Diurnal Concentration of Urinary Nitrogen and Rumen Ammonia Are Modified by Timing and Mass of Herbage Allocation
Diurnal Concentration of Urinary Nitrogen and Rumen Ammonia Are Modified by Timing and Mass of Herbage Allocation
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DOI：
10.3390/ani9110961
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发表时间：
2019-11-01
期刊：
影响因子：
3
通讯作者：
Pulido, Ruben G.
中科院分区：
文献类型：
--
作者：
Beltran, Ignacio E.;Gregorini, Pablo;Pulido, Ruben G.
放牧奶牛氮素利用率低，导致尿氮排泄量高，增加温室气体排放。这一问题与高氮和低能量摄入，增加瘤胃氨（NH3）浓度，从而增加尿氮排泄有关。在这种情况下，重要的是要发现营养和放牧管理策略，使减少尿氮排泄在牧场。本研究探讨了牧草分配时间和牧草质量的变化是否会改变泌乳奶牛尿氮浓度和瘤胃NH3的日变化规律。结果表明，牧草分配时间和牧草量的组合对瘤胃NH_3的产生和尿氮浓度有明显的影响。结果表明，在上午和下午挤奶后，将奶牛在挤奶厅的畜栏中保持两小时，可以在氮浓度峰值期间收集泥浆池中奶牛的尿液，在尿氮浓度降低的时间将奶牛送回牧场。摘要本研究的目的是评估牧草分配时间和牧草质量（HM）（低（L））或中等（M））对泌乳奶牛尿氮（N）和瘤胃氨（NH_3）的日变化有一定的影响。选用4头装有瘤胃瘘管的荷斯坦黑白花奶牛，随机分为4组：1）上午低草量组（L-AM）（早上挤奶后获得新的牧草分配，牧草质量（HM）为2000 kg DM/ha）; 2）下午牧草质量低（L-PM）（下午挤奶后，以2000 kg DM/ha的HM获得新的牧草分配）; 3）上午的中等牧草质量（M-AM）（在早晨挤奶后获得新的牧草分配，HM为3000 kg DM/ha）;和4）下午中等牧草质量（M-PM）（下午挤奶后获得新的牧草分配，HM为3000 kg DM/ha）。采用4 × 4拉丁方设计（4个处理、4头奶牛和4个实验期）评价处理效果。在13：00和16：00 h时，L-AM的瘤胃NH3浓度高于L-PM和M-PM。与L-AM相比，M-AM的尿尿素和N浓度较低。在10：00时，L-AM的尿氮浓度高于其他处理，在16：00时，M-PM的尿氮浓度高于M-AM。结果表明，对于L-AM，在上午补充草青贮饲料后将奶牛保持在挤奶厅的保持围栏中2小时，对于M-PM，在下午补充草青贮饲料后保持奶牛保持围栏中2小时，可以允许在保持围栏中收集奶牛的尿液，并在峰值N浓度期间将尿液储存在泥浆池中，在一天中尿氮浓度降低的时间将奶牛送回牧场。
Simple Summary Low nitrogen use efficiency in grazing dairy cows leads to high urinary N excretion, which contributes to greenhouse gases emission. This problem has been associated with high N and low energy intake, increasing rumen ammonia (NH3) concentration, and thereby, increasing urinary N excretion. Under this situation, it is important to discover nutritional and grazing management strategies that allow reduced urine N excretion in the pasture. This study evaluated whether changes in time of herbage allocation and herbage mass modify the diurnal pattern of urinary nitrogen (N) concentration and ruminal NH3 of lactating dairy cows. We found that the combination of time of herbage allocation and herbage mass modified rumen NH3 production and urinary N concentration. Results suggest that maintaining cows in the holding pen at the milking parlor for two hours after morning and afternoon milking could allow collection of urine from cows in the slurry pit during peak N concentration, returning cows to the pasture at a time of day when urinary N concentration is decreased.Abstract The objective of this work was to evaluate whether changes in time of herbage allocation and herbage mass (HM) (low (L) or medium (M)) modify the diurnal pattern of urinary nitrogen (N) concentration and ruminal ammonia (NH3) of lactating dairy cows. Four Holstein-Friesian cows fitted with rumen cannula were randomly allocated to one of four treatments: 1) low herbage mass in the morning (L-AM) (Access to new herbage allocation after morning milking with a herbage mass (HM) of 2000 kg DM/ha); 2) low herbage mass in the afternoon (L-PM) (Access to new herbage allocation after afternoon milking with a HM of 2000 kg DM/ha); 3) medium herbage mass in the morning (M-AM) (Access to new herbage allocation after morning milking with a HM of 3000 kg DM/ha); and 4) medium herbage mass in the afternoon (M-PM) (Access to new herbage allocation after afternoon milking with a HM of 3000 kg DM/ha). A four by four Latin Square design with four treatments, four cows, and four experimental periods was used to evaluate treatment effects. Rumen NH3 concentration was greater for L-AM compared to L-PM and M-PM at 13:00 and 16:00 h. Urine urea and N concentrations were lower for M-AM compared to L-AM. Urine N concentration was greater for L-AM than other treatments at 10:00 hours and greater for M-PM compared to M-AM at 16:00 hours. Results suggest that maintaining the cows in the holding pen at the milking parlor for two hours after morning grass silage supplementation for L-AM and for two hours after afternoon grass silage supplementation for M-PM, could allow collection of urine from cows at the holding pen and storage of urine in the slurry pit during the time of peak N concentration, returning cows to the pasture at a time of day when urinary N concentration is decreased.