氨基酸缺乏对母犊牛生长和日粮养分消化代谢的影响

研究赖氨酸(Lys)、蛋氨酸(Met)和苏氨酸(Thr)缺乏对3-6月龄中国荷斯坦母犊牛生长和日粮养分消化代谢的影响,为生产中判断母犊牛氨基酸缺乏症提供依据,并对后续母犊牛氨基酸需要量的确定提供理论依据。【方法】72头84日龄中国荷斯坦母犊牛,按体重和出生时间相近原则随机分为4个处理组,限量饲喂4种不同氨基酸模式的饲粮,分别为氨基酸平衡组(PC组)、赖氨酸扣除组(PC-Lys)、蛋氨酸扣除组(PC-Met)和苏氨酸扣除组(PC-Thr),氨基酸扣除量均为PC组的30%。试验期97d,其中预饲期7d,正试期90d。于正试期第1、30、60、90天测定犊牛体重、体尺和乳头长度;在132—138和173—179日龄每组分别选取6头健康犊牛进行2期消化代谢试验,收集粪、尿和饲料样品,测定营养物质表观消化率及氮代谢;正试期每天记录采食量。【结果】与饲喂氨基酸平衡饲粮的犊牛相比:(1)扣除Lys显著降低90—180日龄犊牛饲料转化效率(P<0.05),日增重(ADG)为各组最低(P>0.05);扣除Met和Thr对90—180日龄犊牛ADG和饲料转化效率没有显著影响(P>0.05...

Effects of Amino Acid Deficiency on Growth Development,Dietary Nutrients Digestion and Metabolism in Heifers

【Objective】The objective of this study was to evaluate the effects of deleting dietary lysine (Lys), methionine (Met) and threonine (Thr) on growth performance, and nutrients digestion and metabolism in 3-6 month-old Chinese Holstein heifers. It can provide not only the evidences for diagnosing the deficiency disease of amino acid of heifers in production, but also the guidance for determining amino acid requirements of heifers in the future.【Method】The experiment was conducted for 90 days with 72 Holstein heifers aged about 84 day-old fed in restricted amounts. Following a 7-day covariate period, heifers were allocated to 4 groups according to date of birth and body weight: 30% Lys reducing treatment (PC-Lys), 30% Met reducing treatment (PC-Met), 30% Thr reducing treatment (PC-Thr) and theoretical amino acid balanced treatment (PC). Body weight, body size and length of nipples were measured on 1, 30, 60 and 90 day. Six healthy calves were selected from each group at the ages of 132-138 and 173-179 day for twice and metabolism test. Feces, urine and feeds samples were collected to determine the apparent digestibility of nutrients and nitrogen metabolism. Dry matter intake was recorded daily throughout the whole trial period. 【Result】Compared with PC, the results showed that (1) Lys deficiency significantly decreased Gain/Feed (G/F) in 90 to 180 day-old heifers (P＜0.05). Average daily gain (ADG) of PC-Lys group was lowest among four groups in 90 to 180 day-old heifers (P＞0.05). ADG and G/F were not influenced by Met and Thr deficiency in 90 to 180 day-old heifers (P＞0.05); (2) No differences of diarrhea rate were found among four groups (P＞0.05), while diarrhea rate was highest in PC-Lys group (P＞0.05). However, Lys and Thr deficiency decreased fecal score (P＜0.05); (3) Lys, Met and Thr deficiency did not affect body size (P＞0.05), but the growth rate of nipples of PC-Lys group were lower than that of PC group (P＜0.05); (4) The apparent digestibility of nutrients were not influenced by different treatments. Retained N of intake N and biological value of N were significantly decreased in PC-Lys group (P＜0.05). 【Conclusion】On the basis of the theoretical amino acid balanced diet, reducing 30% dietary Lys had adverse effect on growth performance and nitrogen metabolism, and reducing 30% dietary Thr could deteriorate diarrhea, while reducing 30% dietary Met had no effects in heifers.