甜菜碱对肉鸭生长性能和胴体组成的影响

为了探讨甜菜碱对肉鸭（1～42日龄）生长及胴体组成的影响。把690羽1日龄的商品代樱桃谷肉鸭随机分成5个组，每组3个重复。饲养试验分成2个阶段：肉鸭前期（1～21日龄）和肉鸭后期（22～42日龄）。在肉鸭前期的5个饲粮处理组中，甜菜碱的添加量分别为每千克饲粮0、500、1 000、1 500、2 000 mg，在肉鸭后期，甜菜碱的添加量分别为每千克饲粮0、250、500、750、1 000 mg。饲养试验结束后，选取90羽（每组18羽）进行屠宰试验，收集肝脏和肌肉样品。研究结果表明，在肉鸭前期，每千克饲粮中添加500～2 000 mg 甜菜碱均显著提高了肉鸭的平均日增重（ADG）（P<0.01），但对料重比无显著影响。在肉鸭后期，每千克饲粮中添加750 mg和1 000 mg甜菜碱也显著提高了ADG（P<0.05），其中1 000 mg甜菜碱还明显降低了料重比（P<0.05）。胴体性状分析结果表明，与不添加甜菜碱的对照组相比，甜菜碱能明显增加肉鸭的胸肌率（P<0.01）、降低腹脂率（P<0.01）。甜菜碱还显著提高了肝脏甜菜碱高半胱氨酸甲基转移酶的活性（P<0.01）、肝脏游离肉碱（P<0.01）和肌肉酸不溶肉碱（P<0.01）的含量。研究揭示，甜菜碱有可能是通过促进肉鸭机体甲基代谢和改善长链脂肪酸的β-氧化而促进肉鸭的生长并改善了胴体的组成。

Effect of betaine on growth performance and carcass traits of meat ducks

The study was conducted to examine the effects of betaine on growth and carcass characteristics of meat ducks. Day-old commercial strain Cherry Valley meat ducks (n=690) were randomly allocated into five groups for a six-week feeding trial. Five dietary levels of betaine supplementation were arranged for each of the two experimental periods: and the finishing ducks (22-42 d) at 0, 250, 500, 750 and 1 000 mg/kg of diet. At the end of the feeding trial, 90 ducks (18 ducks per group) were selected to determine the carcass traits. Liver and breast muscle samples were also collected. For growing ducks, betaine supplementation (500～2 000 mg/kg) significantly increased average daily gain (ADG)(P<0.01). It also increased average daily feed intake (ADFI) (P<0.01) except for group 4 at 2 000 mg/kg as compared with the control group. However, such an increase the finishing period, ADG increased linearly and the feed-to-gain ratio decreased linearly with increasing betaine levels. Betaine supplementation at 750 mg/kg and 1 000 mg/kg improved ADG (P<0.05). Betaine supplementation at 1 000 mg/kg also significantly decreased the feed-to-gain ratio. Analysis of carcass traits indicated that betaine could increase the percentage of breast muscle (P<0.01) and decrease the percentage of abdominal fat (P<0.01) as compared with the control group. Betaine at 1 000 mg/kg increased the total and specific activities of betaine-homocysteins-methyltransferase (P<0.01), increased the content of free carnitine in the liver (P<0.01) and of acid insoluble carnitine in the breast muscle (P<0.01). These results imply that betaine could enhance synthesis of carnitine by improving methylation metabolism and stimulate β-oxidation of long chain fatty acids in the inner mitochondria membrane of muscle cells.