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Effect of zeolite administration on nitrogen metabolism and excretion in lactating dairy cows offered pasture herbage
Animal Production Science ( IF 1.4 ) Pub Date : 2020-01-01 , DOI: 10.1071/an19674
K. Stelwagen , P. C. Beukes , C. Hemmings

Context Due to high protein concentrations in pastures, dairy cows offered a pasture-based diet often consume excess nitrogen (N), which leads to high ruminal ammonia concentrations and excessive urinary N excretion, thereby contributing to pasture N leaching. Aims To study the effect of administration of natural zeolite on ruminal pH and ammonia production and N excretion in lactating cows offered an all-pasture herbage diet. Methods In a metabolism stall trial using a crossover trial design, rumen-cannulated Friesian cows were administered either zero (Control, n = 16) or 400 g/day of zeolite (Zeolite; n = 16). Zeolite was divided into two equal portions and administered directly into the rumen before feeding fresh-cut ryegrass-clover herbage at 07:30 and 15:30 hours. Cows were kept in the metabolism stalls for two measurement periods of 5 days each, with each period preceded by an adaptation/washout period of 2 weeks. Feed intake, milk yield, total urine and faecal outputs were measured daily. During the last day of each measurement period ruminal fluid and blood were frequently sampled. Key results Zeolite administered at 2.2% of dry matter intake (DMI) did not affect daily DMI. Moreover, milk yield and milk composition, including milk urea, were not affected by zeolite administration. In cows administered zeolite the mean 24-h ruminal ammonia concentration was reduced by 1.5 mmol/L (9%) and the ruminal pH pattern in zeolite-administered cows over 24 h was above that of Control cows, but the overall effect on pH was not significant. Zeolite had no effect on plasma urea, total urinary N excreted or faecal N. Of the total N excreted across the groups, 21.7, 50.6 and 27.7% was excreted into milk, urine and faeces respectively. Conclusions Zeolite administration reduced ruminal ammonia concentration but this did not result in reduced urinary N excretion in dairy cows offered pasture. Implications Dietary supplementation with zeolite may help to improve aspects of ruminal function in cows consuming pasture, but is unlikely to be an effective tool for reducing N leaching from pastures.

中文翻译:

沸石给药对牧草泌乳奶牛氮代谢和排泄的影响

背景 由于牧场中蛋白质浓度高,提供以牧场为基础的饮食的奶牛经常消耗过量的氮 (N),这导致瘤胃氨浓度高和尿中氮排泄过多,从而导致牧场氮浸出。目的 研究施用天然沸石对全牧场牧草日粮的泌乳奶牛瘤胃 pH 值、氨产量和氮排泄的影响。方法 在使用交叉试验设计的代谢停顿试验中,给瘤胃插管的弗里斯兰奶牛施用零(对照,n = 16)或 400 克/天的沸石(沸石;n = 16)。沸石被分成两等份,在 07:30 和 15:30 喂食鲜切黑麦草 - 三叶草之前直接注入瘤胃。将奶牛保持在新陈代谢棚中进行两个测量周期,每个周期为 5 天,每个周期之前有 2 周的适应/淘汰期。每天测量采食量、产奶量、总尿量和粪便量。在每个测量期的最后一天,经常对瘤胃液和血液进行取样。主要结果 以干物质摄入量 (DMI) 的 2.2% 施用沸石不会影响每日 DMI。此外,牛奶产量和牛奶成分,包括牛奶尿素,不受沸石给药的影响。在服用沸石的奶牛中,平均 24 小时瘤胃氨浓度降低了 1.5 mmol/L (9%),服用沸石的奶牛在 24 小时内的瘤胃 pH 值高于对照奶牛,但对 pH 的总体影响为不重要。沸石对血浆尿素、排泄的总尿 N 或粪便 N 没有影响。在各组排泄的总氮中,分别有 21.7%、50.6% 和 27.7% 排泄到牛奶、尿液和粪便中。结论 沸石给药降低了瘤胃氨浓度,但这并没有导致饲喂牧草的奶牛尿氮排泄减少。影响 日粮中添加沸石可能有助于改善吃草的奶牛的瘤胃功能,但不太可能成为减少从草中渗出的氮的有效工具。
更新日期:2020-01-01
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