Standardized ileal digestible lysine requirements based on growth performance and histochemical characteristics of male broilers from 10 to 21 d of age

Abstract

The growth performance and histochemical characteristics of breast muscle fibers were used to estimate the standardized ileal digestible (SID) Lys requirements for 10- to 21-d-old male broilers. Three hundred and sixty 10-d-old Ross 308 broilers (290 ± 16.6 g) were allocated to 6 diets in a randomized complete block design with 6 replicate cages per treatment and 10 birds per cage. The 6 experimental diets were formulated to contain equally spaced increasing levels of SID Lys from 0.86% to 1.36%. The data were analyzed using the MIXED procedure of SAS. The Lys requirements were estimated by the NLIN procedure of SAS. An increase in dietary SID Lys from 0.86% to 1.36% resulted in a quadratic increase (P < 0.05) in body weight gain (BWG), gain to feed ratio (G:F), breast weight, muscle cross-sectional area (MCSA), and fiber area. The SID Lys requirements based on the one-slope broken-line, quadratic line, the first intercept between the plateau of the one-slope broken-line and quadratic-line models and 95% of the upper asymptote of the quadratic-line model were estimated to be 1.01%, 1.19%, 1.08%, and 1.13% for BWG, 1.06%, 1.22%, 1.11%, and 1.16% for G:F, 1.10%, 1.29%, 1.19%, and 1.22% for breast weight, 1.06%, 1.22%, 1.12%, and 1.16% for MCSA, and 1.14%, 1.22%, 1.16%, and 1.16% for breast muscle fiber area, respectively. It was concluded that the SID Lys requirements for broilers at the age of 10 to 21 d depended on the response variables used for estimation, and that histochemical characteristics of breast muscle fibers could be good indicators for estimating SID Lys requirements.

Keywords: Broiler chicken; Growth performance; Lysine; Muscle fiber characteristics; Requirement.

Fig. 1

Fitted broken (solid) and quadratic line (dot) of growth performance in weight gain as a function of standardized ileal digestible (SID) lysine in the diet. Data points express the means of 6 cages per treatment. The one-slope broken-line model shows that the SID lysine requirement is 1.01%. Y = 599.9 + 1,017.7 × (X − 1.01), (X < 1.01); r² = 0.985; P < 0.01. The SID lysine requirement with the first intercept between the plateau of the one-slope broken-line and quadratic models is 1.08%. The quadratic line model shows that the SID lysine requirement is 1.19%. Y = 619.3 – 1,513.2 × (1.19 − X)², (X < 1.19); r² = 0.961; P < 0.01; and 95% of the upper asymptotic value of the quadratic model indicates that the SID lysine requirement is 1.13%.

Fig. 2

Fitted broken (solid) and quadratic line (dot) of growth performance in the gain to feed ratio as a function of standardized ileal digestible (SID) lysine in the diet. Data points express the means of 6 cages per treatment. The one-slope broken-line model shows that the SID lysine requirement is 1.06%. Y = 686.4 + 456.5 × (X − 1.06), (X < 1.06); r² = 0.921; P = 0.02. The SID lysine requirement with the first intercept between the plateau of the one-slope broken-line and quadratic models is 1.11%. The quadratic line model shows that the SID lysine requirement is 1.22%. Y = 695.2 − 789.0 × (1.22 − X)², (X < 1.22); r² = 0.934; P = 0.02; and 95% of the upper asymptotic value of the quadratic model indicates that the SID lysine requirement is 1.16%.

Fig. 3

Fitted broken (solid) and quadratic line (dot) of muscle characteristics in the breast meat as a function of standardized ileal digestible (SID) lysine in the diet. Data points express the means of 6 cages per treatment. The one-slope broken-line model shows that the SID lysine requirement is 1.10%. Y = 121.5 + 164.7 × (X − 1.10), (X < 1.10); r² = 0.976; P = 0.004. The SID lysine requirement with the first intercept between the plateau of the one-slope broken-line and quadratic models is 1.19%. The quadratic line model shows that the SID lysine requirement is 1.29%. Y = 123.7 − 229.7 × (1.29 − X)² , (X < 1.29); r² = 0.983; P = 0.002], and 95% of the upper asymptotic value of the quadratic model indicates that the SID lysine requirement is 1.22%.

Fig. 4

Fitted broken (solid) and quadratic line (dot) of muscle characteristics in the muscle cross-sectional area (MCSA) as a function of standardized ileal digestible (SID) lysine in the diet. Data points express the means of 6 cages per treatment. The one-slope broken-line model shows that the SID lysine requirement is 1.06%. Y = 10.9 − 16.6 × (X − 1.06), (X < 1.06); r² = 0.928; P = 0.02. The SID lysine requirement with the first intercept between the plateau of the one-slope broken-line and quadratic models is 1.12%. The quadratic line model shows that the SID lysine requirement is 1.22%. Y = 11.2 − 28.0 × (1.22 − X)², (X < 1.22); r² = 0.869; P = 0.04, and 95% of the upper asymptotic value of the quadratic model indicates that the SID lysine requirement is 1.16%.

Fig. 5

Fitted broken (solid) and quadratic line (dot) of muscle characteristics in the fiber area as a function of standardized ileal digestible (SID) lysine in the diet. Data points express the means of 6 cages per treatment. The one-slope broken-line model shows that the SID lysine requirement is 1.14%. Y = 1,583 – 1,303.1 × (X − 1.14), (X < 1.14); r² = 0.917; P = 0.02. The SID lysine requirement with the first intercept between the plateau of the one-slope broken-line and quadratic models is 1.16%. The quadratic line model shows that the SID lysine requirement is 1.22%. Y = 1,593.3 − 3,113.3 × (1.22 − X)² , (X < 1.22); r² = 0.909; P = 0.04, and 95% of the upper asymptotic value of the quadratic model indicates that the SID lysine requirement is 1.16%.