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Forskningsartikel2024Vetenskapligt granskadÖppen tillgång

Models to predict nitrogen excretion from beef cattle fed a wide range of diets compiled from South America

Souza, Vinicius C.; Congio, Guilhermo F. S.; Rodrigues, Joao P. P.; Filho, Sebastiao C. Valadares; Silva, Flavia A. S.; Renno, Luciana N.; Reis, Ricardo A.; Cardoso, Abmael S.; Rodrigues, Paulo H. M.; Berchielli, Telma T.; Messana, Juliana D.; Cajarville, Cecilia; Granja-Salcedo, Yury T.; Borges, Ana L. C. C.; Kozloski, Gilberto, V; Rosero-Noguera, Jaime R.; Gonda, Horacio; Hristov, Alexander N.; Kebreab, Ermias

Sammanfattning

The objective of this meta-analysis was to develop and evaluate models for predicting nitrogen (N) excretion in feces, urine, and manure in beef cattle in South America. The study incorporated a total of 1,116 individual observations of N excretion in feces and 939 individual observations of N excretion in feces and in urine (g/d), representing a diverse range of diets, animal genotypes, and management conditions in South America. The dataset also included data on dry matter intake (DMI; kg/d) and nitrogen intake (NI; g/d), concentrations of dietary components, as well as average daily gain (ADG; g/d) and average body weight (BW; kg). Models were derived using linear mixed-effects regression with a random intercept for the study. Fecal N excretion was positively associated with DMI, NI, nonfibrous carbohydrates, average BW, and ADG and negatively associated with EE and CP concentration in the diet. The univariate model predicting fecal N excretion based on DMI (model 1) performed slightly better than the univariate model, which used NI as a predictor variable (model 2) with a root mean square error (RMSE) of 38.0 vs. 39.2%, the RMSE-observations SD ratio (RSR) of 0.81 vs. 0.84, and concordance correlation coefficient (CCC) of 0.53 vs. 0.50, respectively. Models predicting urinary N excretion were less accurate than those derived to predict fecal N excretion, with an average RMSE of 43.7% vs. 37.0%, respectively. Urinary and manure N excretion were positively associated with DMI, NI, CP, average BW, and ADG and negatively associated with neutral detergent fiber concentration in the diet. As opposed to fecal N excretion, the univariate model predicting urinary N excretion using NI (model 10) performed slightly better than the univariate model using DMI (model 9) as predictor variable with an RMSE of 36.0% vs. 39.7%, RSR 0.85 vs. 0.93, and CCC of 0.43 vs. 0.29, respectively. The models developed in this study are applicable for predicting N excretion in beef cattle across a broad spectrum of dietary compositions and animal genotypes in South America. The univariate model using DMI as a predictor is recommended for fecal N prediction, while the univariate model using NI is recommended for predicting urinary and manure N excretion because the use of more complex models resulted in little to no benefits. However, it may be more useful to consider more complex models that incorporate nutrient intakes and diet composition for decision-making when N excretion is a factor to be considered. Three extant equations evaluated in this study have the potential to be used in tropical conditions typical of South America to predict fecal N excretion with good precision and accuracy. However, none of the extant equations are recommended for predicting urine or manure N excretion because of their high RMSE, and low precision and accuracy.The models developed in this study to predict N excretion in beef cattle can help to improve the environmental and economic sustainability of beef production systems in South America.Reductions in nitrogen (N) excretion in beef cattle not only yield environmental advantages but also confer economic benefits associated with reduced purchase of protein feed ingredients. As measuring N excretion under farm conditions is not feasible, models that can accurately predict N excretion using variables that are more easily obtained in beef production systems are needed. A meta-regression analysis was conducted to develop models that can predict N excretion in feces, urine, and manure in beef cattle in South America. The univariate model using dry matter intake as a predictor is recommended for fecal N prediction, while the univariate model using N intake is recommended for predicting urine and manure N excretion because the use of more complex models resulted in little to no benefits. However, more complex models that incorporate nutrient intakes and diet composition might be more useful for decision-making when N excretion is a factor to be considered. Such models enable simulations of N excretion with modifications to diet composition with similar accuracy. The models developed in this study are applicable for predicting N excretion in beef cattle across a broad spectrum of dietary compositions and animal genotypes in South America.

Nyckelord

environmental impacts; grazing cattle; meta-analysis; protein metabolism

Publicerad i

Translational animal science
2024, Volym: 8, artikelnummer: txae072
Utgivare: OXFORD UNIV PRESS INC