Effects of Dietary Protein Levels on Performance of Japanese Quail

Abstract

Prior to studies on amino acid requirements of the Japanese quail, the effects of dietary protein levels on performance were studied during the quail's productive life. Two growing diets, 1 and 6, were formulated to contain 12.5% and 28.9% of crude protein (CP), and 3, 000kcal/kg of ME. At 40 days, the growing diets were switched to laying diets. Two laying diets, 1 and 6, contained 12.2% and 28.2% of CP, and 2, 900 kcal/kg of ME. Amino acids, liable to be limiting, were added to these diets. Growing diets 1 and 6 and laying diets 1 and 6 were mixed at ratios 5:0, 4:1, 3:2, 2:3, 1:4 and. 0:5 and formulated diets with 6 levels of CP, respectively. Body weight, feed intake, egg production rate and egg size were recorded every week from 2 to 70 weeks of age. The body weights of Japanese quail increased in the same patterns on the high CP diets and were constantly maintained after reaching a plateau at 10 weeks of age. Body weight gains from 2 to 5 weeks before the beginning of egg production increased linearly with increasing dietary CP levels and remained relatively constant thereafter. The CP level requirement for maximum body weight gain and the minimum feed conversion ratio were estimated to be 20.8% and 19.0% of the diet, respectively. Egg production started at 43 to 44 days of age on a diet with more than 23.3% of CP. A 50% egg production rate was achieved after 44 days on the highest CP diet. However, the start of egg production and reaching 50% egg production were delayed, especially at the 12.5% CP level. The egg production rate reached its maximum level at 10 weeks, remained constant until 60 weeks, and then decreased sharply for all diets. The egg mass shifted with a similar pattern to that of the egg production rate. However, egg size increased with increasing dietary CP levels and remained relatively constant throughout all laying periods for each diet. Feed consumption shifted in a similar pattern to egg production. The CP requirements for maximum egg mass and the minimum feed conversion ratio for 10 to 56 weeks of age were estimated to be 19.4 and 18.7% of the diet, respectively. These values were lower than those reported. Protein efficiency for egg production was calculated to be 27.6%, which is significantly lower than that obtained in laying hens. The highest mortality was observed at 25.1% and 28.3% of dietary CP levels, respectively.