MATERIALS AND METHODS

The experiment was conducted in a curtain-sided poultry house of 4.40 m height, 61.7 m length and 12.30 m width with asbestos-tiled roof with air inlet. Reeled nylon curtain system was used to open and close for air circulation in summer against high radiation and for cold protection in winters in the north and south facing sides of the house. A total of 55.660 birds (Hubbard, Avian and Anac) were housed. This flock was fed during a six-week (37-46 day feeding period). Feeding dates, growing period and the number of birds housed during the experiment are given in Table 1. The experimental period corresponded to the growth phase (37-46 days) of birds. Rice hull was used as bedding material.

Radiant heaters were used to heat poultry house during winter period. Daily average Poultry House Inside Temperatures (PHIT), °C, were measured using computer aided measurement set comprising of a computer, a data logger (12 AD/DA) and diode type temperature sensors consisting (KTY-81) in growing periods between December 1997 and November 1998. All the temperature sensors were placed in 26 locations distributed in the house and located 50 cm above the floor to measure the temperatures in the vicinity of chickens properly.

Method of Degree-Day
Generally, a degree-day fixes the value that expresses the added temperature of the environment. It gives the value of quantity and duration when the air temperature becomes lower or higher than a determined threshold value, which is known as its base temperature (Hitchen, 1981; Matzarakis and Balafoutis, 2004). Degree-day values are defined when inside barn temperatures drop below certain temperatures and these values are called as the Suggested Poultry House Inside Temperatures (SPHIT), °C and are given in Table 2 based on growing period of birds. In other words, SPHIT are simply the desired temperatures and they vary depending on the purpose, animals, region, latitude and topographic conditions.

The daily degree-day value of a poultry house is the difference between the PHIT and SPHIT. In the same manner, degree-day value over a period is the cumulative sum of the difference between PHIT and SPHIT for weeks. Therefore, poultry house should be heated when PHIT drops below SPHIT and cooled when PHIT increase above SPHIT.

Heating degree-days are defined as the mean number of degrees by which the outside temperature on a given day is less than some base temperature, totaled for all the days in a period. For example, if the outside temperature for the whole day is 1°C less than the base temperature, this would constitute 1 degree-day. Cumulative sum of daily Heating Degree-day (HDD) values are obtained with the following equation (Gultekin, 1995; Buyukalaca et al., 2001; Kadioglu et al., 2001):

(1)

where;
HDD = the cumulative sum of daily heating degree-days for n number of days
n = the total number of days during the period.

Table 1:	Feeding dates, growing period and the number of birds housed during the experiment

Table 2:	Suggested poultry house inside temperatures for gradual reduction (Thomason et al., 1987; Erensayin, 1991; Lindley and Whitaker, 1996; Lacy, 2002)

Cooling degree-days are defined similarly, as the mean number of degrees by which the outside temperature on a given day exceeds a base temperature (Anonymous, 2005). Cumulative sum of daily Cooling Degree-day (CDD) values are obtained with the following equation (Gultekin, 1995; Buyukalaca et al., 2001; Kadioglu et al., 2001):

(2)

RESULTS AND DISCUSSION

The daily average Poultry House Inside Temperature (PHIT), Poultry House Outside Temperature (PHOT) and Suggested Poultry House Inside Temperatures (SPHIT) as a function of days for 6 growing periods to determine the cumulative sum of daily Heating Degree-Days and (HDD) and cumulative sum of daily Cooling Degree-Day (CDD) are presented in Fig. 1 a-f. It is evident from Fig. 1a that radiant heating system overworked during the first growing period except the fifth week since PHIT exceeded SPHIT at this period of time. This will affect health and growth of poultry inside and increase fuel consumption, hence cost of operation. On the other hand, during the second growing period (February19-March 30), even though winter conditions are prevalent, it was determined that radiant heating system did not work sufficiently during the second growing period except the sixth week since PHIT was lower than SPHIT at this period of time (Fig. 1b). SPHIT exceeded PHIT during the fifth growing period (August 5-September 10), indicating that poultry house was not sufficiently cooled even though reeled nylon curtain system was open for air circulation in summer conditions (Fig. 1e).

The daily average PHIT as a function of time (Fig. 1a-f) have been examined for heating and cooling degree-day method in order to identify the temperature variation during each growing period. Heating and cooling degree-days calculated based on Eq. 1 and 2 and the ideal temperature counted from each growing period are summarized in Table 3. The number of heating and cooling days determined for the first growing period (December 29-February 9) is 9 and 31, respectively. Poultry house inside temperature stayed at ideal temperature only for three days at the mentioned period of time. On the other hand, the number of heating and cooling days during the second growing period (February19-March 30) was 31 and 6, respectively. The number of ideal temperature counted was 2. It is evident from Fig. 1a and b and Table 3, being the number of heating and cooling degree-day higher or lower than that of ideal temperature for the first and second growing periods indicates that optimum temperature conditions were not maintained for broiler chickens. The similar analysis can be applied to the other growing periods.

Fig. 1:	Change in heating and cooling days during the growth periods

Table 3:	Number of days for heating, cooling and ideal temperature during 6 growing periods

Method of degree-day can be used for calculation of energy requirements for heating and cooling of buildings future and energy planning in the developed countries. This method can be also applied to predict the energy requirement of agricultural structures such as poultry houses. Furthermore, capacity of ventilation, heating and cooling of poultry house can be calculated utilizing this method (Gultekin and Kadioglu, 1996). Therefore, it can be concluded that the method may be used to assess the potential for heating and cooling of a given barn for which the balance temperature point is measured or estimated. Hence, grower could save money cutting down the unnecessary energy expenses.

CONCLUSIONS

Temperature observations are necessary for many human and animal related activity assessments through the heating and cooling degree-days concept. The heating and cooling degree-days considering SPHIT values for broiler poultry house were determined using temperature measured from 26 locations distributed in the curtain-sided poultry house. Chicken growth took place during 6 periods amounting to 241 days. This time included 86 heating, 11 ideal and 144 cooling days. The numbers of the heating and cooling degree-days for six growing periods were calculated. Using the findings of this study, excessive cooling and/or heating could be prevented, which is important in minimizing excessive expenses that could result from lower or higher than necessary levels of temperature.