature of 37.5°C, relative humidity (RH) of 50%, and regular turning (rocking) of the eggs so that the longitudinal axis of the eggs is slowly rotated through approximately 80° (40° each side of vertical) once every 45 to 180 minutes.
• RH relative humidity
• the embryos typically move into the hatching position within the egg.
• the eggs should no longer be turned at this stage.
• European Patent no. 0 295 964 describes an in-vitro avian embryo culture technique.
• this specification is directed to the incubation of an embryo in a closed container after the embryo has been removed from its shell.
• the container used is preferably part of an egg shell which has been chosen from the same species as is being cultured or, in the terms of the present invention, from a similar hen.
• European Patent no. 0 511 431 discloses an in-vitro culture method for a fertilised ovum of a hen in which an embryo which has just been fertilised is taken from an upper portion of the magnum of the oviduct of a hen within an hour or so after oviposition and then subsequently cultured. Both of these specifications merely disclose the artificial culturing of eggs which have been removed without their shell.
• the present invention is directed to special techniques for the incubation and hatching of surgically-derived premature eggs in their shell, in particular those derived from the method of European Patent application no. 01650109. These techniques give improved results in terms of yield of surgically-derived eggs when compared to conventional egg incubation and hatching techniques.
• a method for incubating and hatching of a premature egg in its shell in a sterile environment comprising the steps of optionaliy cooling and pre-incubation storage of the egg; placing the premature egg in an incubation isolator adapted to provide variable rocking of the eggs; monitoring ventilation and weight loss of the eggs; during the incubation phase decreasing the relative humidity (RH) in the isolator to a level of from approximately 15% to 40%; during the hatching phase increasing the relative humidity to a level of from approximately 60 to 75% and stopping the rocking of the eggs; and maintaining the eggs in the isolator until hatching.
• RH relative humidity
• the desired relative humidity in the first 18 days of the incubation phase is much lower than required for normal eggs. If this low relative humidity of 15- 40% was used for hatching normal/conventional eggs (i.e. eggs permitted to mature fully in the reproductive tract and laid naturally through the cloaca) it would give very low hatchability rates( ⁇ 40%) whereas for premature eggs, this low relative humidity is the optimal RH range. Thus, using such low relative humidity levels in the incubation phase goes against the conventional teachings in this field.
• a method for incubating and hatching surgically-derived premature eggs in their shell in a sterile environment comprising the following steps: a. Pre-incubation storage of the surgically-derived premature egg; b. Placing the eggs in an incubation isolator adapted to provide variable rocking of the eggs; c. Controlling the ventilation in the isolator; d. Weighing the eggs to monitor weight loss; e. During the incubation phase decreasing the relative humidity to approximately 15% to 40% and altering the temperature in the incubation isolator to obtain a target weight loss during the incubation phase; f.
• the germ-free status of the surgically-derived egg is maintained throughout the method.
• the present invention is directed to incubation and hatching methods for a surgicaily- derived premature egg from optional pre-incubation storage through to incubation and hatching of a viable bird.
• Surgically-derived eggs are premature. In some cases their development, for example gastrulation, may be delayed. Furthermore, it is possible that premature eggs may lack certain features of a full-term naturally laid egg, for example there may be reduced cuticle on the shell and pore formation in the shell may be impaired. It has been found that some surgically-derived eggs, due to premature egg shell formation and effects of surgical anaesthesia, euthanasia methods and timing, may not adequately loose moisture and corresponding body weight which are essential for correct embryo development and chick viability. Therefore, standard hatchery practices for normal laid eggs are not be appropriate to achieve optimum viability of the premature surgically-derived eggs.
• a method for incubating and hatching surgically-derived premature eggs in their shell comprising the following steps: a. Pre-incubation storage of the surgically-derived premature egg; b. Placing the eggs in an incubation isolator adapted to provide variable rocking of the eggs; c. Controlling the ventilation in the isolator; d. Weighing the eggs to monitor weight loss; e. During the incubation phase decreasing the relative humidity to approximately 15% to 40% and altering the temperature in the incubation isolator to obtain a target weight loss during the incubation phase; f.
• the surgically-derived premature egg in its shell is germ-free and the method of the invention is carried out in a sterile atmosphere to ensure germ-free conditions during hatching and incubation.
• the ventilation within the incubator is controlled. Ventilation using a combination of HEPA filtered air and sterile air supplemented with sterile oxygen when appropriate may be used.
• the isolator is provided with facilities to weigh the eggs. This enables direct monitoring of egg weight loss.
• a target weight loss from the start of incubation to prior to the hatching period for an individual egg is from approximately 10 to 15% of the initial egg weight.
• the isolator may be provided with one or more incubators, such that each incubator may simultaneously provide different conditions, specifically relative humidity levels, necessary to optimise weight loss and viability for individual eggs. Separate incubators are used in the situation where wide variations in egg weight loss are anticipated.
• the incubation period is defined as the time period from Day 0 to Day 18 in the incubator. Rocking of the eggs in this time period is essential. Day 0 corresponds to the first day the egg is placed in an incubator. The hatching period is defined as the time period from Day 19 to Day 21. Rocking of the eggs is not required during this time period.
• Relative humidity at normal levels during incubation and hatching is understood to be from approximately 50% to 70%.
• the present method recognises the need to alter conventional incubation and hatchery practices to levels that would not be contemplated in this field.
• the unique characteristics of surgically derived eggs provides specific circumstances where conventional teachings in this field do not achieve the desired hatchability/viabiiity rates.
• relative humidity levels are lowered to from 15 to 35%, preferably, from 25 to 35% during the incubation phase. Additionally, the incubation phase occurs at a temperature of from 36 to 38°C.
• relative humidity levels are raised to from 60 to 75%, preferably approximately 65% during the hatching phase.
• the hatching phase may occur at a temperature of from 36 to 37.5 0 C.
• the hatching phase (step (e)) may commence on or around Day 18.
• the method of the invention is carried out in an incubation isolator.
• the incubator may be a conventional incubator used in standard hatchery techniques or it may be an incubator adapted to conform to the sterility requirements for incubating and hatching a germ-free egg i.e. an incubation isolator.
• an incubation isolator Ideally, the incubation method and incubation isolator maintains the sterility and germ-free status of the premature egg.
• the incubation isolator maybe provided with facilities to monitor and control ventilation rate, to dehumidify air and to achieve oxygen-enriched air (21-23% at 760mm Hg).
• a conventional incubation isolator is used which has been modified and enabled to control ventilation is used.
• the method may further comprise the step of adding oxygen to the incubation isolator. Most preferably, oxygen is added when the humidity in the incubator is decreased.
• the surgically derived eggs are removed from a surgical isolator where surgical removal took place and delivered to the incubation isolator within a short time, for example within 30 minutes from surgery. It is advantageous to ensure that eggs are ventilated with air prior to commencement of incubation.
• the incubation method may also include the additional initial step of cooling the eggs after surgical removal from the parent bird. It may also include a pre-incubation storage step where the eggs may then be stored, undisturbed for, at least 24 hours, preferably not more than 72 hours. In general, preincubation storage may be from 0 to 72 hours. Preferable, storage conditions for the premature egg are: HEPA filtered air, temperature between 15 0 C and 23 0 C, relative humidity of 50% to 75% and storage free from vibration or sudden jarring.
• the eggs may be incubated using sterile equipment and specified contamination or germ-free air.
• the method comprises the following steps: For the first 24 hours standard incubation conditions for the species of egg may be used. Thereafter, each egg should be carefully monitored for weight loss, incubation temperature, relative humidity and, if appropriate respiratory gaseous exchange especially carbon dioxide and oxygen concentrations in air.
• the incubation and hatching conditions can be adjusted according to the invention. Ideally, for 55g surgically-derived premature egg a target weight loss of from approximately 0.4g/day is desirable.
• Incubation temperatures of approximately 37.2-37.6 0 C are preferable initially on Day 0 until Day 18 of incubation and then temperatures of approximately 36.5 - 37.5 0 C are desirable until hatching.
• Relative humidity may initially be set at approximately 40% but should be adjusted daily according to ventilation rate and daily egg weight loss until Day 18 when relative humidity should be increased to approximately 65%.
• the surgical procedure for removal of the premature egg from the uterus of the bird includes incision through the skin of the bird and manipulation of the uterus. It is important that the egg is not contaminated with waste material from the gut of the bird and the egg itself is not damaged during the technique.
• the egg may be removed from the bird either in the intact, sealed (e.g. clamped-off) uterus or directly by incision of the uterus. All direct contact between fluid forms of sterilising solutions should be avoided to counteract any risk of impairment of embryo viability. Aseptic techniques are essential.
• the surgical removal comprises:-
• the bird is anesthetized but may alternatively be sacrificed by euthanasia or killing prior to removal of the egg in its shell.
• Female parent birds may be either live or recently killed. Live birds may, as consistent with ethical, legal and animal welfare considerations, be fully conscious, sedated or anaesthetised. Eggs and ova may be either fertilised or unfertilised.
• the removal of the egg is at a time prior and as close as possible to the transfer time when the egg would transfer naturally to the cloaca in the parent bird.
• the surgically removed egg may then be placed in a sterile container and sealed.
• the container should allow the egg to cool and be of suitable design and size to for egg storage.
• a sterile container is one with an approximate volume 10 times that of the egg, with the egg supported and protected by a plastic frame to ensure both stability and ventilation.
• a suitable environment for hatched chicks, rearing birds, laying and reproductively active birds is a rigid walled isolator, with HEPA- filtered air.
• the air is maintained at positive pressure and exchanged at frequent intervals (e.g. 10 times per hour for adult birds, taking into account cubic capacity of the isolator and stocking density).
• the floor area is ideally from 0.2 - 0.4 m 2 per bird. Gloves on entry ports are protected from damage by birds. Air temperature and lighting controlled to provide conditions similar to those for conventional birds of the same species and stage of life-cycle.
• organic micronutrients such as fat or water-soluble vitamins may be added to compensate for losses occurring during sterilization of the diets and from an absence of supply from commensal micro-organisms. Diets sterilised by gamma radiation have reduced concentrations of fat-soluble and water soluble vitamins. Furthermore, gamma irradiated diets have a limited shelf life and should be monitored for fat rancidity.
• a method for rearing and breeding the surgically derived eggs comprising administering antibiotics to the surgically derived premature eggs in ova.
• antibiotics Preferably, orally administered fluroquinolones are administered and, as appropriate, to the specific micro-organisms to be eliminated, other antimicrobial agents.
• the antibiotics eliminate transovarian bacterial and mycoplasmal infections and have a positive effect on viability and sterility of embryos and subsequent chicks.
• Antivirals, pharmaceuticals, small molecules, peptides and monoclonal antibodies may also be used to eliminate or prevent viral infections.
• fertile eggs are used to produce offspring or derived birds, then the eggs may be hatched, reared, maintained and bred in either conventional husbandry systems, germ-free systems or in isolators to control the entry of micro-organisms.
• eggs should preferably be derived aseptically from parent females (unless they are also germ- free) and the iife-cycle should be completed in isolators.
• the life-cycle may be completed outside isolators when germ-free eggs and birds are produced.
• Premature eggs in their shell were obtained from a parent bird according to the techniques of European Patent application no. 01650109.
• the premature eggs were cooled after surgical removal from the parent bird. They were then stored, undisturbed for, at least 24 hours but not more than 72 hours. Storage conditions were HEPA filtered air, a temperature between 15 and 23 0 C, relative humidity of 50 to 75% and the eggs were stored free from vibration or sudden jarring.
• the eggs were incubated using sterile equipment and specified contamination free air.
• the humidity of the isolator was decreased from 40% on Day 1 to 20 to 25% to increase moisture loss through the egg shell. This encouraged weight loss of the premature egg.
• the humidity was kept at this level up till Day 13 and was then increased to 40% from Days 14 to 18 to obtain 13% weight loss overall from Day 0 to Day 18. After Day 18 the humidity was increased to a normal hatching level of 65%.
• a suitable environment for hatched chicks, rearing birds, laying and reproductively active birds is a rigid wailed isolator, with HEPA-filtered air. The air is maintained at positive pressure and exchanged at frequent intervals (e.g.
• antibiotics e.g. orally administered fluroquinolones
• micronutrient-supplemented diets including, vitamins A, C, E and K, B vitamin complex
• the eggs were weighed and then 40 of the eggs were randomly allocated to one of four small rocking incubators. Two incubators were maintained at a RH of between approx 16 and 29% (nominated 25% RH) and two incubators were maintained at a RH of approx 43 and 54% ⁇ nominated 50% RH). Eggs were held air cell uppermost and were weighted individually on days 0, day 7 and 18 of the incubation. On day 18, all incubators where adjusted to provide a RH of approx 55-71%. Numbers of eggs that pipped and of live viable chicks were recorded.
• Viable chickens were hatched successfully from the artificially derived premature eggs. No anaerobic or aerobic bacteria were isolated from the chickens sampled.
• Infectious organisms that may be controHed by the invention include organisms that can be pathogenic or non-pathogenic to the relevant species. These include avian species (typically chickens, fowls and turkeys), humans and other mammals (typically dogs, cats, horses, cattle, pigs, sheep, goats, rats and mice).
• micro-organisms include parasites, bacteria (including anaerobic and aerobic species, commensal species and species associated with the gut), mycoplasma, viruses (including retroviruses), prions, fungi, yeasts, moulds and DNA and RNA fragments.
• the aseptic derivation of eggs and, if appropriate hatching, rearing, maintenance and breeding of birds may be used in combination with another method of controlling microbial contamination.
• Such methods include disinfectants, antimicrobials, antibiotics, antiviral agents, antiparasitics, immunomodulators and vaccines.

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• 2007
  • 2007-02-22 EP EP07712286A patent/EP1991049A2/de not_active Withdrawn

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