Heat loss occurs due to the movement of the air
which permits the transfer of heat from the hen’s body to the air.
This process can be promoted by providing fast air movement around the hen.
Heat transfer from surface to surface. Normally,
it is relatively unimportant as the contact surface is small
and the temperature of the litter or of the cage is not signiﬁcantly
different from the body temperature.
This is the transmission of heat from a warm object to a cold one.
Heat loss is proportional to the temperature difference between the
body surface and the surrounding air.
Birds use evaporation to stabilize their body temperature by increasing
the respiration rate through panting, which is very effective.
A uniform temperature throughout the house is very important.
Good ventilation management and thermal insulation should help
to reduce or eliminate temperature variations, specially between day and night.
The temperature should not be seen as an isolated
parameter but always considered in combination with humidity.
In addition, air speed is also an important element of the perceived ambient temperature.
High temperatures, especially over a long period, can cause serious losses to the poultry farmer. The effects of heat stress are delayed onset of lay, lower performance, decreased feed intake and increased mortality. Therefore, to minimize ﬁnancial losses, every effort should be made to maintain an ambient temperature in the house that is within the bird’s comfort zone. If this is not possible, corrective measure should be taken:
The ventilation system should be checked before the hot weather arrives. Fans should be cleaned and fan belts should be tightened and replaced if necessary. The inlets must be adequate to supply the air ﬂow needed, they should be clean and not obstruct the ﬂow of the incoming air. Tunnel ventilation and cooling pads are the preferred ventilation system. It is advised to check and update climat computer, fans, inlets, sensors every year.
The stocking density should be in accordance with the environmental conditions. If the housing density is too high, the radiant heat between the birds will accumulate, the temperature will increase and air will be prevented from circulating around the birds properly. There should be enough space for the birds to separate in order to pant and droop and slightly lift their wings away from the body to maximize responsible heat loss.
When birds are heat stressed, they increase their consumption of water in an effort to cool down. The ratio of water to feed increases from 2:1 under normal conditions to over 5:1 under hot conditions. Cool water of good quality should be supplied so that birds can ﬁnd relief from the heat. To ensure that all the birds have access to water, provide a minimum of one cup or nipple drinker at the cage partition or 2.5 cm of water trough per bird.
Do not feed at the hottest time of the day. A good strategy is to withhold feed ﬁve to eight hours prior to the anticipated time of peak temperature. Feeder chains should be run frequently to stimulate feed intake. The feeder should remain at a low feed level for about one hour per day in the afternoon, to promote a better appetite and ensure that the ﬁne particles are consumed, which usually consist of minerals, vitamins and amino acids. To increase feed consumption, a mid- night snack can be implemented.
Since feed intake is reduced during hot weather periods, the general feeding approach is to increase the energy content in the feed to keep daily energy intake at the level necessary for optimum performance under these conditions.
Water is the most important and critical nutrient for hens. Any water deprivation will directly impact feed consumption and production. If deprivation exceed 24 hours, egg production will be severely affected. If privation exceed 48 hours, high mortality will occur in the ﬂock. It is therefore essential to provide a good quality, stable and reliable source of water. Better still, ensure there are two water sources.
Water can act as a disease carrier if it is contaminated at the source. Moreover, a poor microbiological quality of water can affect gut health and lead to pathologic issues that affect production. The microbiological quality at the water source should be monitored and samples should be taken at least once per year. This is even more important if water comes from surface sources. Even if the water source is of excellent quality, chlorination or an alternative treatment is highly recommended. Treatment of surface water is compulsory.
The content of minerals and other elements can greatly impact egg production and hen health. Even if corrective measures can be taken, it is very diﬃcult and expensive to alter the chemical characteristics of water. A good quality water source is a huge advantage when a new farm is under construction. The physical and chemical water quality must be monitored and samples taken at least every year.
In some cases, hens can refuse water. This situation is the same as water deprivation:
Good air quality should be guaranteed in the house by using proper ventilation, so there is a low concentration of gases and dust. At the same time, the temperature in the house should be optimally maintained between 18 – 20 °C with a relative humidity of 50 – 60 %.The rate of ventilation is determined by the temperature, however when this parameter is reached a minimum ventilation level must be guaranteed. This minimum is normally calculated in m&/body weight/hour but the real aim is the correct management of these parameters:
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