Affiliation:
1. Animal Nutrition and Rangeland Management in the Tropics and Subtropics University of Hohenheim Stuttgart Germany
2. Institute of Animal Nutrition and Physiology Christian‐Albrechts‐Universität zu Kiel Kiel Germany
3. Department of Animal Science University of El Salvador San Salvador El Salvador
4. Doctoral and Master Program on Sciences of Production and Animal Health National Autonomous University of Mexico Mexico City Mexico
Abstract
AbstractThe present study aims at evaluating whether current semimechanistic models developed for temperate cattle systems can be adopted for cattle under (sub‐) tropical husbandry systems to adequately (accurately and precisely) predict total nitrogen (TN), urine nitrogen (UN), faecal nitrogen (FN) excretion and its partition into different FN fractions. Selected models were built based on the feeding recommendations for ruminants of the British (Model A), German (Model G) and French (INRA; Model I) system. Model evaluation was conducted using eight nitrogen balance studies performed in El Salvador, Kenya and Peru (n = 392 individual observations including lactating cows, heifers and steers). Concordance correlation coefficient, root mean square errors (RMSE), and mean biases were estimated to evaluate the models' adequacy in predicting nitrogen excretion. Input variables causing greatest variation in nitrogen excretion prediction were identified by a sensitivity analysis and adjusted. Model G was able to adequately (i.e., RMSE of <25% of observed mean, systematic error of <5% of the mean square error) predict TN excretion through a compensation between overestimation of UN excretion and underestimation of FN excretion. None of the models were able to adequately predict UN, FN, and different FN fractions. Model I adequately predicted FN (RMSE = 18%) when duodenal microbial crude protein flow was increased, and the intercept used to predict FN excretion was reduced from 4.30 to 3.82 g of nitrogen per kilogram of dry matter intake. These adjustments, however, were not sufficient to predict adequately UN excretion (RMSE = 38%), individual FN fractions (RMSE > 56%), and TN (RMSE = 22%) excretion, by Model I.
Subject
Animal Science and Zoology,Food Animals
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