عنوان مقاله [English]
Introduction The knowledge of the bird requirements is one of the existing solutions to increase poultry production in the country in order to take advantage of their maximum production capacity. Due to the high cost of feed in poultry production units, it is very important to consider the main components of the feed. Energy and protein are very important nutrients for poultry. Energy is necessary for body function and protein is essential constituent of all tissues of bird's body. Proteins have a major effect on growth performance of the birds, and it is the most expensive nutrient in the broiler diets. A large part of the production cost in poultry farms is related to feeding and so far a lot of research has been done to better use of the feed by the animal and reduce feeding costs. Diets contain excessive amounts of some nutrients lead to the loss of these nutrients and to increase the cost of breeding. Khazak hen is a native hen of Sistan region with a small body. Achieving better growth performance in this bird requires determining the optimal levels of energy and dietary protein in different phases of production. Since there is no information about the optimal level of energy and protein in the growth period for Khazak chickens, so this study was conducted to determine the effect of different levels of energy and protein on growth performance of Khazak native chickens and select the best combination of energy and protein levels at 7 to 91 days of age.
Materials and Methods The research was performed on Khazak chickens in the Research Center of Domestic Animals (RCDA) in the University of Zabol, Zabol, Iran. A total of 360 seven- day- old chicks were randomly allocated to 9 dietary treatments including three levels of energy (2600, 2800 and 3000 kcal / kg) and protein (17, 19 and 21%) as a factorial experiment in a completely randomized design with four replications, and 10 birds in each replication. The chicks entered the experimental pen in seven days of old and they were examined with experimental diets for 12 weeks. The birds had ad libitum access to feed and water throughout the experiment. Eenvironmental conditions in terms of light, temperature and humidity were considered similar for experimental treatments. Weighing chickens and feed intake were measured weekly. Other parameters including average daily body weight gain, feed conversion ratio, daily energy and protein intake, energy and protein efficiency ratio were calculated based on the body weight and feed intake data, in three age ranges (7 to 35, 35 to 63 and 63 to 91 days of age) and the whole period. The collected data were analyzed using GLM procedure of SAS software version 9.1 and the means were compared with Tukey test at 5% level.
Results and Discussion The results showed that the effect of different energy and protein levels had a significant effect on weight gain, feed intake (except for 63-91 days of age period), feed conversion ratio, energy and protein intake (except for 63-91 days of age period) in three studied periods and whole period (P˂0.05). Also, the energy and protein interaction showed a significant effect on all studied variables in all periods (P /0 0.05). The effect of energy and protein levels were not significant on protein efficiency ratio (PER) and energy efficiency ratio (EER), respectively. During the starter period, birds may have physical limitations when they consume low-density diets. In fact, there is a decrease in energy consumption due to physical limitations when the birds consume a diet with low energy and protein in the starter period. As the results of the present study showed, determining the optimal energy and protein levels of the diet is very important to maximize the performance of native chickens. In order to balance poultry performance and economic production, an applied feeding program represent a compromise between the nutritional requirement of the animal and management needs. Thus, one possible way to achieve this balance is a diet formulation that can regulate a specific ratio of protein to renewable energy
Conclusion Although, the many performance variables were not significant between energy levels of 3000 with 2800 kcal/kg and protein levels of 21 with 19%, but the negative effect on performance was observed by reducing energy level to 2600 kcal/kg and protein level to 17 %. So level of 2800 kcal/kg and 19% for energy and protein suggested for these ages of chickens.