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Hristov AN, Bannink A, Crompton LA, Huhtanen P, Kreuzer M, McGee M, Nozière P, Reynolds CK, Bayat AR, Yáñez-Ruiz DR, Dijkstra J, Kebreab E, Schwarm A, Shingfield KJ, Yu Z. Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques. J Dairy Sci 2019; 102:5811-5852. [PMID: 31030912 DOI: 10.3168/jds.2018-15829] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 02/27/2019] [Indexed: 01/17/2023]
Abstract
Nitrogen is a component of essential nutrients critical for the productivity of ruminants. If excreted in excess, N is also an important environmental pollutant contributing to acid deposition, eutrophication, human respiratory problems, and climate change. The complex microbial metabolic activity in the rumen and the effect on subsequent processes in the intestines and body tissues make the study of N metabolism in ruminants challenging compared with nonruminants. Therefore, using accurate and precise measurement techniques is imperative for obtaining reliable experimental results on N utilization by ruminants and evaluating the environmental impacts of N emission mitigation techniques. Changeover design experiments are as suitable as continuous ones for studying protein metabolism in ruminant animals, except when changes in body weight or carryover effects due to treatment are expected. Adaptation following a dietary change should be allowed for at least 2 (preferably 3) wk, and extended adaptation periods may be required if body pools can temporarily supply the nutrients studied. Dietary protein degradability in the rumen and intestines are feed characteristics determining the primary AA available to the host animal. They can be estimated using in situ, in vitro, or in vivo techniques with each having inherent advantages and disadvantages. Accurate, precise, and inexpensive laboratory assays for feed protein availability are still needed. Techniques used for direct determination of rumen microbial protein synthesis are laborious and expensive, and data variability can be unacceptably large; indirect approaches have not shown the level of accuracy required for widespread adoption. Techniques for studying postruminal digestion and absorption of nitrogenous compounds, urea recycling, and mammary AA metabolism are also laborious, expensive (especially the methods that use isotopes), and results can be variable, especially the methods based on measurements of digesta or blood flow. Volatile loss of N from feces and particularly urine can be substantial during collection, processing, and analysis of excreta, compromising the accuracy of measurements of total-tract N digestion and body N balance. In studying ruminant N metabolism, nutritionists should consider the longer term fate of manure N as well. Various techniques used to determine the effects of animal nutrition on total N, ammonia- or nitrous oxide-emitting potentials, as well as plant fertilizer value, of manure are available. Overall, methods to study ruminant N metabolism have been developed over 150 yr of animal nutrition research, but many of them are laborious and impractical for application on a large number of animals. The increasing environmental concerns associated with livestock production systems necessitate more accurate and reliable methods to determine manure N emissions in the context of feed composition and ruminant N metabolism.
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Affiliation(s)
- A N Hristov
- Department of Animal Science, The Pennsylvania State University, University Park 16802.
| | - A Bannink
- Wageningen Livestock Research, Wageningen University & Research, PO Box 338, 6700 AH Wageningen, the Netherlands
| | - L A Crompton
- School of Agriculture, Policy and Development, Centre for Dairy Research, University of Reading, PO Box 237 Earley Gate, Reading RG6 6AR, United Kingdom
| | - P Huhtanen
- Department of Agricultural Science, Swedish University of Agricultural Sciences, S-90, Umeå, Sweden
| | - M Kreuzer
- ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland
| | - M McGee
- Teagasc, Animal & Grassland Research and Innovation Centre, Grange, Dunsany, Co. Meath, Ireland C15 PW93
| | - P Nozière
- Université Clermont Auvergne, INRA, VetAgro Sup, UMR Herbivores, F-63122 Saint-Genès-Champanelle, France
| | - C K Reynolds
- School of Agriculture, Policy and Development, Centre for Dairy Research, University of Reading, PO Box 237 Earley Gate, Reading RG6 6AR, United Kingdom
| | - A R Bayat
- Milk Production Solutions, Production Systems, Natural Resources Institute Finland (Luke), FI 31600 Jokioinen, Finland
| | - D R Yáñez-Ruiz
- Estación Experimental del Zaidín (CSIC), Profesor Albareda, 1, 18008, Granada, Spain
| | - J Dijkstra
- Animal Nutrition Group, Wageningen University & Research, PO Box 338, 6700 AH, Wageningen, the Netherlands
| | - E Kebreab
- Department of Animal Science, University of California, Davis 95616
| | - A Schwarm
- ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland
| | - K J Shingfield
- Milk Production Solutions, Production Systems, Natural Resources Institute Finland (Luke), FI 31600 Jokioinen, Finland; Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3EB, United Kingdom
| | - Z Yu
- Department of Animal Sciences, The Ohio State University, Columbus 43210
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Hristov AN. Comparative characterization of reticular and duodenal digesta and possibilities of estimating microbial outflow from the rumen based on reticular sampling in dairy cows. J Anim Sci 2007; 85:2606-13. [PMID: 17591704 DOI: 10.2527/jas.2006-852] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this experiment was to investigate the possibility of estimating the outflow of nutrients and microbial protein from the rumen based on sampling reticular contents as an alternative to duodenal sampling. Microbial protein flow estimates were also compared with a third method based on sampling of ruminal contents. Reticular and duodenal digesta and ruminal contents were recovered from 4 cows used in a 4 x 4 Latin square design experiment, in which the ruminal effects of 4 exogenous enzyme preparations were studied. Large and small particulate and fluid markers were used to estimate digesta flow in a triple-marker model; 15N was used as a microbial marker. Reticular and duodenal digesta were segregated into small and large particles (SP and LP, respectively) and a fluid phase, and ruminal digesta was segregated into particulate and fluid phases. Compared with digesta recovered at the duodenum, reticular digesta had lower OM and greater NDF contents. The proportion of microbial N was notably greater in the fluid phase of reticular digesta. Ruminal outflow of DM and OM was greater (by 17 and 28%) and that of NDF was lower (by 14%) when estimated from duodenal compared with reticular samples. There was no difference in the estimated flow of starch and nonammonia and microbial N between the reticular and duodenal techniques. Microbial N flow estimated based on ruminal sampling was similar to those based on duodenal and reticular sampling. The ruminal method, however, grossly overestimated flow of DM, OM, and NDF. This study supports the concept that microbial protein outflow from the rumen can be measured based on sampling of ruminal or reticular digesta. The reticular sampling technique can also provide reliable estimates for ruminal digestibility of OM, N, and fiber fractions. These findings need to be confirmed in experiments with basal diets varying in structure and forage-to-concentrate ratios.
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Affiliation(s)
- A N Hristov
- Department of Animal and Veterinary Science, University of Idaho, Moscow 83844-2330, USA.
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