Nutrient utilization of differing forage-to-concentrate ratios by growing Holstein heifers.
Nutrient utilization of differing forage-to-concentrate ratios by growing Holstein heifers.
复制标题
生长荷斯坦小母牛对不同饲料与精料比例的养分利用。
DOI：
10.3168/jds.2007-0570
复制
发表时间：
2007
影响因子：
3.5
通讯作者：
A. Heinrichs
中科院分区：
文献类型：
--
作者：
M. L. Moody;G. Zanton;J. M. Daubert;A. Heinrichs
传统上，随意饲喂的高草料、低浓度日粮一直是饲养奶牛的主要系统。然而，高浓缩日粮可以限制摄入量，以达到所需的增重率并提高营养效率。在 2 项试验中，以限制摄入量饲喂含有高玉米青贮饲料（CS；HCS：77% CS，23% 浓缩物）或低 CS（LCS：67% 浓缩物，33% CS）的总混合日粮，以评估生长中小母牛的养分利用率。在第一项试验中，饲喂 4 头瘤胃插管小母牛（体重 298 +/- 16 kg），以研究瘤胃 pH 值、挥发性脂肪酸和氨浓度以及瘤胃内容物质量的差异。对总混合日粮和CS进行了原位测定。与 HCS 相比，低 CS 日粮的原位消化速度更快（4.5 vs. 2.3 +/- 0.3%/h），并且在饲喂任一日粮的小母牛的瘤胃中培养时，CS 消化率没有观察到差异。 LCS 的平均瘤胃 pH 值往往低于 HCS（5.9 vs. 6.2 +/- 0.1）。处理之间个体和总瘤胃挥发性脂肪酸浓度和瘤胃氨浓度没有差异。 LCS 的瘤胃内容物总质量较低。在第二次试验中，使用了四头 6 个月大的小母牛（体重 172 +/- 14 公斤）和四头 12 个月大的小母牛（体重 337 +/- 10 公斤）。在两个年龄组中，LCS 日粮的干物质消化率均高于 HCS 日粮（12 个月大的小母牛为 76.3% vs. 71.1%；6 个月大的小母牛为 71.4% vs. 68.9%）。氮的表观消化率在处理之间没有差异；然而，对于两个年龄组的 LCS 日粮来说，保留的氮都较高。 LCS 饮食中两个年龄组的粪便排出量均显着减少。以有限的摄入量向生长中的奶牛饲喂低草料、高浓度日粮，虽然更易消化，但导致瘤胃发酵模式和粪便产量较低的显着差异。
Traditionally, high-forage, low-concentrate diets fed ad libitum have been the primary system of feeding dairy heifers. However, high-concentrate diets can be fed at restricted intakes to reach desired rates of gain and increase nutrient efficiency. A total mixed ration containing high corn silage (CS; HCS: 77% CS, 23% concentrate) or low CS (LCS: 67% concentrate, 33% CS) was fed at restricted intakes in 2 trials to evaluate nutrient utilization by growing heifers. In the first trial, 4 ruminally cannulated heifers (298 +/- 16 kg of body weight) were fed to study differences in rumen pH, volatile fatty acid and ammonia concentrations, and mass of rumen contents. In situ determinations were made on the total mixed ration and CS. Low CS rations were digested more rapidly in situ when compared with HCS (4.5 vs. 2.3 +/- 0.3%/h), and no differences were observed in CS digestibility when incubated in the rumen of heifers fed either ration. Mean rumen pH tended to be lower for LCS than for HCS (5.9 vs. 6.2 +/- 0.1). Individual and total rumen volatile fatty acid concentrations and rumen ammonia concentration were not different between treatments. Total mass of rumen contents was lower for LCS. In the second trial, four 6-mo-old heifers (172 +/- 14 kg of body weight) and four 12-mo-old heifers (337 +/- 10 kg of body weight) were used. Digestibility of dry matter was greater for the LCS than the HCS diet in both age groups (76.3 vs. 71.1% for 12-mo-old heifers; 71.4 vs. 68.9% for 6-mo-old heifers). Apparent digestibility of N was not different between treatments; however, retained N was higher for the LCS diets for both age groups. Fecal output was significantly reduced in the LCS diets for both age groups. Feeding low-forage, high-concentrate diets to growing dairy heifers at restricted intakes, although more highly digestible, resulted in few significant differences in rumen fermentation patterns and lower fecal output.