Effect of Dietary Energy and Protein Level on Growth Performance of Native Khazak Chickens from 7 to 91 Days of Age

Introduction: 

In order to maximize poultry production, it is important to have knowledge of the bird's requirements. This can help to increase their production capacity. Since feed is a major expense in poultry production, it is crucial to consider the main components of the feed. Energy and protein are vital nutrients for poultry. Energy is necessary for body function, while protein is an essential constituent of all tissues in the bird's body. Proteins have a significant impact on the growth performance of birds, and they are also the most expensive nutrient in broiler diets. A lot of research has been done to better utilize feed by the animal and reduce feeding costs. This is important because diets that contain excessive amounts of certain nutrients can lead to nutrient loss and increased breeding costs. The Khazak hen is a native hen of the Sistan region and is known for its small body size. 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.

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.

The study results indicate that varying energy and protein levels had a significant impact on weight gain, feed intake (except during the 63-91 day age range), feed conversion ratio, and energy and protein intake (excluding the 63-91 day age range) during all three periods studied as well as over the entire period (P < 0.05). Furthermore, the interaction between energy and protein showed a significant effect on all variables studied across all periods (P < 0.05). However, the impact of energy and protein levels on protein efficiency ratio (PER) and energy efficiency ratio (EER) was not significant. During the starter period, physical limitations may cause birds to consume less energy with low-density diets. Thus, when birds consume diets that are low in energy and protein during this period, their energy consumption declines due to these physical limitations. The study results indicate that determining optimal energy and protein levels in the diet is crucial for maximizing the performance of native chickens. To balance poultry performance and economic production, an applied feeding program that compromises between the animal's nutritional requirements and management needs is necessary. Consequently, one approach to achieving this balance is by developing a diet formulation that can regulate a specific ratio of protein to renewable energy.

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.