The domestic chicken originated from the jungle fowl (Gallus gallus) found in south east Asia. Nomads captured these birds and travelled with them using their eggs and meat as a food source. Over time breeding in captivity with colour and phenotypes selection has produced the array of pure breeds we have today. The Victorians in particular enjoyed exploration and collected breeds from their travels around the world. Poultry keeping became incredibly popular for ornamental value, as they were impressive and collectable, often costing hundreds of pounds. Breed standards were developed and written to ensure that breeds are true to type, this continues with the strong following of poultry fanciers breeding for show purposes. The most successful way of keeping chickens is to have a preventative approach to bird health with a structured management plan, no matter what the flock size.
Chicken behaviour
All breeds of chickens need to be able to display their unique behavioural traits easily and freely; if they cannot do this, soon they become depressed and develop health and disease problems. Fundamentally they will require an environment that enables perching, dust-bathing, nesting, broodiness, preening and living in a flock with a pecking order (Figure 1). These behaviours relate back to the jungle fowl and survival. As with any animal, it is important to provide them with their specific needs so they thrive; housing especially must meet these needs. The chicken naturally perches when it roosts at night to get away from predators, so the perch must be of a suitable strength, diameter and height to suit the breed. Narrow perches can cause foot problems, as can rough ones. The perch height is relevant as heavy breeds can damage their breast bone if they jump down from a great height. Perches need to be slightly higher than the nest, otherwise birds will roost in the nest boxes making them dirty. Dust bathing serves many purposes to keep birds in good condition. The dust bathing ritual involves scratching a shallow pit in the ground and fluffing up the feathers so the soil or litter penetrates the feathers to the skin. This cools the bird down, is a social event and also assists in removing ectoparasites, excess oil and dirt from the feathers. If birds are not able to dust bath feathers will become brittle and out of condition, boredom can set in and feather pulling or pecking may result, which can lead to cannibalism (Wood-Gush, 2002).
Husbandry
Understanding the needs of the bird will assist greatly in management of the coop, run and range area.Chickens like to have access to grass and run around to stretch and spread their wings. The house itself needs to be draught free and of a size to enable the inhabitants to perch comfortably and stand tall, for example when a cockerel crows he will stand upright becoming taller. If birds are shut in all day they need to be able to move around, scratch the litter, and feed and drink with ease. If they are too cramped chickens may become aggressive towards each other (Wood-Gush, 2002). Good ventilation is important, so that when the chickens are shut in they have enough fresh air. A poultry house that is cheap may not be very well insulated which leads to problems in very cold weather. This can be overcome by bringing the house into a building during periods of cold.
Hygiene
Implementing best practice with hygiene will lower the risk of chickens getting disease. Basic hygiene of the coop, feeders, drinkers and the range will reduce the build up of pathogens. Keeping the coop free of droppings under the perches and in the nest boxes will help keep the litter fresh and prevent eggs becoming dirty. Fresh bedding enables birds to scratch and dust bathe, which may lower the number of pathogens present in the environment. A really thorough clean out every few months is necessary (Box 1); the frequency depends on how many birds there are and the size of the house. By removing the litter to the compost heap or to the recycling centre as green waste limits any disease build up on site. After cleaning out the house it should be washed using a detergent, allowed to dry and then a disinfectant should be applied specific for poultry diseases. Interkokask (chemical component 25% 4-chlorine-3methylphenol) is an ideal disinfectant for using on poultry coops as it is proven in killing viruses, bacteria, fungal spores, worm eggs and coccidial oocysts (a protozoa which affects young poultry in particular) (Defra, 2012). One golden rule with keeping chickens is not to mix young birds with older birds by segregating age groups. Different aged birds will have varying disease challenges, so this is paramount to reduce the risk of disease (Jordan et al, 2002). Most commercial poultry sites are of one age; the all in, all out rationale.
Health
During the day chickens should be lively and interested in what is going on around them. If this is not the case, generally there may be something wrong. A healthy bird is alert, upright and showing glossy plumage and a bright eye (Figure 2). Birds which are ailing (Figure 3) have a distinctive stance where they are quiet, the head is sunken into the neck or shoulder area and they tend to sit down, withdrawing from the rest of the flock and usually going off food and water. Feathers tend to be ruffled and eyes may be closed. All chickens will go into a moult usually once per year where they gradually lose their feathers; a new feather emerges from the feather follicle and pushes the old one out. At this time they will look unthrifty and a little subdued (Figure 4). The ‘normal’ weight and temperature of a chicken can be seen in Table 1.
| Lifespan | 3–8 years |
| Adult weight hen | 1800 g |
| Rectal temperature | 40°C |
| Heart rate | 275 beats per minute |
| Respiratory rate | N/A no diaphragm |
| Incubation period | 21 days |
| Sexual maturity | 22–24 weeks |
| Daily feed intake | 120 g |
| Daily water intake in lay | 200 ml |
Nutrition
Chickens are omnivores and need a specific balance of nutrients to exist and thrive. If the ration is deficient, problems can rapidly develop usually starting with feather pulling episodes often due to an imbalance of amino acids (Larbier and Leclercq, 2004). Feeding the correct ration for the age of bird is essential to meet its physiological requirements and demands. Preparatory compound poultry rations are used for the life of the bird and according to its needs at the time.
Chicks are fed chick crumb from the day they hatch to about 5 weeks of age, depending on the breed. Following crumb is a grower or rearer pellet and then the adult ration of layer’s pellets from about 18 weeks of age. This will also depend on the age of maturity. For example, a hybrid layer, which matures or comes into lay at around 22 weeks of age, would go onto layer’s pellets at about 17–18 weeks of age. Some rare breeds do not mature until over 30 weeks of age, so they can stay on grower’s pellets for longer. Compound feeds should be used within the use by date to ensure all nutrients, especially vitamins are fully effective. Some deficiencies of micronutrients may result if old feed is fed, this is especially apparent in chicks; rickets may result due to a vitamin D deficiency. Apart from the main compound ration about 20 g of mixed corn can be fed as a scratch feed to stimulate scratching and natural feeding behaviour. Chickens are natural foragers therefore it is part of their day to look for food. Fresh, clean drinking water and mixed grit need to be provided. Soluble grit, or oyster shell is required to assist in the formation of the egg shell and insoluble grit is used by the chicken to grind down food particles in the gizzard (muscular stomach).
Titbits
Many poultry keepers get huge pleasure from letting their birds eat out of their hand and like to seethem come running when some mixed corn is scattered around. The problem is many of these ‘extras’ are high in energy making the bird overweight if not fed in moderation. Maize is probably the worst cereal to feed due to the high calorific value. The explosion of chicken treats available in pet stores does not assist in curtailing the incidence of obese birds. Chickens need to be agile to function properly and to lay quality eggs. Extra pressure on their skeletal structure will cause stress; therefore ensuring birds are within their weight band for their breed is important by limiting treats and providing a quality ration.
Parasites
Some of the issues commonly encountered in chickens are those caused by ectoparasites. Red mites Dermanysssus gallinae are nocturnal, sucking blood from the birds while roosting. In heavy infestations anaemia and death can occur (Jordan et al, 2002). Red mites live in crevices in the poultry house and tend not to be noticed until they multiply in numbers. They are visible to the naked eye and are pale grey in colour before they have sucked blood, then they appear red and later on their colour turns to black. The treatment for red mite needs to be topical (ivermectin 1% drops) and environmental (an application of diamatacious earth — a natural rock mineral — to the poultry house and the dust bathing area). Lice at times can infest chickens and will live in the feathers and congregate under the wings and around the vent (Figure 5). Lice lay eggs in small white clusters around the vent which are quite distinctive. These clusters should be cut off and burned otherwise they will hatch causing further problems. Dusting the bird with louse powder (pyrethroid base) or diamatacious earth will assist in treating these parasites. Holding the bird securely by its legs, upside down, will enable the base of the feathers and skin to be dowsed with the powder and effectively control the parasites.
Worms
Worms can affect all poultry giving rise to diarrhoea, weight loss and poor egg production. Intestinal worms are easily controlled with a regular worming strategy. Worming in the spring and again in the autumn is usually sufficient where small numbers of chickens are present. Carrying out a worm egg count is good practice if worms are suspected, or to establish if the birds actually need to be wormed, a faeces sample can be sent to a laboratory which carries out McMasters worm egg counts. The round worm Ascardia spp. and the ceacal worm Heterakis gallinae are commonly found. The gape worm Syngamus trachea is less common, but all these can be successfully controlled using flubendazole (Flubenvet 1% medicated premixture, domestic poultry wormer). Tape worms are very uncommon in domestic chickens, but should they arise the same treatment applies (Jordan et al, 2002).
Point of lay
Point of lay is the term which refers to when the young hen or pullet comes into lay. It is the point of sexual maturity and this is reached at about 22–24 weeks of age with a hybrid and upwards of 30 weeks with most rare breeds. It is popular to buy point of lay pullets as you will get the best eggs from them and they will keep laying for several seasons. As the pullet starts to lay it is common to get some irregular shaped eggs or shell less eggs (Figure 6). This is also common when a hen gets older as her reproductive organs start to lose muscle tone. Clients can become alarmed at the sight of eggs which are not completely normal. Usually the pullet will settle down into laying normal eggs very quickly, older hens however can develop other problems; as a hen ages she will lay larger eggs, but each egg will have the same amount of calcium carbonate (shell), but it will have to go further to cover the larger egg mass of the yolk and white (Coutts and Wilson, 2002). Therefore thin shells are common in older hens and often break in the nest boxes. Apart from feeding mixed grit and ensuring the birds are fed suitable rations there is little that can be done. This is why on a commercial basis the hen has a life span of approximately 72 weeks. A hybrid hen can lay up to 320 eggs per year, so after 72 weeks she has come to the end of her economic life from a commercial basis. Rare breeds are not so prolific with egg laying and may only lay about 30 eggs per year and are more likely to go broody. Broodiness is the state a hen goes into when she sits on a clutch of eggs in order to hatch them out (Figure 7). Her behaviour will change by becoming aggressive, making squawking noises and puffing herself up on the nest. Hen eggs have an incubation period of 21 days.
Handling
Chickens can easily be tamed so they become less awkward to handle and examine should a problem occur. The correct way to hold a bird is to put one hand and arm underneath its body to support its weight with the hand reaching between the legs (Figure 8), hold the other hand over the top of the body to prevent the bird from flapping its wings. Chickens panic in strange surroundings so it is advisable to ensure the consulting room door is shut before they are taken out of their carry box. When transporting chickens make sure they are in a secure, well ventilated but dark box, to reduce stress.
Conclusion
There is much interest in chickens across the UK and they are becoming popular in the companion animal domain. There are many poultry breeds kept for numerous reasons; re-homed hens as pets, show birds, laying hens, broiler chickens for meat and rare breeds bred as a business to sell to others, so it is very likely that chickens will be encountered at some point. Poultry nutrition is particularly important with the laying hen as there are many conditions that stem from nutritional deficiencies and imbalances. Whatever reason poultry are coming into the surgery chickens are becoming more popular and their owners take any ill health seriously, expecting the practice to know how to treat the condition.