Exigência de metionina+cistina para aves de reposição leves e semipesadas alimentadas com ração farelada ou peletizada

Abstract

Three experiments were carried out with the objective of evaluating the requirements of total methionine+cyistine as related to the physical form of the diet (mashed and pelleted) and of the strains of the pullets (light: L or semi-heavy: SH). 1.600 birds of from 1 to 4, 1.120 of from 5 to 11 and 800 birds of from 12 to 16 weeks were utilized, the half of each strain (Dekalb White and Bovans Goldline). The birds were housed in boxes of 1.0 m x 1.5 m. The used experimental design was completely randomized in a factorial scheme 5x2x2 (levels of total Met+Cys x two strains x two physical forms), being (0.65; 0.70; 0.75; 0.80 and 0.85% of Met+Cys from 1 to 4); (0.56; 0.60; 0.64; 0.68 and 0.72% from 5 to 11) and (0.50; 0.55; 0.60; 0.65 and 0.70% of Met+Cys from 12 to 16 weeks), with twenty treatments, four repetitions of 20 birds (1 to 4), 14 (5 to 11) and 10 (12 to 16 weeks). The basal diet was supplemented with DL-Methionine (99%) to provide five levels of total Met+Cys, according to recommendations of the Brazilian literature and of the handbook of the strain (Granja Planalto, 2005) and they were kept isonutritive for ME (2,900 kcal/kg), CP (21%), Ca (0,94%) and available P (0.44%) from 1 to 4 weeks, ME (2.900 kcal/kg), CP (17%), Ca (1.00%) and available P (0.45%) from 5 to 11 weeks and ME (2,850 kcal/kg), CP (15%), Ca (0,85) and available P (0.35%) from 12 to 16 weeks. The variables total feed (TFI) and daily intake (DFI), total weight gain (TWG), daily weight gain (DWG) and feed conversion (FC) were evaluated at 28 days of age and the variables yield (PR), egg weight (EW), egg mass (EM), conversion by egg mass (EMC) and specific gravity (GE), as well as the variables of egg quality: weight of (AW), of yolk (MW), shell (PW) and the percentages were studied in the laying period (22 to 40 weeks) to evaluate the residual effect of the treatments used in the growing period. There was no interaction effect among the levels of Met+Cys, the strain and the physical form of the diet. However, the levels of Met+Cys affected in a quadratic way (P≤0,001) TFI, DFI, TWG, DWG and FC, according to the following equations: ŷ = - 3168 + 15810x - 10333x2, (R2=0,89); ŷ = - 19.865 + 100.3x - 64.909x2, (R2=0.83); ŷ = - 7862 + 23480x - 14836x2, (R2=0.88); ŷ = - 32.312 + 103.19x - 64.396x2, (R2=0.81) and ŷ = - 32.312 + 103.19x - 64.396x2, (R2=0.81), respectively. The strain SH presented better TFI, DFI, TWG, DWG and FC (P≤0.01). The pelleted diet promoted better TWG, DWG and FC for the two strains (P≤0.01). 0.78% of Met+Cys is recommended for L and SH pullets of from 1 to 4 weeks of age or daily feed intake of Met+Cys of 146 and 160 mg, respectively. The SH birds performed better than the L ones. The pelleted diet improves TWG, DWG of the SH birds and the FC of the L ones of from 1 to 4 weeks of age. In the period of 5 to 11 weeks, the SH strain performed better as compared with the L one (P < 0.01). The pelleted diet provided better TFI, DFI (P <0.01) for strain L and better FC (P <0.01) for the SH strain. By evaluating the residual effect in the laying phase, only the strain affected (P <0.01) EP, EW, EM and EMC, the L laying hens presenting better performance of EP, EM and EMC, while the SH ones showed better EP. The levels of M+C and FF of the diet used during the growing phase affect the subsequent performance of the birds in the laying period, while L strain presents better performance than SH strain. 320 and 364 mg daily of Meth+Cys are recommended for L and SH pullets, respectively, from 5 to 11 weeks of age, daily feed intake of Meth+Cy 320 and 364 mg, respectively. In the phase from 12 to 16 weeks the pullets SH obtained better acting compared L (P < 0.01). The pelleted diet provided better TFI, DFI (P <0.01) for L strain and better FC (P<0.01) for SH strain. By evaluating the residual effect, the strain affected (P<0.01) EP, EW and EMC, and the L laying hens performed better than the SH ones. The levels of M+C and FF of the diet used in the growing phase affect the subsequent performance. Daily doses of 418 and 453 mg of Meth+Cys are recommended, respectively for L and SH birds, for the phases of 12 to 16weeks of age.