نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction: Quail production, as an emerging sector within the livestock and poultry industry, has attained a distinctive position in animal production systems and continues to expand in response to increasing market demand. Owing to their short generation interval, early sexual maturity, and desirable egg-laying capacity, quails are regarded by industrial and commercial producers as an efficient and profitable species. In recent years, the rising cost of feed has prompted poultry producers to place greater emphasis on precision nutrition strategies aimed at accurately meeting the animals’ nutrient requirements in order to optimize growth performance. Among the nutritional requirements of poultry, dietary energy and protein are recognized as the primary limiting factors influencing productive performance. The objective of the present study was to apply the Gompertz growth model to estimate the growth parameters of Japanese quails fed diets containing different levels of dietary energy and protein. Predicting growth rates at various stages of rearing enables the determination of nutrient requirements and facilitates the development of the most economically efficient feeding management program. One of the most commonly used approaches for predicting growth performance is the application of mathematical growth models.
Materials and Methods: A total of 360 Japanese quails were used in a completely randomized design arranged in a 2×3 factorial structure, including two levels of metabolizable energy (2800 and 2900 kcal/kg) and three levels of crude protein (22%, 24%, and 26%). Each treatment consisted of four replicates with 15 quails per replicate. The levels of other nutrients, except for energy and protein, were adjusted according to the nutrient requirements of poultry recommended by the National Research Council (NRC, 1994), and diets were formulated using the UFFDA software. The lighting program during the experimental period included 23 hours of light and 1 hour of darkness. Birds had free access to feed and water throughout the trial. Body weights were recorded on days 0, 5, 10, 14, 21, 28, 35, and 42 of the rearing period. For weighing, birds were fasted for three hours and weighed at 8:00 a.m. using a digital scale.
Results and Discussion: The results showed that the initial body weights did not differ significantly among treatments. Quails fed diets containing 22% crude protein and 2800 kcal/kg metabolizable energy (treatment 1) exhibited higher final weight and the weight of inflection point compared with those fed diets containing 26% crude protein with 2800 kcal/kg energy (treatment 3) and 22% crude protein with 2900 kcal/kg energy (treatment 4). The lower final weight observed in treatments 3 and 4 could be attributed to an imbalance between available energy and amino acid supply. Increasing dietary protein without sufficient energy likely caused part of the amino acids to be oxidized for energy production rather than used for muscle protein synthesis. Conversely, excessive energy with inadequate protein may have stimulated lipogenesis (fat deposition), resulting in greater fat accumulation instead of muscle growth. In treatment 1 (22% crude protein), the time of inflection point occurred later (46.33 days) than in treatment 3 (30.77 days) and treatment 6 (32.89 days), both of which contained 26% crude protein. These findings indicate that increasing dietary protein up to about 26% can shorten the age at the inflection point. However, increasing the protein level in combination with an appropriate energy level (Treatment 6: 26% crude protein and 2900 kcal of energy) did not result in a statistically significant difference in final body weight and weight at the inflection point compared with Treatment 1; nevertheless, the age at the inflection point was shorter in this treatment.
Conclusion: Based on the Gompertz growth model, the dietary energy-to-protein ratio played a significant role in shaping the growth pattern of quail. Treatment 1, with an energy-to-protein ratio of 127.3, exhibited the highest final body weight (674.54 g), the greatest body weight at the inflection point (248.15 g), and the highest age at the inflection point (46.31 days). In contrast, Treatments 3 (107.7) and 4 (131.8) showed the lowest final body weight and body weight at the inflection point, indicating a reduced growth potential. Although Treatment 6, with an energy-to-protein ratio of 111.5, did not differ significantly from Treatment 1 in terms of final body weight or body weight at the inflection point, its age at the inflection point (32.89 days) was lower than that of Treatment 1, suggesting that the birds reached their maximum growth rate at an earlier age.
Considering final body weight, body weight at the inflection point, and age at the inflection point simultaneously, an energy-to-protein ratio ranging from 111.5 to 127.3 can be recommended as the optimal range for achieving desirable growth performance in quail.
کلیدواژهها English
