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

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.

Improving the accuracy of beef cattle methane inventories in Latin America and Caribbean countries.

On-farm methane (CH4) emissions need to be estimated accurately so that the mitigation effect of recommended practices can be accounted for. In the present study prediction equations for enteric CH4 have been developed in lieu of expensive animal measurement approaches. Our objectives were to: (1) compile a dataset from individual beef cattle data for the Latin America and Caribbean (LAC) region; (2) determine main predictors of CH4 emission variables; (3) develop and cross-validate prediction models according to dietary forage content (DFC); and (4) compare the predictive ability of these newly-developed models with extant equations reported in literature, including those currently used for CH4 inventories in LAC countries. After outlier's screening, 1100 beef cattle observations from 55 studies were kept in the final dataset (∼ 50 % of the original dataset). Mixed-effects models were fitted with a random effect of study. The whole dataset was split according to DFC into a subset for all-forage (DFC = 100 %), high-forage (94 % ≥ DFC ≥ 54 %), and low-forage (50 % ≥ DFC) diets. Feed intake and average daily gain (ADG) were the main predictors of CH4 emission (g d-1), whereas this was feeding level [dry matter intake (DMI) as % of body weight] for CH4 yield (g kg-1 DMI). The newly-developed models were more accurate than IPCC Tier 2 equations for all subsets. Simple and multiple regression models including ADG were accurate and a feasible option to predict CH4 emission when data on feed intake are not available. Methane yield was not well predicted by any extant equation in contrast to the newly-developed models. The present study delivered new models that may be alternatives for the IPCC Tier 2 equations to improve CH4 prediction for beef cattle in inventories of LAC countries based either on more or less readily available data.

Bem-estar dos cordeiros submetidos ao transporte rodoviário e avaliação das carcaças e carnes / Welfare of lambs subjected to road transport and assessment of carcasses and meat

Objetivou-se avaliar o grau de bem-estar dos cordeiros submetidos ao transporte rodoviário e suas carcaças e carnes. Para isto, fez-se a avaliação dos parâmetros comportamentais durante o transporte, dos parâmetros fisiológicos após o desembarque e antes do abate e a caracterização das carcaças e carnes dos cordeiros. Realizaram-se quatro transportes rodoviários com durações crescentes (1h45min, 3h52min, 7h30min e 10h30min), cada transporte continha vinte cordeiros. O peso corporal dos animais foi de 36,64±2,13 kg antes do transporte. Os cordeiros foram abatidos 15 horas após o desembarque. Os cordeiros deitaram por pouco tempo (mediana igual à zero a cada 20min) em jornadas menores que 3h52min. O número de eventos potencialmente traumáticos foi baixo (mediana próxima a zero, a cada 20min) para quaisquer durações dos transportes. As concentrações de adrenalina e cortisol, bem como os metabólitos que são controlados por eles, foram semelhantes entre os tratamentos. Contudo, a massa das carcaças diminuiu e as concentrações de creatina quinase aumentaram linearmente quando os transportes foram mais longos, o que podem revelar diminuição do bem-estar. A qualidade da carne de cordeiros não sofreu interferências da duração dos transportes.(AU)

This study aimed to assess the level of welfare in lambs by road transport and their carcasses and meat. Thus, we assessed behavioral parameters during transport, physiological parameters after landing and before slaughter and carcass and meat characteristics of lambs. Four road transports were achieved with increasing durations (1h45min, 3h52min, 7h30min and 10h30min), there were twenty lambs in each transport. Animals body weight was 36.64±2.13 kg before transport. The lambs were slaughtered 15 hours after landing. The lambs lie down (median equal to zero every 20min) for a short time in journeys shorter than 3h52min. The number of potentially traumatic events is low (median near zero every 20min) for any transport duration. The adrenaline and cortisol concentrations, as well as metabolites that are controlled by them, did not testify that longer transport. However, the carcasses mass decreased and creatine kinase concentrations increased linearly with longer transports, which may reveal decrease in welfare. The meat quality of lambs was not influenced by the transport duration.(AU)