Feeding behavior of feedlot lambs fed diets with different energy and protein sources.

This study aimed to evaluate the effect of the replacement of ground corn by crude glycerin and soybean meal by cottonseed cake, in association or not, on feedlot lambs' feeding behavior. Thirty-two non-castrated crossbred ½ Dorper ½ Santa Inês lambs, with an average body weight of 18.52 ± 3.24 kg (mean ± standard deviation), were distributed in a completely randomized design, into four treatments and eight replicates per treatment, in a 2 × 2 factorial scheme. Four experimental diets were tested with different sources or combinations of energy and protein ingredients in the concentrate, respectively: (1) ground corn + soybean meal; (2) ground corn and cottonseed cake; (3) crude glycerin and soybean meal; and (4) crude glycerin and cottonseed cake. The glycerin decreased dry matter (DM) and neutral detergent fiber (NDF) (P < 0.001) intakes, whereas it increased times spent in feeding (P = 0.009; from 21.8 to 28.6), rumination (P = 0.006; from 56.2 to 67.2), and chewing (P < 0.001; from 79.4 to 97.2), in minutes/100 g of DM. Feeding efficiencies of DM (P = 0.003) and NDF (P = 0.008) were decreased by the diets. Protein sources increased (P = 0.018) the times spent in chewing and per period in rumination (P = 0.014). Cottonseed cake, as a protein source, up to a 112 g/kg DM level, can totally replace soybean meal in diets for feedlot lambs without effects on the intake, behavioral activities, and feeding efficiencies. In contrast, the crude glycerin energy source is not adequate to replace ground corn in lambs' diets.

Silage of rehydrated corn grain / Silagem de grão de milho reidratado

The objective with this study was to evaluate the effect of different levels of water inclusion on the chemical composition and fermentation profiles of reconstituted corn grain silage. The experiment was carried out in a factorial arrangement in a completely randomized design, with three replicates per treatment. Five treatments were evaluated with different levels of water inclusion (% of the natural matter): dry corn grain (control); 90% dry corn grain (DCG) and 10% water; 80% DCG and 20% water; 70% DGC and 30% water; and 60% DCG and 40% water, totaling 45 experimental silos. Inclusion of water in the silage of reconstituted corn grain promoted a reduction in the CP (%) and NDF (%) contents. However, the water increase elevated the NPN/TN contents and the amount of effluent, gas and dry matter (%) losses. The treatment with inclusion of 30% water in the natural matter leads to a better fermentation profile and fewer losses of effluent and dry matter, so it is recommended for ensiling dry ground corn grain.(AU)

Objetivou-se avaliar o efeito de diferentes níveis de inclusão de água na composição química e no perfil fermentativo de silagem de grão de milho reidratado. O experimento foi conduzido em esquema fatorial, em um delineamento inteiramente ao acaso. Cinco tratamentos com diferentes níveis de inclusão de água (% da matéria natural) foram avaliados: milho grão seco (controle); 90% de milho grão seco (MGS) e 10% de água; 80% de MGS e 20% de água; 70% de MGS e 30% de água e 60% de MGS e 40% de água, totalizando 45 silos experimentais. A inclusão de água na silagem do grão de milho reconstituído promoveu redução nos conteúdos de PB (% MS) e FDN (% MS). Contudo, o incremento de água aumentou os teores de NNP/NT e as perdas por efluente, gás e matéria seca. O tratamento com a inclusão de 30% de água na matéria natural propicia um melhor perfil fermentativo e menores perdas por efluente e matéria seca, sendo recomendado para a ensilagem de grão de milho seco moído.(AU)

Quantitative and qualitative traits of carcass and meat of goats fed diets with cactus meal replacing corn.

The purpose of this study was to evaluate the quantitative and qualitative characteristics of the carcass and meat of goats fed diets containing cactus meal (pectin source) replacing corn (starch source). Twenty-eight goats with an average initial weight of 16 ± 2.02 kg were confined in a completely randomized design with four treatments (the replacement levels of 0, 330, 660, and 1000 g kg-1 of dry matter) and seven replicates. The productive performance of the animals was not affected by the replacement of corn by cactus meal. The carcass commercial yield and the dressing percentage decreased with the addition of cactus meal levels in the diets. The commercial cuts, however, especially prime cuts like hind limbs and loin, were not changed by the use of cactus meal. Muscle:bone and fat:bone ratios and muscularity index of hind limbs were influenced by the substitution. The protein and ash contents of the longissimus lumborum muscle decreased while cholesterol levels increased with the presence of cactus meal. Sensory traits of goats' meat fed cactus meal in the diets were not affected. The substitution of corn for cactus meal reduced carcass yield but did not change the yield of commercial cuts or the qualitative characteristics of the meat.

Walking stability of Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae) / Estabilidade de caminhamento de Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae)

Abstract Results obtained in studies can contribute to the advancement of science and innovative methods and techniques for developing practical activities. Reporting conditions that may restrict the implementation of research is critical to ensure the optimal development of further technical studies. The objective of this study was to assess the walking stability of R. dominica on a flat and smooth surface. The study was based on the determination of mortality, morphology and walking stability of the insect outside the grain mass, on a flat and smooth surface. Mortality of adults of this Coleoptera in conditions with and without food was similar, which explains the difficulty that this insect had for accessing the food source on the flat and smooth surface. The measurements of body length (BOL), width (BOW) and height (BOH) of R. dominica were compared with those of Tribolium castaneum (Coleoptera: Tenebrionidae), which showed good ability to walk in these conditions. This study indicated that the former presents lower BOL and BOW, and greater BOH than the second, and all these variables showed differences when analyzed simultaneously by means of the construction of multivariate morphometric indices (Width × Height, Length × Height and Height × Length × Width). These morphometric variables, together with the definition of the geometry most similar to the body shape, resulted in determination of the center of gravity (CG) and static rollover threshold (SRTgeom) for both species. Rhyzopertha dominica and T. castaneum presented CGs considered high and low, respectively, and together with the values obtained for SRTgeom, may justify that R. dominica can be considered a less stable species during movement, and presents greater risk of rollover on flat and smooth surfaces.

Resumo Resultados obtidos em pesquisas podem contribuir com o avanço da ciência e inovar métodos e técnicas para o desenvolvimento de atividades práticas. Relatar condições que podem restringir à execução de pesquisas é fundamental para garantir que seja observada a técnica ideal para o desenvolvimento de estudos posteriores. O objetivo deste trabalho foi estudar a estabilidade de caminhamento de R. dominica em superfície plana e polida. O estudo se baseou na determinação da mortalidade, morfologia e estabilidade de caminhamento do inseto fora da massa de grãos, em superfície plana e polida. A mortalidade dos adultos desse Coleoptera nas condições com e sem alimento foram semelhantes, o que justifica a dificuldade que esse inseto tem em acessar a fonte alimentar andando em superfície plana e polida. As medidas obtidas do comprimento (BOL), largura (BOW) e altura (BOH) do corpo de R. dominica foram comparadas com as de Tribolium castaneum (Coleoptera: Tenebrionidae), que pode ser considerado um bom caminhador nessas condições. Esse estudo mostrou que o primeiro é menor no BOL e BOW, e maior BOH que o segundo, e que, todas essas variáveis apresentaram diferenças quando analisadas simultaneamente por meio da construção de índices morfométricos multivariados (Largura × Altura; Comprimento × Altura e Altura × Comprimento × Largura). Essas variáveis morfométricas, juntamente com a definição da forma geométrica que mais se aproxima do formato corporal, proporcionaram a determinação do centro de gravidade (CG) e do limite lateral de tombamento (SRTgeom) para ambas as espécie. Rhyzopertha dominica e T. castaneum apresentaram CGs considerados alto e baixo, respectivamente, e juntamente com os valores obtidos para os SRTgeom, podem justificar que R. dominica pode ser considerada uma espécie menos estável durante o caminhamento, e que, apresenta maiores riscos de tombamento em superfícies plana e polida.

Walking stability of Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae).

Results obtained in studies can contribute to the advancement of science and innovative methods and techniques for developing practical activities. Reporting conditions that may restrict the implementation of research is critical to ensure the optimal development of further technical studies. The objective of this study was to assess the walking stability of R. dominica on a flat and smooth surface. The study was based on the determination of mortality, morphology and walking stability of the insect outside the grain mass, on a flat and smooth surface. Mortality of adults of this Coleoptera in conditions with and without food was similar, which explains the difficulty that this insect had for accessing the food source on the flat and smooth surface. The measurements of body length (BOL), width (BOW) and height (BOH) of R. dominica were compared with those of Tribolium castaneum (Coleoptera: Tenebrionidae), which showed good ability to walk in these conditions. This study indicated that the former presents lower BOL and BOW, and greater BOH than the second, and all these variables showed differences when analyzed simultaneously by means of the construction of multivariate morphometric indices (Width × Height, Length × Height and Height × Length × Width). These morphometric variables, together with the definition of the geometry most similar to the body shape, resulted in determination of the center of gravity (CG) and static rollover threshold (SRTgeom) for both species. Rhyzopertha dominica and T. castaneum presented CGs considered high and low, respectively, and together with the values obtained for SRTgeom, may justify that R. dominica can be considered a less stable species during movement, and presents greater risk of rollover on flat and smooth surfaces.

Accuracy of the estimates of ammonia concentration in rumen fluid using different analytical methods / Exatidão das estimativas de concentração de amônia em fluido ruminal utilizando diferentes métodos analíticos

The accuracy of two different methods in measuring the ammonia nitrogen (N-NH3) concentration in rumen fluid were evaluated: a catalyzed indophenol colorimetric reaction (CICR) and the Kjeldahl distillation (KD). Five buffered standard solutions containing volatile fatty acids, true protein, and known ammonia concentrations (0, 3, 6, 12, and 24 N-NH3 mg/dL) were used to simulate rumen fluid. Different ratios (10:1, 7.5:1, 5:1, 2.5:1, 1:1, 1:2.5, 1:5, 1:7.5, and 1:10) of a potassium hydroxide solution (KOH, 2 mol/L) to standard solutions were evaluated by the KD method. The accuracy of each method was evaluated by adjusting a simple linear regression model of the estimated N-NH3 concentrations on the N-NH3 concentrations in the standard solutions. When the KD method was used, N-NH3 was observed to be released from the deamination of true protein (P<0.05), and an incomplete recovery of N-NH3 was observed (P<0.05), except for 7.5:1 and 5:1 ratios of KOH solution to standard solutions (P>0.05). The estimates of the N-NH3 concentration obtained by the CICR method were found to be accurate (P>0.05). After the accuracy evaluation, ninety-three samples of rumen fluid were evaluated by the CICR and KD methods (using the 5:1 ratio of KOH solution to rumen fluid sample), assuming that the CICR estimates would be accurate. The N-NH3 concentrations obtained by the two methods were observed to be different (P<0.05) but strongly correlated (r = 0.9701). Thus, it was concluded that the estimates obtained by the Kjeldahl distillation using a 5:1 ratio of KOH solution to rumen fluid sample can be adjusted to avoid biases. Furthermore, a model to adjust the N-NH3 concentration is suggested.

Avaliou-se a exatidão de dois métodos para mensuração da concentração de nitrogênio amoniacal (N-NH3) em fluido ruminal: reação colorimétrica catalisada por indofenol (RCCI) e destilação de Kjeldahl (DK). Cinco soluções-tampão contendo ácidos graxos voláteis, proteína verdadeira e concentrações conhecidas de amônia (0, 3, 6, 12 e 24 N-NH3mg/dL) foram utilizadas para simular o fluido ruminal. Diferentes relações (10:1; 7,5:1; 5:1; 2,5:1; 1:1; 1:2,5; 1:5; 1:7,5 e 1:10) entre a solução de hidróxido de potássio (KOH, 2 mol/L) e as soluções-padrão foram avaliadas no método DK. A exatidão de cada método foi avaliada por intermédio do ajustamento de um modelo de regressão linear simples das concentrações estimadas de N-NH3sobre as concentrações reais de N-NH3nas soluções-padrão. Com a utilização da DK observou-se que N-NH3foi liberada a partir da deaminação de proteína verdadeira (P<0,05). Adicionalmente, a utilização da DK promoveu recuperação incompleta da N-NH3(P<0,05), com exceção das razões entre a solução de KOH e as soluções-padrão de de 7,5:1 e de 5:1 (P>0,05). As estimativas de concentração de amônia obtidas por intermédio do método de RCCI foram exatas (P>0,05). Após a avaliação da exatidão, noventa e três amostras de fluido ruminal foram avaliadas por intermédio dos métodos de RCCI e de DK (neste caso usando a razão entre solução de KOH e fluido ruminal de 5:1). Nesta avaliação assumiu-se que as estimativas obtidas com a RCCI seriam exatas. Observou-se que as concentrações de N-NH3obtidas pelos dois métodos foram diferentes (P<0,05), mas fortemente correlacionadas (r = 0,9701). Concluiu-se que as estimativas obtidas com a DK utilizando-se razão entre a solução de KOH e a amostra de fluido ruminal de 5:1 poderiam ser ajustadas para correções de vieses Um modelo para realização desse ajustamento foi sugerido.

Evaluation of chromium concentration in cattle feces using different acid digestion and spectrophotometric quantification techniques / Avaliação da concentração de cromo em fezes de bovinos utilizando diferentes técnicas de digestão ácida e de quantificação espectrofotométrica

The objective of this work was to evaluate combinations between acid digestion techniques and spectrophotometric quantification to measure chromium concentration in cattle feces. Digestion techniques were evaluated based on the use of nitric and perchloric acids, sulfuric and perchloric acids, and phosphoric acid. The chromium quantification in the solutions was performed by colorimetry and by atomic absorption spectrophotometry (AAS). When AAS was used, the addition of calcium chloride to the solutions as a releasing agent was also evaluated. Several standard samples containing known chromium contents were produced (0, 2, 4, 6, 8 and 10g of chromium per kg of feces) using cattle feces obtained from three different animals to evaluate the accuracy of the different combinations of techniques. The accuracy was evaluated by adjusting a simple linear regression model of the estimated values on the actual values of chromium content in the standard samples. Regardless of the digestion technique, the chromium content estimates in the standard samples obtained by colorimetry were not accurate (P<0.05). Considering the AAS quantification, the digestion techniques based on nitric and perchloric acids and based on sulfuric and perchloric acids provided complete chromium recovery (P>0.05). The use of the digestion technique in phosphoric acid provided incomplete recovery of the fecal chromium (P<0.05). Subsequently, the digestion techniques in nitric and perchloric acids and digestion in sulfuric and perchloric acids, both evaluated by AAS, were compared using 84 cattle feces samples. The results indicate that these techniques provide similar (P>0.05) fecal chromium contents.

Objetivou-se avaliar combinações entre técnicas de digestão ácida e quantificação espectrofotométrica para estimar a concentração de cromo em amostras de fezes bovinas. Foram avaliadas técnicas de digestão baseadas na utilização de ácidos nítrico e perclórico, ácidos sulfúrico e perclórico e ácido fosfórico. A quantificação da concentração de cromo nas soluções foi realizada por colorimetria e por espectrofotometria de absorção atômica (EAA). Na quantificação por EAA, foi avaliada a adição de cloreto de cálcio como agente de liberação. Amostras-padrão contendo quantidades conhecidas de cromo foram produzidas (0, 2, 4, 6, 8 e 10g de cromo por kg de fezes) utilizando-se fezes bovinas obtidas de três animais diferentes, para avaliar a acurácia das diferentes técnicas. A acurácia foi avaliada pelo ajustamento de modelo de regressão linear simples dos valores estimados sobre os valores reais de cromo nas amostras-padrão. Independentemente da técnica de digestão ácida, as estimativas da concentração de cromo nas amostras-padrão obtidas por colorimetria não foram acuradas (P<0,05). Considerando-se a quantificação de cromo por EAA, as técnicas de digestão baseadas nos ácidos nítrico e perclórico e nos ácidos sulfúrico e perclórico promoveram completa recuperação de cromo (P>0,05). A utilização da técnica de digestão em ácido fosfórico promoveu recuperação incompleta do cromo fecal (P<0,05). Posteriormente, as técnicas de digestão em ácidos nítrico e perclórico e em ácidos sulfúrico e perclórico, ambas avaliadas por EAA, foram comparadas utilizando-se 84 amostras de fezes bovinas. Os resultados indicam que aquelas combinações de técnicas promovem resultados similares (P>0,05) da concentração fecal de cromo.

Nutritional diversity of agricultural and agro-industrial by-products for ruminant feeding / Diversidade nutricional de subprodutos agrícola e agro-industrial para alimentação de ruminantes

Fifty-seven by-products were collected from regions throughout Brazil. Chemical composition, in vitro neutral detergent fiber digestibility (IVNDFD), and total digestible nutrients (TDN) were determined with the objective of grouping by-products with similar nutritional characteristics. The by-products belonging to group one (G1) presented the highest content of neutral detergent fiber exclusive of ash and nitrogenous compounds [aNDFom(n)] and lowest energy content, with 42.5% and 38.8% of IVNDFD and TDN, respectively. A new cluster analysis was carried in order to better characterize G2 by-products, six subgroups (SGs) were established (SG1 to SG6). SG1 by-products had the highest and the lowest values for lignin and TDN, respectively. SG2 by-products had the highest aNDFom(n) value, with TDN and IVNDFD values greater than 600 and 700g/kg, respectively, and crude protein (CP) value below 200g/kg in dry matter (DM). Among all the subgroups, SG3 had the highest TDN (772g/kg) and IVNDFD (934g/kg) values and the lowest lignin (23g/kg in DM) value. The ether extract was what most influenced the hierarchical establishment of residual grouping in SG4. SG5 by-products had the highest concentration of non-fibrous carbohydrate. Different from the other subgroups, SG6 by-products had the highest value of available CP.

Cinquenta e sete subprodutos foram coletados de diferentes regiões do Brasil. Foram determinados a composição química, a digestibilidade in vitro da fibra em detergente neutro (DIVFDN) e os nutrientes digestíveis totais (NDT), com o objetivo de agrupar os subprodutos com características nutricionais semelhantes. Os subprodutos pertencentes a um grupo (G1) apresentaram maior conteúdo de fibra em detergente neutro corrida para cinzas e compostos nitrogenados (FDNcp) e menor teor energético, e tinham 42,5% e 38,8% de DIVFDN e NDT, respectivamente. Uma nova análise de cluster foi realizada no intuito de melhor caracterizar os subprodutos do G2; seis subgrupos (SG) foram estabelecidos (SG1 a SG6). Os subprodutos SG1 tiveram os maiores e os menores valores de lignina e NDT, respectivamente. Os subprodutos SG2 tiveram o maior valor de FDNcp, com valores de NDT e DIVFDN acima de 600 e 700g/kg, respectivamente, e de proteína bruta (PB) abaixo de 200g/kg de matéria seca (MS). Entre todos os subgrupos, SG3 tiveram os maiores valores de NDT (772g/kg) e DIVFDN (934g/kg) e o menor valor de lignina (23g/kg de MS). O extrato etéreo foi o que mais influenciou no estabelecimento hierárquico de agrupamento em SG4. Os subprodutos SG5 tinham maior concentração de carboidratos não fibriosos. Diferentemente dos demais subgrupos, subprodutos SG6 tinham o valor mais elevado de PB disponível.

Consumo, digestibilidade total, produção de proteína microbiana e balanço de nitrogênio em dietas para ruminantes de subprodutos / Intake, total digestibility, microbial protein production, and the nitrogen balance in ruminant diets based on agricultural and agro-industrial by-products

Avaliaram-se os efeitos da inclusão da fonte - subproduto do cacau, mandioca-casca, mandioca-caule e farelo de glúten de milho - e da proporção - 10 e 30 por cento - de subprodutos, em substituição parcial à silagem de milho sobre consumo, digestibilidade dos nutrientes, produção de proteína microbiana, balanço de nitrogênio, predição das frações digestíveis e nutrientes digestíveis totais. Os consumos de matéria seca e de fibra em detergente neutro foram influenciados pela fonte de subproduto. A fonte de subproduto influiu na digestibilidade do extrato etéreo e dos carboidratos não fibrosos. O subproduto farelo de glúten de milho apresentou valor energético 17 por cento maior do que a da silagem de milho, enquanto os da mandioca-casca, da mandioca-caule e do cacau apresentaram valores energéticos 10, 19 e 38 por cento menores do que o valor observado para silagem de milho. A fonte e o nível de subproduto não influíram na excreção urinária de derivados de purinas totais, de purinas absorvidas e de nitrogênio microbiano, e na eficiência microbiana. A fonte do subproduto influenciou a ingestão, a excreção nas fezes e na urina dos compostos nitrogenados e o balanço de nitrogênio. O farelo de glúten de milho e a mandioca-casca podem substituir, parcialmente, os concentrados energéticos, sem prejuízos para consumo, digestibilidade, eficiência microbiana e retenção de nitrogênio.

The effects of inclusion of by-products (cocoa, cassava peel, cassava stalk, and corn gluten meal) and their levels (10 and 30 percent), replacing part of corn silage on intake, digestibility of nutrients, microbial protein production, nitrogen balance, prediction of digestible fractions, and total digestible nutrients were evaluated. The intakes of dry matter and neutral detergent fiber were affected by source of by-product, which affected the digestibility of ether extract and non-fibrous carbohydrates. The energy corn gluten meal was 17 percent higher than that of corn silage, while the values for cassava peel, cocoa, and cassava stalk were 10, 19, and 38 percent lower than the value for corn silage. The source and the level of by-product did not affect the urinary excretion of total purine, purine absorbed, microbial nitrogen, and microbial efficiency. The source of by-product affected intake, nitrogen compounds, excretion in feces and urine, and nitrogen balance. The corn gluten meal and cassava peel are by-products with potential to partly replace the energhetic concentrates, with no influence on the intake, digestibility, microbial efficiency, and nitrogen retention.

Endogenous fraction and urinary recovery of purine derivatives obtained by different methods in Nellore cattle.

Two experiments were conducted to assess the endogenous fraction of purine derivative (PD) excretion, urinary recovery, and intestinal digestibility of purines in Nellore heifers. For both experiments, 8 Nellore heifers fitted with ruminal and abomasal cannulas were allocated to two 4 × 4 Latin squares. The diets were based on corn silage and concentrate (60 and 40% DM basis, respectively); feces and urine samples were obtained by total collection, and abomasal DM flow was estimated using indigestible NDF as an internal marker. In Exp. I, 4 of the 8 heifers (BW 258 ± 20 kg) were also fitted with ileal cannula. The planned treatments were 4 different DMI: 1.2, 1.6, 2.0, and 2.4% of BW (DM basis). The endogenous losses and purine recovery as urinary PD were estimated using linear regression between daily urinary PD excretion (Y) and daily abomasal flow of purine bases (X), expressed in millimoles per kilogram of BW(0.75). In Exp. II, the same 8 Nellore heifers (BW of 296 ± 15 kg) were fed at 1.37% BW (DM basis). The treatments were the infusion of purines (RNA from torula yeast, type VI, Sigma) into the abomasum in increasing amounts (0, 33, 66, and 100 mmol/d). All statistical analyses were performed using the PROC MIXED procedure in SAS. In Exp. I, the DMI range was 1.16 to 1.84% of BW and did not affect (P > 0.05) the apparent RNA digestibility in the small intestine, which had a mean of 75.6%, and a true digestibility of 93.0%. The mean ratio of the N-RNA to the total-N in the ruminal bacteria was 0.137. The daily urinary PD excretion (Y, mmol/kg of BW(0.75)) was a function of RNA flow in the abomasum (X, mmol/kg of BW(0.75)): Y = 0.860X + 0.460, where 0.860 and 0.460 were the PD recovery of purines and the endogenous fraction (in mmol/kg of BW(0.75)), respectively. In Exp. II, the daily urinary PD excretion was a function of RNA flow in the abomasum: Y = 0.741X + 0.301, where 0.741 and 0.301 were the recovery of PD in urine of infused purines and the endogenous losses (in mmol/kg of BW(0.75)), respectively. In conclusion, our data suggest that in Nellore heifers the respective values of endogenous PD excretion (mmol/kg of BW(0.75)), urinary recovery of the purines absorbed in the abomasum, and true digestibility of RNA in the small intestine were 0.30, 0.80, and 0.93.

Influence of different levels of concentrate and ruminally undegraded protein on digestive variables in beef heifers.

This experiment evaluated the effect of 2 levels of diet concentrate (20 and 40% of DM) and 2 levels of ruminally undegraded protein (RUP: 25 and 40% of CP) on nutrient intake, total and partial apparent nutrient digestibility, microbial protein synthesis, and ruminal and physiological variables. Eight Nellore heifers (233 +/- 14 kg of BW) fitted with ruminal, abomasal, and ileal cannulas were used. The animals were held in individual sheltered pens of approximately 15 m(2) and fed twice daily at 0800 and 1600 h for ad libitum intake. Heifers were allocated in two 4 x 4 Latin square designs, containing 8 heifers, 4 experimental periods, and 4 treatments in a 2 x 2 factorial arrangement. All statistical analyses were performed using PROC MIXED of SAS. Titanium dioxide (TiO(2)) and chromic oxide (Cr(2)O(3)) were used to estimate digesta fluxes and fecal excretion. Purine derivative (PD) excretion and abomasal purine bases were used to estimate the microbial N (MN) synthesis. No significant interaction (P > 0.10) between dietary levels of RUP and concentrate was observed. There was no effect of treatment (P = 0.24) on DMI. Both markers led to the same estimates of fecal, abomasal, and ileal DM fluxes, and digestibilities of DM and individual nutrients. Ruminal pH was affected by sampling time (P < 0.001), but no interaction between treatment and sampling time was observed (P = 0.71). There was an interaction between treatment and sampling time (P < 0.001) for ruminal NH(3)-N concentration. A linear decrease (P = 0.04) over sampling time was observed for the higher level of RUP, whereas a quadratic effect (P < 0.001) of sampling time was observed for the lower level of RUP. The higher level of dietary concentrate led to greater MN yield regardless of the level of RUP. The MN yield and the efficiency of microbial yield estimated from urinary PD excretion produced greater (P < 0.01) values than those estimated by either TiO(2) or Cr(2)O(3), which did not differ (P = 0.63) from each other. However, all methods yielded values that were within the range reported in the literature. In conclusion, no interactions between dietary levels of RUP and concentrate were observed for ruminal and digestive parameters. Neither RUP nor concentrate level affected DMI. Titanium dioxide showed to be similar to Cr(2)O(3) as an external marker to measure digestibility and nutrient fluxes in cattle.