In­cu­ba­tion A-Z

An eclec­tic al­pha­bet of chicken facts with a dif­fer­ence, by Andy Cawthray

Your Chickens - - Contents -


If eggs are ex­posed to tem­per­a­tures in ex­cess of 39.5C in forced air in­cu­ba­tors (or 41.5C in still air in­cu­ba­tors) for just a few hours it is lethal for the em­bryo in­side. On the flip side, if there is a power cut, or a broody leaves a nest for a long pe­riod of time, em­bry­onic devel­op­ment slows down but doesn’t re­sult in the death of the em­bryo un­less the time pe­riod ex­ceeds 15 hours. The eggs will have chilled, but the me­tab­o­lism of the em­bryo will only have slowed down, and will re­cover once the tem­per­a­ture in­creases. Such breaks in in­cu­ba­tion will de­lay the hatch and may re­sult in slightly re­duced suc­cess, but it will not nec­es­sar­ily re­sult in em­bry­onic death.


Dur­ing in­cu­ba­tion, eggs re­quire turn­ing. Turn­ing the eggs will dra­mat­i­cally im­prove the hatch rate of those which are fer­tile. The rea­sons for turn­ing are to prevent the em­bryo from stick­ing to the

side of the shell. This will stop the chick from be­ing able to move into the hatch­ing po­si­tion when the eggs have reached term. Turn­ing also en­sures an even tem­per­a­ture is achieved within the egg. It also im­proves and re­freshes the con­tact be­tween the em­bry­onic mem­brane and the nu­tri­ent rich al­bu­men within the egg. There is no need to turn eggs placed un­der a broody hen as they nat­u­rally turn their eggs through shuf­fling on the nest and gen­eral move­ment


The eggs should be po­si­tioned in the in­cu­ba­tor so that the blunt end is higher than the pointy end as this is where the air sac is lo­cated. Eggs should also be stood blunt end up and turned dur­ing stor­age.


If too few eggs are set or, upon can­dling, too few are found to be fer­tile, there is a risk that only a sin­gle chick will hatch. If a broody is be­ing used this doesn’t present too much of a prob­lem. If, how­ever, an in­cu­ba­tor is be­ing used the re­sult­ing sin­gle chick will still re­quire the same lev­els of brood­ing heat post-hatch as a clutch would, plus it will be­come quite vo­cal as it tries to get a re­sponse and find fel­low chicks.

Un­less there is a ready sup­ply of day old chicks that can be added to the sin­gle bird to en­able flock in­ter­ac­tion, cor­rect im­print­ing and devel­op­ment, then it would be worth con­sid­er­ing stop­ping the in­cu­ba­tion early if the risk of a sin­gle chick hatch­ing is high.


The ‘egg tooth’ is a small, sharp tem­po­rary cap that sits on the end of the beak of a chick. It de­vel­ops whilst the chick is within the egg and has two key uses. The first is to help the chick break into the air sac within the egg. It is then the more com­monly known func­tion of the ‘tooth’ comes into play, which is when the chick uses it to break out of the shell; this is known as pip­ping.


Not all fer­tile eggs will hatch. Some may show good devel­op­ment on can­dling, but em­bryos can die at any point prior to reach­ing term. This is usu­ally re­ferred to as ‘death in shell’ and es­tab­lish­ing the point of devel­op­ment at which the chick died can help in di­ag­nos­ing the pos­si­ble cause. There are, how­ever, many fac­tors at play, and iso­lat­ing any par­tic­u­lar sin­gle, or group, of fac­tors re­spon­si­ble can be dif­fi­cult. It is worth keep­ing hatch­ing records as these will help iden­tify any pat­terns that might emerge. It is also worth not­ing the tim­ings of the hatches. Un­der nor­mal cir­cum­stances chicken eggs will take 21 days to hatch. Any sig­nif­i­cant dif­fer­ences can be at­trib­uted as fol­lows: Eggs hatched early – small eggs, high temp, low hu­mid­ity, young breeder stock; Eggs hatched late – large eggs, low temp, high hu­mid­ity, old breeder stock.


Not all de­for­mi­ties that oc­cur in chicks can, or should, be put down to ge­net­ics (although a num­ber can be). The man­ner in which eggs are kept prior to set­ting can also be a root cause.

De­for­mi­ties such as crooked toes and splayed legs can of­ten be at­trib­uted to poor egg stor­age.


Once the chicks are full feathered (usu­ally around 6-7 weeks) they should no longer re­quire heat and (sub­ject to the weather) be quite ca­pa­ble of liv­ing out­doors full time. Prior to that, there is no rea­son why chicks can’t take ‘day trips’ out­doors on fine days and be re­turned in­doors to shel­ter and heat overnight. This will help them de­velop and grow faster – though bear in mind that very young chicks can soon chill, so only let them out­doors on warm days and when some­one is present to bring them in­doors should the weather change for the worse.


In­tro­duc­tions can get a bit messy if the peck­ing or­der within the ex­ist­ing flock is well es­tab­lished and dom­i­nated by one top hen. The best thing to do is to put the new birds in to the coop af­ter dark when the res­i­dents have al­ready gone to roost. This not only helps the new birds un­der­stand where home is, but also gives the res­i­dents a chance to in­ter­act with the new birds come first light. In many cases this can be enough for the birds to be ac­cepted, but the fol­low­ing day there will be some ini­tial squab­bling as the peck­ing or­der is re­set. If per­sis­tent bul­ly­ing oc­curs then look to re­move the bully (and not the bul­lied) for a few days un­til the peck­ing or­der has set­tled. Un­der­stand­ing the be­hav­iour and flock dy­nam­ics will also help in iden­ti­fy­ing is­sues and as­cer­tain­ing the right course of ac­tion.

ABOVE: An­tique still-air in­cu­ba­tor

ABOVE: Cra­dle eggs ABOVE RIGHT: Chicks out­doors BE­LOW: Hatch­ing prob­lems FAR RIGHT: A sin­gle chick

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