The incubation process, eh, for broiler eggs, lasts 22 days. Eh, a number of factors can affect the success of hatchability of the broilers, eh, starting at the breeder farm and the parent management. Eh, once the hatchery receive the eggs from point of lay to setting should be no more than seven days. If the eggs are stored for longer than that period, there's a drop-off in hatchability. So the eggs should be appropriately stored during that period prior to setting eh, to further ensure there is no detrimental effects. Once received, the, the eggs are placed in a setter. They're placed in a vertical position with the broad end up, on the tray. The eggs are placed on these trays in a turning mechanism, and are rotated through 90 degrees once an hour for the first 19 days of incubation. This prevents the developing embryo from sticking to the side of the shell, and as it later develops, it gets into the correct position for hatching. So for that 19 days, they're turned once an hour as incubation progresses. Other factors that you have to control during that period are temperature. Generally, the temperature setting in the center is about 37 and a half degrees centigrade. Depending on the make of the manufacturer and the mode of operation, it can vary slightly from this. The eggs they get too hot they die. If they get too cold they take longer to hatch. So 37 and a half is the midpoint for that. You also want to control humidity, this can be supplied through either an aerosol spray or through a water bath placed in the base of the incubator. You want to control ventilation as well, to get rid of the waste products of respiration of the developing embryos. So, that's carbon dioxide and humidity from the eggs. So that, that is controlled by opening or closing ventilation. You also need a cooling mechanism, which is generally high pressured water fired through a copper pipe, which stops the eggs from overheating. So we want to keep them, in a fairly tight temperature band which doesn't vary widely. Overall, the aim during the first part of incubation is to ensure a 12% weight loss of the fresh egg weight. That ensures that the developed embryo inside the egg isn't too large, or too desiccated by the time it, it reaches the hatching process. So, there are detrimental effects, either side of this reasonably broad band, so rather than relying on control systems which indicate temperatures, it's far better to weigh the eggs, at appropriate periods around the first stage of incubation. Then you can correct weight loss to this 12% line. So that's the target for the first stage. Eggs can be candled from six days on to check whether firstly whether they're fertile. And then to withdrawal any embryos that died during the initial stages. There are peaks in mortality in the incubation process. One is at the formation of the blood system. Some fail to develop beyond that stage. And then there is a mid peak which is generally smaller. And then a late peak comes 19 to 20 days where the, the embryos fail to get into the correct position for pipping the shell. And if they can't get into that position, they won't successfully hatch. So they can be candled at six days or any time there on. But typically they'll be candled at transfer at 19 days. So the eggs are looked at through a bright light source in a darkened room that may be UV or a fluorescent strip. The trays are passed over this light source and rejects are taken out. Importantly at this point you want to take out any eggs which are degraded or haven't developed properly. Particularly rots you want to take out. So, some eggs go off completely; if they're transferred to the hatching tray, they can contaminate a large number of eggs on the tray. So you want to remove these from the system. So at 19 days the eggs are taken from the setting tray and transferred onto paper in a flatbed tray in the hatcher. So they're in here for a further four days, they will start to pip the shell, the day after the transfer to the hatcher. And then over the next 24-48 hours all of the eggs will be hatched, hopefully. Up to about 95% typically will hatch. Once hatched by 21 days of incubation, well, about..., we allow them enough, a further day in the hatcher to dry off and get their energy back before they're boxed and dispatched. So, the environment in the hatcher is manipulated, firstly to allow them to pip the inner air cell and then to pip the shell. So first it's dried and then supplementary humidity is supplied to ease their escape from the shell. And then it's dropped back down again to dry them off. So their nice, fluffy and yellow when they're dispatched. In this eh, hatchery, yes the turning is automated, temperature control is automated, eh, everything is monitored by telephone lines, so if, if anything falls outwith the set parameters, eh, somebody gets a phone call in the middle of the night to come and correct it. That's automated. In some larger hatches, hatcheries, there's conveyor belts with chicks,and things are moved easier, but typically it's always a human eye that picking up problems, yes. Yes, so at 21 days they are, all the eggs should be hatched by that point, so there..., some may be wet, or the down is not fluffed up, so they'll allow them another perhaps 16 hours before taking them off, from that point. All of the debris from this hatchery is incinerated. Firstly, the, just because the chick hasn't hatched it doesn't necessarily mean it's dead at that point, so we have to ensure they're humanely killed. Which, where we are, eh, what we are allowed to do is either macerate the debris and then incinerate, or use gas, eh, mixtures to kill anything that isn't going out. If you get something wrong, at any point it is critical. So the four main elements are temperature, humidity and turning and ventilation. But these work in combination with each other, and you need to ensure these are functional by the egg weighing, and the inspection of the developing embryo by candling. You, when you're dealing with large numbers, numbers small mistakes can have, fairly catastrophic effects. So if my temperature is lower than I assumed it was going to be, the eggs'll take longer. It may only be a few hours, but that few hours will then cause a wider spread of hatching. And if, if they don't all hatch at the same time, the perfect conditions for hatching aren't achieved. So it needs to be synchronous, or they don't dry off, there are straggly chicks, their navels don't heal. And if their navels don't heal, that's a source of infection into the flock. So they may be sent out to the farm but they'll pick up infection quickly and die within a few days.
