Obtaining optimal hygrothermal conditions for the production of laying hens

According to the ^{World Meteorological Organization (1989)} (Table 1) 4 different ITH values are shown for animals in production that define their hygrothermal condition, which are: normal, alert, danger and emergency.

In the Table 2 shows the range of values of relative humidity and temperature for which the best results in egg production were obtained. ^{Talukder et al. (2010)} evaluated the effect of different environmental conditions on the performance of laying hens, gathering data on temperature, relative humidity, ammonia concentrations and carbon dioxide. The parameters evaluated were: egg production, food consumption, weight and egg shape, showing that the tolerable temperature of the hens ranges from 15 °C -27 °C. At temperatures above 27 °C, food consumption, weight and egg shape begin to be affected. Relative humidity has a lower impact on the production, weight and shape of the egg.

Obtained the optimum temperature and humidity ranges, proposed by the different authors, the ITH was used to limit these comfort values. Table 3 shows that in some investigations (^{Lacetera, 2003}; ^{Guevara et al., 2013}), there are 4 different values for the ITH that are: normal, alert, danger, emergency. ^{St-Pierre et al. (2003)} carried out an analysis using an ITH< 70 for laying hens with the purpose of demonstrating that the economic losses in the poultry industry of the United States of America were due to the fact that the animals were reared in zones and seasons where the temperature leaves the comfort zone of the animal.

Climate and parametric analysis of the site

The classification of the bioclimates was made using the climatic classification proposed by García, which is an adaptation of the Köppen climate classification system (2004), for existing bioclimates in Mexico. The representative meteorological station was randomly selected from a set of meteorological stations that belong to the same bioclimate because they are within the same range of temperature and annual rainfall.

Determination of the thermal comfort zone for laying hens

A table was elaborated (Figure 1) with the determination of ITH values, using the equation (^{Dikmen and Hansen, 2009}):

Where: Tdb= represents the dry bulb temperature in °C; and RH= the relative humidity in (%).

It was determined that for the values: comfort temperature for hens in the range between 18 °C-22 °C and relative humidity between 60%-70%, the ranges proposed by all authors for a better production of the Table are met 2 and do not exceed values greater than 70 of ITH proposed by the authors of Table 3.

The green color shows the ITH values in the range of temperatures and relative humidities proposed as comfort parameters found in this research work.

Analysis by bioclimate

Using the equation of ^{Dikmen and Hansen (2009)} and the hourly temperature and humidity analysis proposed by ^{Olygey (2014)}, the schedule conditions are shown for each of the existing bioclimates in the state of Oaxaca.

For the analysis of this semi-cold bioclimate, the standardized annual data of meteorological station number 20400 located in the municipality of San Pedro Quiatoni, Oaxaca, were acquired. These data show us that the chicken will only be in the hygrothermal state of alert 7.64% of the year as shown in Figure 2.

Figure 2 Analysis of hourly ITH for semi-cold bioclimate. 

In the analysis of the semi-cold, dry bioclimate, the standardized annual data of the meteorological station number 20076, located in the municipality of Asunción Nochixtlán, Oaxaca, were acquired. These data show that the hen will only be in the hygrothermal state of alert 12.50% of the year as shown in Figure 3.

Figure 3 Analysis of hourly ITH for dry semi-cold bioclimate. 

In the Figure 4 shows the analysis of the humid semi-cold bioclimate. Standardized annual data were obtained from the meteorological station number 20308 located in the municipality of San Mateo Río Hondo, Oaxaca, where the hen is found during the hottest hours in an area of ideal comfort, in night hours, the bird is in a cold state which will cause a greater consumption of food.

Figure 4 Analysis of hourly ITH for humid semi-cold bioclimate. 

The hourly data of the temperature and humidity index for a temperate bioclimate (Figure 5), here the hygrothermal data were obtained from the meteorological station number 20329 located in the municipality of Oaxaca of Juárez, where the hen will be in a danger zone 39.93% of the year.

Figure 5 Analysis of hourly ITH for temperate bioclimate. 

For the hourly data of the temperature and humidity index of a dry temperate bioclimate (Figure 6). The hygrothermal data were obtained from the meteorological station number 20022 located in the San Bartolo Coyotepec municipality, Oaxaca, where it is observed that the hen will be in a danger zone at 35.76% of the year.

Figure 6 Analysis of hourly ITH for dry temperate bioclimate. 

In the Figure 7 shows the hourly data of the temperature and humidity index of a humid temperate bioclimate. The hygrothermal data were obtained from the meteorological station number 20177 located in the municipality of San Ildefonso, Villa Alta, Oaxaca and it is observed that the chicken will be in a danger zone 24.65% of the year.

Figure 7 Analysis of hourly ITH for humid temperate bioclimate. 

The hourly data of the temperature and humidity index of a warm bioclimate (Figure 8). The hygrothermal data were obtained from the meteorological station number 20149 located in the municipality of Santo Domingo Tehuantepec, Oaxaca in which it is observed that the hen will be in a danger zone 32.99% of the year and in a state of emergency of 20.14%.

Figure 8 Analysis of hourly ITH for warm bioclimate. 

In the Figure 9 shows the hourly data of the temperature and humidity index of a dry warm bioclimate. The hygrothermal data were obtained from the meteorological station number 20170 located in the municipality of San Pedro Totolapan, Oaxaca in which it is observed that the hen will be in a danger zone 18.75% of the year and in a state of emergency of 1.74%.

Figure 9 Schedule ITH analysis for dry warm bioclimate. 

The hourly data of the temperature and humidity index of a humid warm bioclimate is shown in Figure 10. The hygrothermal data were obtained from the meteorological station number 20048 located in the municipality of Juchitán de Zaragoza, Oaxaca where it is observed that the hen will be in a danger zone 38.54% of the year and in a state of emergency 4.86%.

Figure 10 Analysis of hourly ITH for humid warm bioclimate. 

In the Table 4 presents a summary of the statistical percentages that will be given in each of the bioclimates during the year based on the standard data of 1982-2010 provided by the meteorological stations of the National Water Commission (CONAGUA). It is observed that the bioclimates in which the bird will have greater development difficulty, loss of body mass and in egg production, correspond mainly to warm bioclimates and to a lesser extent to the hot, humid and warm dry bioclimate.

In all the regions of the state of Oaxaca or anywhere else in Mexico, it is enough to find the bioclimate of the desired site in order to know how the bird would behave in that area, in case of establishing a poultry farm. In addition, with the ITH schedules, a prediction of the losses of egg production and weight of hens can be made in each of the existing bioclimates in Mexico using the mathematical model proposed by ^{St-Pierre et al. (2003)}. Something similar was done by ^{Guevara et al. (2013)} for ITH conditions in livestock production, in a province of Venezuela.