Timothy hays differing in dietary cation-anion difference affect the capability of dairy cows to maintain their calcium homeostasis.
Timothy hays differing in dietary cation-anion difference affect the capability of dairy cows to maintain their calcium homeostasis.
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DOI：
10.3168/jds.2008-1357
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发表时间：
2009
影响因子：
3.5
通讯作者：
V. Heron;G. Tremblay;M. Oba
中科院分区：
文献类型：
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作者：
V. Heron;G. Tremblay;M. Oba
日粮阴阳离子差（DCAD）低的饲料可用于降低反刍动物日粮中的DCAD，但DCAD需要降低的程度是最近的兴趣。本研究的目的是评估不同DCAD的Timothy Hays在维持钙稳态方面的有效性。6头非泌乳期和非妊娠期经产荷斯坦奶牛饲喂含有草苔草（Phenomethy pratense L.）在重复3 x 3拉丁方设计中，每100 g DM的DCAD值为4.1 +/-3.6（低）、14.1 +/- 3.0（中）或25.1 +/- 2.5（高）mEq的干草，试验期为14天。低干草和中等干草是由已建立的梯牧草地以每公顷224公斤CaCl（2）的比例生产的，而高干草是从生产低干草的同一块地获得的，但来自未施CaCl（2）的部分。实验饮食，含有低，中等，或高梯牧草在71%的膳食DM，DCAD值为0.7，7.3，和14.4毫当量每100克DM，分别。动物以代谢体重的6%喂食，这提供了其每日能量需求的108%。对于每个阶段，在12天饮食适应后，对奶牛进行EDTA攻毒（第13天和第14天各3头奶牛）。经颈静脉输注EDTA溶液可降低血离子钙浓度，EDTA激发方案确定了抵抗时间和恢复时间：血离子钙浓度降至60%所需的时间，恢复至激发前浓度的90%所需的时间。与高饮食相比，饲喂低饮食的奶牛尿液pH值较低（6.88 vs. 7.83），但饲喂MED饮食的奶牛尿液pH值（7.15）与饲喂低或高饮食的奶牛尿液pH值无差异。然而，在EDTA激发前，与高饲料相比，低或中等饲料喂养奶牛的血液pH值较低（7.44 vs. 7.47）。虽然抵抗时间不受治疗的影响，但与MED或HIGH饮食相比，当奶牛饲喂LOW时，恢复时间较短（分别为185 vs. 248和263 min）。血液pH值下降时，奶牛饲喂低或MED饮食，但能力，以维持钙稳态增强，只有当奶牛接受低饮食，其中DCAD值降低到1毫当量每100克DM。
Forages low in dietary cation-anion difference (DCAD) can be used to decrease the DCAD in prepartum diet but the extent to which DCAD needs to be reduced is of recent interest. The objective of this study was to evaluate the effectiveness of timothy hays differing in DCAD at maintaining Ca homeostasis. Six nonlactating and nonpregnant multiparous Holstein cows were fed diets containing timothy (Phleum pratense L.) hay with DCAD values of 4.1 +/- 3.6 (LOW), 14.1 +/- 3.0 (MED), or 25.1 +/- 2.5 (HIGH) mEq per 100 g of DM in a duplicated 3 x 3 Latin square design with 14-d experimental periods. The LOW and MED hays were produced by fertilizing established timothy fields at a rate of 224 kg CaCl(2) per ha, and HIGH hay was obtained from the same field where LOW hay was produced, but from a section not fertilized with CaCl(2). Experimental diets, containing LOW, MED, or HIGH timothy hay at 71% of dietary DM, had DCAD values of 0.7, 7.3, and 14.4 mEq per 100 g of DM, respectively. Animals were fed at 6% of metabolic body weight, which provided 108% of their daily energy requirement. For each period, after a 12 d diet adaptation, cows were subjected to an EDTA challenge (3 cows each on d 13 and 14). Infusion of EDTA solution into the jugular vein decreases the concentration of blood ionized Ca, and the EDTA challenge protocol determined the resistance time and recovery time: the time required for the blood ionized Ca concentration to decrease to 60%, and the time required to recover to 90% of the prechallenge concentrations, respectively. Urine pH was lower when cows were fed LOW compared with HIGH diet (6.88 vs. 7.83), but urine pH when cows were fed MED diet (7.15) did not differ from that when cows received the LOW or HIGH diet. However, immediately before the EDTA challenge, blood pH was lower when cows were fed LOW or MED compared with HIGH diet (7.44 vs. 7.47). Although the resistance time was not affected by treatments, the recovery time was shorter when cows were fed the LOW compared with MED or HIGH diet (185 vs. 248 and 263 min, respectively). Blood pH decreased when cows were fed the LOW or MED diet, but the capability to maintain Ca homeostasis was enhanced only when cows received the LOW diet, in which the DCAD value was decreased to 1 mEq per 100 g of DM.