Abstract The objective of this study was to evaluate the productive performance, egg quality and the morphometry of the organs of Japanese quails (Cotournix cotournix japônica) when kept in comfort and under thermal stress. 192 nine-week-old quail were used, distributed in a completely randomized design at two temperatures (T1 = 24 °C and T2 = 32 °C), with 12 replicates of eight birds each, with an experimental period of 63 days, divided into three 21-day periods. Feed intake (g fowl-1 day-1), water consumption (mL fowl-1 day-1), egg production (%), egg weight (g), egg mass (g fowl- 1 day-1) and feed conversion (kg kg-1 and kg dozen-1). Laying quails after their production cycle are marketed as beef animals. It is observed that the average final live weight was reduced (P = 0.0362) by 27.58 g in birds kept at a temperature of 32 oC, which can compromise its commercial value. The feed intake of the birds was reduced (P = 0.0051) by 14.75% with an increase in ambient temperature. Birds kept at a temperature of 32 oC for 12 h daily showed a reduction in feed intake, final weight, yolk, and gizzard weight, but without affecting egg production, weight and mass.

The objective of this study was to evaluate the potassium requirement for laying Japanese quails. Two hundred and forty quails were distributed in a randomized block design, with five treatments and six replicates, with eight birds each. The treatments consisted of a basal diet deficient in potassium (K) (2.50 g/kg), supplemented with potassium carbonate, to replace the inert, to reach levels of 2.50, 3.50, 4.50, 5.50 and 6.50 (g/kg) of K in the diet. There was a quadratic effect of K levels on feed intake, egg production, egg mass and feed conversion per egg mass and per egg dozen, estimating the requirements of 4.26, 4.41, 4.38, 4.43 and 4.48 (g/kg) of K diet, respectively. There was no significant effect on the levels of K in the diet on egg weight, albumen weight, percentage of yolk or shell and yolk color. However, yolk and shell weights reduced and the albumen percentage increased linearly with increasing levels of K in the diet. Despite the reduction of shell weight, the increased levels of K did not influence the specific gravity and shell thickness. The use of 4.41 g/kg of potassium is recommended in the diet for laying Japanese quails.