School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
J Dairy Sci. 2019 Sep;102(9):8027-8039. doi: 10.3168/jds.2019-16244. Epub 2019 Jul 3.
Two experiments were carried out to evaluate different dietary buffers and their influence on (1) rumen pH in dairy cows and (2) milk production in dairy cows. The supplements included were calcareous marine algae (CMA; Lithothamnion calcareum), with or without marine magnesium oxide (MM; precipitated magnesia derived from seawater), and sodium bicarbonate (SB). Dietary treatments in experiment 1 consisted of the control [32.9% starch and sugar, and 19.9% neutral detergent fiber from forage per kg of dry matter (DM)] including no dietary buffer (CON); the control plus 0.45% DM CMA (CMA); the control plus 0.45% DM CMA and 0.11% DM MM (CMA+MM); the control plus 0.9% DM SB (SB). Diets were formulated to a dry matter intake (DMI) of 18 kg per cow/d. Dietary treatments in experiment 2 also consisted of CON (28.3% starch and sugar, and 23% neutral detergent fiber from forage per kg of DM), CMA, CMA+MM, and SB and were formulated to achieve identical intakes of experimental ingredients (80 g of CMA, 80 g of CMA plus 20 g MM, and 160 g of SB per cow/d) with a DMI of 22.6 kg per cow/d. Experiment 1 used 4 rumen-cannulated dairy cows in a 4 × 4 Latin square design. Rumen pH was measured over five 2-h periods, following feeding, using rumen pH probes. In experiment 2, 52 multiparous and 4 primiparous cows (62.7 ± 3.4 d in milk) were assigned to 4 experimental treatments for 80 d. Both CMA treatments maintained a greater mean rumen pH than the CON during 4 of the 5 periods following feeding and the CON had a greater number of hours below rumen pH 5.5 compared with all other treatments. Dry matter intakes tended to be higher on the SB compared with CON. The CMA treatment increased the production of milk fat and protein yield (kg/d) compared with all other treatments. Both CMA and CMA+MM increased milk fat yield compared with CON but were similar to each other and SB. Protein yield was highest in the CMA treatment compared with CON, CMA+MM, and SB. All 3 buffer treatments increased milk fat concentration compared with CON but did not differ from each other. The SB treatment reduced milk protein concentration and milk production efficiency, energy-corrected milk per kilogram of DMI. Results indicate that the addition of CMA can benefit milk fat and protein production when included in diets based on typical feedstuffs of the northern European region. The use of CMA when compared with SB, in such diets, can increase milk protein production and milk production efficiency.
进行了两项实验来评估不同的日粮缓冲剂及其对（1）奶牛瘤胃 pH 值和（2）奶牛产奶量的影响。所用的补充剂包括钙质海洋藻类（CMA； Lithothamnion calcareum），有或没有海洋氧化镁（MM；来自海水的沉淀氧化镁）和小苏打（SB）。实验 1 的日粮处理包括对照[32.9%淀粉和糖，以及每公斤干物质（DM）中 19.9%中性洗涤纤维]，不含日粮缓冲剂（CON）；对照+0.45% DM CMA（CMA）；对照+0.45% DM CMA 和 0.11% DM MM（CMA+MM）；对照+0.9% DM SB（SB）。日粮是按照每头奶牛 18 公斤的干物质采食量（DMI）配制的。实验 2 的日粮处理也包括 CON（28.3%淀粉和糖，以及每公斤 DM 中 23%中性洗涤纤维）、CMA、CMA+MM 和 SB，并按照相同的实验成分摄入量（每头奶牛 80 克 CMA、80 克 CMA 加 20 克 MM 和 160 克 SB）进行配制，DMI 为每头奶牛 22.6 公斤。实验 1 采用 4 头瘤胃插管奶牛进行 4×4 拉丁方设计。在饲喂后使用瘤胃 pH 探头测量了 5 个 2 小时的时间段的瘤胃 pH 值。在实验 2 中，将 52 头经产和 4 头初产奶牛（产奶 62.7±3.4 天）分配到 4 个实验处理中，持续 80 天。与所有其他处理相比，CMA 处理在饲喂后的 5 个时期中的 4 个时期维持更高的平均瘤胃 pH 值，而 CON 有更多的时间低于瘤胃 pH 值 5.5。与 CON 相比，SB 处理的干物质采食量趋于更高。与所有其他处理相比，CMA 处理增加了牛奶脂肪和蛋白质产量（kg/d）。与 CON 相比，CMA 和 CMA+MM 都增加了牛奶脂肪产量，但彼此相似，与 SB 相同。与 CON、CMA+MM 和 SB 相比，CMA 处理的蛋白质产量最高。与 CON 相比，所有 3 种缓冲剂处理都增加了牛奶脂肪浓度，但彼此之间没有差异。与 CON 相比，SB 处理降低了牛奶蛋白浓度和牛奶生产效率，每公斤 DMI 的校正能量奶产量。结果表明，当包含在基于北欧地区典型饲料的日粮中时，CMA 的添加可以有益于牛奶脂肪和蛋白质的生产。与 SB 相比，在这种日粮中使用 CMA 可以增加牛奶蛋白的生产和牛奶生产效率。
