Department of Animal Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS 91540-000, Brazil.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad265.
Iron is routinely supplemented in broiler feeds intending to prevent dietary deficiencies. The present research was conducted with the objective of assessing Fe requirements of broilers when fed supplemental phytase. A total of 1,280 1-d-old male Cobb × Cobb 500 were distributed in a 2 × 5 factorial arrangement (phytase-supplemented feeds × 5 graded increases of supplemental Fe) in 80 battery cages, eight replications of eight chicks each. The trial was replicated once. Chicks were fed a Fe-deficient diet without phytase (Fe analyzed at 31.30 ± 3.79 mg/kg) from placement to 7 d and then randomly distributed into battery cages with corresponding dieting treatments with or without phytase and graded increases of supplemental Fe. Feeds were formulated with corn and soybean meal (SBM), laboratory-grade calcium carbonate, and phosphoric acid; therefore, the vast majority of dietary Fe originated from corn and SBM (analyzed diet had 53.3 ± 1.41 mg/kg Fe). Phytase was added in excess to the producer recommendation of 1,000 FYT (4,452 ± 487 FYT/kg analyzed) such that phytate degradation was expected to be maximized. Supplemental Fe was from laboratory-grade ferrous sulfate heptahydrate (FeSO47H2O) which was increasingly added to the feeds (analyzed Fe in the supplemented feeds were: 53.3 ± 1.41, 65.5 ± 0.59, 77.2 ± 1.97, 87.6 ± 1.72, 97.7 ± 1.33 mg/kg). There were no interactions between phytase and dietary Fe for any response throughout the study (P > 0.05). Supplementing phytase had no effects on Fe intake or Fe excretion, as well as on hematocrit (Ht), hemoglobin (Hb), ferritin, Fe contents in the liver or thigh muscle color (P > 0.05). However, phytase-supplemented feeds produced better live performance as well as higher ileal digestible energy and Fe digestibility (P < 0.05). No effects were found for dietary Fe in live performance at day 28 (P > 0.05). On the other hand, increasing dietary Fe led to linear increases in Fe retention and excretion, Fe contents in livers, as well as Ht and Hb at 14 d (P < 0.05). Quadratic responses (P < 0.05) were observed for Hb at 21 d, serum ferritin on days 14, 21, and 28 (maximum responses were 83.3, 104.0, 91.9, and 88.3 mg/kg Fe, respectively). In conclusion, supplementing Fe adding to a total of 97.7 mg/kg dietary Fe did not affect live performance traits. However, the average of Fe-related blood parameters was maximized at 91.9 mg/kg dietary Fe. Supplementing phytase provided a significant increase in Fe digestibility.
铁通常会被添加到肉鸡饲料中以预防营养缺乏。本研究旨在评估添加植酸酶时肉鸡对铁的需求。试验选用 1280 只 1 日龄雄性科宝×科宝 500 肉鸡，采用 2×5 因子设计（添加植酸酶的饲料×5 个递增的补充铁水平），80 个电池笼，每个重复 8 个鸡笼，共 8 个重复。试验重复进行了一次。肉鸡从入笼到 7 日龄时被喂食缺乏铁的基础日粮（未添加植酸酶，铁含量为 31.30±3.79mg/kg），然后随机分配到含有相应日粮处理的电池笼中，包括添加植酸酶和递增补充铁水平。饲料中使用了玉米和豆粕（SBM）、实验室级碳酸钙和磷酸；因此，绝大多数日粮铁来自于玉米和 SBM（分析日粮铁含量为 53.3±1.41mg/kg）。植酸酶的添加量超过了生产商推荐的 1000 FYT（4452±487 FYT/kg 分析），从而有望最大限度地提高植酸盐的降解。补充铁来自于实验室级七水硫酸亚铁（FeSO47H2O），逐渐添加到饲料中（补充饲料中的铁含量分别为：53.3±1.41、65.5±0.59、77.2±1.97、87.6±1.72、97.7±1.33mg/kg）。在整个研究过程中，植酸酶和日粮铁之间没有任何互作（P＞0.05）。添加植酸酶对铁的摄入量或排泄量、红细胞压积（Ht）、血红蛋白（Hb）、铁蛋白、肝脏或大腿肌肉的铁含量（P＞0.05）没有影响。然而，添加植酸酶的饲料在生产性能方面表现更好，回肠可消化能量和铁消化率更高（P＜0.05）。在 28 日龄时，日粮铁对生产性能没有影响（P＞0.05）。另一方面，随着日粮铁的增加，铁的保留和排泄、肝脏中的铁含量以及 14 日龄的 Ht 和 Hb 呈线性增加（P＜0.05）。21 日龄的 Hb（P＜0.05）、14、21 和 28 日龄的血清铁蛋白（最大响应分别为 83.3、104.0、91.9 和 88.3mg/kg Fe）呈二次响应。综上所述，添加铁总量达到 97.7mg/kg 不会影响生产性能。然而，在 91.9mg/kg 日粮铁时，与铁相关的血液参数达到平均最大值。添加植酸酶显著提高了铁的消化率。
