Recent advances in estimating protein and energy requirements of ruminants
L. O. Tedeschi A D , M. L. Galyean B and K. E. Hales C
+ Author Affiliations
- Author Affiliations
A Department of Animal Science, Texas A&M University, College Station, TX 77843-2471, USA.
B Office of the Provost, Texas Tech University, Lubbock 79409-2019, USA.
C USDA, ARS, US Meat Animal Research Center, Clay Center, NE 68933, USA.
D Corresponding author. Email: luis.tedeschi@tamu.edu
Animal Production Science 57(11) 2237-2249 https://doi.org/10.1071/AN17341
Submitted: 22 May 2017 Accepted: 18 July 2017 Published: 18 August 2017
Abstract
Considerable efforts have been made in gathering scientific data and developing feeding systems for ruminant animals in the past 50 years. Future endeavours should target the assessment, interpretation and integration of the accumulated knowledge to develop nutrition models in a holistic and pragmatic manner. We highlight some of the areas that need improvement. A fixed metabolisable-to-digestible energy ratio is an oversimplification and does not represent the diversity of existing feedstock, but, at the same time, we must ensure the internal consistency and dependency of the energy system in models. For grazing animals, although data exist to compute energy expenditure associated with walking in different terrains, nutrition models must incorporate the main factors that initiate and control grazing. New equations have been developed to predict microbial crude protein (MCP) production, but efforts must be made to account for the diversity of the rumen microbiome. There is large and unexplained variation in the efficiency of MCP synthesis (9.81–16.3 g MCP/100 g of fermentable organic matter). Given the uncertainties in the determination of MCP, current estimates of metabolisable protein required for maintenance are biased. The use of empirical equations to predict MCP, which, in turn, is used to estimate metabolisable protein intake, is risky because it establishes a dependency between these estimates and creates a specificity that is not appropriate for mechanistic systems. Despite the existence of data and knowledge about the partitioning of retained energy into fat and protein, the prediction of retained protein remains unsatisfactory, and is even less accurate when reported data on the efficiency of use of amino acids are employed in the predictive equations. The integrative approach to develop empirical mechanistic nutrition models has introduced interconnected submodels, which can destabilise the predictability of the model if changed independently.
Additional keywords: computer, development, evaluation, refinement, simulation.
References
Agricultural and Food Research Council (1992) AFRC Technical Committee on Responses to Nutrients, report 9: nutritive requirements of ruminant animals: protein. Nutrition Abstracts and Reviews (Series B: Livestock Feeds and Feeding) 62, 787–835.Agricultural and Food Research Council (Ed. G Alderman) (1993) ‘Energy and protein requirements of ruminants.’ (Agricultural and Food Research Council, and CABI Publishing: Wallingford, UK).
Agricultural Research Council (1980) ‘The nutrient requirements of ruminant livestock.’ (Agricultural Research Council, and The Gresham Press: London, UK).
Ainslie SJ, Fox DG, Perry TC, Ketchen DJ, Barry MC (1993) Predicting amino acid adequacy of diets fed to Holstein steers. Journal of Animal Science 71, 1312–1319.
Arriola Apelo SI, Knapp JR, Hanigan MD (2014) Invited review: current representation and future trends of predicting amino acid utilization in the lactating dairy cow. Journal of Dairy Science 97, 4000–4017.
| Invited review: current representation and future trends of predicting amino acid utilization in the lactating dairy cow.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXmvVWrsb4%3D&md5=359333d7474d1616bc5ecbcf966e6d6eCAS |
Bach A, Calsamiglia S, Stern MD (2005) Nitrogen metabolism in the rumen. Journal of Dairy Science 88, E9–E21.
| Nitrogen metabolism in the rumen.Crossref | GoogleScholarGoogle Scholar |
Bequette BJ, Hanigan MD, Calder AG, Reynolds CK, Lobley GE, MacRae JC (2000) Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production. Journal of Dairy Science 83, 765–775.
| Amino acid exchange by the mammary gland of lactating goats when histidine limits milk production.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXivFWlt7g%3D&md5=44558b3d192fc3d494ca4b0a5ec83358CAS |
Blaxter KL (1962) ‘The energy metabolism of ruminants.’ (Hutchinson: London).
Brouwer E (1965) Report of the sub-committee on constants and factors. In ‘Proceedings of the 3rd symposium of energy metabolism’. (Ed. KL Blaxter) pp. 441–443. (Academic Press: Troon, Scotland).
Burroughs W, Trenkle A, Vetter RL (1974) A system of protein evaluation for cattle and sheep involving metabolizable protein (amino acids) and urea fermentation potential of feedstuffs. Veterinary Medicine, Small Animal Clinician 69, 713–722.
Carro MD, Miller EL (1999) Effect of supplementing a fibre basal diet with different nitrogen forms on ruminal fermentation and microbial growth in an in vitro semi-continuous culture system (RUSITEC). British Journal of Nutrition 82, 149–157.
| Effect of supplementing a fibre basal diet with different nitrogen forms on ruminal fermentation and microbial growth in an in vitro semi-continuous culture system (RUSITEC).Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1MXltlelu7w%3D&md5=d0f313b0cc3399196afc0a0e0de6148bCAS |
Cartwright SJ, Bowgen KM, Collop C, Hyder K, Nabe-Nielsen J, Stafford R, Stillman RA, Thorpe RB, Sibly RM (2016) Communicating complex ecological models to non-scientist end users. Ecological Modelling 338, 51–59.
| Communicating complex ecological models to non-scientist end users.Crossref | GoogleScholarGoogle Scholar |
Commonwealth Scientific and Industrial Research Organization (1990) ‘Feeding standards for Australian livestock. Ruminants.’ (CSIRO: Melbourne).
Commonwealth Scientific and Industrial Research Organization (2007) ‘Nutrient requirements of domesticated ruminants.’ (CSIRO: Melbourne).
Czerkawski JW (1987) Reassessment of the contribution of protozoa to the microbial protein supply to the host ruminant animal. Journal of Theoretical Biology 126, 335–341.
| Reassessment of the contribution of protozoa to the microbial protein supply to the host ruminant animal.Crossref | GoogleScholarGoogle Scholar |
Eisemann JH, Tedeschi LO (2016) Predicting the amount of urea nitrogen recycled and used for anabolism in growing cattle. The Journal of Agricultural Science 154, 1118–1129.
| Predicting the amount of urea nitrogen recycled and used for anabolism in growing cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtFCkurfF&md5=216b1477f1f103f4f96b7ed1b7b90a6dCAS |
Ferrell CL, Oltjen JW (2008) ASAS centennial paper: net energy systems for beef cattle: concepts, application, and future models. Journal of Animal Science 86, 2779–2794.
| ASAS centennial paper: net energy systems for beef cattle: concepts, application, and future models.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXht1ams7nI&md5=586adcd2ee3212bde2702527f29733ebCAS |
Fox DG, Tedeschi LO, Tylutki TP, Russell JB, Van Amburgh ME, Chase LE, Pell AN, Overton TR (2004) The Cornell Net Carbohydrate and Protein System model for evaluating herd nutrition and nutrient excretion. Animal Feed Science and Technology 112, 29–78.
| The Cornell Net Carbohydrate and Protein System model for evaluating herd nutrition and nutrient excretion.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXmvFymsQ%3D%3D&md5=d548ba44c4e36faaa3a8a6114dc557e4CAS |
France J, Theodorou MK, Davies D (1990) Use of zoospore concentrations and life cycle parameters in determining the population of anaerobic fungi in the rumen ecosystem. Journal of Theoretical Biology 147, 413–422.
| Use of zoospore concentrations and life cycle parameters in determining the population of anaerobic fungi in the rumen ecosystem.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK3M7lsFeqtA%3D%3D&md5=1a891727bb7d3fa1c7a2111c8b00a467CAS |
Galyean ML (2014) Invited review: nutrient requirements of ruminants: derivation, validation, and application. The Professional Animal Scientist 30, 125–128.
| Invited review: nutrient requirements of ruminants: derivation, validation, and application.Crossref | GoogleScholarGoogle Scholar |
Galyean ML, Tedeschi LO (2014) Predicting microbial protein synthesis in beef cattle: relationship to intakes of total digestible nutrients and crude protein. Journal of Animal Science 92, 5099–5111.
| Predicting microbial protein synthesis in beef cattle: relationship to intakes of total digestible nutrients and crude protein.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXisFWju7c%3D&md5=84d46fa7a4d42d15d23e3d3533094ec3CAS |
Galyean ML, Cole NA, Tedeschi LO, Branine ME (2016) Board-invited review: efficiency of converting digestible energy to metabolizable energy and reevaluation of the California Net Energy System maintenance requirements and equations for predicting dietary net energy values for beef cattle. Journal of Animal Science 94, 1329–1341.
| Board-invited review: efficiency of converting digestible energy to metabolizable energy and reevaluation of the California Net Energy System maintenance requirements and equations for predicting dietary net energy values for beef cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhsVektbzE&md5=3ca4c875e97181f9ef469fc68b83bb30CAS |
Garrett WN (1980) ‘Energy utilization by growing cattle as determined in 72 comparative slaughter experiments. In ‘Proceedings of the 8th symposium on energy metabolism of farm animals’, no. 26. (Ed. LE Mount) pp. 3–7. (Butterworths & Co.: Cambridge, UK).
Garrett WN (1987) Relationship between energy metabolism and the amounts of protein and fat deposited in growing cattle. In ‘Proceedings of the 10th symposium on energy metabolism of farm animals’. (Eds PW Moe, HF Tyrrell, PJ Reynolds) pp. 98–101. (Rowman & Littlefield: Airlie, VA).
Garrett RP, Hinman H (1969) Re-evaluation of the relationship between carcass density and body composition of beef steers. Journal of Animal Science 28, 1–5.
| Re-evaluation of the relationship between carcass density and body composition of beef steers.Crossref | GoogleScholarGoogle Scholar |
Godoy-Vitorino F, Gao Z, Pei Z, Blaser MJ, Ley RE, Gordon JI, Pericchi LR, Ortiz H, Garcia-Amado MA, Michelangeli F, Dominguez-Bello MG (2006) ‘Molecular diversity of bacteria and fungi in the crop of a south-american leaf-eating bird: the hoatzin (Opisthocomus hoazin). In ‘Proceedings of the Comparative Nutrition Society’. pp. 42–47. (Keystone, CO).
Griswold KE, Hoover WH, Miller TK, Thayne WV (1996) Effect of form of nitrogen on growth of ruminal microbes in continuous culture. Journal of Animal Science 74, 483–491.
| Effect of form of nitrogen on growth of ruminal microbes in continuous culture.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK28XhslCnu70%3D&md5=b59e449e9d79ceab8001bfd9a57c7fccCAS |
Griswold KE, Apgar GA, Bouton J, Firkins JL (2003) Effects of urea infusion and ruminal degradable protein concentration on microbial growth, digestibility, and fermentation in continuous culture. Journal of Animal Science 81, 329–336.
| Effects of urea infusion and ruminal degradable protein concentration on microbial growth, digestibility, and fermentation in continuous culture.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhtFagt7w%3D&md5=9d352b9f1c447f2a85dce60682920b6eCAS |
Hales KE, Cole NA, MacDonald JC (2012) Effects of corn processing method and dietary inclusion of wet distillers grains with solubles on energy metabolism, carbon−nitrogen balance, and methane emissions of cattle. Journal of Animal Science 90, 3174–3185.
| Effects of corn processing method and dietary inclusion of wet distillers grains with solubles on energy metabolism, carbon−nitrogen balance, and methane emissions of cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XhsVKku7nK&md5=cc7fe2aa4906b3f3897585affbdd8a8bCAS |
Hales KE, Cole NA, MacDonald JC (2013) Effects of increasing concentrations of wet distillers grains with solubles in steam-flaked, corn-based diets on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle. Journal of Animal Science 91, 819–828.
| Effects of increasing concentrations of wet distillers grains with solubles in steam-flaked, corn-based diets on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXlvVKmsrs%3D&md5=824ff7e835a1f02ed99396b1a032d7b2CAS |
Hales KE, Brown-Brandl TM, Freetly HC (2014) Effects of decreased dietary roughage concentration on energy metabolism and nutrient balance in finishing beef cattle. Journal of Animal Science 92, 264–271.
| Effects of decreased dietary roughage concentration on energy metabolism and nutrient balance in finishing beef cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXht12ntbo%3D&md5=486efae47fef653b4164be77b3d74322CAS |
Hales KE, Foote AP, Brown-Brandl TM, Freetly HC (2015a) Effects of dietary glycerin inclusion at 0, 5, 10, and 15 percent of dry matter on energy metabolism and nutrient balance in finishing beef steers. Journal of Animal Science 93, 348–356.
| Effects of dietary glycerin inclusion at 0, 5, 10, and 15 percent of dry matter on energy metabolism and nutrient balance in finishing beef steers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXkt1Wrsbk%3D&md5=38dc793f4a40c1523231f2d2bfcd5c66CAS |
Hales KE, Jaderborg JP, Crawford GI, DiCostanzo A, Spiehs MJ, Brown-Brandl TM, Freetly HC (2015b) Effects of dry-rolled or high-moisture corn with twenty-five or forty-five percent wet distillers’ grains with solubles on energy metabolism, nutrient digestibility, and macromineral balance in finishing beef steers. Journal of Animal Science 93, 4995–5005.
| Effects of dry-rolled or high-moisture corn with twenty-five or forty-five percent wet distillers’ grains with solubles on energy metabolism, nutrient digestibility, and macromineral balance in finishing beef steers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XjsVOnt7c%3D&md5=1efd097c61cc6090661c16dc03d9b06cCAS |
Hales KE, Foote AP, Brown-Brandl TM, Freetly HC (2017) The effects of feeding increasing concentrations of corn oil on energy metabolism and nutrient balance in finishing beef steers. Journal of Animal Science 95, 939–948.
| The effects of feeding increasing concentrations of corn oil on energy metabolism and nutrient balance in finishing beef steers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2sXhtV2js7rO&md5=1883266666658ff1f64471ab97753eefCAS |
Hall MB, Huntington GB (2008) Nutrient synchrony: sound in theory, elusive in practice. Journal of Animal Science 86, E287–E292.
| Nutrient synchrony: sound in theory, elusive in practice.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD1c3lsVyqsQ%3D%3D&md5=7b9e40afe1f3ff3936900384bb896bc7CAS |
Hanigan MD, Cant JP, Weakley DC, Beckett JL (1998) An evaluation of postabsorptive protein and amino acid metabolism in the lactating dairy cow. Journal of Dairy Science 81, 3385–3401.
| An evaluation of postabsorptive protein and amino acid metabolism in the lactating dairy cow.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1MXjvVantA%3D%3D&md5=d9fe60189602c44f46aa91b82c4d4538CAS |
Hespell RB, Bryant MP (1979) Efficiency of rumen microbial growth: influence of some theoretical and experimental factors on YATP. Journal of Animal Science 49, 1640–1659.
| Efficiency of rumen microbial growth: influence of some theoretical and experimental factors on YATP.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaL3cXhtVOjt7w%3D&md5=c56eca28796386888f03d864d1805018CAS |
Hobson PN, Stewart CS (1997) ‘The rumen microbial ecosystem.’ (Blackie Academic & Professional: New York).
Jarrige R (Ed.) (1988) ‘Alimentation des bovins, ovins & caprins.’ (INRA-Quae: Paris).
Keren EN, Olson BE (2006) Thermal balance of cattle grazing winter range: model development. Journal of Thermal Biology 31, 371–377.
| Thermal balance of cattle grazing winter range: model development.Crossref | GoogleScholarGoogle Scholar |
Lapierre H, Lobley GE, Ouellet DR, Doepel L, Pacheco D (2007) ‘Amino acid requirements for lactating dairy cows: reconciling predictive models and biology. Proceedings of Cornell nutrition conference for feed manufacturers.’ (New York State College of Agriculture & Life Sciences, Cornell University: Syracuse, NY).
Lardy GP, Adams DC, Klopfenstein TJ, Patterson HH (2004) Building beef cow nutritional programs with the 1996 NRC beef cattle requirements model. Journal of Animal Science 82, E83–E92.
Leng RA, Nolan JV (1984) Nitrogen metabolism in the rumen. Journal of Dairy Science 67, 1072–1089.
| Nitrogen metabolism in the rumen.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaL2cXkt1ahtbo%3D&md5=578f7884ddfd561b5fb0f9ce6b2dada7CAS |
Lobley GE, Bremmer DM, Zuur G (2000) Effects of diet quality on urea fates in sheep as assessed by refined, non-invasive [15N15N]urea kinetics. British Journal of Nutrition 84, 459–468.
| Effects of diet quality on urea fates in sheep as assessed by refined, non-invasive [15N15N]urea kinetics.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXotV2mtLk%3D&md5=2ab825a317929c28cea4b19e483b74b9CAS |
Lofgreen GP (1965) A comparative slaughter technique for determining net energy values with beef cattle. In ‘Proceedings of the 3rd symposium of energy metabolism’. (Ed. KL Blaxter) pp. 309–317. (Academic Press: Troon, Scotland).
Lofgreen GP, Garrett WN (1968) A system for expressing net energy requirements and feed values for growing and finishing beef cattle. Journal of Animal Science 27, 793–806.
| A system for expressing net energy requirements and feed values for growing and finishing beef cattle.Crossref | GoogleScholarGoogle Scholar |
Marini JC, Van Amburgh ME (2003) Nitrogen metabolism and recycling in Holstein heifers. Journal of Animal Science 81, 545–552.
| Nitrogen metabolism and recycling in Holstein heifers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhsFKht78%3D&md5=395f7104b9d67c3b7bf5515509d6b046CAS |
Matsuda I, Murai T, Clauss M, Yamada T, Tuuga A, Bernard H, Higashi S (2011) Regurgitation and remastication in the foregut-fermenting proboscis monkey (Nasalis larvatus). Biology Letters 7, 786–789.
| Regurgitation and remastication in the foregut-fermenting proboscis monkey (Nasalis larvatus).Crossref | GoogleScholarGoogle Scholar |
Mazanov A, Nolan JV (1976) Simulation of the dynamics of nitrogen metabolism in sheep. British Journal of Nutrition 35, 149–174.
| Simulation of the dynamics of nitrogen metabolism in sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaE28XntF2mtw%3D%3D&md5=194ceb44bdf4cbdb807267b5a0ea4e5cCAS |
Moe PW, Tyrrell HF, Flatt WP (1970) Partial efficiency of energy use for maintenance, lactation, body gain and gestation in the dairy cow. In ‘Proceedings of the 5th energy metabolism of farm animals’. (Eds A Schürch, C Wenk) pp. 65–68. (EAAP: Vitznau, Switzerland).
National Academies of Sciences, Engineering, and Medicine (2016) ‘Nutrient requirements of beef cattle.’ (National Academy Press: Washington, DC).
National Research Council (1981) ‘Effect of environment on nutrient requirements of domestic animals.’ (National Academy Press: Washington, DC).
National Research Council (1984) ‘Nutrient requirements of beef cattle.’ (National Academy Press: Washington, DC).
National Research Council (1985) ‘Ruminant nitrogen usage.’ (National Academy Press: Washington, DC).
National Research Council (1996) ‘Nutrient requirements of beef cattle.’ (National Academy Press: Washington, DC).
National Research Council (2000) ‘Nutrient requirements of beef cattle.’ (National Academy Press: Washington, DC).
National Research Council (2001) ‘Nutrient requirements of dairy cattle.’ (National Academy Press: Washington, DC).
Nolan JV, Dobos RC (2005) Nitrogen transactions in ruminants. In ‘Quantitative aspects of ruminant digestion and metabolism’. (Eds J Dijkstra, JM Forbes, J France) pp. 177–206. (CABI Publishing: Wallingford, UK).
Nolan JV, Leng RA (1972) Dynamic aspects of ammonia and urea metabolism in sheep. British Journal of Nutrition 27, 177–194.
| Dynamic aspects of ammonia and urea metabolism in sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaE38XpslartQ%3D%3D&md5=78695b66d3c30977ac5f107fb3c4e491CAS |
Oba M, Allen MS (2003) Effects of diet fermentability on efficiency of microbial nitrogen production in lactating dairy cows. Journal of Dairy Science 86, 195–207.
| Effects of diet fermentability on efficiency of microbial nitrogen production in lactating dairy cows.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhtlCksbo%3D&md5=204e87c0d463b7e23c9a6042ab7d2638CAS |
Oldham JD (1987) Efficiencies of amino acid utilization. In ‘Feed evaluation and protein requirement systems for ruminants’. (Eds R Jarrige, G Alderman) pp. 171–186. (Commission of the European Communities: Brussels).
Petersen MK, Mueller CJ, Mulliniks JT, Roberts AJ, DelCurto T, Waterman RC (2014) Beef species symposium: potential limitations of NRC in predicting energetic requirements of beef females within western US grazing systems. Journal of Animal Science 92, 2800–2808.
| Beef species symposium: potential limitations of NRC in predicting energetic requirements of beef females within western US grazing systems.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhtFyrt77M&md5=04a64284a43f69ef649b2a2ac4b02d83CAS |
Reid JT, Wellington GH, Dunn HO (1955) Some relationships among the major chemical components of the bovine body and their application to nutritional investigations. Journal of Dairy Science 38, 1344–1359.
| Some relationships among the major chemical components of the bovine body and their application to nutritional investigations.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaG28XitVylsA%3D%3D&md5=afdf0e48e23c0168ea81258de6ee20dbCAS |
Reynolds CK, Kristensen NB (2008) Nitrogen recycling through the gut and the nitrogen economy of ruminants: an asynchronous symbiosis. Journal of Animal Science 86, E293–E305.
| Nitrogen recycling through the gut and the nitrogen economy of ruminants: an asynchronous symbiosis.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD1c3lsVyrsg%3D%3D&md5=b38af6131b9cb8a7a53234a62709f2f8CAS |
Rotta PP, Menezes ACB, Costa e Silva LF, Valadares Filho SC, Prados LF, Marcondes MI (2016) Protein requirements for beef cattle. In ‘Nutrient requirements of Zebu and crossbred cattle: BR-Corte’. (Eds SC Valadares Filho, LF Costa e Silva, MP Gionbelli, pp. Rotta, MI Marcondes, ML Chizzotti, LF Prados) pp. 185–212. (Suprema Gráfica e Editora Ltda: Viçosa, MG, Brazil).
Roy JHB, Balch CC, Miller EL, Ørskov ER, Smith RH (1977) Calculation of the N requirement for ruminants from nitrogen metabolism studies. In ‘Proceedings of the 2nd international symposium on protein metabolism and nutrition’ (Ed. S Tamminga) (EAAP Publication: Flevohoff, The Netherlands).
Ruiz R, Tedeschi LO, Marini JC, Fox DG, Pell AN, Jarvis G, Russell JB (2002) The effect of a ruminal nitrogen (N) deficiency in dairy cows: evaluation of the Cornell Net Carbohydrate and Protein System ruminal N deficiency adjustment. Journal of Dairy Science 85, 2986–2999.
| The effect of a ruminal nitrogen (N) deficiency in dairy cows: evaluation of the Cornell Net Carbohydrate and Protein System ruminal N deficiency adjustment.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38Xptlagt70%3D&md5=d9b1f00799adabb96cd282c5c33c5470CAS |
Schroeder GF, Titgemeyer EC, Awawdeh MS, Smith JS, Gnad DP (2006a) Effects of energy level on methionine utilization by growing steers. Journal of Animal Science 84, 1497–1504.
| Effects of energy level on methionine utilization by growing steers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XkvFOqsL8%3D&md5=3e600e276c2c9ff35041589a0c9dab68CAS |
Schroeder GF, Titgemeyer EC, Awawdeh MS, Smith JS, Gnad DP (2006b) Effects of energy source on methionine utilization by growing steers. Journal of Animal Science 84, 1505–1511.
| Effects of energy source on methionine utilization by growing steers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XkvFOqsLw%3D&md5=4c60b928c7a372fbc1d522d4b8254e01CAS |
Schwab CG, Huhtanen P, Hunt CW, Hvelplund T (2005) Nitrogen requirements of cattle. In ‘Nitrogen and phosphorus nutrition of cattle: reducing the environmental impact of cattle operations’. (Eds E Pfeffer, AN Hristov) pp. 13–70. (CABI Publishing: Wallingford, UK).
Smith RH (1969) Nitrogen metabolism and the rumen. The Journal of Dairy Research 36, 313–331.
| Nitrogen metabolism and the rumen.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaF1MXksFynsb4%3D&md5=76d00ee8c0006a6655e1d008d1796d05CAS |
Smuts DB (1935) The relation between the basal metabolism and the endogenous nitrogen metabolism, with particular reference to the estimation of the maintenance requirement of protein. The Journal of Nutrition 9, 403–433.
Stern MD, Hoover WH (1979) Methods for determining and factors affecting rumen microbial protein synthesis: a review. Journal of Animal Science 49, 1590–1603.
| Methods for determining and factors affecting rumen microbial protein synthesis: a review.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaL3cXntlWrtQ%3D%3D&md5=1fd349b600290b1eabf3462267c0fe0aCAS |
Tedeschi LO (2006) Assessment of the adequacy of mathematical models. Agricultural Systems 89, 225–247.
| Assessment of the adequacy of mathematical models.Crossref | GoogleScholarGoogle Scholar |
Tedeschi LO, Fox DG (2015) Energy and nutrient requirements of grazing and confined growing beef cattle: refining the assessment of energy expenditure for grazing animals. In ‘Proceedings of the X NESPRO Meeting and II International Symposium on Beef Cattle Production Systems’, Porto Alegre, RS, Brazil. (Eds GR Pereira, TE de Oliveira, JOJ Barcellos) pp. 21–56. (Universidade Federal do Rio Grande do Sul (UFRGS)) Available at http://www.ufrgs.br/nespro/ [Verified 25 May 2016]
Tedeschi LO, Fox DG (2016) ‘The Ruminant Nutrition System: an applied model for predicting nutrient requirements and feed utilization in ruminants.’ (XanEdu: Acton, MA).
Tedeschi LO, Cavalcanti LFL, Fonseca MA, Herrero M, Thornton PK (2014) The evolution and evaluation of dairy cattle models for predicting milk production: an agricultural model intercomparison and improvement project (AgMIP) for livestock. Animal Production Science 54, 2052–2067.
Tedeschi LO, Fox DG, Fonseca MA, Cavalcanti LFL (2015a) Invited review: models of protein and amino acid requirements for cattle. Revista Brasileira de Zootecnia 44, 109–132.
| Invited review: models of protein and amino acid requirements for cattle.Crossref | GoogleScholarGoogle Scholar |
Tedeschi LO, Muir JP, Riley DG, Fox DG (2015b) The role of ruminant animals in sustainable livestock intensification programs. International Journal of Sustainable Development and World Ecology 22, 452–465.
Tedeschi LO, Almeida AK, Atzori AS, Muir JP, Fonseca MA, Cannas A (2017a) A glimpse of the future in animal nutrition science. 1. Past and future challenges. Revista Brasileira de Zootecnia 46, 438–451.
Tedeschi LO, Fonseca MA, Muir JP, Poppi DP, Carstens GE, Angerer JP, Fox DG (2017b) A glimpse of the future in animal nutrition science. 2. Current and future solutions. Revista Brasileira de Zootecnia 46, 452–469.
Titgemeyer EC (2003) Amino acid utilization by growing and finishing ruminants. In ‘Amino acids in animal nutrition’. (Ed. JPF D’Mello) pp. 329–346. (CABI Publishing: Cambridge, MA).
Titgemeyer EC (2012) ‘Protein and amino acids for growth. Proceedings of the joint annual meeting of American Society of Animal Science and American Dairy Science Association.’ (Federation of Animal Science Societies: Phoenix, AZ) Available at http://www.jtmtg.org/2012/abstracts.asp [Verified 21 May 2016]
Tylutki TP, Fox DG, Anrique RG (1994) Predicting net energy and protein requirements for growth of implanted and nonimplanted heifers and steers and nonimplanted bulls varying in body size. Journal of Animal Science 72, 1806–1813.
Vermorel M, Bickel H (1980) Utilisation of feed energy by growing ruminants. Annales de Zootechnie 29, 127–143.
| Utilisation of feed energy by growing ruminants.Crossref | GoogleScholarGoogle Scholar |
Waldo DR (1968) Nitrogen metabolism in the ruminant. Journal of Dairy Science 51, 265–275.
| Nitrogen metabolism in the ruminant.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaF1c7ltl2mug%3D%3D&md5=be906550a879519be0ab101dbdd97413CAS |
Walker ND, Newbold CJ, Wallace RJ (2005) Nitrogen metabolism in the rumen. In ‘Nitrogen and phosphorus nutrition of cattle: reducing the environmental impact of cattle operations’. (Eds E Pfeffer, AN Hristov) pp. 71–115. (CABI Publishing: Wallingford, UK).
Waterman RC, Caton JS, Löest CA, Petersen MK, Roberts AJ (2014) Beef species symposium: an assessment of the 1996 Beef NRC: metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems. Journal of Animal Science 92, 2785–2799.
| Beef species symposium: an assessment of the 1996 Beef NRC: metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhtFyrtrfF&md5=ed4d5219cda0c5aca7b38be4bd3f83f4CAS |
Wilkerson VA, Klopfenstein TJ, Britton RA, Stock RA, Miller PS (1993) Metabolizable protein and amino acid requirements of growing cattle. Journal of Animal Science 71, 2777–2784.
