7 signs of ageing in poultry
Appearance
As poultry age, their feet and legs get larger, and the scales on the legs rougher. Make sure it's not scaly leg mites before you put it down to old age.
Old hens may grow spurs on their legs, partly due to lower oestrogen levels and possibly increased testosterone levels. Some also naturally develop spurs as they get older, notably the game breeds.
Other signs include:
• the keel bone will become more rigid and calcified right to the tip;
• the muscles and joints become more solid;
• thicker skin.
Older hens don't tend to be as active, so they may gain extra weight.
Behaviour
Older birds are less inclined to jump up onto a roost and may choose to sleep in a nest or on the floor.
Their position in the pecking order may also fall, so they tend to be found slightly away from the flock, staying out of harm's way.
Sometimes when a hen's ovary ceases egg production, vestigial testicular tissue in their other non-working ovary may take over. This produces the male hormone testosterone, which can cause the hen to develop masculine characteristics. She may attempt to (or actually) crow, develop shiny feathers on her back like a rooster, and spurs.
NB: sometimes, you'll see these signs in a young hen. It's often a sign of a tumour in her one working (left) ovary and means she won't lay again.
Egg production levels
The older a hen gets, the fewer eggs she will lay in a season. The quality of those eggs will also decline (see Egg Quality).
In a heritage or backyard bird with a long lifespan, you may see egg production numbers that look like this:
Year 1 – 180 eggs
Year 2 – 160 eggs
Year 3 – 140 eggs
Year 5 – 110 eggs
Year 8 – 55 eggs
Year 10 – 35 eggs
After the age of 10, she may still lay a few eggs, but she may stop if she gets too fat.
Egg quality
Eggs get bigger as a hen gets older, but the amount of shell she produces stays the same, so they become thinner and weaker.
The first eggs of the season may be smaller than the last eggs of the previous season, but they tend to increase in size and weight over the year.
The internal quality also deteriorates, with the albumen (white) becoming more watery. This is partly due to the thinner shell, which has larger pores. This affects the transfer of gases and moisture through the shell, making the white a more watery consistency.
Brown eggs will get paler as the hen ages as the brown pigment is spread more thinly over a wider surface area of a larger egg.
Bodyweight
Some conditions may cause an older hen to lose weight. Fancy poultry breeders sometimes say a bird is ‘going light.’ Causes include:
• avian tuberculosis;
• lymphoid leucosis;
• chronic coccidiosis, which scars the intestine, meaning the bird absorbs fewer nutrients from its diet.
However, it’s more common for older birds to become obese through poor diet, too many treats, and less activity.
Birds naturally have a fat pad across their abdomen as an emergency source of energy. Times rarely get tough for domestic poultry, but feed such as grains and carbohydrates keep coming, so their fat pad gets thicker.
Heavy breeds (stockier, 3kg+, eg Rhode Island Red, Plymouth Rock) were developed to withstand colder weather. They naturally lay down thicker fat pads than lighter breeds from hotter climates
It's common for older birds to become obese through poor diet, too many treats, and less activity.
such as Leghorns and Minorcas, and so are more inclined to become obese.
To measure the fat pad, lay the bird on its back. You can feel the fat pad between the tip of the keel bone and the vent opening.
Extra fat also builds up around the organs and in the liver. This can cause sudden death from a condition where the liver suddenly bursts. It can also affect young birds that are overfed.
Obesity in hens can cause:
• decreased fertility;
• lower egg production;
• more frequent double yolkers;
• oversized eggs;
• egg bind (the egg is so large, it gets stuck or takes a long time to lay);
• prolapse of the oviduct.
Broodiness
Broodiness may occur more frequently in some birds, especially ageing bantam breeds.
You may also see deferred broodiness where a bird that has never gone broody before suddenly starts sitting on eggs.
Some of these ageing matrons make reliable foster mothers for younger hens' eggs, even if they've stopped laying themselves.
Disease
Some diseases become more common in older birds. As their metabolism slows, their immune system weakens, especially if it hasn't encountered a particular disease for many years.
Diseases you may see include lymphoid leucosis, which causes tumours in the body. Symptoms are fairly vague:
• enlarged abdomen;
• loss of appetite;
• pale, shrivelled comb;
• diarrhoea;
• weight loss;
• weakness.
Another is avian tuberculosis. It's a slow-developing disease caused by a mycobacterium, which lives in the soil. It's incredibly hard to get rid of the mycobacterium as they're resistant to low and high temperatures, dryness, a change in pH, and common disinfectants.
Symptoms of avian TB include:
• progressive weight loss despite a good appetite;
• soiled tail and vent feathers;
• pale or blueish, shrivelled comb;
• a rooster's crow may become hoarse;
• emaciation.
Wild birds, especially ducks, are carriers. It's also spread by rodents, sheep, pigs, mites, and ticks.
It can become a recurring problem in small backyard flocks if the soil around permanent coops is contaminated.
Changing from pellets to crumbles can help the digestive system of older chickens.