Protein Requirement of Japanese quail ( Coturnix coturnix japonica ) During Rearing and Laying Periods

Two completely randomized trials were conducted to estimate protein requirements of Japanese quails during the rearing and laying periods. In each trial, 150 quails were distributed in five treatments with five repetitions. Crude protein levels in the rearing period were 18, 20, 22, 24 and 26% (Trial 1) and during the laying period were 16, 18, 20, 22 and 24% (Trial 2). A quadratic effect of protein level was observed on weight gain from seven to 35 days (Trial 1). There were no effects of protein levels on feed intake and feed conversion. Protein levels in experimental diets during rearing had no effect on egg production up to 63 days. However, laying was delayed and variation in body weight was greater in quails fed lower protein levels. In Trial 2, a quadratic effect of protein levels was seen on egg production and feed conversion; and a linear effect was seen on mean egg weight and feed intake. Crude protein levels of 23.08% and 21.95% were estimated by regression equations for rearing and laying, respectively.


INTRODUCTION
Quail production has shown increasing importance in Brazil because quails show early sexual maturity and have small body size, which results in lower necessity of housing space and feed.
However, most of the data on nutritional requirements were obtained in other countries that have different climatic conditions, preventing that an adequate feeding program is established.It is important to determine more precisely the nutritional requirement of quails raised in Brazil.Although data not produced in our country can be used in feed formulation for quails, this might result in lower productivity and poor economic performance due to the use of a possible excess of some nutrients in the diet.
Protein of high quality with adequate amino acid balance is one of the most important nutrients for quails.It is also one of the most expensive nutrients.Excessive protein intake results in higher nitrogen excretion and lower feed efficiency for egg production.
Four crude protein levels (20, 22, 24 and 26%) were evaluated for Japanese quails and it was concluded that after lysine and methionine + cystine requirements were met, 20% crude protein level resulted in best performance from 1 to 42 days of age (Murakami et al., 1993a).Hyankova et al. (1997) reported that Japanese quails fed 26 and 21.6% crude protein had good performance from 1 to 21 and from 22 to 35 days of age, respectively.Thus, requirements decrease with age, similar to other animal species.
During the laying period, Murakami et al. (1993b) recommended 18% of crude protein, which is lower than the level of 22.42% recommended by Pinto et al. (1998).Levels of 24 and 20% of crude protein are recommended by NRC (1994) for quails in the rearing and production periods, respectively.
The objective of this research was to estimate crude protein requirements of Japanese quails in the growing and laying periods.

MATERIAL AND METHODS
Two trials were conducted in the Poultry Farm, Universidade Estadual do Norte FluminenseUENF, R.J., Brazil, in order to estimate the crude protein requirements of Japanese quails in the growing period (Trial 1) and laying period (Trial 2).
In the first trial, 150 seven-day-old quails were distributed in a completely randomized design in five treatments and five repetitions, with six quails in each experimental unit.
Feed intake (g/bird), weight gain (g) and feed conversion were evaluated in the period from seven to 35 days.Other characteristics were also evaluated, such as age at the first egg, egg production rate and variance of the weight gain for three laying period (up to 63 days of age).
In the second trial, 150 birds, 42-day-old, were distributed in a completely randomized design in five treatments and five repetitions, with six birds in each repetition.From one to 42 days of age, quails were fed a corn-soybean based diet with 24% crude protein and 2,900 kcal/kg ME.Body weight was evaluated at the beginning of the experimental period (42 days of age), which lasted up to 98 days of age.
In both trials, data were analyzed using the software SAEG (Universidade Federal de Viçosa, 2000).Crude protein requirements were estimated by regression equations.

RESULTS AND DISCUSSION
Data from Trials 1 and 2 are shown in Tables 2 and  3, respectively.In the first trial, there was a quadratic effect (p<0.05) of crude protein on weight gain, and a level of 23.08 % was estimated for maximum gain.
There was no significant effect (p>0.05) of crude protein levels on feed intake and feed conversion.
Estimated protein levels in this study were lower than the levels reported by other studies with quails at similar age.Lepore & Marks (1971) reported heavier quails at four weeks of age, when fed diets with 25% crude protein.Lee et al. (1977) evaluated protein requirements of Japanese quails in the growing period and reported better growth performance with levels of 24% to 32% CP.Shim & Vohra (1984) recommended 24% CP in diets for growing Japanese quails, which could be lowered to 20% after three weeks of age.On the other hand, the level recommended by Singh & Narayan (2002) was 24% between 4 and 5 weeks of age.
The levels of crude protein in the rearing diet had no effect on egg production up to 63 days of age.However, quails fed 18% CP during rearing began to lay four days later than quails fed higher protein levels.These data suggest that protein deficiency might have impaired the development of the reproductive system.It was observed that birds fed lower protein levels during the growing period had higher weight gain at 63 days of age.Mean values were 49; 39; 33; 34 and 36 g/bird for the levels of 18; 20; 22; 24 and 26% crude protein, respectively.It should be noted that all birds were fed 20% CP during the laying period, which is higher than protein levels in the diets fed during the growing period (18%).The higher protein intake at the beginning of the laying period might have allowed a compensatory gain of the birds.
In the second trial, it was seen a quadratic effect (p<0.05) of crude protein level on percentage egg production and feed conversion, with levels of 21.95% and 20.7% crude protein, respectively, estimated by regression analysis.There was a linear positive effect (p< 0.05) on feed intake and mean egg weight.Egg production was higher in period 1 (42 to 70 days of age) than in period 2 (71 to 98 days of age).Other parameters were not affected by periods (p>0.05)Murakami et al. (1993b) and Pereira et al. (2000) reported better performance of laying quails when the birds were fed 18% CP, value much lower than found in this study.
Pires Jr (1981) reported that 20% CP determined the highest egg production rate, however, Pinto et al. (1998) found levels of protein requirement (22.42%) similar to that found in our study.Singh & Narayan (2002) also recommended 22% protein for quails in the production period.A higher level of protein requirement was reported by Vilar et al. (1991), who observed higher egg production when the quails were fed 24% CP in the diet.

CONCLUSIONS
The findings of this study suggested that the levels of 23.08% and 21.95% of crude protein in the diet of Japanese quails are recommended for the rearing period (7 to 35 days) and laying period (42 to 98 days), respectively.

Table 1
Percentage composition of experimental diets (Trials 1 and 2) according to crude protein content.

Table 2
Feed intake, weight gain and feed conversion of Japanese quails in the period from 7 to 35 days of age and egg production until 63 days of age according to the crude protein level of the diet (Trial 1).

Table 3
Egg production, egg weight, feed intake and feed conversion rate of Japanese quails according to the crude protein level of the diets (Trial 2), from 42 to 98 days of age.