Ricardo Augusto Mendonça Vieira

The influence of elephant-grass (Pennisetum purpureum Schum., Mineiro variety) growth on the nutrient kinetics in the rumen

Abstract The kinetic behavior of the dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) of the elephant-grass Mineiro variety was estimated through in situ incubation of the samples from this forage harvested at 61, 82, 103, 124 and 145 days after planting. The kinetic parameters were estimated by using a compartmental model of digestion based on sequential first-order kinetics for the lag and digestion events. The potentially degradable and undegradable fractions, the duration of the discrete lag time of the NDF and the apparent ruminal digestibility of the DM, CP and NDF were affected by the forage cutting age. The rise in the NDF undegradable fraction was associated with the increase in the mean retention time (MRT) of forage particles, resulting in a higher rumen fill effect (RFE) of this nutrient. The forage cutting age did not affect the discrete lag time of the DM and CP nor the first-order rate constants for digestion and lag of the DM, CP and NDF. The apparent ruminal digestibility of the DM and NDF was higher when the plants achieved approximately 146 and 152 cm in height. The MRT and the RFE increased linearly with the cutting height of the plants. The limiting factor exercised by the undegradable fraction upon voluntary intake, by assuming an inverse relationship between feed intake and MRT, could explain the lower performance of ruminants fed on this forage when later cuts are employed.

Application of non-linear models in the description of in situ degradation profiles of the elephant grass (Pennisetum purpureum Schum., Mineiro variety)

Abstract Degradation profiles of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) from elephant grass, Mineiro variety, cut and collected at different ages after planting, were obtained by in situ trials using three rumen cannulated Holstein heifers. Models derived from the exponential decay law and the first-order reaction curve, as well as logistic models (compartmental models of digestion), were used to describe the incubation data, with the curve-fitting of the various models compared through the examination of the residuals (e i = Y i -Ŷ i ). The time profiles of the natural logarithm of the insoluble but potentially degradable residue were analyzed by decomposing the mean square of the independent variable (time) in its polynomial effects. Results showed that 56% of the fractions that compose the nutrients were homogeneous; some profiles presented a quadratic fit, indicating the presence of a lag phase in its initial portion. The cubic effect observed indicated non-homogeneity of the pool, suggesting modifications of the first-order model for a correct kinetic interpretation. The lower number of runs of sign of the residuals revealed the tendency of the first-order exponential models to over- or underestimate certain degradation profiles sections, principally the model whose parameters were estimated after logarithmic transformation and linear regression of the data. The fitting of the compartmental model of digestion and the compartmental model of digestion corrected for the discrete lag time resulted in greater stability and greater number of runs of sign of the residuals, and both models did not show a significant lack of fit test for any curve. It was necessary a reparameterization of the digestion compartmental model in order to fit 42.22% of the degradation profiles studied. These models seems to describe adequately the data for in situ incubation of elephant-grass; however, no long lag times were observed, and the correction for the discrete lag seems not to be necessary. If a sigmoidal pattern is followed, the compartmental model of digestion should be used in the description of degradation profiles of nutrients found in other tropical forages. As a consequence, it could also be used to calculate the ruminal availability and the escape of dietary nutrients to the lower tract.

Padrão Nictemeral do pH Ruminal e Comportamento Alimentar de Cabras Leiteiras Alimentadas com Dietas Contendo Diferentes Relações Volumoso: Concentrado

The objectives of the present study were to characterize nictemeral pattern of ruminal pH and feed behavior of dairy goats fed diets presenting different ratios of roughage:concentrate. Five non pregnant non lactating goats, ruminally cannulated, and averaging 58 kg were used during the five experimental periods. A 5x5 Latin square was used to evaluate five treatments consisted of roughage to concentrate ratio of 100:0, 80:20, 60:40, 40:60 e 20:80. Diets were fed every 6h in order to reduce ruminal pH variation during the 24h period. After adaptation to experimental diets, a 48h period was given to measure ruminal pH hourly for 24h, to be used as a covariate, following a study of feeding behavior where measurement was taken at every 10 minutes for the remaining 24h period. It was observed that increasing level of concentrate resulted in reduction of pH, especially when concentrate accounted for more than 60%. Treatment effect was also observed on time spent eating, ruminating and idling. Time spent eating was greater as percentage of roughage in the diet increased, especially over 60%. Roughage content of 100% presented the highest value of rumination time and the lowest value for idle, following diets containing 80 e 60% respectively. There were no difference between diets containing 40 e 20% roughage, which presented the lowest value for rumination and the highest for idle time.

Fracionamento dos carboidratos e cinética de degradação in vitro da fibra em detergente neutro da extrusa de bovinos a pasto

The objectives of the present work were to characterizate and determinate the parameters estimates related to the ruminal degradation kinetics of the carbohydrates in extrusa samples from animals maintained in a natural pasture of the Zona da Mata (MG) region, during the rainy and dry seasons of the year. To obtain representative samples, four esophageal fistulated steers were used in two experimental periods during the rainy season, and three of these animals were used in two experimental periods during the dry season, in the year of 1996. The carbohydrate fractionation according to the Cornell system was done, and the neutral detergent fiber (NDF) degradation rates were obtained from the in vitro degradation profiles of this component. The potentially degradable (B2) and undegradable (C) fractions of NDF corrected for protein and ash, the dynamic lag rates, the degradations rates, and the specific growth rates of microorganism upon fraction B2 were obtained, as well as the degradability coefficients and the rumen fill effect of NDF. As a result, it was possible to observe that the nonstructural carbohydrates comprised a minor fraction of the total carbohydrates in the pasture samples in both seasons. The structural carbohydrates were responsible by the total carbohydrate increase in the extrusa from the rainy to the dry season; nevertheless, due to the C fraction increase and to the lower specific microorganism growth rates during the dry season, it was noticeable the reduction of the extrusa NDF degradability and its increased rumen fill effect.

Avaliação de sistemas de produção de caprinos leiteiros na Região Sudeste do Brasil

A survey was performed on milk production costs of three farms which supply milk for the same milk processing line, on the fluminense mountain region and Zona da Mata of Minas Gerais, in the year of 2002: Capril Pedra Branca (CPB), Capril Vale da Brauna (CVB) and Capril Via Capri (CVC). The Capril Pedra Branca and Capril Vale da Brauna represented confining production systems whereas Capril Pedra Branca bought all the feed while Capril Vale da Brauna produced part of the forage on the farm. In the Capril Via Capri animals were kept on pasture during the day, but received feed supplementation at evening. Technical indexes obtained of those farms were compared and used to identify which components caused more influence on the total costs of the production activity. Herd feeding was the most important item on the productive systems, varying between 60 and 70 percent of the total cost. The production system of Capril Vale da Brauna showed the best profitability because of their own forage production that decreased the costs with feeding, and supplied the nutrients necessary according to the production levels of the animals.

Kinetic parameters of ruminal degradation estimated with a non-automated system to measure gas production

Abstract The kinetic parameters of the dry matter and neutral detergent fiber degradation of some tropical forages were estimated through anaerobic incubations by the cumulative gas production technique and by curve subtraction. The measurements were made using a non-automated system, which has a manometer connected to a syringe. Corn silage and the forages Cynodon dactylon, Pennisetum purpureum, Brachiaria brizantha, Brachiaria decumbens, and Melinis minutiflora were studied. The kinetic interpretations of the cumulative gas production data were analysed by using a multicompartmental logistic model. The data obtained with this system showed lowest coefficient of variation for both dry matter (DM) and neutral detergent fiber (NDF), especially after 12 h of incubation, being similar to those described in other studies with automated systems. A strong linear relationship was observed when the total of gas produced was plotted against the NDF degradation, the amount of neutral detergent soluble carbohydrate and the effective degradability of the forages studied. It was concluded that kinetic parameters of the rapid and slow fractions in the feed constituents could be estimated accurately by cumulative gas production measured with this cheaper non-automated system.

Simulation of the nutrient dynamics in the gastrointestinal tract: application and validation of a mathematical model for grazing cattle

ABSTRACT - The objective of the present work was to validate the ruminal and post-ruminal nutrient dynamics and the ruminalmicrobial growth predictions, by using the equations of the Cornell system. The experiment was carried out during the rainy and dry seasonsof the 1996 year, in a natural pasture area situated in the county of Vicosa (MG). Esophageally, ruminally and abomasally cannulated steerswere used during two experimental periods within each season, and external markers (Cr 2 O 3 and Eu) were used to estimate the intake andthe ruminal digesta passage rate. The total nitrogen and the bacterial nitrogen flows, total and structural carbohydrates digested in the rumen,and the total of digestible nutrients contents were determined. These variables were also predicted from the model described in the Cornell system to validate its estimates. It was verified that the model was sensitive to the passage rate estimates, overestimated (12.38%) thebacterial nitrogen flow to the abomasum, and underestimated (70.64%) the structural carbohydrates availability in the rumen. The correctionbased on .02 h

Fractionation and in vitro degradation kinetics of extrusa nitrogenous compounds from grazing cattle

The objective of the present study was to determinate the nitrogenous compounds fractions present in the extrusa of grazing cattle maintained in a natural grassland in the Zona da Mata region, MG. The samples were obtained by using four esophageal fistulated steers in two experimental periods during the rainy season of 1996, and three of these animals were used to take samples in two experimental periods during the dry season of the same year. In order to obtain the nitrogen fractionation (fractions A, B 1 , B 2 , B 3 e C), the crude protein (CP), non-protein nitrogen (NPN), borate-phosphate buffer insoluble nitrogen, and neutral detergent and acid detergent insoluble nitrogen were determined. The in vitro degradation profiles of the protein fractions were obtained by incubating the pasture samples with Streptomyces griseus proteases. With these techniques it was possible to detect reductions in the CP content and in the percentage (% CP) of B 3 fraction and increases in the percentages of the A, B 1 and C fractions from EC to ES; no differences were found for the percentage of the fraction B 2 between seasons. The degradation rates of fractions B 2 and B 3 were extremely variable: its average estimates were 2.427 and 0.057 h -1 , respectively, during the rainy season, and 2.149 and 0.034 h -1 , during the dry season.

Estimation of the total efficiency of metabolizable energy utilization for maintenance and growth by cattle in tropical conditions

Data of 320 animals were obtained from eight comparative slaughter studies performed under tropical conditions and used to estimate the total efficiency of utilization of the metabolizable energy intake (MEI), which varied from 77 to 419 kcal kg-0.75d-1. The provided data also contained direct measures of the recovered energy (RE), which allowed calculating the heat production (HE) by difference. The RE was regressed on MEI and deviations from linearity were evaluated by using the F-test. The respective estimates of the fasting heat production and the intercept and the slope that composes the relationship between RE and MEI were 73 kcal kg-0.75d-1, 42 kcal kg-0.75d-1 and 0.37. Hence, the total efficiency was estimated by dividing the net energy for maintenance and growth by the metabolizable energy intake. The estimated total efficiency of the ME utilization and analogous estimates based on the beef cattle NRC model were employed in an additional study to evaluate their predictive powers in terms of the mean square deviations for both temperate and tropical conditions. The two approaches presented similar predictive powers but the proposed one had a 22% lower mean squared deviation even with its more simplified structure.

Dairy goat husbandry amongst the household agriculture: herd and economic indexes from a case study in Rio de Janeiro, Brazil

Dois sistemas de producao de caprinos leiteiros praticados de acordo com o modelo familiar foram avaliados quanto a geracao de renda. Um teste para verificacao de viabilidade economica do empreendimento foi executado utilizando-se dados coletados de agosto de 2004 a julho de 2005. As fazendas, denominadas A e B, eram pequenas propriedades produtoras de cabras Saanem em sistema intensivo. Indices de rebanho, rendas, impostos, combustivel, energia, concentrado, custos de oportunidade e capital de interesse foram computados para estimacao da renda liquida e da taxa de retorno do capital para avaliacao do quanto o negocio pode ser atraente em geracao de renda. Os indices de rebanho foram afetados significativamente pelas decisoes tomadas pelos administradores e interferiram sobre as quantidades e tendencias relacionadas a producao de leite. Na unidade B, a variacao sazonal reduziu com a inducao de cio, uma pratica nao realizada na unidade A. O ganho de peso diario das cabritas apos a desmama (89 e 76 g/dia para A e B) foi baixo em comparacao as recomendacoes atuais. As medias dos registros de lactacao (441 e 606 L/cabra) e fertilidade (86,95 e 85,71%) estiveram nos limites preconizados na literatura. Tarefas diarias na unidade B consumiam 5 horas e 55 minutos para producao media de leite de 40,9 L/dia, enquanto na unidade A correspondiam a 8 horas e 16 minutos diarios para producao media de 32,2 L/dia. A unidade B apresentou custo total de producao (R