Formerly, a young domestic fowl (Gallus gallus domesticus) was known as a ‘chicken’ but that term now applies to all age groups and breeds of domestic fowl. Australians consume more chicken meat than from any other species, approximately 38kg / yr each, and 130 eggs, either direct or indirect (compared to 22kg beef & veal, 20kg pork products, 10kg lamb & mutton, and ~15kg aquaculture [70% of which is imported], Australia topped the world for meat consumption at >90kg / pp in 2014). These come from 500m broiler chickens reared per year and about 12m commercial layer hens. In addition, we consume about 1kg turkey meat (5m turkeys processed / year) and 0.8kg duck meat (~8m ducks); plus small volume of quail, pheasants, partridge, geese, squab pigeons etc; there is some wild bird harvesting in some states.
The genetic stock of the commercial poultry strains are imported into private quarantine facilities and then bred-up (about 7m birds in the breeder chain). Modern domestic fowl are derived from the Asian jungle fowl, mostly the Red Jungle Fowl. 95% of the modern layer industry of Australia uses hybrid brown egg layers and 35% of eggs are now produced as ‘free-range’, 10% barn lay, and 2% as ‘organic’. There is significant discussion as to what constitutes ‘free-range’ and ‘organic’. The permission of the broader community for an individual or industry to operate a particular enterprise, ie ‘social licence’, is becoming more important in public discussions about agricultural and farming practices. There are an estimated 2m non-commercial backyard and fancy breed domestic fowl in Australia.
Domestic fowl are omnivores, they cannot rely on a total grain diet, and their digestive system is not developed for handling leafy material such as grasses. Whole grain wheat is deficient for poultry in protein, calcium and vitamins, especially vitamin A, and the content of phytate phorphorus can vary widely.
Modern commercial poultry feeds in Australia are pelleted and wheat or sorghum based, with a significant component of ruminant derived meat and bone meal (unless for vegetarian egg production) and some plant derived protein rich materials (soy-bean meal, canola meal etc), supplemented with vitamins and minerals etc (Note: plant derived protein tends to be deficient in essential amino acids for optimal animal growth and production, and therefore require supplementation, particularly with methionine and lysine). Note that stock feed wheat is a different variety from that used for human food, it is grown under different conditions, it is a ‘soft’ wheat and it is not suitable for milling to flour. Sorghum grown in Australia may vary in protein content, it must be cracked or coarse ground to be of value to chickens, and recent assays have shown that the strains now used are free of condensed tannins.
Poultry feeds in Australia do not routinely contain growth promoting antibiotics following voluntary industry cessation a decade ago: coccidiostats are added to feeds for rearing and ionophores are classed as antibiotics, although they are not used for treatment of human disease. Withdrawal feeds sometimes used towards end of rearing of broiler chickens are free of coccidiostats and the chickens are then vulnerable to outbreaks of coccidiosis should conditions favour that. This is distinct from ‘feed withdrawal’ on the farm prior to pick up which is done to reduce ingesta contamination of carcasses at abattoirs and is to be carried out with great care.
Whole wheat grain is often added into the mix of a commercial feed (5-20% w / w) as delivered onto the farms via trucks, as whole wheat improves gastrointestinal function: the contribution of that grain is calculated into the total nutritive value of the feed as delivered; bagged feed does not contain whole grain.
Hormones as such have never been added into poultry feeds, despite common accusations of this, however, the lay term for growth promoting antibiotics was often ‘growth hormones’ thus creating confusion. In avian species, the male is the neutral sex and the female embryo is de-masculanised by her oestrogen. Oestrogenic hormones were injected into the necks of young male off-sex layer-breed or game-type fowl, to allow better growth as ‘hormonised-capons’: this practice ceased >50 years ago (surgical carstration is still practiced in some countries to produce a surgically-caponised bird but is illegal in Australia).
Broiler starter feed may comprise 22% crude protein and 1% calcium, whereas a layer feed may be 15% CP and 3.5-4% Ca, with significantly different energy concentrations, and other ingredients or components. Pullet rearing feed (18% CP, 1% Ca & coccidiostat) is most appropriate for young growing birds. Feed for layers may be a non-pelleted mash. Feed for backyard and fancy breed poultry should be predominantly (~90%) a commercial-prepared balanced pelleted diet, which can then be supplemented (~10% of daily intake) with kitchen vegetable scraps, whole scratch grain, garden foraging etc.1,2 ‘Organic’ feeds can contain a small proportion of non-certified ingredients. Always check the label to ensure the feed is fit-for-purpose. Guidelines for HomeMix are available.3
Vaccines for poultry are not available in small doses. Many backyard poultry are obtained from commercial poultry farms and may be vaccinated, at least partially, but immunity will fade, sometimes within months without boosters etc. Some fancy breeders obtain large dose commercial vaccine vials (1,000) and sub-divide the vaccine pellets or use some of a preparation and pass on the residue to others: this may or may not be effective and / or be associated with untoward consequences (wrong dose, wrong route ie fowl pox via conjunctival sac / eye-drop, inappropriate procedure ie intramuscular injection of adjuvanted vaccine rather than subcutaneous, inactivation of live vaccines etc).
The vaccine used to control pigeon paramyxovirus 1 (PPMV1) is a killed imported Newcastle vaccine available in 1,000 dose vials, so it is often obtained and used by a club or group; but that necessitates bringing birds together and increases risk of transfer of PPMV1 and / or other infectious diseases: some fancy poultry breeders may do something similar.
Marek’s disease vaccine needs to be given at day-old before significant exposure to feather dander and other sources of infectious virus, significant sectors of the commercial poultry industry now vaccinate chicks in-ovo (18 days incubation) to pre-immunise before hatch and thence exposure to infection: the cell associated vaccine requires liquid nitrogen storage and transport so this is prohibitive for small users.
Availability of commercial poultry vaccines is sometimes a significant problem to the industry, let alone to small holders and fancy breeders. Some vaccines are available as autogenous vaccines for use on the farm of origin (ie fowl cholera Pasteruella multocida killed vaccine containing locally derived strains) under a permit system of the Australian Pesticides and Veterinary Medicines Authority (APVMA).
There is a limited range of chemotherapeutic substances, nutrition supplements etc available for poultry that may have value in treating small flocks and individual poultry. APVMA registered products for poultry, must be prescribed by a registered veterinarian for a bona fide client, having established a therapeutic need based on current knowledge of the health of the animals to be treated. The owner, farmer or manager is to be informed of withholding periods.
Prescribing veterinarians must demonstrate professional intervention in the ordering, storage, supply and use of such antibiotics, and demonstrate adequate veterinary care and supervision of any flock treated.3 Off-label use of chemotherapeutics should be undertaken cautiously and only when necessary: refer to the latest Australian Veterinary Association guidelines, and keep good records of justification, verification, instructions issued for use etc, not just the invoice.
Some products can NEVER be used for poultry that may at some stage in their life produce eggs for human consumption, ie this will apply to backyard chooks: eg trimethoprim-sulphadiazine cannot be used in young chicks that may later produce eggs for human consumption, but trimethoprim-sulphonamide can be used in pullets up to 2 weeks before the onset of lay; oxytetracycline hydrochloride via drinking water (DW) or feed cannot be administered to poultry that may produce eggs for human consumption, but chlortetracycline hydrochloride via DW can be used in layers without egg withdrawal. Chlortetracycline-hydrochloride and lincospectin-R are the only antibiotics for use in poultry with a nil withholding period (WHP) for eggs.
Doxycycline is not registered for use in meat or egg producing birds but has been used under permit for control of chlamydiosis. Tylosin phosphate at 100g/t in feed has a nil WHP for meat birds and eggs; tylosin tartrate in DW has a nil WHP for meat and one form can be used up to a week before onset of lay in pullets (another similar product can never be used in birds that may produce eggs). Neomycin sulphate in feed has nil WHP for eggs, 5 days for broilers, and 14 days for turkeys or spent hen layers. There is no current registered treatment for histomoniasis (blackhead, from the cyanosis in turkeys) in poultry in Australia, although dimetridazole is registered for use in non-poultry birds.
Different coccidiostats act at different stages of the life cycle of Eimeria spp, they are not all the same! Some, such as the ionophores, are unsuitable for treatment of clinical disease: dinitolmide and toltrozuril in feed cannot be used in pullets from 8 weeks prior to lay. Nicarbazin cannot be used in birds that may in future lay eggs for human consumption. Amprolium in DW has a nil WHP for eggs, but amprolium-ethopobate cannot be used in birds that may lay eggs in the future.
Piperazine DW is effective against ascarids and has nil WHP for meat and eggs. Levamisole DW is effective against ascarids, heterakis and capillaria and has nil WHP for eggs and 7 days WHP for meat. There is no registered treatment effective for tapeworms, although praziquantel is registered for non-human food producing birds, and as such has no required WHP. Maldison can be used in layers with nil WHP for eggs, and for meat birds 7days WHP. If in doubt, please check details with APVAM website PubCHRIS before prescibing anything and / or check with current policy on the use of antibiotics by the Australian chicken meat industry etc.
Few serological tests are readily available for individual poultry, and bacteriological testing can be expensive. Faecal examination of birds is fraught with difficulty in interpretation: intestinal droppings are produced approximately every hour (these more closely reflect what has been recently eaten, contain some particulate or fibrous structure; usually with a curtain of urates derived from urine deposited on the periphery of cloacal faeces that has been reversed back up into colon where the water was resorbed from it), and caecal droppings (brown to yellow, semi-fluid, homogenous) produced 2-3 times per day; the avian intestinal tract undergoes regular reverse peristalsis resulting in more-or-less continuous re-mixing of contents of various segments. Note that some birds (pigeons. parrots etc) have vestigial caecae. Tapeworm segments are not uniformly mixed within the faeces. Ascaridia eggs may be released in a pulsatile manner with a peak in early afternoons.
A healthy chicken may live for 8-10 years. Body temperature of a normal chicken is 41-42oC (some articles give range up to 45o?), heart rate 250-300x per minute for adult hen (up to 450 for chick), and respiratory rate of 15-40 / min. Packed cell volume for domestic fowl is usually cited as 35-40%, haemoglobin concentration 11-14g / dL, red cells count ~4x1012 / L, white cell count (performed manually) ~4x109 / L, thrombocytes 25-35x109 / L (be careful with older literature where there may have been excess circulating lymphocytes due to Marek’s disease or ‘lymphomatoses’); plasma protein ~50-60g / L, and fibrinogen <4g / L.
Drinking water consumption is usually cited as 100mL / kg live weight – this will increase for hens in lay ~25%, and will more than double in warm weather (x4 if ‘hot’); feed consumption is about 120g / day for a ~2kg laying hen. Each egg laid by a hen contains about 2gm calcium. The right atrium is divided from ventricle by a circumferential contractile fibromuscular ridge, not a valvular structure. In the adult hen, only the left ovary and oviduct fully mature. The kidney has an afferent portal venous circulation. There are no lymph nodes in chickens. Avian IgY does not fix mammalian complement, therefore avian sera should not be tested using conventional mammalian CFT, such as for Chlamydia (despite this often being requested, required and performed). Further, most conventional serological ELISA tests are valid for one species, ie domestic fowl (chicken) ELISA and cannot be used for another species eg domestic duck; however, some tests such as capture-ELISA can be used across different classes and species eg influenza-A cELISA.
Australia has had several outbreaks of ‘fowl plague’ or highly pathogenic virulent H7 avian influenza virus in commercial poultry flocks (Vic, Qld, NSW); and low pathogenicity H5 (not the serious H5N1) in duck flocks in Victoria in 2012, H9 in turkeys (Hunter valley, NSW), H4 in ducks (north coastal NSW), and H10 in broiler breeders (outer Sydney), and surveys of wild birds continue to show evidence of widespread distribution of other low pathogenicity strains of AIV. These H7 outbreaks were due to an Australian lineage of AIV, not from elsewhere, although the wildlife reservoir has not yet been elucidated.
During the H7N7 outbreak at Keysborough, Vic 1976, non-pathogenic virus was isolated from the nearby duck farm; and in the H7N4 outbreak in Tamworth 1997, high pathogenicity virus (for chickens) was isolated from apparently healthy emus on a de-stocked poultry farm. No outbreaks of high pathogenicity AIV H7 have occurred in non-commercial poultry in Australia. No evidence has been found of high pathogenicity H5N1 in Australian wild birds, let alone in commercial poultry.
It should be noted that, worldwide, from 2003 to July-2015 there were 844 confirmed human infections with high pathogenicity H5N1, of whom 449 died as a result of infection, giving a fatality rate of >50%, but considering the number of people exposed and the close contact between people and poultry in involved countries, the transmission rate from poultry to humans and thence causing clinical disease, is exceedingly low.
It is presumed that non-commercial poultry and free-range commercial poultry will have many opportunities to interact with wildlife, especially free-flying birds, and therefore be at some risk of becoming infected with AIV, be that with a high pathogenicity AIV strain or otherwise. This risk would appear to be of low probability of occurring (based on negligible occurrence to date despite intense surveillance), but of potentially high consequence if it does occur. Therefore, small poultry holdings ought to ensure adequate biosecurity.5,6 However, concern about the possibility of becoming infected with high pathogenicity virulent nasty avian influenza that is not even currently within Australia, ought not be a deterrent to having a small flock of backyard poultry providing home produced eggs.
The notifiable, on suspicion, of exotic diseases of poultry, includes avian influenza and Newcastle disease. Newcastle disease vaccination is currently compulsory for commercial poultry flocks in NSW, but there have been no instances of high pathogenicity or virulent disease since 2002: the current pigeon paramyxovirus 1 problem in NSW and Victoria is due to a different virus, although Newcastle disease vaccine is protective.
Significant flock mortality events can be investigated by delegated authorities (Local Land Services veterinarians in conjunction with DPI) and exotic notifiable disease excluded. Endemic notifiable disease of poultry include chlamydiosis of birds and poultry, egg drop syndrome ’76, infectious laryngotracheitis, pullorum, Salmonella enteritidis, and tuberculosis (avian mycobacteriosis).7 Samples can be submitted to SVDL for specific tests to exclude these diseases (contact the laboratory to discuss options8), but the cost of establishing an alternative diagnosis, that may or may not be treatable, will be charged to the submitter.
Potential zoonotic diseases from poultry include high pathogenicity avian influenza, Newcastle disease (conjunctivitis if you squirt yourself in the eye with infected embryo fluid), avian chlamydiosis, salmonellosis and mycobacteriosis.9 'Starling lice', are actually a mite, and may cause considerable nuisance in houses.10 Allergies to bird dander are well recognised. Chlamydiosis is not commonly encountered in poultry; it is more of a problem in pigeons, parrots, ducks, gamebirds etc, and clinical presentation in birds may include death, conjunctivitis respiratory signs and/or diarrhoea. Having noted these, risk assessment and appropriate personal protective equipment and action at the veterinary clinic, on the bird premises and for the owner must be considered.11
The commonest problems encountered in backyard and fancy poultry are management and nutritional (inadequate or inappropriate diet, malnutrition, vitamin A deficiency, impaction of crop or gizzard with grass – especially kikuyu), and the most serious problems are Marek’s disease (>50% cumulative mortality rates in rearing of non-vaccinated flocks are frequent), infectious laryngotracheitis (following recent purchases, introductions, close contact with other poultry; infection may result in >75% mortality in a week or so), fowl cholera (Pasteurella multocida; the carrier may be other poultry, wild birds, wildlife, rodents, farm cats etc), coccidiosis, histomoniasis, and internal and external parasites.
On an individual basis, common causes of death in layers are egg-associated peritonitis, and respiratory complex aerosacculitis and polyserositis. Fowl pox is common in spring summer, with lesions often on the head, but although unsightly and somewhat debilitating, mortality rate tends to be low. Infectious coryza (Haemophilus Avibacterium paragallinarum) requires spread from other infected chickens, usually recently introduced birds or after close contact shows etc, and presents as an acute outbreak of sinusitis but with low mortality; whereas mycoplasmosis (M. gallisepticum, M. synoviae, M. meleagridis), also requiring close contact with infected birds, tends to produce chronic respiratory tract infections. Trauma from other poultry or predators (cats, foxes, dogs, raptors) is commonly encountered. Diagnosis of death and disease is often difficult, expensive and somewhat elusive, and treatment options thus need to focus on general supportive procedures and broad-spectrum chemotherapeutics.