So last year an estimated 65 and 1/2 million tons of chicken eggs were produced worldwide. Most of these eggs are table eggs, or the eggs that we eat. But some of the eggs are kept for hatching new flocks of broiler chickens or laying hens. And a small proportion of eggs are kept for vaccine production. Asia is the biggest producers of eggs in the world with about 59% of the market, followed by the Americas with 20%, Europe with 16%, and Africa and Oceania bringing up the last 5%. Here in the UK in 2013, we produced almost 27,000 cases of eggs. There are 360 eggs in a case, so you get the picture. It's a lot of eggs. 75% of these were produced in England and Wales. Egg production can be further broken down into housing type. In Europe, laying hens are largely housed in one of four methods of production. We're going to discuss these in greater detail in a few moments. So before we get into production systems, it is helpful to understand what types of commercial breeds of laying hens are used. They can largely be split into two types--brown or white egg layers. Usually, brown hens lay brown eggs, and white hens lay white eggs. In much of the EU and North America, white eggs and thus, white hens, are most popular. These breeds are often smaller in size than brown hens, but they lay more egg mass. That is the weight of all eggs produced in a year than brown hens. A typical white hen probably looks like this. Brown eggs are preferred in the UK, so we have mostly brown hens for table egg production. So let's look at the process of egg production from start to finish. First of all, we need to have breeding flocks that will produce our chicks that will eventually grow to be adult-laying hens. Breeding flocks consist of adult males and females, kept at a ratio of about one male for every 10 females, and this maximizes their breeding potential. These adult breeding flocks are typically housed in loose house systems. In other words, on the floor with litter or wood shavings cover. They are kept with nest boxes, and they're allowed to mate naturally. The eggs that they lay are collected, and these are kept in a cool storeroom for up to about 10 days. And until then, we can collect lots and lots of fertilized eggs. The eggs are stored before incubating, so that the hatchery can build up a large number of eggs, which are then incubated all together. And thus, they also hatch together. This is known as synchronized hatching. Wildfowl employ the same technique by laying an egg a day, but delaying incubating until they have gathered a clutch of eggs, and therefore, all their young hatch together. And there is safety in numbers, and they run around behind their mum. After 21 days of incubation, the chicks hatch. Now, once they've hatched, the chicks have to be sexed. In other words, identified as male or female. Unfortunately, half of all the chicks that hatch are male. And male chicks don't grow up to lay eggs, so those chicks have to be destroyed. There are several methods of humane destruction of chicks that are permitted in the EU, including gas methods of killing, and this is most commonly used here. The gas can be a mixture of inert gas, such as argon, or nitrogen, and carbon dioxide. The chicks are exposed to the gas. They lose consciousness within a few seconds, and they die shortly thereafter. The day-old female chicks then go on to be vaccinated. And in many circumstances, they also get beak trimmed. Laying hens are beak trimmed as a method of controlling feather pecking. To go back to the methods of beak trimming, infrared beak trimming is commonly used throughout Europe. But many countries will still use hot blade beak trimming methods at 7 to 10 days old. The infrared method passes an infrared beam across the chick's upper and lower mandibles, which destroys the blood supply to the beak tip. After a couple of weeks, the dead tissue sloughs off, and a duller beak tip is left behind. In contrast, the hot blade method uses a heated sharp blade to both cut and cauterize the beak tip. The advantages of infrared beak trimming is that it does not require additional handling of the birds at 7 to 10 days of age. And also, that it has been shown not to cause an aroma formation, which is also another name for nerve damage. It also doesn't show evidence of chronic signs of pain in the birds that are treated. In contrast, hot blade trimming does cause nerve damage. Although, young birds are less prone to showing signs of nerve damage than, say, older birds that need to be trimmed when there's been a feather-pecking outbreak. So after beak trimming and vaccination, the chicks are transported in temperature-controlled vehicles to a rearing farm. They're not provided with any feed or water during this period. And that's OK, as long as the transport takes no more than 24 hours. And the chicks must arrive at their destination within 72 hours, or in other words, three days of hatching. The reason we can transport chicks like this is that they have now internalized the yolk sac, that they were living off of, when they were in the egg. And the yolk sac provides them with enough food and water to keep them going, until they get to the rearing farm, and they're supplied with food and water by the farm. It is essential, though, that once they get to the farm, they are given access to food and water straight away. So now, our lovely female layer chicks have arrived on the rearing farm. What might a rearing farm look like? Layer chicks, which are also known as pullets from now on, until they're sexually mature, are broadly reared in one of three types of housing conditions. One of those conditions is cages. Sometimes layer pullets are reared in cages from a day old, but sometimes they're reared in cages from about seven to eight weeks of age after a short period of being reared on the floor. Those birds that are reared in cages go on to be housed in cages as adults. Another housing method is being floor reared. And that means from the day the chicks arrive at the rearing farm, they're on the floor with wood shavings, litter, or something similar. And they stay in that system until they're transported at point of lay. The third system is a multi-tier system. Now, these chicks will be reared in this system only if they're going on to live in a multi-tier system ss adults. So it's important that we try to match the housing system that the pullets go to and rear to-- what they're going to be living in when they're adults in lay. Otherwise, birds don't adapt very well. And that's particularly important if the laying hen system is going to be quite complex. So for example, you could take a rearing pullet from a fairly simple floor rearing system to a pretty uncomplex system like a caged system. But you couldn't go from a very simple rearing system like a floor system to that multi-tier aviary system, because the birds wouldn't have learned how to ascend and descend through the system. We're not going to talk in further detail about pullet rearing or pullet welfare issues here. But if you'd like more information, you can go to your Coursera course page. At about 16 weeks of age, the pullets are transported to the laying farm. This requires catching and handling, placing them into transport modules, and a road trip. Within a few weeks of arriving at the laying farm, the pullets are brought into lay. And we do that by stimulating them by light. We give them a longer day length, and we also increase the light intensity with the overhead lights. This means that they become sexually mature, and they start to lay eggs. And so from now on, I'm going to refer to them as laying hens. So our hens have now arrived at our laying farm. Well, what would their laying farm look like? I mentioned several methods of production earlier on, but I'm just going to focus on free-range egg production and furnished cage egg production. Enriched cages, which are also called furnished cages, are the only type of caged housing that are permissible for laying hens within the EU. They were designed to give hens more opportunities to express their natural behavior, to be more comfortable as well. And they are an improvement over the barren cage in that regard, but they are still criticized for limiting hen behavior. These enriched cages must provide 750 square centimeters of floor space for each hen, plus a nest box, scratch mat, perches, a feed trough, and nipple drinkers. Let's look at these cages in more detail. So this is a small furnished cage unit that we're looking at here. These cages are commercially available cages, but this is a very small cage size. It only holds 21 hens per cage. In a commercial enterprise, most furnished cages would be a lot larger. They'd hold about 60 to 80 birds per cage. But the principles are still the same, and it still has the same furniture, and it still has the same amount of space per bird. So if we look at this cage in front of me, let's look at some of the detail of what the hens have available to them. Here in front of the birds there is a food trough. And in the food trough is the layers' mash that they eat. And then if we look into the cage -- and we will look inside in more detail in a moment. But at this end, where the cage is brightest, there's a pecking and scratching mat underneath these hens here. Then running from side to side, there are perches where the birds can stand and particularly at night-time where they'll roost. At the back of the cage, there are nipple drinkers where they can get access to water. And at this end of the cage, where the cage is darkest, there is a nest box. So you can imagine that all 21 of these hens would really struggle to show pecking and scratching behavior on that pecking and scratching mat at the same time. Hens are very sociable animals, so they do tend to like to do things together. But in this case, it would be impossible. Also, you can imagine that after some food is dispensed onto that scratch mat, after the third or fourth bird has been there to peck and scratch at it, there won't be any food left there anymore. Hens will also probably try and show dust bathing behavior, which I was just talking about, on that pecking and scratching mat. But because the behavior is incomplete, we call it sham or vacuum dust bathing. So the other drawback about this pecking and scratching mat is that although it's good that it's being provided, and it's being provided with food to show the behavior, they still can't show the behavior fully. So in a wild-type environment, these hens would be out showing foraging behavior, which is pecking at and scratching at the dirt on the earth floor in order to find food particles. Now, in this situation, they can only show it in a very limited area. And as I said earlier, that food will quickly disappear. So most of the hens that come to show the behavior don't have anything to find when they show pecking and scratching. So this is the nest box end of the furnished cage. And it's a little dark and gloomy here, but it's supposed to be. Because we want the nest box area to be a bit more dark and secluded from the rest of the cage. Now, you can see on the side of the cage here. There are some plastic strips that are hanging down. The hens can push through the plastic strips, so that they can get into the nest box. But those strips help keep the light from penetrating the nest box. And in this particular design, the front of the nest box is solid. Again, that stops the light getting into the next box. And then if we look into the nest box itself--before, the nest box is different from the rest of the cage, it's not just the plain wire. In this case, it's overlaid with a plastic mat. And that gives the hens a more comfortable place to sit and lay her eggs. So we're in a commercial furnished cage unit here, and it's very different scale to the one we saw a little earlier in this MOOC. A commercial unit like this would typically have four sheds. And we're standing in one of them. And within that shed, there will be seven banks of cages. And we're standing between two banks here. Now, in a bank, in this particular house, there are 10 tiers of cages. And we're standing on sort of the second floor with the top five beside us and above us. And the cages are 22-- or it's rather-- the bank is 22 cages long. So that means in this one shed alone, given that each cage holds typically 80 birds. But there are more than 123,000 hens in this one shed, and there are four of them on this farm. Now, much like the cages we saw earlier, the furnishings are the same. They still have to fulfill the legal requirement. So every one of these cages has 15 centimeters of perch space per hen. It has 12 centimeters of feed space, and it has a nest box and a scratching area. And we'll look at some of them specifically in a moment. But something that's important to point out about this unit is that although the floor print of the building is fairly small--because we can put birds in cages when above one another, it means that we really have made good use of space, and we can hold a lot of animals in this one building. Now, if these hens were all kept free-range, we would need a lot more space to keep them. And this is really driven by egg marketing demand. So people like to eat a lot of eggs, so we need to keep a lot of hens. Now, because the way the egg market is working at the moment, these cages--although they house 80 birds per cage at the moment, they're only stocked at about 85% of their capacity. And that's because the demand for caged eggs is a little lower than normal. And that just means that the hens in here have a bit more space than they would normally. And perhaps in the next block, they'll be up to 100% stocking density. One of the advantages to a caged system is that the laying hens are separated from their droppings. So it means that the risk of them getting infected with parasites or getting diseases is reduced, because the animals are separated from their feces. Another advantage to this system, which is, in part, affected by that reduced incidence of disease, is that mortality is low. In a typical furnished cage system like this one, mortality would only be about 2%. So much like the furnished cage system we saw earlier, we have a scratch mat here. And in this case, it's here at about the middle of the cage. And the food comes out of the food trough through a hole and will go onto the scratch mat, where the birds can peck at it and scratch at it. Now, the layout of this cage design is a little different from the one we looked at earlier. The perches this time go front to back. But the nest box is, again, up one end of the cage where it's darkest. Because these cages are much bigger than the ones we saw earlier, there's actually a nest box at this end to my left and also, one down past me to the right. And this cage is also twice as deep as the cage system we saw earlier, because it needs to hold a lot more hens. This is a fully-automated system. So as the eggs are laid, they roll out of the nest box and onto this egg belt, where they're gradually transported to the egg elevator at the end where they will be sent on to the packing station. So regardless of the type of housing system that a hen lives in, after about one year in her production housing system, her productivity and chill quality start to decline. And so hens will go through one of two processes. In some cases, the hens will be put through a molt. And this is where hens are fed a very low-energy diet to make them lose about half their body weight. And as a consequence, they've stopped laying, and then they're allowed to recover. The quality of their diet is increased. They regrow the feathers
that have dropped out, which is why it's called a molt, and they come back in to lay. And this improves the quality of the shell while maintaining the big excise. And the hens will be kept after the molt for a few more months to produce these big eggs. In other cases, after about a year of production, the hen is sent away for depopulation. So that's when the house is emptied, and the hens are transported for slaughter. So what are some of the common welfare problems that laying hens will experience? Well, a common cause of
death for laying hens from all types of housing systems is egg peritonitis. This is a condition where the egg is laid internally and becomes infected. And unfortunately, unless the hen can be identified and treated, then normally, she will die. Another cause of suffering is bone fracture. Laying hens are rather fragile animals, because we're asking them to produce an egg a day. And the eggshell is formed in part by calcium. And that has to come from the bone structure of the bird. As a consequence, the bird is often fairly osteoporotic. Her bones are quite fragile. And so she is likely to cause herself injury when she bumps into things like perches, or cage furniture, or furniture in the house such as nest boxes and drinkers.