Calcium and Available Phosphorus Requirements of Japanese Quails in the Starter and Grower Phases

ABSTRACT

This study aimed to estimate the nutritional requirements for calcium (Ca) and available phosphorus (Pd) for Japanese quails (Coturnix coturnix japonica) during the growth phases, as well as to evaluate the residual effect of the rearing phase during laying. An entirely randomized design was used in a factorial scheme with 4 levels of Ca (0.57; 0.81; 1.05; and 1.29%) × 4 levels of Pd (0.21; 0.32; 0.43; and 0.54%), totaling 16 treatments with 3 repetitions, with 38 and 35 quails per experimental unit in the rearing (n=1824) and growing (n=1680) phases, respectively. The data were analyzed using polynomial regression for the levels of Ca and Pd to estimate the best-fit model, and the nutritional requirements were determined through the application of overlapping contour plots. Considering the estimates obtained for the performance variables (p<0.05), the levels of 0.92% Ca and 0.37% Pd were estimated for the rearing phase (1 to 14 days), and 0.94% Ca and 0.39% Pd for the growing phase (15 to 42 days). A third experiment was conducted using the same design (n=576), whereby birds received conventional feed to evaluate the residual effect; the best results reinforce the levels estimated during the growth of the birds.

Keywords:
Coturnix coturnix japonica; overlaid contour plots; quail layers

INTRODUCTION

Proper attention to nutrition is of paramount importance in bird production, as it supports bone formation and ensures optimal production performance. Calcium (Ca) and phosphorus (P) are among the most important minerals in poultry diets, necessary for growth, bone mineralization, and the efficient functioning of numerous physiological processes, such as nerve impulse transmission, muscle contraction, blood coagulation, and activation of enzyme systems (Klasing, 1998; Jlali et al., 2020; David et al., 2023; Haetinger et al., 2024).

Balanced levels of Ca and P that meet the requirements for each laying phase contribute to good performance in egg production and quality due to their role in bone mineralization and eggshell formation. A deficiency of these minerals significantly affects egg production and quality, primarily resulting in eggs with thinner shells and deformities that hinder commercialization (Ribeiro et al., 2016; Rossetto et al., 2019; Cheng & Ning, 2023; Mehri et al., 2025).

It is important to note that during the growth phase of laying hens, most of the absorbed calcium is directed towards bone formation, and with the onset of reproductive life, these hens will utilize such calcium reserves for eggshell formation. P, in association with Ca, contributes to bone formation through hydroxyapatite; it is also responsible for generating energy in the form of adenosine diphosphate and triphosphate (Nie et al., 2013; Kerschnitzki et al., 2014; Souza et al., 2017).

Diets with either insufficient or excessive amounts of these minerals may induce a cascade of alterations in the intestinal lumen (Weglarz & Angel, 2013). When present in excess, Ca hinders the absorption of minerals such as iron, copper, zinc, magnesium, sodium, and potassium (Smith & Kabaja, 1984). Additionally, excess Ca can impair P absorption, mainly through the formation of Ca-P complexes (Rutherfurd et al., 2012).

Understanding nutritional requirements is crucial for the production of all poultry species, as diets play a key role in development and enable birds to express their full genetic potential (Mariz et al., 2016). Mineral requirements vary by bird age and species; therefore, nutritional recommendations differ according to the developmental phase and production system (Vargas et al., 2004).

In order to address the lack of information on the nutrition of Japanese quails (Coturnix coturnix japonica), several studies have been conducted to determine applicable nutritional levels and thus maximize production and achieve better zootechnical indices. Furthermore, such studies support the national genetic material of this species, which undergoes daily improvements, showing significant advancements in the field of genetic improvement for egg production. Therefore, the objective of this study was to evaluate the requirements for calcium and available phosphorus for laying quails during the rearing (1 to 14 days) and growing (15 to 42 days) phases, aiming to maximize zootechnical performance, as well as to assess the residual effect of the growing phase during the laying period.

MATERIALS AND METHODS

All experimental procedures were approved by the Animal Research Ethics Committee at the State University of Maringá, Paraná, Brazil (protocol No. 5250070515). The experiments were conducted at the Quail Production Sector of the Iguatemi Experimental Farm, State University of Maringá.

Birds, Facilities, and Management

In Experiment I, 1,824 female Japanese quails (Coturnix coturnix japonica) of the Vicami commercial lineage were used. They were acquired as day-old chicks from a commercial breeding facility, and were raised until they reached 14 days of age, encompassing the rearing phase. These birds were housed in a conventional shed divided into 48 pens of 2.5 m² with rice straw bedding, and received their respective treatments.

Experiment II encompassed the growing phase (15 to 42 days of age). 1,680 female laying quails acquired as day-old chicks from the same commercial breeding facility were used. They had been raised until the start of this experiment receiving conventional feed composed of corn and soybean meal according to the requirements of Rostagno et al. (2011). At 15 days of age, the birds were housed in a conventional shed, divided into pens and received their respective treatments.

Experiment III was designed to examine the residual effects of dietary Ca and aP intake on the laying phase. For this, 576 birds from Experiment II were transferred at 42 days of age to a laying house. They were housed in galvanized wire cages equipped with nipple drinkers and trough feeders until 168 days of age.

Feed and water were provided ad libitum. From 1 to 10 days of age, chicks were housed in brooding rings equipped with a heat lamp. In Experiments I and II, only natural light was used. In Experiment III, the photoperiod began with 14 h of light, which was followed by 30 min weekly increments in light duration until reaching 17 h of natural + artificial light. Illuminance was maintained at 21 lux by an automatic timer.

Temperature and relative humidity were recorded in the morning (8:00 h) and afternoon (15:30 h) throughout the experimental period with the use of thermohygrometers. Measurements were taken at three different points (beginning, middle, and end of the shed). Mean minimum and maximum temperatures and relative humidity were respectively as follows: Experiment I, 25 ºC (8:00) and 33 ºC (15:30) and 50% and 76%; Experiment II, 20/]C (8:00) and 33 ºC (15:30) and 42% and 87%; and Experiment III, 16 ºC (8:00) and 24 ºC (15:30) and 57% and 87%.

Experimental Design and Diets

The experimental design was completely randomized with a 4 × 4 factorial arrangement. Treatments comprised four Ca levels (0.57%, 0.81%, 1.05%, and 1.29%) and four aP levels (0.21%, 0.32%, 0.43%, and 0.54%), totaling 16 treatments with 3 replications. Experimental units comprised 38 birds each in Experiment I (starter phase), and 35 birds each in Experiment II (grower phase). In both experiments, birds were fed experimental diets (Tables 1 and 2) based on corn and soybean meal, formulated according to the chemical composition values and nutritional recommendations described by Rostagno et al. (2011), except for Ca and aP levels.

Table 1
Ingredient and nutrient composition of the experimental diets containing different levels of calcium and available phosphorus for Japanese quails in the starter (1 to 14 days of age) and grower (15 to 42 days of age) phases.

Calcium (%)	0.57				0.81				1.05				1.29
Available phosphorus (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
Corn grain	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631	57.631
Soybean meal (45% protein)	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380	33.380
Corn gluten meal (60% protein)	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544	2.544
Soybean oil	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005	1.005
Inert1	2.726	2.454	2.182	1.91	2.089	1.817	1.546	1.274	1.453	1.181	0.909	0.637	0.816	0.544	0.272	0.000
Monocalcium phosphate	0.529	1.108	1.687	2.266	0.529	1.108	1.687	2.266	0.529	1.108	1.687	2.266	0.529	1.108	1.687	2.266
Calcitic limestone	0.971	0.664	0.357	0.050	1.608	1.301	0.993	0.686	2.244	1.937	1.630	1.323	2.881	2.574	2.267	1.960
Vitamin-mineral premix2	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400	0.400
Common salt	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397	0.397
L-Lysine HCl	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152	0.152
DL-Methionine	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157	0.157
L-Threonine	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098	0.098
Antoxidant3	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010	0.010
Total	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100

• ¹
  Washed sand.
• ²
  Provided (per kg of product): vitamin A, 3125.000 IU/g; vitamin D3, 625,000.000 IU/g; vitamin K3, 975.000 mg; vitamin B1, 1225.000 mg; vitamin B2, 2200.000 mg; vitamin B6, 2062.500 mg; vitamin B12, 6250.000 mcg; vitamin E, 15,645.000 IU; calcium pantothenate, 14,843.750 mg; niacin, 15,312.500 mg; folic acid, 416.667 mg; biotin, 62.500 mg; choline, 81,375.00 mg C; and antioxidant, 1250.000 mg.
• ³
  Butylhydroxytoluene (BHT).

Table 2
Calculated nutritional composition of the experimental diets containing different levels of calcium and available phosphorus for Japanese quails in the starter (1 to 14 days of age) and grower (15 to 42 days of age) phases.

Calcium (%)	0.57				0.81				1.05				1.29
Available phosphorus (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
Metabolizable energy (kcal/kg)	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900	2.900
Crude protein (%)	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00	22.00
Calcium (%)	0.570	0.570	0.570	0.570	0.810	0.810	0.810	0.810	1.050	1.050	1.050	1.050	1.290	1.290	1.290	1.290
Available phosphorus (%)	0.210	0.320	0.430	0.540	0.210	0.320	0.430	0.540	0.210	0.320	0.430	0.540	0.210	0.320	0.430	0.540
Digestible lysine (%)	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120	1.120
Digestible methionine + cysteine (%)	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760	0.760
Digestible threonine (%)	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790	0.790
Digestible tryptophan (%)	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219	0.219
Sodium (%)	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176	0.176
Chlorine (%)	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315	0.315
Potassium (%)	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781	0.781
Electrolyte balance (mEq/kg)	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54	187.54

In Experiment III, birds were distributed according to treatments of the grower phase, totaling 16 treatments with 3 repetitions and 12 birds per experimental unit. Conventional feed formulated with corn and soybean meal was supplied according to the requirements for laying quails determined by Rostagno et al. (2011).

Performance Indices

During the starter and grower phases, quails and feed were weighed weekly for determination of body weight (g), feed intake (g), weight gain (g), and feed conversion ratio (FCR). Weight gain was determined as the difference between final and initial weights of each experimental unit. Feed intake was calculated as the difference between supplied feed and leftover feed. FCR was estimated considering the relationship between feed intake and weight gain. The residual effects of grower nutrition conditions on egg laying were assessed by collecting eggs from day 64 onward for five production cycles, lasting 21 days each. Eggs were collected daily (8:00 h), and the laying rate (%) and egg mass production (g egg/bird·day) were determined. Broken, cracked, and soft-shelled eggs were counted separately. The mean egg weight was determined by weighing all viable eggs on the last three days of each cycle. Quail and feed were weighed on the last day of each cycle to determine body weight, feed intake, and FCR per dozen eggs and per kilogram of egg mass.

Dead birds were counted daily to correct feed intake and determine the viability of each experimental unit. Viability was estimated by the ratio of the number of birds at the end of the experiment to the number of birds at the beginning.

Internal and External Egg Quality

Internal and external egg quality analyses were conducted during the last three days of each cycle in Experiment III. Specific gravity was determined by immersing all eggs in saline solution, according to the method described by Hamilton (1982). For the other quality analyses, three eggs, chosen based on the mean weight of the experimental unit, were identified and evaluated. Eggs were sectioned, and the internal contents were placed on a dark glass to determine the height (mm) and diameter (mm) of the yolk and albumen using a digital caliper. Yolk height was determined by measuring from its highest point and albumen height was determined by measuring from the region closest to the yolk. The diameter was obtained by calculating the mean of two transverse measurements of yolk. From these data, it was possible to estimate the yolk index and the Haugh unit (1937) of the eggs.

Subsequently, the yolk and albumen were separated, the yolk was weighed on a precision scale, and eggshells were washed, left to dry, and weighed. The albumen weight was estimated by subtracting the yolk weight and eggshell weight from the total egg weight. Then, the relative percentages of the yolk, albumen, and eggshell were determined in relation to the total egg weight.

Eggshell weight per unit surface area was calculated using the formula adapted by Rodrigues et al. (1996). This information was used to calculate the dry matter, mineral matter, and Ca content of eggs, according to the methods described by AOAC (2005).

Statistical Analysis

Statistical analysis was performed using RStudio software (R Core Team, 2013). The model below (Equation 1) was used to test the effects, and it was found that the assumptions of normality were met.

$Y_{ijk}={\beta }_0+{\beta }_i+{\beta }_j+{\beta }_i{\beta }_j+{\epsilon }_{ijk}$ (1)

where Y _ijk is the response variable of experimental unit k fed a diet containing Ca level i and aP level j; β₀ is a general constant; β_i is the effect of Ca level; β_j is the effect of aP level; β_i β_j is the interaction effect between Ca and aP levels; and ɛ_ijk is the random error associated with each observation.

When the effect of factors was significant (p<0.05), the data were subjected to polynomial regression. The model that provided the best fit was selected, as recommended by Sakomura & Rostagno (2016).

Overlaid Contour Plots

The performance variables determined in Experiments I and II that had a quadratic relationship with the independent variables were selected for the construction of overlaid contour plots, according to the methods of Oliveira-Bruxel (2016). The analysis was performed using RStudio software (R Core Team, 2013).

These graphs present the top view of a surface graph, displaying the solutions to the equations as a function of continuous values of factors (axes). The lines connect interpolated points of equal value, representing the limits of the solution. The contour curves of all variables are overlaid on a graph, and the solutions are defined by unfolding the equations for each variable. Then, the intersection area, which simultaneously satisfies all overlapping functions, is identified by the contour lines. This strategy was applied to identify the optimal Ca and aP values.

RESULTS AND DISCUSSION

Performance Indices

In the starter phase (1-14 days of age), feed intake was the only variable influenced by the interaction effect of Ca and aP, which was found to be quadratic (p<0.05). Thus, the lowest feed intake was estimated to be achieved by supplementing quails with 0.99% Ca and 0.39% aP (Table 3). Ca and aP independently exerted significant quadratic effects (p<0.05) on body weight, weight gain, and FCR. The best values were estimated to be achieved with 0.90%, 0.90%, and 0.94% Ca, respectively; and 0.37%, 0.37%, and 0.38% aP, respectively. Viability was the only variable not influenced (p>0.05) by mineral supplementation levels.

Table 3
Starter performance (1 to 14 days) of Japanese quail fed experimental diets containing different levels of calcium (Ca) and available phosphorus (aP).

Ca (%)	0.57				0.81				1.05				1.29				SE
aP (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
BW (g)	40.02	41.68	42.33	39.30	41.62	43.58	43.66	40.35	43.23	43.48	43.14	43.40	39.80	38.25	40.49	39.47	0.294
WG (g)	33.67	35.29	36.07	32.79	35.25	37.07	37.39	33.90	36.78	37.14	36.70	37.25	33.47	31.85	34.09	33.13	0.296
FI (g/bird)	97.10	91.93	92.32	95.41	90.58	90.05	86.17	83.39	91.92	84.99	84.45	87.84	90.31	88.25	85.63	96.55	0.664
FCR	2.88	2.61	2.56	2.91	2.57	2.43	2.31	2.46	2.50	2.29	2.30	2.36	2.70	2.77	2.51	2.92	0.033
Viability (%)	96.87	97.36	94.14	95.99	93.69	97.33	98.23	95.04	96.38	95.58	93.24	95.52	95.13	96.44	95.99	94.58	0.367
Regression equation								R 2	p-value				Estimate
									Ca		aP		Ca x aP		Ca	aP
BW = 18.7036 + 41.3840Ca - 22.9167Ca2 + 35.5456aP − 48.5537aP2								0.54	<0.0001 (Q)		0.0070 (Q)		0.6141		0.90	0.37
WG = 12.2942 + 41.3939Ca − 22.9022Ca2 + 35.5119aP − 48.3815aP2								0.53	<0.0001 (Q)		0.0083 (Q)		0.5646		0.90	0.37
FI = 158.5346 − 92.6784Ca + 41.3484Ca2 − 146.0280aP + 151.3430aP2 + 28.4192(Ca × aP)								0.59	<0.0001 (Q)		<0.0001 (Q)		0.0421		0.99	0.39
FCR = 5.9008 − 5.37036Ca + 2.8610Ca2 − 5.9702aP + 7.8340aP2								0.73	<0.0001 (Q)		<0.0001 (Q)		0.6828		0.94	0.38

• SE, standard error; BW, body weight; WG, weight gain; FI, feed intake; FCR, feed conversion ratio; Q, quadratic effect.

In the grower phase (15-42 days of age), Ca and aP supplementation exerted significant interaction effects (p<0.05) on body weight, weight gain, feed intake, and FCR. The relationship between the dependent and independent variables was quadratic. As such, optimal levels of body weight, weight gain, feed intake, and FCR were estimated to be achieved using 0.93%, 0.94%, 0.94%, and 0.94% Ca, and 0.39%, 0.40%, 0.36%, and 0.38% aP, respectively (Table 4). Once again, viability was not influenced (p>0.05) by mineral supplementation levels.

Table 4
Grower performance (15 to 42 days) of Japanese quail fed experimental diets containing different levels of calcium (Ca) and available phosphorus (aP).

Ca (%)	0.57				0.81				1.05				1.29				SE
aP (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
BW (g)	133.56	138.09	141.74	142.67	144.29	147.12	147.70	143.19	144.70	147.90	149.01	142.19	137.41	141.18	141.95	138.51	0.667
WG (g)	93.54	96.41	99.40	102.88	102.66	103.83	104.77	102.55	101.80	104.59	106.12	99.25	97.40	102.14	101.24	98.63	0.589
FI (g/bird)	507.47	464.00	482.63	495.90	482.97	432.60	439.39	434.79	458.22	445.29	464.69	472.56	458.80	468.67	493.29	507.49	3.463
FCR	5.43	4.82	4.86	4.82	4.71	4.17	4.20	4.24	4.50	4.26	4.38	4.77	4.71	4.59	4.87	5.15	0.053
Viability (%)	95.76	93.81	95.83	94.95	88.09	94.75	90.14	94.03	91.19	97.98	90.52	90.06	96.55	90.63	94.79	95.15	0.853
Regression equation								R 2	p-value				Estimate
									Ca		aP		Ca x aP		Ca	aP
BW = 66.0589 + 116.0046Ca − 55.3349Ca2 + 144.7863aP − 145.5406aP2 − 31.9760(Ca × aP)								0.72	<0.0001 (Q)		<0.0001 (Q)		0.0074		0.93	0.39
WG = 42.6981 + 83.4660Ca − 36.8056Ca2 + 115.2715aP − 102.2039aP2 − 34.6111(Ca × aP)								0.50	<0.0001 (Q)		0.0073 (Q)		0.0127		0.94	0.40
FI = 860.2602 − 609.4726Ca + 268.8043Ca2 − 744.3943aP + 659.38361aP2 + 288.0366(Ca × aP)								0.71	<0.0001 (Q)		0.0002 (Q)		<0.0001		0.94	0.36
FCR = 11.3535 − 10.0323Ca + 4.3764Ca2 − 12.9602aP + 11.2603aP2 + 4.6920(Ca × aP)								0.82	<0.0001 (Q)		<0.0001 (Q)		<0.0001		0.94	0.38

• SE, standard error; BW, body weight; WG, weight gain; FI, feed intake; FCR, feed conversion ratio; Q, quadratic effect.

Birds have the ability to regulate calcium (Ca) consumption to meet their nutritional needs (Classen & Scott, 1982), which explains the decrease in feed conversion ratio (FCR) as calcium levels in the diet increased. The consequent increase may be due to calcium reducing the metabolizable energy of the diet by combining with dietary fat to form insoluble soap (El-Katcha et al., 2014). The same behavior was observed for phosphorus (P), likely related to the antagonism created by excess calcium, which hinders the absorption of certain minerals, including phosphorus (Smith & Kabaja, 1984; Lamp et al., 2020), thus increasing the birds’ intake needs in an attempt to compensate for this deficiency.

In this study, body weight and weight gain had an inverse relationship with feed intake. Although intake decreased, body weight and weight gain increased. Such a result can be attributed to the absorption process of these minerals, which is more efficient when minerals are provided in adequate quantities. According to Maiorka & Macari (2002), one of the factors influencing Ca absorption is its intake level. Excess Ca results in decreased absorption, likely caused by the saturation of Ca transport proteins. Such saturation directly influences aP absorption. One of the mechanisms of aP absorption is active transport dependent on calcitriol (as occurs for Ca) and sodium (Pizzolante, 2000). Therefore, aP absorption is related to the equilibrium of blood Ca levels (Bertechini, 2004).

Feed intake and weight gain directly influenced FCR. The best levels of Ca and aP were similar for all performance variables in both growth phases (starter and grower), confirming the influence of these minerals in Japanese quail development.

Overlaid contour plots revealed the optimal levels of Ca and aP. The optimal levels were 0.92% Ca and 0.37% aP for the starter phase (Figure 1), and 0.94% Ca and 0.39% aP for the grower phase (Figure 2). The point selected in the graph indicates the values of the independent variables that provided the best results for all parameters. Within the overlapping area, there is no specific criterion to select the best value. Thus, the final values were chosen with the aim of minimizing costs (Oliveira-Bruxel, 2016).

Figure 1
Overlaid contour plot of body weight (BW), weight gain (WG), feed intake (FI), and feed conversion ratio (FCR) indicating the optimal levels of calcium (Ca) and available phosphorus (aP) for 1- to 14-day-old Japanese quails.

Figure 2
Overlaid contour plot of body weight (BW), weight gain (WG), feed intake (FI), and feed conversion ratio (FCR) indicating the optimal levels of calcium (Ca) and available phosphorus (aP) for 15- to 42-day-old Japanese quails.

Brazilian animal nutrition guidelines (Rostagno et al., 2024) suggest using lower levels of Ca (0.752%) and higher levels of aP (0.435%) in the starter phase (1 to 14 days), followed by lower levels of both minerals (0.574% Ca and 0.293% aP) in the grower phase (15 to 35 days) than those tested here. The large variation in mean body weight between starter (25 g) and grower (80 g) phases may explain the differences in recommended levels. In the Brazilian Tables of 2017 (Rostagno et al., 2017), the authors elucidate that there is a lack of standardization among commercial strains, and for this reason, there is variation in the levels of requirements in the results observed in research. Previous studies also reported this lack of standardization among production phases (Brandão, 2005; Silva & Costa, 2009; Costa et al., 2009; Camelo, 2011).

Thus, differences between studies are expected, given that physiological age and genetic patterns significantly influence mineral requirements in poultry, particularly with regard to the dynamics of bone growth. Figueroa et al. (2023) revealed differences in bone growth dynamics by evaluating the morphometric, biomechanical, and chemical properties of long bones.

For adequate absorption of both Ca and aP, their dietary levels and ratios must be adequate. A balance between metabolism and excretion can be achieved with a Ca/aP ratio of about 2:1, with little to no variation between values (Scott et al., 1982). The NRC (1994) recommends a Ca/aP ratio of 2:1 for most poultry feeds, whereas Rostagno et al. (2024) recommend ratios of 1.73:1 in the starter phase and 1.96:1 in the grower phase. In this experiment, the Ca:P ratios remained above the recommended levels in the literature. By using the value proposed by the overlapping contour graph, we will have a ratio of 2.49:1 for the rearing phase and 2.41:1 for the growing phase.

Mineral supplementation during the grower phase independently influenced the body weight, laying rate, egg weight, and FCR per dozen eggs of laying quails (Table 5). Body weight was found to decrease linearly with increasing Ca levels. The laying rate had a quadratic relationship with Ca levels, with the maximum rate estimated to be achieved at 0.93% Ca. On the other hand, Ca and aP levels reduced FCR per dozen eggs and exerted a quadratic effect on egg weight. The maximum egg weight was estimated to be achieved by using 0.91% Ca and 0.39% aP. Egg mass was the only variable influenced by the interaction effect of mineral supplementation levels. The relationship was quadratic, with estimated maximum values at 0.91% Ca and 0.38% aP. Feed intake, FCR per kilogram of egg mass, viability, and age at first egg were not significantly influenced by the studied factors. Regarding egg quality, the factors exerted significant interaction effects on eggshell percentage and eggshell weight per surface area (Table 6): the maximum values of both variables were estimated to be achieved with 0.87% Ca and 0.40% aP.

Table 5
Laying performance of Japanese quails fed diets containing different levels of calcium (Ca) and available phosphorus (aP) during the grower phase.

Ca (%)	0.57				0.81				1.05				1.29				SE
aP (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
BW (g)	163.30	169.24	171.23	168.18	169.65	164.07	166.58	170.84	166.03	163.31	169.22	165.59	163.34	163.36	164.75	160.97	0.666
DFI (g)	28.32	26.72	28.72	26.83	26.39	29.87	26.59	28.92	28.81	32.00	29.92	25.37	25.56	30.84	25.92	26.10	0.316
LR (%)	83.72	85.42	82.10	88.16	87.97	92.23	83.58	88.21	87.95	89.17	88.61	87.61	86.49	85.84	82.91	83.21	0.504
EW (g)	10.16	10.88	10.82	10.79	10.46	10.90	12.07	10.75	10.69	11.46	11.21	10.63	10.12	10.78	11.35	9.93	0.084
EM	8.50	9.30	8.88	9.51	9.20	10.05	10.09	9.47	9.41	10.23	9.93	9.31	8.75	9.26	9.41	8.26	0.094
FCEM	3.33	2.88	3.23	2.82	2.87	2.97	2.64	3.06	3.07	3.14	3.02	2.73	2.92	3.34	2.76	3.16	0.035
FCDE	0.58	0.58	0.48	0.48	0.51	0.43	0.42	0.47	0.50	0.50	0.51	0.36	0.37	0.50	0.39	0.40	0.010
VIA (%)	83.33	88.89	91.67	77.78	80.56	86.11	97.22	83.33	86.11	88.89	77.78	94.45	88.89	88.89	100.00	91.67	1.700
AFE (days)	56.67	56.67	55.33	56.33	57.33	56.33	56.67	56.00	56.00	55.33	55.67	56.00	57.33	52.00	55.33	54.33	0.363
Regression equation								R 2	p-value				Estimate
									Ca		aP		Ca x aP		Ca	aP
BW = 172.5840 − 6.8330Ca								0.16	0.0046 (L)		0.3504		0.2757		-	-
LR = 62.9480 + 55.3125Ca − 29.8213Ca2								0.25	0.0003 (Q)		0.5697		0.1022		0.93	-
EW = 3.9527 + 6.5608Ca − 3.6169Ca2 + 23.8160aP − 30.71625aP2								0.58	0.0007 (Q)		<0.0001 (Q)		0.0827		0.91	0.39
EM = −0.4650 + 13.4598Ca − 6.31149Ca2 + 23.3788aP − 24.5007aP2 − 4.9962(Ca × aP)								0.60	<0.0001 (Q)		<0.0001 (Q)		0.0018		0.91	0.38
FCDE = 0.6810 − 0.1389Ca − 0.2227aP								0.43	<0.0001 (L)		0.0011 (L)		0.2070		-	-

• SE, standard error; BW, body weight; DFI, daily feed intake; LR, laying rate; EW, egg weight; EM, egg mass; FCEM, feed conversion per egg mass; FCDE, feed conversion per dozen eggs; VIA, viability; AFE, age at first egg.

Table 6
Egg quality of Japanese quails fed diets containing different levels of calcium (Ca) and available phosphorus (aP) during the grower phase.

Ca (%)	0.57				0.81				1.05				1.29				SE
aP (%)	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54	0.21	0.32	0.43	0.54
SG (g/mL)	1.08	1.07	1.07	1.07	1.07	1.08	1.07	1.06	1.07	1.07	1.08	1.07	1.07	1.08	1.06	1.07	0.001
HU	93.03	93.99	90.31	94.30	93.52	92.95	92.67	92.99	89.87	93.50	85.89	92.96	93.71	92.81	92.11	93.43	0.558
YI	0.47	0.48	0.47	0.46	0.48	0.48	0.47	0.48	0.47	0.47	0.47	0.47	0.47	0.47	0.48	0.45	0.002
Yolk (%)	30.43	30.18	31.31	30.49	30.74	30.41	30.77	29.99	30.06	30.31	31.05	31.40	30.21	30.84	30.74	31.56	0.095
Albumen (%)	62.37	62.46	61.38	61.93	61.94	62.37	61.91	62.82	62.72	62.50	61.75	61.21	62.60	61.74	61.97	61.33	0.101
Shell (%)	6.80	7.37	7.31	7.58	7.32	7.22	8.16	7.19	7.22	7.19	8.04	7.39	7.18	7.42	7.45	6.43	0.062
SWUSA	3.38	3.74	3.70	3.84	3.67	3.67	4.27	3.63	3.65	3.71	4.11	3.73	3.57	3.76	3.83	3.18	0.037
Regression equation								R 2	p-value				Estimate
									Ca		aP		Ca x aP		Ca	aP
Shell = 1.8046 + 6.0367Ca − 2.3763Ca2 + 16.6835aP − 15.6853aP2 − 4.8068(Ca × aP)								0.47	<0.0001 (Q)		0.0002 (Q)		0.0017		0.87	0.40
SWUSA = 0.1259 + 3.8107Ca − 1.5625Ca2 + 11.1435aP − 11.0882aP2 − 2.7045(Ca × aP)								0.56	<0.0001 (Q)		<0.0001 (Q)		0.0016		0.87	0.40

• SE, standard error; SG, specific gravity; HU, Haugh unit; YI, yolk index; SWUSA, shell weight per unit surface area.

Despite the fact that body weight decreased as a function of Ca level, and that the model explaining this relationship had a low coefficient of determination (R ² = 0.16), the recorded body weights were within the normal ranges for Japanese quails of this strain. When studying the growth of quails using growth curves, Finco et al. (2016) reported estimated weights of 158.18 to 164.00 g. The authors argued that birds reach their maximum development at the peak of laying, that is, at 119 days of age. Therefore, the values found in this study are within the expected range for the strain.

Egg mass is a performance variable that influences production costs (Piccinin, 2006), whereas egg weight is positively correlated with eggshell, albumen, and yolk weights, as well as with yolk height, diameter, and yolk index (El-Tarabany, 2016). In this experiment, egg mass and weight exhibited similar behaviors, underscoring their importance as performance parameters. The performance of laying birds is also influenced by nutritional management during the grower phase (Lima et al., 2016).

CONCLUSION

According to this study, it was possible to estimate the nutritional requirements for calcium (Ca) and phosphorus (P) and the ratio between these minerals for Japanese quails of the commercial Vicami strain. In the rearing phase (1 to 14 days of age), the estimates were 0.92% Ca and 0.37% P, with a ratio of 2.49:1. In the growing phase (15 to 42 days of age), the estimates were 0.94% Ca and 0.39% P, with a ratio of 2.41:1. This study provides support for the nutrition of growing Japanese quails, and increases the understanding of optimal Ca and P levels during growth, contributing to improving egg quality.

ACKNOWLEDGEMENTS

Use The funding agency (CNPq) and the Postgraduate Program in Animal Science (PPZ).

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• FUNDING
  This research was funded by the Agency of the Ministry of Science, Technology and Innovation (CNPq).
• DATA AVAILABILITY STATEMENT
  The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.
• DISCLAIMER/PUBLISHER’S NOTE
  The published papers’ statements, opinions, and data are those of the individual author(s) and contributor(s). The editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.

Edited by

• Section Editor:
  Tatiana Carlesso dos Santos

Data availability

The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Publication Dates

• Publication in this collection
  12 Jan 2026
• Date of issue
  2025

History

• Received
  22 Mar 2025
• Accepted
  09 Oct 2025