November 22, 2008

Animal behaviour and welfare: Poultry Part 4


Layer housing systems: Feeding rhythms

By Dr Clive Dalton

Free range
  • This is the traditional way laying hens were kept and still has the image of "farm fresh" eggs where birds have their complete freedom to live as nature intended.
  • Low profits from free-range hens have been the driving force behind the move to intensification. But there are other disadvantages of free range listed below:
  • Little protection from the weather
  • More labour needed for feeding, egg collecting and moving houses.
  • More feed/dozen eggs needed.
  • The bird's diet may be unbalanced.
  • Dirty eggs and fouled pastures.
  • Lower egg quality, stale eggs and offensive flavours.
  • Birds run risk of diseases from soil-borne infections.
  • Greater incidence of internal and external parasites.
  • Risks from predators.
  • Poor working environment for staff.
  • A very low percentage of producers use the system is only likely to remain if there is overwhelming pressure from Welfarists, and consumers are prepared to pay up to 20% more for eggs.
  • Behaviour problems are few on this system as the unlimited space allows low-ranking birds freedom to escape molestation.
  • Feather pecking can occur and may need beak trimming.
  • Egg eating can be a problem as it's difficult to find the offending birds to cull them. Egg eating seems to start when birds discover a broken egg and find the contents attractive. Then they learn to break them with their beaks and are very hard to break from the habit.
  • Filling eggs with mustard or bitter tasting flavours usually doesn't deter them. Culling is the best option before other birds learn from them. The problem is to find them - either by catching them in the act or looking for egg yolk on their beaks.

Slatted or wire floors
  • Here hens are kept on totally slatted or wire mesh floors at high densities, e.g. up to 0.09 m²/bird.
  • The system tries to be a compromise between cages and deep litter.
  • Nest boxes are accessible from outside to avoid disturbing the birds.
  • A perching area is the main feature of this system and is built over a dropping pit which is cleaned out once a year.
  • The main behavioural concerns in these houses are as follows:
  • Nests must be placed near the perching area.
  • Eggs can be gathered easily.
  • Ventilation system can handle the foul air from the droppings pit.
  • Floor eggs can be a major problem if nesting boxes are not attractive.
  • Long narrow pens are best to reduce interaction between birds.
  • Inspection by the attendant can cause panic and bruising.
Deep litter
  • Here, birds of all types are kept on litter at various stocking densities with full or partial environmental control.
  • They are seen by those concerned about hen welfare as a much more acceptable system than cages.
  • The litter is usually sawdust, although straw is used (called straw yards).
  • Behaviour problems in deep litter houses include:
  • Drop in egg production.
  • Increased aggression - feather and vent pecking.
  • Increased mortality from disease.
  • Feed wastage.
  • Floor laying.
  • Here are some points to consider when trouble shooting:
  • Temperature, humidity and ventilation.
  • Access to feed.
  • Condition of the litter - is it wet or dry.
  • Ammonia smell.
  • Lighting pattern and intensity - check time clocks.
  • Stocking density.
  • Beak trimming or spectacles - may be needed.
  • Birds in large houses keep to specific areas, and don't range widely through the house.
  • Social orders are set up within these territories, so although they are free to move, there are strict social limits on their mobility.
  • Birds can recognise about 11 other birds and stay in that group to avoid being pecked when they move outside their territory.
  • Studies showed that the area over which a bird ranges varies greatly between houses, some being much larger than others.
  • Thus the notion of individual or personal space is more acceptable in birds on litter than that of territory and home range.

Battery cages

  • Welfarists and the public in many countries are trying to ban the battery cage, and in some they have succeeded. Currently the RNZSPCA are working hard to ban them in New Zealand.
  • Producers use the battery cages for a number of reasons:
  • Birds can be fed a complete and balanced diet.
  • It's easy to maintain total environmental control.
  • Egg eating is less likely.
  • Inspection of birds is easy.
  • Catching birds is easy.
  • Parasites and disease are easy to control - if the system is good.
  • Birds bred for cages will have high egg production.
  • The eggs will be clean and of high quality.
  • These points carry little weight in the minds of welfarists as they see birds in cages almost denuded of feathers, fighting for space and unable to express the fifth freedom to express normal behaviour.
  • To increase profits, the single cage soon became the multiple cage housing from 2-4 birds. Then the multiple cage got bigger and became a colony cage.
  • Producers used to consider 460cm²/bird to be near an economic optimum but welfarists stressed that 500cm²/bird was better and if possible it should be raised to 600 cm2/bird.
  • In New Zealand the height of all new cages installed after 1 January 1997 had to be at least 40cm over 65% of the cage floor area and not less than 35cm at any other point.
  • Similarly the slope of the floor must not exceed 8 degrees for new cages after 1 January 1997.

Behaviour in cages
  • There is great pressure on designers to improve the environment for the caged bird. The problem is that when space is increased and the bird allowed choices, the size of the cage has to be increased - with an associated rise in costs.
  • Various designs have included a dark nest box and a lighted scratch area. A major problem with these more complex cages is that inspection of the birds is still difficult.
  • Solid sides to the cage have helped to prevent feather pecking from birds in adjacent cages.
  • Poor trough design, sharp edges and incorrect wire placement on the cage front cause feather wear on the throat. Horizontal bars are better than vertical bars as they allow greater feed access with less pecking.
  • Correct trough depth is also important to prevent neck blisters.
  • Sandpaper on the trough lip next to the bird will help ensure that claws are worn down and feet shape is improved.
  • Injuries (up to 3.5%) can occur to birds such as getting their necks, wings, legs and combs caught between the bars, depending on cage design and manufacture.
  • It's important for equipment designers to understand the difference between density and crowding- remembering a bird is most concerned about having adequate personal space around its head.
  • Density is the number of birds/unit area or unit space, but crowding is a product of density, contact, communication and activity. Crowding contains psychological factors as well as physical ones.
  • Cracked eggs can be a major problem on wire floors. Cracks occur when eggs hit the floor after being laid, and cage design is very much involved. Floor mass, the slope, height of egg drop (which varies with the size of the bird) and the angle the egg is presented from the cloaca are all involved.
  • In cages, more cracked eggs occur on heavy gauge wire floors which birds prefer over finer gauge wire.

Feeding and drinking rhythms
  • In caged birds living in 16 hours of daylight, three main periods of eating have been recorded.
  • The two main ones are at the start and end of the light period, and the third one was less fixed. Most feed is eaten at the last period of the day.
  • When kept in continuous light, birds also engaged in regular rhythmic bouts if they could detect any changes like temperature fluctuations or feeding times to allow patterns to be formed.
  • Egg laying rhythm also helped birds to develop feeding rhythms.
  • Social facilitation is important in hens and results in greater feed intake. Group-fed birds are calmer and more relaxed about eating. This behaviour is useful if all birds are producing well but triggering low producers to eat is counter productive and unprofitable.
  • In free-range birds, scratching is also part of the eating ritual and a hungry hen scratches more than a satiated one.
  • Running with food in the beak to avoid competitors is a regular habit of young chicks, but it's seen in free-range hens too.
  • Water is vital for high producing birds. Egg number and size are affected within 48 hours of water being cut off.
  • Drinking rhythm is closely related to feeding rhythm.
  • Food and water are not taken in at night and intake of both peaks at the last feed bout before dark.
  • Within a temperature range of 18 - 24°C, intakes of both are regular and stable. However in heat waves, water intake may increase by 50% in the afternoon when most water is taken.
  • As pullets grow, they change their major water intake from morning to afternoon.
  • A laying hen needs about 170ml water/day and maximum water intake is related more to body recovery after laying than to ovulation.
  • When birds, especially pullets are moved to new quarters, some of their old familiar waterers should be moved with them until they learn to use the new ones.

This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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