Digestible Methionine + Cysteine-To-Lysine Ideal Ratio for Meat-Type Quails at Initial Phase

This trial was performed to determine the ideal ratio of digestible methionine + cysteine (Met/Lys) with digestible lysine for meat-type quails from 1 to 14 days of age. A total of six hundred thirty, oneday-old, not sexed meat type quails were randomly assigned to six groups of treatments, each one with seven replicates and fifteen quails per experimental unit. A basal diet, methionine + cysteine-deficient, was graded supplemented with DL-Methionine (0.108; 0.169; 0.230; 0.291; 0.352 and 0.413%) to obtain the treatments, represented by six digestible Met/Lys ratios (0.60; 0.65; 0.70; 0.75; 0.80 and 0.85). Data was analyzed using ANOVA and polynomial regression and brokenline models were used to estimate the digestible Met/Lys ideal ratio, considering adjust of data to both models. Statistical significance was considered when p≤0.05. Feed intake, weight gain and final body weight was linearly increased as dig. Met/Lys ratio increased. Feeding conversion was improved with increasing in dig. Met/Lys ratios. A quadratic response on feathering percentage was observed with increasing dig. Met/Lys ratios. Digestible Met/Lys ratio which, maximized feathering percentage in meat-type quails, was 0.74. According to linear broken-line model, dig. Met/Lys ratio estimated for optimum feed intake, weight gain, final body weight and feeding conversion were, respectively, 0.66; 0.71; 0.71 and 0.74. The dig. Met/Lys ideal ratio for meat-type quails from one to 14 days of age is 0.74.


INTRODUCTION
Ideal protein concept has allowed reduction on crude protein content of poultry diets.Over the last decade studies have demonstrated that crystalline amino acid (e.g.lysine, methionine and threonine) supplementation on low-protein diets is an efficient method to enhance nitrogen retention by poultry and reduce costs without compromising bird performance.The application of ideal protein concept on poultry diet formulation mainly depends on the previously establishment of ideal ratios between amino acids with lysine on digestible basis.Data about ideal amino acid pattern for optimum broiler growth have been extensively studied, being already well established.However, researches reporting data about meat-type quail amino acid requirements are sparse and discrepant.
Tables for Japanese and European Quails (Silva & Costa, 2009) describe nutritional requirements of both species.However, as described by the authors, the ideal amino acid pattern for meat-type quails is based on broiler amino acid requirements recommended by NRC (1994), which might not represent quail requirements.Among essential amino acids, methionine + cysteine are the first limiting amino acids in poultry diets, based on corn and soybean meal (Ravindran & Bryden, 1999).In addition to their essentiality for adequate poultry growth, Sulphur amino acids and methionine + cysteine are required to the formation of feathers and glutathione synthesis (Baker, 1991).As a methyl donor molecule, methionine also plays an essential role on creatine, polyamines, melatonin and phosphatidylcholine synthesis.Few reports about methionine + cysteine-to-lysine ideal ratio for meattype quails are available in literature.Scherer (2009) has estimated the dig.Met/Lys ideal ratio for meattype quails at initial phase in 0.84, whereas Silva & Costa (2009) has recommended a dig.Met/Lys ratio of 0.76 for quails in this phase.Considering few of the published data about dig.Met/Lys ideal ratio for meat-type quails at initial phase; but recognizing its importance, this trial was performed to determine the dig.Met/Lys ideal ratio for meat-type quails from 1 to 14 days of age.

Animal care and use
All procedures adopted in this trial involving animal care and use, were previously approved by the institutional Animal Care and Use Committee of the Universidade Federal de Viçosa.

Bird housing and management, experimental design and diets
Six hundred thirty, one-day-old meat-type quails, obtained from local commercial hatchery, were randomly assigned to six groups of treatments with seven replicates and fifteen quails per experimental unit.The birds, not sexed, were housed in 50 m x 50 m x 30 m galvanized metal cages, placed above concrete countertops covered by shaving woods.All the cages were equipped with one nipple drinker and

Performance measurements
At 14 days of age, the quails and feeders from all experimental units were weighed to determine final body weight and feed intake.Weight gain was obtained from the difference between average final body weight and initial body weight, considering the days the trial lasted (14 days).Feed conversion was calculated through the division of feed intake by weight gain.Mortality was recorded to adjust feed intake and feed conversion rate.After weighing birds and feeders, feeding was withdrawn for 4 hours to determine bird weight after fasting period.Then, 3 birds were stunned by electronarcosis and slaughtered by bleeding in jugular vein.Feathers were removed and weighed to obtain feathering percentage, which was calculated by dividing feather weight by bird weight after fasting.

Statistical analysis
The effects of dietary dig.Met/Lys ratios were analyzed using ANOVA and optimal dig.Metl/Lys ratio was estimated using both polynomial and broken-line regression.Significant effect was considered when p≤0.05.The software package used to analyze data was Sistema de Análises Estatísticas e Genéticas (SAEG, 2007).

RESULTS AND DISCUSSION
Feed intake increased (p<0.05)linearly as dig.Met/ Lys ratios increased (Table 2).Based on linear brokenline model estimative, dig.Met/Lys, which optimize quail feed intake, was 0.66 (Table 3).Castro (2014) reported linear increase in meat-type quail feed intake with increasing dig.Met/Lys ratios from 1 to 7 days of age.From 8 to 14 days of age, the same authors estimated the ratio of 0.70 as ideal for optimum quail feed intake.Increasing dig.Met/Lys ratios led to linear (p≤0,05) increase in quail weight gain and final body weight (Table 2), which, according to linear broken-line model estimates, were both optimized by the ratio of 0.71 (Table 3).Likewise, Castro (2014) observed a linear increase in meat-type quail weight gain from 1 to 7 days of age after ranging dig.Met/Lys ratios from 0.61 to 0.81.The author, however, estimated the dig.Met/ Lys ratio for optimum meat-type quail growth from 8 to 14 days of age in 0.73, considering the intersection between broken-line and quadratic curve.In contrast with our results, Scherer (2009) determined 0.84 and 0.81 as dig.Met/Lys ratio for optimum quail weight gain and final body weight at initial phase.Feeding conversion improved (p<0.05) linearly in response to increasing in dig.Met/Lys ratios (Table 2).Linear brokenline regression was used to estimate the optimum quail feeding conversion, which was observed with the dig.Met/Lys ratio of 0.74 (Table 3).Such results are in agreement with those reported by Dozier &

Mendonça MO, Mencalha R, Ribeiro CLN, Barbosa LMR Digestible Methionine + Cysteine-To-Lysine Ideal Ratio for Meat-Type Quails at Initial Phase one
Rostagno et al. (2011)tal treatments consisted of six dig.Met/Lys ratios (0.60; 0.65; 0.70; 0.75; 0.80 and 0.85) obtained from the graded supplementation of DL-Methionine (0.108; 0.169; 0.230; 0.291; 0.352 and 0.413%) in a basal diet deficient in methionine + cysteine.Basal diet was formulated to meet or exceedSilva & Costa (2009)recommendations.To formulate diets, a nutritional composition of ingredients described byRostagno et al. (2011)was considered.Minimum and maximum temperature as well as air humidity were daily measured by thermo-hygrometers birds-height placed inside the experimental facility.Experimental diets (mash form) and water were provided ad libitum during the trial and light was supplied 24 hours a day (natural + artificial).

Table 2 -
Feed intake (FI), weight gain (WG), final body weight (FBW), feed conversion rate (FCR) and feathering percentage (FP) of meat-type quails from 1 to 14 days of age fed digestible Met/Lys ratios

Table 3 -
Linear broken-line and quadratic regression equations for feed intake (FI), weight gain (WG), final body weight (FBW), feed conversion rate (FCR) and feathering percentage of meat-type quails from 1 to 14 d of age.