【作者】 云强；

【导师】 刁其玉；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2010， 硕士

【摘要】 本论文以断奶荷斯坦犊牛为试验动物,研究开食料中粗蛋白水平、低蛋白开食料中赖氨酸和蛋氨酸比例对犊牛生长性能、营养物质消化代谢和瘤胃发育的影响,旨在得出犊牛开食料的适宜粗蛋白水平及赖氨酸和蛋氨酸比,为后备牛的培育提供科学依据。具体分以下两个部分:试验一开食料中粗蛋白质水平对犊牛生长、消化及瘤胃发育的影响。试验选取15头8周龄荷斯坦公犊牛分为3个处理,每个处理5头牛。分别饲喂粗蛋白水平为16.22%、20.21%和24.30%的开食料,研究日粮蛋白水平对断奶犊牛生长、血清指标、物质代谢和瘤胃发育的影响,试验持续8周。试验期间每两周对犊牛进行称重、体尺测量、采血;在10和13周龄时每组选取3头犊牛进行代谢试验;犊牛12、16周龄采集瘤胃液测定瘤胃发酵能力和微生物酶活性。16周龄时对犊牛进行屠宰,取瘤胃组织样品研究瘤胃上皮细胞发育情况。结果表明,中蛋白组(20.21%)和高蛋白组(24.30%)犊牛的平均日增重分别为514g/d和518g/d,比低蛋白组(16.22%)高17.4%和18.2%;高蛋白组犊牛的血清尿素氮浓度显著高于中蛋白组(P<0.05)。高蛋白组犊牛粗蛋白的表观消化率高于低蛋白组(P<0.05),犊牛的吸收氮和沉积氮随开食料中粗蛋白水平升高而升高(P<0.05)。犊牛瘤胃液氨态氮、挥发性脂肪酸浓度、纤维素酶的活性有随开食料中粗蛋白水平的升高而升高的趋势(P>0.05)。开食料中粗蛋白水平对犊牛瘤胃乳头发育没有影响(P>0.05)。试验二开食料中Lys/Met对断奶犊牛生长性能和消化代谢的影响。选取24头健康的荷斯坦断奶母犊牛随机分为4个处理,每个处理6头牛。限量饲喂4种不同开食料,即对照组开食料(粗蛋白为19.64%)和3种赖氨酸、蛋氨酸比例分别为2.5﹕1,3.1﹕1,3.7﹕1的开食料(粗蛋白为15.22%),试验期为8周。在试验开始和结束时对犊牛进行称重和采血,在试验第3周每组选取4头犊牛进行代谢试验。结果表明,3.1﹕1组犊牛的增重达到834g,比对照组高10.21%(P﹥0.05),试验组犊牛血清尿素氮、精氨酸和缬氨酸浓度皆显著低于对照组(P﹤0.05),且各试验组之间没有显著差异(P﹥0.05)。开食料中赖氨酸和蛋氨酸比例对犊牛营养物质消化率没有影响(P﹥0.05)。低蛋白开食料中Lys/Met为3.1﹕1和3.7﹕1时,有减少N的排放,提高N的总利用率及N的表观生物学价值的趋势(P﹥0.05)。综上所述,本研究通过动物生长试验、消化代谢试验和屠宰试验,就断奶犊牛开食料适宜粗蛋白水平进行了较为系统的研究,确定了断奶犊牛开食料中粗蛋白水平为20.21%时有利于犊牛的生长发育;在此基础上,研究了在低蛋白开食料中优化赖氨酸和蛋氨酸比例对于犊牛开食料的可行性。结果表明,在低蛋白开食料(粗蛋白为15.22%)中赖氨酸和蛋氨酸比例为3.1﹕1时,犊牛的生长性能优于饲喂对照组开食料(粗蛋白为19.64%)的犊牛,并可提高粗蛋白的总利用率。更多还原

【Abstract】 Weaned calves were used in a series of trials to study the effect of protein levels in starter feeds on growth performance, digestive physiology and rumen development, and the effects of lysine to methionine ratios in starter feeds with low protein levels on growth performance, nutrient digestibility and nitrogen metabolism.Experiment 1 was designed to study the effect of protein levels in starter feeds on growth performance, digestive physiology and rumen development in weaned calves. Fifteen male Holstein calves were fed a starter feed containing 16.22 (low protein), 20.21 (medium protein) or 24.30% crude protein (high protein) respectively to examine the effect of dietary protein on growth performance, serum parameters, nutrient metabolism and rumen development. Restricted amounts of starter feeds were fed to calves from 8 to 16 wk of age. Live weights, growth parameters and concentrations of blood metabolites were determined every two weeks. Three calves were selected from each group and two digestion trials were conducted at 10 and 13 wk. The rumen fluid was taken 3 h after feeding at 12 wk of age and then euthanized at 16 wk of age to investigate rumen fermentation, digesition and enzymes activity. All calves were euthanized at 16 wk of age and rumen tissues were sampled for measurements of the development of ruminal epithelium. The results showed that, although no statistical differences were detected among treatments (P>0.05), the weight gain of calves fed low protein starter feeds was lower than that of the other calves. The serum urea nitrogen of calves fed high protein starter feeds was higher than that of the other calves. Calves on low protein starter feeds had lower apparent digestibility of the nutrient except crude protein at 10 wk of age. The apparent digestibility of nutrients except dry matter at 13 wk of age tended to increase as the crude protein content in starter feeds increased. Fecal nitrogen, urinary nitrogen, absorbed nitrogen, retained nitrogen and total utilization of nitrogen increased linearly with the increasing dietary protein levels. The calves in group HP had a lower ruminal pH at 12 wk of age, had a higher ruminal pH at 16 wk of age. Ruminal concentrations of ammonia nitrogen and volatile fatty acids in calves fed starter feeds with HP were higher than those in the other calves. Theα-amylase activity was lower in calves fed MP starter feed than that fed the other starter feeds. The protease and cellulases activities tended to increase as the crude protein content increased. And they were higher in 16wk than in 12wk in the same treatment. Dietary protein levels had no effects on the development of the rumen .Experiment 2 was designed to examine the effects of the lysine to methionine ratio in diets on growth performance, nutrient digestibility and metabolism in weaned calves. Twenty four weaned calves were randomly divided into four groups and fed with a control starter diet with a crude protein level of 19.64% DM, or a test diet (15.22 crude protein% DM) with a lysine to methionine ratio of 2.5:1, 3.1:1 or 3.7:1 for 8 wk. The calves were weighed and blood samples were collected on the initial and final day of the trial. Four calves were selected from each group and digestion trials were conducted from the third week of the trial by total feces collection method. The result indicated that the gain of calves in group 3.1﹕1 was 834 g/d, which was 10.21% higher than that of calves in control group numerically (P﹥0.05). Serum urea nitrogen, arginine and valine concentrations in calves fed the test diet were lower than those in control calves (P﹤0.05). But it did not differ among test groups. The ratio of lysine to methionine had no influence on nutrient digestibility (P﹥0.05). But the utilization and apparent biological value of nitrogen in group 3.1﹕1 and group 3.7﹕1 were higher than group 2.5﹕1 and control group numerically(P﹥0.05).In conclusion, 20.21% protein was found to be the optimal to promote growth and development of the calves. In addition, the possibility of optimizing the lysine to methionine ratio at low protein levels was discussed and the calves fed the low protein diet with a lysine to methionine ratio of 3.1:1 had improved growth performance, and increase operating factor of protein.更多还原