This study investigated the effects of free-range days on growth performance, carcass traits, meat quality, lymphoid organ indices, and blood biochemical parameters of Wannan Yellow chickens. A total of 1,000 one-day-old male Wannan Yellow chickens were reared to 56 D. At 56 D of age, 960 birds with similar body weight (BW) were randomly allocated to free-range treatment at 56, 70, 84, and 98 D of age (assigned to free-range treatment for 42, 28, 14, and 0 D, respectively); 6 replicates with 40 chickens per treatment. In the free-range system, chickens were reared in indoor floor pens with an outdoor free-range paddock measuring 4 × 7 m (28 m2, 1.5 birds/m2). Results showed that BW of birds decreased significantly in the first 2 wk after birds were assigned to free-range treatment compared with those in the conventional treatment (P < 0.05). Average daily gain (ADG) and average daily feed intake (ADFI) decreased significantly (P < 0.05) for chickens assigned to free-range treatment from 56 to 70 D of age, while feed conversion ratio increased significantly (P < 0.05). Breast yield increased linearly with increasing free-range days (P < 0.05), whereas leg and foot yields decreased linearly (P < 0.05). Drip loss and L* value of thigh muscle decreased linearly with increasing free-range days (P < 0.05), while shear force improved linearly (P < 0.05). Additionally, the absolute thymus weight and thymus to BW ratio showed significant increasing and then decreasing quadratic responses to increasing free-range days (P < 0.05). Furthermore, serum glucose, total protein, cholesterol, and triglyceride content declined linearly, while high-density lipoprotein cholesterol (HDL-C) content increased linearly with increasing free-range days (P < 0.05). In conclusion, increasing free-range days had positive effects on breast yield, shear force, thymus weight, and HDL-C content, but negatively affected leg yield, foot yield, drip loss, L* value of thigh muscle, glucose, total protein, cholesterol, and triglyceride levels of Wannan Yellow chickens.

中文翻译：

---

放养天数对皖南黄鸡生长性能、胴体性状、肉质、淋巴器官指标和血液生化的影响。

本研究调查了放养日对皖南黄鸡生长性能、胴体性状、肉质、淋巴器官指标和血液生化指标的影响。共有 1000 只 1 日龄雄性皖南黄鸡饲养至 56 日龄。在 56 日龄时，960 只体重（BW）相似的鸡被随机分配到 56 日、70 日、84 日和98 D 年龄（分别分配到 42、28、14 和 0 D 的自由放养治疗）；6 个重复，每个处理 40 只鸡。在散养系统中，鸡在室内地板围栏中饲养，室外散养围场面积为 4 × 7 m（28 m2，1.5 只/m2）。结果表明，与常规处理相比，在分配到散养处理后的前2周，鸡的体重显着降低（P < 0.05）。从 56 日龄到 70 日龄，散养处理的鸡的平均日增重 (ADG) 和平均日采食量 (ADFI) 显着下降 (P < 0.05)，而饲料转化率显着增加 (P < 0.05)。乳房产量随着自由放养天数的增加呈线性增加（P < 0.05），而腿和足的产量呈线性下降（P < 0.05）。大腿肌肉的滴水损失和L*值随着自由放养天数的增加呈线性下降（P < 0.05），而剪切力呈线性增加（P < 0.05）。此外，胸腺绝对重量和胸腺与体重的比值随着放养天数的增加呈显着增加然后减少的二次响应（P < 0.05）。此外，血清葡萄糖、总蛋白、胆固醇和甘油三酯含量呈线性下降，而高密度脂蛋白胆固醇（HDL-C）含量随着放养天数的增加呈线性增加（P < 0.05）。总之，增加自由放养天数对乳房产量、剪切力、胸腺重量和 HDL-C 含量有积极影响，但对腿部产量、足部产量、滴水损失、大腿肌肉 L* 值、葡萄糖、总蛋白有负面影响、皖南黄鸡的胆固醇和甘油三酯水平。