ABSTRACT

1. Two experiments were conducted to determine the effects of different methionine (Met) sources regarding their absorption kinetics and utilisation in female single-meal-fed broiler chickens.

2. A total of 340, one day old female Ross 308 broiler chickens were fed commercial starter and grower diets for 38 d. Birds were then allocated to treatment diets in two experiments as a completely randomised design with four replicates of five chicks per each until 60 d of age. In experiment 1, a 2 × 5 factorial design was used to investigate the effect of two sources (DL-Met and AQUAVI®Met-Met) and five equimolar levels (0.4, 0.8, 1.2, 1.6, and 2 g/kg) in the diet. In experiment 2, different proportions of protein-bound methionine (PB-Met) to DL-Met (0.4:1.6, 0.8:1.2, 1.2:0.8: 1.6:0.4, and 2:0 g/kg) were incorporated into a basal diet deficient in Met. During the experiment, chickens received 90 g of pelleted feed for a time period of 17 ± 2.5 min, once daily.

3. The results indicated that chickens fed diets supplemented with DL-Met and Met-Met showed a rapid rise in plasma Met 1 h after feeding, with a sudden drop at 2 h after feeding. In contrast, chickens fed PB-Met substituted diets showed a gradual plasma peak at 1 and 2 h postprandial (P < 0.01). Plasma homocysteine (HCY) content increased to 34.38 and 40.43 μmol/l with DL-Met_2.0 and Met-Met_2.0 diets, while it decreased to 25.68 μmol/l with PB-Met_2.0(P ≤ 0.01). Chickens that received the PB-Met_2.0 diet had higher (P ≤ 0.01) protein utilisation (0.54 g/g) and lower excreta nitrogen content (4.04 g/100 g excreta), which demonstrated the benefits of feeding a protein-bound Met source. The efficiency of Met utilisation was 0.69 g/g in chickens fed PB-Met_2.0 diet, but only 0.36 and 0.41 g/g in those fed DL-Met_2.0 and Met-Met_2.0 (P ≤ 0.01).

4. The observed utilisation coefficient of DL-Met and Met-Met for single-meal meat-type chickens was lower than expected. The synchronisation of intestinal Met absorption maintained the efficiency of utilisation, which was related to the sources of added Met, with protein-bound Met showing the best utilisation and least excretion.

摘要

1. 进行了两个实验来确定不同蛋氨酸 (Met) 来源对雌性单餐饲喂肉鸡的吸收动力学和利用的影响。

2. 总共 340 只 1 日龄雌性 Ross 308 肉鸡被饲喂商业起始日粮和生长日粮 38 天。然后在两个实验中将鸡只分配到处理饮食，作为完全随机的设计，每组 5 只小鸡重复 4 次，直到 60 日龄。在实验 1 中，使用 2 × 5 因子设计来研究两种来源（DL-Met 和 AQUAVI®Met-Met）和五个等摩尔水平（0.4、0.8、1.2、1.6 和 2 g/kg）在饮食。在实验 2 中，将不同比例的蛋白质结合蛋氨酸 (PB-Met) 与 DL-Met (0.4:1.6、0.8:1.2、1.2:0.8: 1.6:0.4 和 2:0 g/kg) 掺入基础饮食缺乏Met。实验期间，鸡每天一次在 17 ± 2.5 分钟的时间内接受 90 克颗粒饲料。

3、结果表明，饲喂添加DL-Met和Met-Met日粮的鸡在饲喂1 h后血浆Met迅速升高，2 h后突然下降。相比之下，饲喂 PB-Met 替代日粮的鸡在餐后 1 和 2 小时表现出逐渐的血浆峰（P < 0.01）。_{DL-Met 2.0}和 Met-Met _2.0日粮的血浆同型半胱氨酸 (HCY) 含量分别增加至 34.38 和 40.43 μmol/l ，而 PB-Met _2.0则降至 25.68 μmol/l (P ≤ 0.01)。获得 PB-Met _2.0的鸡日粮具有较高的 (P ≤ 0.01) 蛋白质利用率 (0.54 g/g) 和较低的排泄物氮含量 (4.04 g/100 g 排泄物)，这证明了饲喂与蛋白质结合的 Met 来源的好处。_{饲喂 PB-Met 2.0}日粮的鸡的 Met 利用率为 0.69 g/g ，而饲喂 DL-Met _2.0和 Met-Met _2.0的鸡只只有 0.36 和 0.41 g/g （P ≤ 0.01）。

4.观察到的DL-Met和Met-Met对单餐肉型鸡的利用系数低于预期。肠道Met吸收的同步保持了利用的效率，这与添加的Met的来源有关，蛋白质结合的Met显示出最好的利用和最少的排泄。