Viviane Aparecida Carli Costa

Degradação in vitro da fibra em detergente neutro de forragem tropical de baixa qualidade em função de suplementação com proteína e/ou carboidratos

The effect of the protein and (or) carbohydrates supplementation on the rumen degradation of neutral detergent fiber (NDF) from low quality forage was evaluated. The experiment simulated the supplementation of finishing cattle grazing low quality Brachiaria decumbens pasture during dry season (70:30 forage to concentrate ration, %DM). The concentrate referring to the basal treatment was formulated to contain 30% CP, using starch as the energetic source and casein as the protein source. The treatments were established by omission of protein and (or) carbohydrates sources, associated with substitution of starch by pectin. In that way, six treatments were evaluated: 1. Forage, 2. Forage plus Starch, 3. Forage plus Pectin, 4.Forage plus Casein, 5. Forage plus casein plus starch and 6. Forage plus casein plus pectin. The treatments were evaluated under rumen environment, simulated by in vitro incubation, where the experimental diets were submitted to different incubation periods: 0, 3, 6, 9, 12, 24, 36, 48, 72, and 96 hours. The incubation procedure was repeated four times in a way that four evaluations within each incubation time were done for each treatment. The incubation residues were evaluated according to its contents of NDF and interpreted using a non-linear logistic model. It was observed that the degradation rate of potentially degradable NDF (pdNDF) was increased almost 46% with casein supplementation, resulting in an increment of 14.6% on the effective degraded fraction. A minor effect was observed with the inclusion or substitution of the supplemental carbohydrate source. The starch supplementation resulted in reduction on pdNDF degradation rate, whereas the supplementation with pectin did not affected this parameter, when compared to no carbohydrate supplementation. In the presence of casein, the starch supplementation raised the discrete lag time for NDF degradation.

Consumo e digestibilidade em bovinos em pastejo durante o período das águas sob suplementação com fontes de compostos nitrogenados e de carboidratos

Objetivou-se avaliar os efeitos de diferentes formas quimicas de compostos nitrogenados (proteicos e nao-proteicos) e de carboidratos (amilaceos e fibra soluvel) sobre o consumo, a digestibilidade e a sintese ruminal de proteina microbiana em bovinos sob suplementacao durante o periodo das aguas. Foram utilizados cinco novilhos mesticos Holandes × Zebu, com peso vivo (PV) medio inicial de 211 ± 35 kg, fistulados no rumen e abomaso. Os tratamentos foram: controle (somente pasto); e suplementos formulados a base de milho + farelo de soja; milho + ureia; polpa citrica + farelo de soja; e polpa citrica + ureia. Os suplementos foram balanceados para apresentar 30% de proteina bruta (PB), com base na materia seca (MS), e fornecidos na quantidade de 3 g/kg PV. O experimento foi conduzido segundo delineamento em quadrado latino 5 × 5, em esquema fatorial 2 × 2 + 1, composto de duas fontes de compostos nitrogenados, duas fontes de carboidratos e tratamento controle. O consumo de pasto reduziu com o fornecimento de suplementos, com coeficiente medio de substituicao de 2,11 g de MS de pasto/g de MS de suplemento. A suplementacao nao alterou os coeficientes de digestibilidade total e ruminacao da MS nem o teor dietetico de nutrientes digestiveis totais (NDT). Os animais sob suplementacao apresentaram maiores coeficientes de digestibilidade total e ruminal da proteina bruta. A eficiencia de sintese de proteina microbiana (EFSM), media de 123,1 g PB microbiana/kg de NDT, nao foi alterada pela suplementacao. Contudo, os animais sob suplementacao com milho apresentaram maior EFSM em comparacao aos animais sob suplementacao com polpa citrica (137,6 e 106,1 g PB microbiana/kg de NDT, respectivamente). A suplementacao proteico-energetica para bovinos mantidos em pastos tropicais durante o periodo das aguas nao causa beneficios nutricionais, o que reflete o alto coeficiente de substituicao da forragem pelo suplemento.

Digestibilidade total e parcial e balanço nitrogenado em bovinos em pastejo no período das águas recebendo suplementos com nitrogênio não-proteico e/ou proteína verdadeira

The objective of this study was to evaluate the effect of different true protein:non-protein nitrogen ratios in supplements on digestibility, microbial protein synthesis and nitrogen balance in grazing cattle during rainy season. Five crossbred Holstein × Zebu steers, averaging 335±35 kg of body weight and fitted with rumen and abomasum canullae were used. The treatments were: control (only pasture), and supplements based on urea, 2/3 of nitrogenous compounds from urea and 1/3 of nitrogenous compounds from albumin, 1/3 of nitrogenous compounds from urea and 2/3 of nitrogenous compounds from albumin, and albumin. Two hundred grams of crude protein (CP) were daily supplied from supplements. The experiment was carried out according to a 5 × 5 Latin square design, with five 15-day experimental periods. Supplementation did not affect the total digestibility coefficients or the diet content of total digestible nutrients. Supplementation increased ruminal apparent digestibility coefficient of CP, which moved from negative for the control treatment to positive, but not different from zero, for treatments involving supplementation. Supplementation increased the rumen ammonia nitrogen concentration. Nitrogen balance was enhanced by supplementation. The replacement of urea by albumin caused a cubic effect on the nitrogen balance, with the higher value obtained at 1/3 of supplemental CP as urea. The efficiency of microbial protein synthesis was not influenced by supplementation or supplement composition. Supplementation with ruminal degradable nitrogenous compounds for grazing cattle during the rainy season increases the efficiency of use of pasture mainly by improving the body nitrogenous compounds retention.

Consumo e dinâmica ruminal da fibra em detergente neutro em bovinos em pastejo no período das águas recebendo suplementação com nitrogênio não-proteico e/ou proteína verdadeira

The objective of this study was to evaluate the effect of different true protein:non-protein nitrogen ratios in supplements on intake and ruminal transit and degradation dynamics of neutral detergent fiber (NDF) in grazing cattle during rainy season. Five crossbred Holstein × Zebu steers, averaging 335±35 kg of body weight and fitted with rumen and abomasum canullaes were used. The treatments were: control (only pasture), and supplements based on urea, 2/3 of nitrogenous compounds from urea and 1/3 of nitrogenous compounds from albumin, 1/3 of nitrogenous compounds from urea and 2/3 of nitrogenous compounds from albumin, and albumin. Two hundred grams/d of crude protein (CP) were supplied from supplements. The experiment was carried out according to a 5 × 5 Latin square design, with five 15-day experimental periods. There were no effects of supplementation on voluntary intake, except for CP intake, which was increased by supplementation. The replacement of urea by albumin in the supplements caused linear effect on the CP intake. The intakes of the other diet components were not affected by the supplement composition. There was no effect on ruminal rate of passage of fibrous compounds. Supplementation increased the estimates of common rate of lag and degradation of NDF. However, no effect of supplement composition alteration was observed on this parameter. Supplementation of cattle with rumen degradable (protein or non-protein) nitrogenous compounds for grazing cattle during rainy season does not affect voluntary intake of pasture.

Fecal excretion patterns and short term bias of internal and external markers in a digestion assay with cattle

Objetivou-se avaliar o perfil de excrecao fecal e o vicio de tempo curto dos indicadores externos oxido cromico e dioxido de titânio e dos indicadores internos materia seca indigestivel (MSi), fibra em detergente neutro indigestivel (FDNi) e fibra em detergente acido indigestivel (FDAi) em ensaio de digestao com bovinos alimentados com diferentes dietas. Foram utilizados 14 novilhos F1 Red Angus × Nelore, nao-castrados, com idade e peso medios de 12 meses e 287 kg, mantidos em baias individuais. Os animais foram alimentados com silagem de capim-elefante, silagem de milho ou feno de capim-braquiaria, suplementados ou nao com 20% de mistura concentrada. O experimento foi constituido de dois periodos de 13 dias, segundo delineamento em quadrado latino 2 × 2, com agrupamento de sete quadrados. Os animais receberam diariamente 10 g de oxido cromico e 10 g de dioxido de titânio por meio de sonda esofagica. Foram realizadas coletas fecais pontuais (grab samples), diretamente do reto dos animais, nos horarios de 1h30, 3h00, 4h30, 6h00, 7h30, 9h00, 10h30, 12h00, 13h30, 15h00, 16h30, 18h00, 19h30, 21h00, 22h30 e 24h00. Nao foram observados efeitos das forragens ou dos niveis de concentrado sobre a dimensao do ciclo excretorio. O periodo fundamental do ciclo excretorio foi de 15,06 e 18,66 horas para o oxido cromico e dioxido de titânio, e de 9,93; 9,29 e 10,55 horas para MSi, FDNi e FDAi respectivamente. Verificou-se maior amplitude de oscilacao para os indicadores externos. Considerando-se conjuntamente as caracteristicas dos indicadores avaliados, recomendam-se delineamentos de amostragem fecal com o minimo de quatro coletas, distribuidas ao longo do dia ou somente no periodo diurno, para obtencao de estimativas de excrecao fecal isentas de vicio de tempo curto.

Accuracy of the estimates of ammonia concentration in rumen fluid using different analytical methods

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). 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.

In vitro and in situ activity of carboxymethyl cellulase and glutamate dehydrogenase according to supplementation with different nitrogenous compounds

Two experiments were carried out to evaluate the effect of supplementation with different nitrogenous compounds on the activities of carboxymethil cellulase (CMCase) and glutamate dehydrogenase (GDH). In the first experiment, four treatments were evaluated in vitro: cellulose, cellulose with casein, cellulose with urea, and cellulose with casamino acids. After 6, 12 and 24 hours of incubation, CMCase and GDH activity, pH, and concentrations of ammonia nitrogen (AN) and microbial protein were measured. In the three incubation periods, the concentration of AN was higher when urea was used as a supplemental source of nitrogen. The activity of CMCase was higher with the addition of urea and casamino acids when compared with the control and the casein treatment. Supplementation with casamino acids provided higher GDH activity when compared with the control at 6 hours of incubation. At 12 hours of incubation, the GHD activity was also stimulated by casein. At 24 hours, there was no difference in GHD activity among treatments. In the second experiment, three rumen-fistulated bulls were used for in situ evaluation. Animals were fed Tifton hay (Cynodon sp.) ad libitum. The treatments consisted of control (no supplementation), supplementation with non-protein nitrogenous compounds (urea and ammonium sulphate, 9:1) and supplementation with protein (albumin). In treatments with nitrogenous compound supplementation, 1 g of crude protein/kg of body weight was supplied. The experiment was conducted in a 3 × 3 Latin square design. The measurements were performed at 6, 12 and 24 hours after supplementation. No difference in GDH activity was observed among treatments. The control treatment showed higher CMCase activity when compared with the treatments containing supplemental sources of nitrogen. However, urea supplementation provided higher CMCase activity compared to albumin.

Evaluation of models for prediction of the energy value of diets for growing cattle from the chemical composition of feeds

The objective of this study was to estimate and evaluate the contents of apparently digestible fractions of crude protein, ether extract and non-fibrous carbohydrates, the digestible fraction of the neutral detergent fiber and the content of total digestible nutrients (TDN) from the chemical composition of feeds in growing cattle fed different diets. Fourteen F1 Red Angus × Nellore young bulls with average age and weight of 12 months and 287±36 kg were used. Animals were fed elephant grass silage, corn silage or signal grass hay, with or without supplementation of 200 g concentrate per kg of the total diet. The experiment consisted of two 13-days periods, in which the concentrate supplementation was crossed over animals. The values of digestible fractions and the TDN content observed were obtained based on total collection of feces. Several sub-models applied to the different digestible fractions were assessed and discussed. Estimates of the TDN content in the diet were produced from the combination of sub-models applied to the individual digestible fractions. The TDN content was more efficiently predicted from the sub-models proposed by Detmann et al. (2010) when biological procedures for the estimation of the undegradable fraction of the protein and the potentially degradable fraction of the neutral detergent fiber were considered.