以反應曲面法檢測甲硫胺酸羥基類似物螯合銅與甲硫胺酸羥基類似物螯合鋅於白肉雞飼糧的推薦量

Abstract

本研究旨在以反應曲面法（response surface methodology, RSM）評估 0-36 日齡 Ross 308 白肉雞對甲硫胺酸羥基類似物螯合銅（MHA-Cu）與甲硫胺酸羥基類似物螯合鋅（MHA-Zn）之最佳飼糧添加量，並探討不同銅（copper, Cu）與鋅（zinc, Zn）濃度組合對白肉雞生長表現、組織礦物質沉積與骨骼相關指標之影響。為降低基礎飼糧中Cu與Zn濃度，本研究以雞蛋蛋白粉部分取代大豆粕。試驗採中心複合設計（central composite design, CCD），建立 9 組不同 Cu（0.6-30.0 mg/kg）與 Zn（18.1-120.0 mg/kg）濃度組合之處理。試驗期間測定白肉雞各階段生長表現、血液與組織中 Cu 與 Zn 濃度及骨骼與翅膀等相關指標，並以 RSM 評估各反應變項之整體模型顯著性（total model）、欠合性試驗（lack of fit）、調整後判定係數（adjusted R²）及最佳化結果。 結果顯示，在生長表現方面，以採食量（feed intake, FI）及飼料轉換率（feed conversion ratio, FCR）於各生長階段及全期飼養中所建立之 total model 皆未達顯著；部分體重（body weight, BW）與體增重（body weight gain, BWG）指標所建立之 total model 雖達顯著，但同時伴隨顯著的 lack of fit及偏低之Adjusted R²，顯示生長表現之相關指標不足以建立穩定且具預測能力之反應曲面模型。在組織中 Cu 與 Zn 含量方面，血清中 Cu 與 Zn 含量所建立之 total model 皆未達顯著，相較之下，骨骼之 Zn 含量與肝臟之 Cu 含量具有明確之模式化反應，能反映飼糧中Cu與Zn濃度組合對組織礦物質沉積之影響。經 RSM 最佳化分析後，0–36 日齡 Ross 308 白肉雞飼糧中總 Cu 與總 Zn 之最佳濃度分別為 20.8 mg/kg 與 106.3 mg/kg。扣除一般玉米－大豆粕基礎飼糧所提供之 Cu 與 Zn 後，MHA-Cu 與 MHA-Zn 所提供之 Cu 與 Zn 建議添加濃度分別為 20.17 mg/kg 與 88.19 mg/kg。此結果高於 NRC（1994）之最低需求參考值，且較接近現代商用白肉雞營養手冊之建議範圍；其中 Ross 308 營養規格建議 Cu 與 Zn 之添加量分別為 16 與 120 mg/kg（Aviagen, 2022）。進一步套用於含 2–5% 魚粉或肉骨粉之三階段商業配方估算後，MHA-Cu 所需提供之元素 Cu 約為 11.5–12.7 mg/kg，MHA-Zn 所需提供之元素 Zn 約為 72.5–76.8 mg/kg，可作為 MHA-Cu 與 MHA-Zn 於白肉雞飼糧中添加量評估之參考。

This study aimed to evaluate the optimal dietary supplementation levels of methionine hydroxy analog chelated copper (MHA-Cu) and methionine hydroxy analog chelated zinc (MHA-Zn) for Ross 308 broilers from 0 to 36 days of age using response surface methodology (RSM), and to investigate the effects of different dietary combinations of copper (Cu) and zinc (Zn) on growth performance, tissue mineral deposition, and skeletal-related traits. To reduce the Cu and Zn concentrations in the basal diet, egg white powder was used to partially replace soybean meal. A central composite design (CCD) was employed to establish nine dietary treatments with different combinations of Cu (0.6–30.0 mg/kg) and Zn (18.1–120.0 mg/kg).Growth performance, blood and tissue Cu and Zn concentrations, and bone- and wing-related parameters were determined throughout the experimental period. Response surface methodology was used to evaluate the significance of the total model, lack of fit test, adjusted coefficient of determination (adjusted R²), and optimization results for each response variable. The results showed that, for growth performance, the total models established for feed intake (FI) and feed conversion ratio (FCR) during different growth phases and across the entire rearing period were not significant. Although some models developed for body weight (BW) and body weight gain (BWG) were significant, they were accompanied by significant lack of fit tests and relatively low adjusted R² values, indicating that growth performance variables were insufficient for developing robust and predictive response surface models.Regarding tissue mineral concentrations, the total models for serum Cu and Zn concentrations were not significant. In contrast, bone Zn concentration and liver Cu concentration exhibited clear response patterns, reflecting the effects of dietary Cu and Zn combinations on tissue mineral deposition. Based on RSM optimization analysis, the optimal total dietary concentrations of Cu and Zn for Ross 308 broilers from 0 to 36 days of age were estimated to be 20.8 mg/kg and 106.3 mg/kg, respectively. These values represent the total dietary concentrations of Cu and Zn, including both the basal dietary Cu and Zn and the additional Cu and Zn supplied by MHA-Cu and MHA-Zn. After subtracting the Cu and Zn provided by a conventional corn–soybean meal basal diet, the recommended supplemental concentrations of Cu and Zn supplied by MHA-Cu and MHA-Zn were 20.17 mg/kg and 88.19 mg/kg, respectively. These recommended concentrations exceeded the minimum requirements suggested by NRC (1994) and were closer to the recommendations provided in modern commercial broiler nutrition guidelines; specifically, the Ross 308 nutrition specifications recommend supplemental Cu and Zn levels of 16 and 120 mg/kg, respectively (Aviagen, 2022). When the optimized total Cu and Zn concentrations were further applied to three-phase commercial diets containing 2–5% fish meal or meat and bone meal, the estimated supplemental requirements were 11.5–12.7 mg/kg Cu from MHA-Cu and 72.5–76.8 mg/kg Zn from MHA-Zn, respectively. These findings may serve as a useful reference for the feed industry and poultry production.