CON­TROL­LING LIT­TER MOIS­TURE IN WIN­TER

The Poultry Bulletin - - FRONT PAGE - This is an edited ex­tract of an ar­ti­cle first pro­duced by the Depart­ment of Poul­try Sci­ence, Univer­sity of Ge­or­gia.

As win­ter ap­proaches, con­trol lit­ter mois­ture with fresh air, heat and air move­ment.

Any suc­cess­ful mois­ture con­trol pro­gram in cold weather must con­sist of three es­sen­tial com­po­nents. These are fresh air, which is needed to move ex­cess mois­ture from the in­side of the house to the out­side; heat to in­crease the tem­per­a­ture as well as the mois­ture hold­ing ca­pac­ity of the cool, in­com­ing air; and air move­ment to help ex­tract mois­ture from lit­ter so it can be ex­pelled from the house.

Miss­ing any of these com­po­nents can be detri­men­tal to your pro­gram. For in­stance, if you bring in cold air, cir­cu­late it over the lit­ter, but don’t add heat, lit­tle - if any - mois­ture will be re­moved from the lit­ter. Like­wise, it’s dif­fi­cult to dry lit­ter if you

bring in fresh air and heat, but don’t move it over the lit­ter. And of course, if you heat and cir­cu­late air, but don’t pro­vide an ex­change of air, you can’t keep a house dry.

Dry­ing clothes

This con­cept is re­ally no different to dry­ing clothes. You can put wet clothes in a dryer, add heat and tum­ble them, but with­out fresh air to re­move mois­ture from the dryer, es­sen­tially no mois­ture would be re­moved from the clothes. You can add heat as well as fresh air but if you don’t cir­cu­late the clothes in the dryer it would be dif­fi­cult to get the clothes fully dried. Last but not least, wet clothes can be cir­cu­lated in a drier and fresh air in­tro­duced, but with­out heat you’ll have a very long wait. It all comes down to the sim­ple truth that in or­der to max­imise mois­ture re­moval, be it from clothes or lit­ter, you need air ex­change, heat, and air move­ment.

Keep­ing it tight

A mois­ture con­trol sys­tem in a poul­try house con­sists of timer fans to ex­change the air, brood­ers/fur­naces to sup­ply ex­tra heat, and most im­por­tantly, in­lets help to con­di­tion, warm and dry the cool in­com­ing air, as well as to pro­mote the move­ment of air over the lit­ter. But how ef­fec­tive this sys­tem is in re­mov­ing mois­ture from the lit­ter, de­pends to a large ex­tent on house tight­ness. This is be­cause it is only the air that en­ters through a house’s in­lets that will be prop­erly con­di­tioned be­fore mov­ing down to and over the lit­ter. Cold, damp air en­ter­ing through cracks in the side walls, fan shut­ters, tun­nel doors/cur­tains, etc. will tend to drop quickly to the floor, chill­ing the birds and re­mov­ing lit­tle mois­ture from the lit­ter. As a re­sult, the greater the pro­por­tion of air com­ing in through cracks the more dif­fi­cult it is to con­trol lit­ter mois­ture. For in­stance, when op­er­at­ing three 90 cen­time­tres min­i­mum ven­ti­la­tion in a loose house, well over 50% of the fresh air brought in en­ter­ing through cracks and not through side wall in­lets. This means less than half the fresh air brought in will re­ally help to con­trol lit­ter mois­ture. Con­trast this to a tight house where bet­ter than 80% of the fresh air is be­ing prop­erly con­di­tioned by the house’s in­let sys­tem be­fore mov­ing down to floor level.

Check­ing the in­lets

Once a house is made tight, spe­cial at­ten­tion needs to be paid to the in­let sys­tem; is it set to achieve max­i­mum heat­ing of the in­com­ing air be­fore it moves down to floor level? The ideal is for the air en­ter­ing through side wall in­lets to travel along the ceil­ing un­til it just makes it to the cen­tre of the house at which point it gen­tly moves down to­ward the floor. Es­sen­tially, we want to max­imise the travel dis­tance along the ceil­ing so the cool in­com­ing air will be suf­fi­ciently heated by the warm air col­lect­ing at the ceil­ing pro­duced by the house’s heat­ing sys­tem as well as that pro­duced by the birds. As the air moves along the ceil­ing, the tem­per­a­ture of the air in­creases and the rel­a­tive hu­mid­ity of the air de­creases, mak­ing it eas­ier to dry the lit­ter with­out chill­ing the birds. In ad­di­tion, the in­lets cre­ate a ben­e­fi­cial air cir­cu­la­tion pat­tern. The air em­a­nat­ing from the in­lets moves up to­ward the peak of the ceil­ing, then down to­ward the floor and fi­nally back to the side wall, pulling mois­ture out of the lit­ter as it goes.

The ex­act in­let open­ing and pres­sure re­quired to prop­erly con­di­tion the cool, damp in­com­ing air varies from house to house. The op­ti­mal in­let open­ing and pres­sure re­quired de­pends on a wide va­ri­ety of fac­tors in­clud­ing type of in­let, in­let lo­ca­tion, house width, ceil­ing smooth­ness, and out­side vs. in­side tem­per­a­ture dif­fer­ence. As with most things, it takes a lit­tle ex­per­i­ment­ing to de­ter­mine what com­bi­na­tion of in­let open­ing and pres­sure will pro­vide the op­ti­mal in­let air flow pat­tern.

One of the best ways to vi­su­alise the air flow pat­tern from your in­lets is to hang small pieces of old VCR or sur­vey­ors tape from the ceil­ing, ev­ery five feet or so from the side wall to the ceil­ing peak. What you are look­ing for is the first few tapes to be mov­ing fairly vi­o­lently with the lasts ones near the peak of the ceil­ing barely mov­ing. An­other way to de­ter­mine if you have your in­lets set prop­erly is that house tem­per­a­ture should not de­crease dur­ing at least the first 30 sec­onds or so the min­i­mum ven­ti­la­tion fans are op­er­at­ing. In fact, with larger birds it is fairly com­mon to see the house tem­per­a­ture ac­tu­ally in­crease a de­gree or more dur­ing the first minute the min­i­mum ven­ti­la­tion fans are op­er­at­ing in a tight house with

prop­erly set side wall in­lets. If the tem­per­a­ture quickly de­creases when the timer fans come on, you are not fully con­di­tion­ing the cold in­com­ing air be­fore it moves down to floor level, mak­ing it more dif­fi­cult to re­move mois­ture from the lit­ter.

Op­er­at­ing timer fans

Asud­den drop in house tem­per­a­ture can also be the sign that you are op­er­at­ing too many timer fans. The goal is not to flood the house with a large amount of cold fresh air but rather to bring smaller vol­ume of air in the house over a longer pe­riod of time so as not to cause large vari­a­tions in house tem­per­a­ture and air qual­ity.

How do you know how much you should be op­er­at­ing timer fans? Since we are try­ing to con­trol mois­ture, one way is to use a min­i­mum ven­ti­la­tion chart based on bird wa­ter con­sump­tion. The more wa­ter the birds drink, the more wa­ter we need to re­move, the more the timer fans we need to op­er­ate. In re­al­ity, the best method of de­ter­min­ing how much timer fans should be op­er­ated is to sim­ply mon­i­tor the rel­a­tive hu­mid­ity of the air in a house. The op­ti­mal hu­mid­ity is be­tween 50% and 60%. If the hu­mid­ity is too high you should in­crease fan run time; if too low run­time should be de­creased.

Rel­a­tive hu­mid­ity

It is im­por­tant to re­alise that though a prop­erly set in­let sys­tem will cre­ate some amount of air move­ment over the lit­ter, it’s typ­i­cally not enough by it­self to in­sure max­i­mum lit­ter mois­ture re­moval. The prob­lem in part is that though it is true that the in­lets when prop­erly set do pro­duce some level of air move­ment over the lit­ter, in most sit­u­a­tions, es­pe­cially with younger birds, they only do so when the ex­haust fans are op­er­at­ing, which is of­ten less than 50% of the time. When the ex­haust fans are not op­er­at­ing, the air tends to be­come still which is not con­ducive to re­mov­ing mois­ture from the lit­ter. An­other chal­lenge is that in an ef­fort to keep fuel us­age to a min­i­mum, the rel­a­tive hu­mid­ity dur­ing cold weather of­ten tends to run around 60% to 70% as op­posed to the op­ti­mal 50% to 60%. The higher hu­mid­ity makes it more dif­fi­cult for the air to re­move mois­ture from the lit­ter. The neg­a­tive im­pact of higher rel­a­tive hu­midi­ties can be some­what off­set by in­creas­ing the level of air move­ment over the lit­ter. It isn’t that different from us­ing a towel to soak up a spill. If the towel is very dry you can sim­ply set it on a spill and it’ll soak up all the liq­uid. But, if the towel is damp you’ll prob­a­bly need to move it around a good bit to soak up the spill. The damper the towel the more you will need to move it around.

Cir­cu­la­tion fan sys­tems

One of the best ways to off­set these chal­lenges is through the use of a cir­cu­la­tion fan sys­tem. A cir­cu­la­tion fan sys­tem is used not only to break up strat­i­fi­ca­tion and cre­ate more con­di­tions from one end of a house to the other, but just as im­por­tantly is used to in­crease the level of air move­ment over the lit­ter to aid in mois­ture re­moval. A proper cir­cu­la­tion fan sys­tem gen­tly moves air across the lit­ter. Ide­ally, cir­cu­la­tion fans should op­er­ate con­tin­u­ally to max­imise mois­ture re­moval but may be need to be tem­po­rar­ily turned off when the timer fans op­er­ate if they in­ter­fere with the air cir­cu­la­tion pat­tern cre­ated by the air in­lets.

Keep­ing costs down

One of the big­gest con­cerns when it comes to con­trol­ling lit­ter mois­ture is how to do so while keep­ing heat­ing costs to a min­i­mum. Though it will al­ways take some amount of heat to con­trol lit­ter mois­ture dur­ing cold weather, how much de­pends to a large ex­tent on the per­for­mance of a house’s in­let sys­tem. If a house is tight, air ex­change rates will be more closely con­trolled and air en­ter­ing through the in­lets will be max­imised, which in turn will lead to bet­ter con­di­tion­ing of the in­com­ing air as well as bet­ter util­i­sa­tion of both heat added by brood­ers/fur­naces and that pro­duced by the birds.

Though at times con­trol­ling lit­ter mois­ture may seem like an im­pos­si­ble task, with proper man­age­ment of in­com­ing air and house rel­a­tive hu­mid­ity, it can be done. Proper lit­ter man­age­ment will re­sult in bet­ter en­vi­ron­ment for the birds and ul­ti­mately bet­ter health and per­for­mance.

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