The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Redução de minerais na dieta de Nelore confinados: impactos no consumo, desempenho e exigências nutricionais; e predição da composição química da seção entre as costelas usando a densitometria óssea em zebuínos

The present work was developed based on three studies. The objective of the first study was to evaluate a method to predict the 9th to 11th rib section (rib9-11) composition through empirical equations using Dual Energy X-ray Absorptiometry (DXA). DXA is a validated method used to describe tissue composition in humans and other animals, but few studies have evaluated this technique in beef cattle, and especially in the Zebu genotype. A total of 116 rib9-11 sections were used to evaluate published prediction equations for rib9-11 composition and to develop new regression models using a cross-validation procedure. For the proposed models, 93 ribs were randomly selected to calculate the new regression equations, and 23 different ribs were randomly selected to validate the regressions. The rib9-11 sections from left carcasses were taken from Nellore and Nellore × Angus bulls from three different studies and scanned using DXA equipment (GE Healthcare, Madison, Wisconsin, USA) in the Health Division at Universidade Federal de Viçosa. The outputs of the DXA report were DXA lean (g), DXA fat free mass (g), DXA fat mass (g), and DXA BMC (bone mineral content; g). After being scanned, the rib9-11 sections were dissected, grounded, and chemically analyzed for total EE, CP, water, and ash content. The predictions of rib fat and protein from previous published equations were different (P < 0.01) from the observed composition. New equations were established through leave-one-out cross-validation using REG procedure using SAS. The equations were as follows: Lean (g) = 37.082 + 0.907× DXA lean (R 2 = 0.95); Fat free mass (g) = 103.224 + 0.869 × DXA fat free mass (R2 = 0.93); EE mass (g) = 122.404 + 1.119 × DXA fat mass (R2 = 0.86); Ash mass (g) = 18.722 + 1.016 × DXA BMC (R2 = 0.39). The equations were validated using Mayer’s test, the concordance correlation coefficient (CCC), and the mean square error of prediction (MSEP) for decomposition. Comparing observed and predicted values using the new equations, Mayer’s test was not significant for lean mass (P = 0.26), fat free mass (P = 0.67), EE mass (P = 0.054), and ash mass (P = 0.14). We concluded that the rib9-11 composition of Nellore and Nellore × Angus bulls can be estimated from DXA using the proposed equations. The second study was developed using weaned Nellore bulls (n = 36; 274 ± 34 kg) in a randomized complete block 2 × 2 factorial design experiment to evaluate intake, fecal excretion and performance with different levels of minerals. The design included two levels of Ca and P (macro mineral factor; CaP+ or CaP-) and two levels of micro minerals (micro mineral factor; ZnMnCu+ or ZnMnCu-). The factor CaP- was without supplementation of limestone and dicalcium phosphate and the factor ZnMnCu- was without inorganic supplementation of micro minerals. The diets were isonitrogenous (13.3% CP). Intake was individually monitored every day. Indigestible NDF was used as an internal marker for fecal excretion measurements. The animals were slaughtered (84 and 147 days on feed; DOF), carcass characteristics were measured and liver and rib samples were collected. Feed, feces, rib bones and liver samples were analyzed for DM, ash, CP, EE, Ca, P, and micro minerals (Zn, Mn, and Cu). There were no significant interactions (P ≥ 0.06) between macro and micro minerals supplementation for any variables in the study. Calcium, P and micro minerals concentrations did not affect (P ≥ 0.20) intakes of DM, OM, NDF, EE, CP, TDN and NFC. Calcium and P intake were affected (P < 0.01) by macro mineral factor. Animals fed without Ca and P supplementation consumed lower levels of these minerals. Dry matter and nutrient fecal excretion were similar (P ≥ 0.23) among factors. Performance and carcass characteristics were similar (P ≥ 0.09) among diets. The content of ash in rib bones was not affected (P ≥ 0.06) by diets. Phosphorus and phosphatase alkaline plasma concentration were similar (P ≥ 0.52) among diets. Calcium plasma concentration was affected (P < 0.01) by micro mineral factor; nevertheless, all blood metabolites were within the reference values. Fecal excretion of Ca and P was different (P < 0.01) among macro mineral factor. These results indicate that supplementation of minerals (Ca, P, Zn, Mn, and Cu) is not necessary in conventional feedlot diets for finishing Nellore. Dietary reductions in these minerals would represent a decrease in the costs of feedlot diets. Dietary reductions in Ca and P decrease fecal excretion of these minerals. Decreasing the P fecal excretion through decreasing content minerals is an opportunity to reduce environmental impact of feedlot operations. The third study aimed to evaluate the water intake, the chemical body composition, the residual feed intake and gain, and the nutritional requirements of energy, protein for maintenance and gain, and calcium and phosphorus for maintenance of Nellore bulls, as well as their efficiencies. Weaned Nellore bulls (n = 44; 273 ± 34 kg) were fed in a randomized complete block design 2 × 2 factorial arrangement to evaluate the nutritional requirements with absence or presence of mineral supplementation. The design included two levels of Ca and P (macro mineral factor; CaP+ or CaP-) and two levels of micro minerals (micro mineral factor; ZnMnCu+ or ZnMnCu-). The diets were isonitrogenous (13.3% CP). Intake was individually monitored every day. Indigestible NDF was used as an internal marker for digestibility measurements. Four animals were used in the reference group (harvested d 0); four bulls were fed at the maintenance level (1.1% of BW); and the remaining 36 bulls were fed ad libitum. Bulls are blocked by days on fed, they were slaughtered on d 84 and 147, after slaughter, samples of the whole body were taken. All samples were lyophilized, ground with liquid nitrogen and grouped as percentage of component in empty BW from each bull. Samples were analyzed for DM, ash, CP, EE, Ca, and P. The water intake was similar (P ≥ 0.07) among treatments. The average of free water intake was 17 L/d for each bull. High residual feed intake and gain (RFIG) bulls had lower DMI (P < 0.01) than low RFIG bulls, but similar ADG (P = 0.82). The CP, EE and water present in the EBW increased as the animal grew, the ash growth is lower than the EBW. Non-linear regression equations were developed to predict heat production (HP) from metabolizable energy (ME) intake and retained energy (RE). The net energy requirements for maintenance (NEm) and metabolizable energy for maintenance (MEm) were 66.5 and 107 kcal/EBW0.75/d, respectively. The efficiency (km) was 62%. The equation obtained for net energy for gain (NEg) was: NEg (Mcal/day) = 0.0388 × EBW0.75 × EBWG1.095 and the efficiency was 25%. For net protein for gain was: NPg (g/day) = 179.74 × EBWG – 5.43 × RE. The net maintenance requirement for Ca was 2.33 mg/EBW and for P was 9.10 mg/EBW. The coefficient of absorption for Ca was 54% and P was 64%. In conclusion, the requirement of net energy for maintenance for Nellore feedlot cattle is 66.5 kcal/EBW0.75/day. Requirements of net energy for gain and net protein for gain can be obtained by the following equations: NEg (Mcal/day) = 0.0388 × EBW0.75 × EBWG1.095 and NPg (g/day) = 179.74 × EBWG – 5.43 × RE. Net maintenance requirement for Ca is 2.33 mg/EBW and for P is 9.10 mg/EBW. The coefficient of absorption for Ca is 54% and P is 64%. The water intake is not influenced by supplementation of Ca, P, Zn, Mn, and Cu. High residual feed intake and gain bulls has lower DMI than low RFIG bulls, with similar ADG. The CP, EE and water present in the EBW increased as the animal grew, the ash growth is lower than the EBW. Overall, intake and performance was not affect by minerals (Ca, P, Zn, Mn, and Cu) diet reduction. It was concluded that the reduction of minerals contents in feedlot diets for Nellore finishing bulls appears not influence in intake, performance, chemical body composition, and nutrient requirements of Nellore finishing bulls in feedlot.O presente trabalho foi desenvolvido baseado em três estudos. O objetivo do primeiro estudo foi avaliar um novo método para estimar a composição química entre a 9 e 11a seção das costelas (costela9-11) através de equações usando um aparelho de absorptometria radiológica de dupla energia (DXA). O DXA é um método validado usado para caracterizar a composição de tecidos em seres humanos e outros animais, mas poucos estudos avaliaram esta técnica em bovinos de corte e, especialmente, em animais Zebus. Um total de 116 costela9-11 foram utilizadas para desenvolver novos modelos de regressão usando o procedimento de validação cruzada (cross-validation). Para os modelos propostos, 93 costela9-11 foram selecionadas aleatoriamente para gerar as novas equações de regressão, e 23 costela9-11 diferentes foram selecionados aleatoriamente para validar as equações geradas. As seções da costela9-11 de carcaças foram retiradas de animais Nelore e Nelore × Angus de três diferentes experimentos e escaneadas usando o equipamento DXA (GE Healthcare, Madison, Wisconsin, EUA) na Divisão de Saúde da Universidade Federal de Viçosa. Os outputs do relatório do DXA foram DXA massa magra (g), DXA massa livre de gordura (água, proteína e matéria mineral), DXA massa gorda (g), e DXA BMC (conteúdo mineral ósseo; g). Depois de serem escaneadas, as seções das costela9-11 foram dissecadas, liofilizadas, e analisadas para EE, PB, MS e teor de cinzas. Novas equações foram estabelecidas através do procedimento de validação cruzada usando o procedimento REG do SAS. As equações foram como se segue: magro (g) = 37,082 + 0,907 × DXA magra (R2 = 0,95); massa livre de gordura (g) = 103,224 + 0,869 × DXA massa livre de gordura (R2 = 0,93); EE (g) = 122,404 + 1.119 × DXA massa gorda (R2 = 0,86); cinzas (g) = 18,722 + 1,016 × DXA BMC (R2 = 0,39). As equações foram validadas pelo teste de Mayer (teste conjunto do intercepto e inclinação), o coeficiente de correlação e concordância (CCC), e a decomposição do quadrado médio do erro predição (MSEP). Comparando valores observados e preditos usando as novas equações propostas, o teste de Mayer foi não significativo para a massa magra (P = 0,26), massa livre de gordura (P = 0,67), EE (P = 0,054), e cinzas (P = 0,14). Concluiu-se que a composição da costela9-11 de novilhos Nelore e Nelore × Angus pode ser estimada a partir do DXA usando as equações propostas. O segundo estudo foi desenvolvido utilizando novilhos Nelore desmamados (n = 36; 274 ± 34 kg) em delineamento em blocos casualizados em arranjo fatorial 2 × 2, para avaliar o consumo, a excreção fecal e desempenho com diferentes níveis de minerais na dieta de terminação. O experimento incluiu dois níveis de Ca e P (fator macro mineral; CaP+ ou CaP-) e dois níveis de micro minerais (fator micro mineral; ZnMnCu + ou ZnMnCu-). O fator CaP- foi sem suplementação de calcário e fosfato bicálcico e o fator ZnMnCu- foi sem suplementação inorgânica de micro minerais (premix). As dietas foram isoprotéicas (13,3% PB). A ingestão foi monitorada individualmente todo dia. A fibra em detergente neutro indigestível foi usada como indicador interno para calcular a digestibilidade. Os animais foram abatidos em diferentes períodos (84 e 147 dias de confinamento), características de carcaça foram medidas e amostras de fígado e ossos da costela foram retirados. Amostras de alimentos, fezes, costelas e fígado foram analisadas para MS, cinzas, PB, EE, Ca, P, e micro minerais (Zn, Mn e Cu). Não houve interação significativa (P ≥ 0,06) entre a suplementação de macro e micro minerais para todas as variáveis estudadas. Concentração de Ca, P e micro minerais na dieta não afetou (P ≥ 0,20) os consumos de MS, MO, FDN, EE, PB e CNF. Ingestão de Ca e P foram influenciados (P <0,01) pelo fator macro mineral. Animais alimentados sem suplementação de Ca e P consumiram menores quantidades destes minerais. A excreção de matéria seca e de nutrientes foram similares (P ≥ 0,23) entre os fatores estudados. Desempenho e características de carcaça foram similares (P ≥ 0,09) entre as dietas. O teor de cinzas nos ossos das costelas não foi afetado (P ≥ 0,06) pelas dietas. O fósforo e a concentração de fosfatase alcalina no plasma foram semelhantes (P ≥ 0,52) entre as dietas. A concentração plasmática de cálcio foi afetada (P < 0,01) pelo fator micro mineral; no entanto, todos os metabólitos do sangue analisados estavam dentro dos valores de referência. A excreção fecal de Ca e P foi diferente (P < 0,01) entre o fator macro mineral. Estes resultados indicam que a suplementação de minerais (Ca, P, Zn, Mn e Cu) não é necessária em dietas convencionais de confinamento para animais Nelore em terminação. A redução nas dietas destes minerais representaria uma diminuição nos custos de dietas de confinamento. Reduções nas concentrações de Ca e P na dieta pode diminuir a excreção fecal destes minerais. Diminuir a excreção fecal de P através da diminuição deste mineral na dieta é uma oportunidade para reduzir o impacto ambiental dos confinamentos. O terceiro estudo teve como objetivo avaliar o consumo de água, a composição química corporal, o consumo alimentar residual e ganho residual conjunto, e as exigências nutricionais de energia, proteína para mantença e ganho, e cálcio e fósforo para a mantença de novilhos da raça Nelore, bem como suas eficiências. Foram utilizados animais Nelore desmamados (n = 44; 273 ± 34 kg), os novilhos foram alimentados em um delineamento em blocos casualizados em arranjo fatorial 2 × 2 com ausência ou presença de suplementação mineral (Ca, P, Zn, Mn e Cu). O experimento incluiu dois níveis de Ca e P (fator macro mineral; CaP+ ou CaP-) e dois níveis de micro minerais (fator micro mineral; ZnMnCu+ ou ZnMnCu- ). As dietas foram isoprotéicas (13,3% PB). A ingestão foi monitorada individualmente todo dia. Fibra em detergente neutro indigestível foi usada como indicador interno para mensurar a digestibilidade. Quatro animais foram utilizados no grupo de referência (abatidos no dia 0); quatro novilhos foram alimentados ao nível de mantença (1,3% do peso corporal); e os 36 animais restantes foram alimentados ad libitum. Após o abate, as amostras de todo o corpo foram amostradas. Todas as amostras foram liofilizadas, moídas com nitrogênio líquido e agrupadas como percentagem do peso de corpo vazio (PCVZ) de cada animal. As amostras foram analisadas para MS, cinzas, PB, EE, Ca e P. O consumo de água foi semelhante (P ≥ 0,07) entre os tratamentos. A média de ingestão de água livre foi de 17 L/d. O consumo alimentar residual e ganho residual conjunto (GCAR) alto de touros tiveram menor CMS (P < 0,01) do que touros de baixo GCAR, mas com GMD semelhante (P = 0,82). A PB, EE e água presente no PCVZ aumentou à medida que o animal cresceu, o crescimento de cinzas foi menor do que o PCVZ. Equações de regressão não-lineares foram desenvolvidos para predizer a produção de calor, o consumo de energia metabolizável (CEM) e a energia retida (ER). As exigências líquidas de energia para mantença (ELm) e energia metabolizável para mantença (EMm) foram 66,5 e 107 kcal/PCVZ0,75/d, respectivamente. A eficiência (km) foi de 62%. A equação obtida para energia líquida para ganho (ELg) foi: ELg (Mcal/dia) = 0,0388 × PCVZ0,75 × GPCVZ1.095 e a eficiência foi de 25%. Para a proteína líquida para ganho obteve-se: PLg (g/dia) = 179,74 × GPCVZ - 5,43 × ER. A exigência de mantença líquida do Ca foi de 2,33 mg/PCVZ e de P foi de 9,10 mg/PCVZ. O coeficiente de absorção de Ca foi de 54% e do P de 64%. Em conclusão, a exigência de energia líquida para mantença de bovinos Nelore confinados é 66,5 kcal/PCVZ0,75/dia. Exigências de energia líquida para ganho e de proteína líquida para ganho podem ser obtidas através das seguintes equações: ELg (Mcal/dia) = 0,0388 × PCVZ0,75 × GPCVZ1.095 e PLg (g/dia) = 179,74 × GPCVZ - 5,43 × ER. Exigência de mantença líquida do Ca é 2,33 mg/PCVZ e para o P é 9,10 mg/PCVZ. O coeficiente de absorção do Ca é de 54% e do P é de 64%. O consumo de água não é influenciado pela suplementação de Ca, P, Zn, Mn e Cu. Animais que possuem alto consumo alimentar residual e ganho residual conjunto tem menor CMS que animais que apresentam baixo GCAR, e apresentando o mesmo ganho de peso. A PB, EE e água presente no PCVZ aumenta à medida que o animal cresce, o crescimento de cinzas não segue o mesmo padrão que o PCVZ. No geral, o consumo e o desempenho de animais Nelore em terminação confinados não foram afetados pela redução de minerais (Ca, P, Zn, Mn e Cu) na dieta. Concluiu-se que a redução dos teores de minerais em dietas de confinamento para Nelore em terminação não influencia no consumo, desempenho, composição química corporal e exigências nutricionais de bovinos Nelore terminados em confinamento.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Performance and nutritional requirements of cattle feed diets containing diferente levels of calcium and phosphorus

O presente trabalho foi desenvolvido com o objetivo de avaliar o consumo, a digestibilidade e o desempenho de bovinos cruzados ¾ Zebu × ¼ Holandês, alimentados com três níveis de cálcio e fósforo na dieta; estimar as exigências nutricionais de energia e proteína de bovinos cruzados ¾ Zebu × ¼ Holandês, não castrados; e testar equações para predição da composição química corporal da carcaça, dos componentes não-carcaça e do corpo vazio obtidas por Hankins & Howe (1946) e pelo BR-CORTE (2006 e 2010), a partir da seção compreendida entre a 9ª e a 11ª costelas. No capítulo 1 objetivou-se avaliar os consumos de matéria seca (CMS) e dos nutrientes, o ganho médio diário, as digestibilidades, o rendimento de carcaça e a área de olho de lombo de animais cruzados ¾ Zebu × ¼ Holandês, alimentados com três níveis de cálcio e fósforo. Foram utilizados 40 bovinos cruzados ¾ Zebu × ¼ Holandês, não castrados, com peso inicial de 214±4 kg e idade média de 11±0,2 meses. Quatro animais foram abatidos para compor o grupo referência e os 36 animais alimentados à vontade foram distribuídos em delineamento inteiramente casualizado, em esquema fatorial 3 × 3, sendo três níveis de cálcio e fósforo (baixo, médio e normal) e três períodos de confinamento (56, 112 ou 168 dias) com quatro repetições. As dietas foram isoprotéicas (126,1 g/kg) e constituídas de silagem de milho e concentrado, na relação de 60:40 na base da matéria seca. Para avaliar as digestibilidades foram utilizadas coletas totais de fezes obtidas durante três dias consecutivos, no final de cada período de confinamento. Não houve interação significativa entre níveis de cálcio e fósforo e períodos de confinamento para nenhuma das variáveis avaliadas. Os consumos de matéria seca (CMS), proteína bruta (PB), extrato etéreo (EE), matéria orgânica (MO), carboidratos não fibrosos (CNF), cálcio (Ca) e fósforo (P), quando expressos em kg/dia ou g/dia, foram maiores (P0,05) por nenhum dos fatores estudados. O ganho de peso médio diário (GMD) dos animais não foi influenciado (P>0,05) por nenhum dos fatores estudados. Os rendimentos de carcaça quente e frio (RQC e RCF) foram menores (P0.05) by any of factors studied. The average daily weight gain (ADG) of animals was not affected (P>0.05) by any of factors studied. The carcass dressing were lower (P<0.05) for animals which spent less time confined. It is conclude that dietary levels of calcium and phosphorus recommended by the BR-CORTE (2010) for feedlot crossbred cattle ( ¾ Zebu × ¼ Holstein) can be reduced, respectively, by 50 and 20%. The second chapter aimed to determine the energy and protein requirements for maintenance and weight gain of crossbred cattle (¾ Zebu × ¼ Holstein) and their efficiency. We used 50 crossbred cattle, uncastrated with an initial weight of 214 ± 4 kg and a mean age of 11 ± 0.2 months. Four animals belonged to reference groug, ten to maintenance group and 36 animals were distributed in a completely randomized design, 3 × 3 factorial arrangement, with three feedlot time (56, 112 or 168 days) and three calcium and phosphorus levels (low, medium and normal) diet. Four animals of maintenance group were sent to the laboratory of metabolism and calorimetry in UFMG to measure heat production through respirometry. Diets were composed of corn silage and concentrate (60:40) and isonitrogenous (126.1 g/kg). After slaughtering, two composite samples were obtained for each animal, called carcass and non-carcass. The net (NEm) and metabolizable (MEm) energy requirement for maintenance were obtained relating heat production (HP) and metabolize energy intake (MEI), while the net energy requirements for gain (NEg) and net protein requirements for gain (PNg) were obtained as a function of empty body weight (EBW) and the gain of empty body weight (EBG). The requirements NEm and MEm were respectively 68.9 and 90.1 kcal/EBW0,75/day. The km was 76%. The NEm requirement obtained in respirometric chamber was 85.5 kcal/BW0,75. The equations to NEg and NPg were NEg (Mcal/day) = 0.0505 ± 0.000986 × EBW 0.75 × EBG 1.095 and NPg (g/day) = 162.79± 18.2546 × EBG - 1,30 ± 5.3010 × NEg. The efficiencies for deposition of protein and fat were 70% and 15%. It is conclude that the NEm and MEm requirements crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated are, respectively: 68.9 and 90.1 kcal/EBW0,75/day, and the NEg and NPg requirements can be obtained by the respective equations: NEg (Mcal/day) = 0.0505 ± 0.000986 × EBW 0.75 × EBG 1.095 and NPg (g/day) = 162.79± 18.2546 × EBG - 1,30 ± 5.3010 × NEg. The third chapter aimed to test the equations for predicting chemical body composition proposed by Hankins & Howe (1946) and BR-CORTE (2006 and 2010) using the section between the 9-11th rib for crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated. We used 46 crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated with an initial weight of 214 ± 4 kg and a mean age of 11 ± 0.2 months. Diets were composed of corn silage and concentrate (60:40), and isonitrogenous (126.1 g/kg). After slaughtering, the section was removed between the 9-11th rib of the right carcass, and it was complete dissected. Similarly, the right carcass of animal was complete dissected. We also evaluated the empty body weight, carcass dressing, percent of visceral fat, percent of organs and viscera and the carcass, not carcass and empty body weight chemical composition. The prediction efficiency between models were made by estimating the mean square error of prediction and its components, concordance correlation coefficient (CCC) and distribution of the prediction errors. The equations proposed by BR-CORTE (2006) estimated adequately crude protein and water of carcass and ether extract and water of empty body. The equations proposed by BR-CORTE (2010) estimated adequately crude protein and ether extract of carcass and crude protein of empty body. The equations proposed by Hankins & Howe (1946) estimated accurately only crude protein of carcass. New equations were generated to predict the chemical composition of non-carcass components. It is conclude that the equations proposed by BR-CORTE (2010) estimated correctly the crude protein and ether extract of carcass and crude protein of empty body for crossbred cattle, and that the equations proposed by BR-CORTE (2006) estimate properly the crude protein and water of carcass, and ether extract and water of empty body. The proposed equations to estimate the chemical composition of non carcass for crossbred cattle (¾ Zebu × ¼ Holstein) were CPNC = 15.55 + 0.11 × CPsec + 0.004 × EBW; EENC = 8.47 + 0.11 × EEsec + 2.99 × VF - 0.74 × OV and WNC = 60.31 + 0.25 × Wsec - 1.97 × VF.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Mycotoxin contamination of diets for beef cattle finishing in feedlot

The objective of this survey was to identify what mycotoxins were present in ingredients used in diets offered to beef cattle in feedlots and their concentrations. The survey covered 30 Brazilian feedlots located in the five major beef-producing states. Samples of total mixed ration (TMR) and ingredients were collected and analyzed for mycotoxin using ultra-performance liquid chromatography coupled to tandem mass spectrometry. Mycotoxin concentrations were further interpreted according to known species-specific sensitivities and normalized according to the principles of toxic equivalent factors (risk equivalent quantities - REQ) expressed in µg kg−1 of aflatoxin B1-equivalent. Forty percent of the visited feedlots had apparent fungi in TMR. However, only one feedlot (3%) used a mycotoxin adsorbent. On the other hand, diets with high contamination presented no apparent fungi. One hundred percent of TMR was contaminated. All samples presented at least one mycotoxin contamination, with 65.5% considered low contamination, 27.6% medium contamination, and 6.90% high contamination. The toxins identified in TMR were fumonisins (most frequently), trichothecenes A, trichothecenes B, fusaric acid, aflatoxins, and ergot (mean concentration values: 2,330, 104.3, 79.5, 105, 10.5, and 5.5 µg kg−1, respectively). According to the contamination of TMR samples per region, Mato Grosso do Sul state presented the highest contaminations. Peanut meal was the most contaminated ingredient. One hundred percent of TMR in Brazilian feedlot is contaminated. Fumonisins were the mycotoxin most frequent and at highest concentrations in TMR samples. Moreover, mycotoxin concentrations have a distinct pattern among ingredients, TMR, and feedlots (local

Exigências de proteína de animais Nelore puros e cruzados com as raças Angus e Simental

Objetivou-se estimar as exigências de proteína de animais Nelore, Nelore-Angus e Nelore-Simental, assim como a eficiência de uso da proteína metabolizável para ganho. Foram utilizados 69 animais (23 Nelore, 23 Nelore-Angus e 23 Nelore-Simental): 12 (quatro de cada grupo genético) foram abatidos antes do início do experimento, como grupo-referência, e nove animais foram separados para um ensaio de digestibilidade. Os animais restantes foram divididos em três dietas (ofertas de concentrado na base de 1 ou 2% do peso corporal à vontade e 1% do nível de mantença). Ao final do experimento, todos os animais foram abatidos e a composição corporal e o peso de corpo vazio (PCVZ) determinados. O consumo de proteína metabolizável (CPmet) foi estimado pela proteína microbiana verdadeira digestível média somada à proteína digestível não-degradada no rúmen. As exigências líquidas de proteína para ganho foram estimadas pela proteína retida (PR) em função do ganho de PCVZ (GPCVZ) e da energia retida. As exigências de proteína metabolizável para mantença foram estimadas pelo CPmet em função do GMD e as exigências líquidas para mantença pela PR em função do CPmet. O grupo genético influenciou apenas a relação entre os diferentes ganhos, mas não teve efeito sobre as exigências líquidas de proteína para ganho, que podem ser estimadas por meio do modelo PR = GPCVZ × (238,5 - 16,73 × (ER/GPCVZ)). Não há influência de grupo genético sobre as exigências líquidas e metabolizáveis de proteína para mantença, cujos valores são de 1,72 g/PCVZ0,75 e 3,09 g/PC0,75, respectivamente. Também não há efeito de grupo genético na energia retida em forma de proteína, assim como na eficiência de uso da proteína metabolizável para ganho, que é de 37,5%

Effect of supplementation level on performance of growing Nellore and its influence on pasture characteristics in different seasons

Eighty-four Nellore bulls (269 ± 27 kg; 13 months) were used in a completely randomized design to evaluate different supplementation strategies on the performance of growing Nellore cattle grazing Panicum maximum cv. Tanzania in the rainy season and rainy-to-dry season transition. In the rainy season, 42 animals received mineral salt (MS) ad libitum and 42 received protein supplement (PR) at 1 g kg−1 body weight (BW). In the rainy-to-dry season transition, 28 animals received MS, 28 received PR at 1 g kg−1 BW, and 28 received a protein-energy (PE) supplement at 3 g kg−1 BW. In the rainy season, the PR supplement increased average daily gain (ADG), providing a significant increase of 17 kg in final BW. In the first period of the rainy-to-dry season transition, PE promoted better performance than MS, while PR did not differ from the two other treatments. In the second period of the rainy-to-dry season transition, PE and PR increased ADG by 41% and 31%, respectively, compared with MS. In the third period, all supplements differed from each other. Bulls fed PE had greater final BW compared with animals fed PR and MS. In conclusion, during the rainy season, PR supplementation should be provided even under good pasture conditions. Also, during the rainy-to-dry season transition, protein-energy supplementation is recommended to compensate for quantitative and qualitative deficiencies of the pasture.Highlights Nellore cattle being backgrounded on pasture with supplementation has greater body weight in the feedlot entry. Supplementation is recommended to compensate for quantitative and qualitative deficiencies of the pasture. Supplementation promotes a positive response in animal performance

Voluntary intake and milk production in F1 Holstein×zebu cows in confinement

The objective of this study was to evaluate the nutrient intake and milk production in Holstein × zebu (F1) cows in feedlot. Eighteen F1 cows were used, divided into three treatments; six were Holstein × Gir (HGI), six were Holstein × Guzerat (HGU), and another six were Holstein × Nelore (HNE), which had recently calved, distributed into simple, random samples, under the same feeding conditions of corn silage and concentrate with 20% crude protein. The three-marker method was used (LIPE®, titanium dioxide, and iADF) to estimate the individual intake and digestibility of the nutrients for the cows in group. The mathematical model used to establish the lactation curves was: Y = at^b e^−ct by Wood (Nature 216:164–165, 1967). The statistical analyses for the nutrient intake and digestibility, as well as parameters of metabolic efficiency, were performed using multiple linear regression (α = 5%). No effect (P > 0.05) of genetic group was observed for any of the variables studied. The intake and digestibility of the nutrients and the microbial nitrogen presented quadratic curves as a function of the lactation period (P < 0.05). The HGU cows exhibited an accumulated milk production of 4,946.81 kg at 305 days, whereas the HGI cows produced 4,821.78 kg. The HNE cows displayed inferior performance, with a production of 3,674.98 kg. It was concluded that, in confinement, F1 cows from different genetic groups do not exhibit different intake, digestibility, or metabolic efficiency. The HGU and HGI cows have greater cumulative production at 305 days

Beef quality traits of Nellore, F1 Simmental × Nellore and F1 Angus × Nellore steers fed at the maintenance level or ad libitum with two concentrate levels in the diet

This trial was conducted to evaluate some beef quality attributes of Nellore, F1 Simmental × Nellore and F1 Angus × Nellore steers finished on feedlot. The effects of feeding regime and genetic group on shear force, thawing losses, cooking (leak + evaporation) losses, total losses and muscle fiber type, as well as carcass pH and temperature during 24 h of chilling were evaluated. There was a genetic group effect on shear force, where the beef from F1 Simmental × Nellore and F1 Angus × Nellore animals had lower values than Nellore animals. Beef of the animals fed the diets with 1% and 2% of body weight on concentrated lost more liquid than the meat of the animals fed at maintenance during thawing and when considering total losses. During cooking there was a difference among the feeding regimes for drip losses which were greater on the animals fed the diet of 1% of body weight on concentrate, followed by the 2% diet and, finally, by the animals fed at maintenance. The muscle of the Nellore steers had larger proportion of intermediate fibers and lower proportion of oxidative fibers than the crossbred animals. The proportion of glycolytic fibers was not influenced by genetic group. The Nellore animals had larger proportion of fibers of fast contraction and smaller proportion of fibers of slow contraction when compared with the crossbred animals. Feeding regime did not influence the proportion of muscular fibers or shear force. Nellore cattle produce tougher beef than crossbred Simmental × Nellore or Angus × Nellore, although all of them have the potential to produce an acceptable beef when slaughtered at young age. Feed restriction up to 90 days is not enough to cause modification on muscle fiber frequencies, then not affecting beef quality