Effect of dietary protein level on egg production and egg-quality characteristics of Japanese quail (Coturnix coturnix japonica) in the tropical environment

Context Quail production is increasingly emerging as a low-capital, cheap, alternative source for supplementing protein intake among peoples in tropical countries such as Nigeria. Aims To increase animal protein sources, promote their availability to rural people, and reduce the unit cost of protein to the people, the effect of dietary crude protein on feed consumption, egg productivity and egg-quality characteristics of quail in the high-altitude Ekiti area of Nigeria was evaluated. Methods In total, 142 mature Japanese quails, divided into four groups with four replicates per group, were fed with four diets differing in dietary protein concentration with a near-isocaloric maize-groundnut cake-soybean meal-based diets for 10 weeks. Three experimental diets (18%, 22% and 24% crude protein (CP)) were tested and compared with a control 20% CP diet, in a completely randomised design of four replicates per treatment. Each consisted of 10 quails/cage at 5 weeks of age. Parameters measured on each quail included feed intake, egg number and egg-quality characteristics. Data were subjected to general linear model, regression and Duncan multiple-range procedures for means separation by SAS(R)v9.4 (2013). Key results Increasing dietary protein from 18% to 24% in the diet of experimental quails decreased daily feed intake, hen-day egg production (HDP) and average egg mass (AEM; P < 0.05) during egg lay, whereas egg weight and diameter, egg shell weight, albumen weight, height and percentage, and yolk height increased significantly (P < 0.05). The 18% CP diet produced the highest HDP and AEM responses (P < 0.05). The 20% CP diet produced the highest numerical shell and yolk percentages (P > 0.05). Birds on 22% CP diet consumed the lowest quantity of feed (daily feed intake, P < 0.05) and had the lowest feed conversion ratio (FCR, P > 0.05). Birds on 24% CP diet produced the highest egg weight and diameter, egg shell weight, albumen weight, height and percentage, and yolk height (P < 0.05). Haugh unit values were high and uninfluenced by an increasing dietary protein concentration (P > 0.05). The high and above-threshold environmental temperature-humidity index value of the test station resulted in heat stress during egg production, and was considered major cause of the generally low productivity and low egg-trait values obtained. Conclusions The 18% CP diet produced the highest HDP and AEM, while the 22% CP diet was the most efficiently utilised diet, and 24% CP diet stimulated higher egg-weight and egg-quality traits. Implications Massive quail egg production could be sustained among rural people with the 18% CP diet, with adequate energy level, and without adverse effects on egg quality.