Department of Animal, Veterinary, and Food Sciences, University of Idaho, Moscow, ID 83843, USA.
University of Idaho Extension, Gooding County, Gooding, ID 83330, USA.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae230.
This study investigated the effects of feeding clinoptilolite (CLN; 2.5% of diet dry matter) with a particle size of either 30- or 400-µm on ruminal fermentation characteristics, measures of nitrogen (N) utilization, and manure ammonia-N (NH3) emissions in feedlot cattle. The impact of directly applying 30- or 400-µm CLN to the pen surface (2,250 kg/ha) on manure NH3-N emissions was also evaluated. Six beef heifers were used in a replicated 3 × 3 Latin square design with 21-d periods. Dietary treatments were 1) finishing ration with no supplement (CON), 2) CON + 30-µm CLN (CLN-30), and 3) CON + 400-µm CL (CLN-400). Intake was measured daily. To evaluate fermentation characteristics, ruminal fluid was collected on day 19. Indwelling pH loggers were used to measure ruminal pH from days 15 to 21. Blood was collected 3-h post-feeding on day 21 for metabolite analysis. Fecal grab and urine spot samples were also collected from days 19 to 21 to measure nutrient digestibility, route of N excretion, and in vitro NH3 emissions. There was no diet effect (P ≥ 0.12) on nutrient intake and apparent total tract digestibility, and ruminal short-chain fatty acid profile and pH. Ruminal NH3 concentration, which was lower (P = 0.04) for CLN-30 than CON heifers, did not differ between CON and CLN-400 heifers. Although there was no diet effect (P = 0.50) on plasma urea-N (PUN) concentration, proportion of urea-N excreted in urine was lower (P = 0.01) for CLN-30 than CON and CLN-400 heifers. Urinary NH3-N excretion, which was greater (P ≤ 0.04) for CLN-400 than CON heifers, did not differ between CLN-30 and CLN-400 heifers. Feeding CLN also increased (P ≤ 0.02) fecal excretion of potassium (K) and iron (Fe) and reduced (P = 0.01) urinary excretion of calcium (Ca). There was a treatment × time interaction (P = 0.01) for NH3 emission rate, which was greatest within the first 36 h of incubation and was lower for manure from CLN-400 compared to CON and CLN-30 heifers and pen surface application treatments. Cumulative NH3 emissions were lower (P < 0.01) for manure from CLN-400 compared to CON and CLN-30 heifers and the pen surface application treatments. Although surface application was ineffective, feeding 400-µm CLN to finishing cattle could result in a beneficial decrease in manure NH3 emissions. However, changes in fecal and urine excretion of minerals like K and Ca, which suggest a decrease in bioavailability, need to be considered when feeding CLN in finishing cattle diets.
本研究旨在探究粒径分别为 30-µm 和 400-µm 的沸石（CLN；日粮干物质的 2.5%）对育肥牛瘤胃发酵特性、氮（N）利用措施和粪便中氨氮（NH3-N）排放的影响。还评估了将 30-µm 和 400-µm 直接施用到畜栏表面（2250kg/ha）对粪便 NH3-N 排放的影响。采用重复 3 × 3 拉丁方设计，6 头肉牛进行了 21 天的试验。日粮处理为 1）无补充剂的育肥日粮（CON），2）CON+30-µm CLN（CLN-30），和 3）CON+400-µm CLN（CLN-400）。每日测量采食量。为评估发酵特性，在第 19 天采集瘤胃液。使用植入式 pH 记录仪从第 15 天到第 21 天测量瘤胃 pH。第 21 天的 3 小时后，采集血液用于代谢物分析。第 19 天至 21 天还采集了粪便和尿液样本，以测量养分消化率、N 排泄途径和体外 NH3 排放。日粮对养分摄入量和表观全肠道消化率以及瘤胃短链脂肪酸谱和 pH 没有影响（P ≥ 0.12）。CLN-30 组的瘤胃 NH3 浓度较低（P = 0.04），CON 组和 CLN-400 组之间没有差异。虽然日粮对血浆尿素氮（PUN）浓度没有影响（P = 0.50），但 CLN-30 组的尿素氮排泄比例低于 CON 和 CLN-400 组（P = 0.01）。CLN-400 组的尿 NH3-N 排泄量高于 CON 组（P ≤ 0.04），而 CLN-30 组与 CLN-400 组之间没有差异。饲喂 CLN 还增加了（P ≤ 0.02）粪便中钾（K）和铁（Fe）的排泄量，并降低了（P = 0.01）尿中钙（Ca）的排泄量。NH3 排放率存在处理×时间的交互作用（P = 0.01），在孵育的前 36 小时内最大，且 CLN-400 组的 NH3 排放率低于 CON 组和 CLN-30 组以及畜栏表面应用处理组。CLN-400 组的粪便 NH3 排放总量低于 CON 组和 CLN-30 组以及畜栏表面应用处理组（P < 0.01）。尽管表面应用无效，但在育肥牛日粮中添加 400-µm CLN 可能会导致粪便中 NH3-N 排放的有益减少。然而，当在育肥牛日粮中添加 CLN 时，需要考虑 K 和 Ca 等矿物质的粪便和尿液排泄变化，这表明生物利用度降低。
