A two-location trial for selecting corn silage hybrids for the humid tropic: forage and grain yields and in vitro fermentation characteristics

The goal of our study was to evaluate the nutritional potential of dented corn hybrids for silage production. We performed a two-location trial in which 19 dented corn hybrids and five corn controls grew in four randomized blocks within two experimental areas located in the Northern (Campos dos Goytacazes) and Northwestern (Itaocara) Rio de Janeiro State, Brazil. We recorded yields of fresh and dry forage matter and yields of fresh and dry grain matter, as well as chemical composition variables. We interpreted variables by assuming a Normal distribution for yield variables and a Beta distribution for chemical composition and ratios. The SAS GLIMMIX procedure fitted the linear model under those assumptions. Dual-pool models fitted the gas production profiles generated by in vitro anaerobic fermentations. We used the nlme of R software to fit the dual-pool models and the information-theoretic approach to evaluate their quality of fit. We did a cluster analysis (NbClust of R) to group corn hybrids based on fresh and DM yields and kinetic parameters of in vitro gas production. Three clusters of corn hybrids stood out, their basic differences relied on fresh and DM yields. Nonetheless, the least-squares means for gas production characteristics among groups did not present disjoint confidence intervals. Therefore, we can infer that dented corn hybrids rank by forage yield, but not by forage quality, and recommend the most productive ones that consistently outstand in both locations (hybrids UENF-2203, UENF-2192, UENF-2193, and UENF-506-11).

Evaluation of mathematical models to describe gas production kinetics of some tropical and temperate forages

Our objective was to identify the best fit mathematical models for in vitro gas production kinetics using rumen fluid and forage plants commonly used in ruminant feed to obtain better estimates of parameters that describe the rumen fermentation. Four mathematical models were tested, two unicompartmental (M1 = first order, M2 = Gompertz) and two bicompartmental (M3 = M1 + M2; M4 = M2 + M2). Two temperate grasses were evaluated, as well as four tropical grasses and three temperate forage legumes. The fit of the models was verified by the corrected Akaike information criterion (AICcr) and the difference among AICcr values (Δr), likelihood probability (Wr), and relative likelihood (ERr). Temperate forages reached maximum gas production between 48 and 72 h. In the tropical forages, it occurred only after 72 h. In profiles in which M3 was the best choice, the values of parameters Vf 1 were higher than those of Vf 2, and k1 values were higher than k2 values. The only exception was for Tifton 85 profile, whose Vf 2 value was higher than Vf 1. The model M3 has a better fit for tropical forages with higher fiber content and lower levels of nonfibrous carbohydrates and crude protein. The model M1 has a better fit for forage with higher nonfibrous carbohydrate contents and low lignin content.(AU)

The geometry of the lactation curve based on Wood's equation: a two-step prediction

Lactation records from cows of the southwestern Paraná state, Brazil, form the dataset of this study. We applied the information-theoretic approach to evaluate the ability of the nonlinear Wood, Brody, Dijkstra, and Gamma functions to fit to these data by employing a two-step technique based on nonlinear mixed-effects models and generalized linear mixed-effects models. Wood's equation was fitted with the combination of a first-order autoregressive correlation structure and a variance function to account for heteroscedasticity. This version was the best choice to mimic lactation records. Some geometric attributes of Wood's model were deduced, mainly the ascending specific rate from parturition to peak milk yield and the descending specific rate as a measure of the lactation persistence of the milk yield at peak production. Breed and parity order of the cows were assumed as fixed effects to obtain a reliable model fitting process. Regardless of breed, first-order parity cows had greater persistency than their older counterparts, and the greater the ascending rate of milk yield from the parturition to the peak, the sharper the decrease in milk yield post-peak; therefore, the rates (absolute values) of ascending and descending phases correlated positively. Nonetheless, the actual estimated values of the descending phase rates are negative. Wood's equation was flexible enough to mimic either concave- and convex-shaped lactation profiles. The correlations between both peak milk yield and random estimates for ß with total milk yield per lactation were positive. However, peak milk yield might not be the only variable used for ranking cows; the total milk yield integrates all information of the lactation profile through the estimated parameters of Wood's equation.(AU)

Chemical composition and ruminal degradation kinetics of white oat (Avena sativa L. ) IPR 126 / Composição química e cinética da degradação ruminal de aveia branca (“Avena sativa” L. ) IPR 126

The present study aiming to determine the nutritional quality of oat (Avena sativa L.) IPR 126 in order to produce forage for ruminants. Four periods between harvests were used: 14, 21, 28 and 35 days, distributed in randomized blocks with four replicates for each treatment. The variables evaluated were: the concentration of dry matter (DM), neutral detergent insoluble fiber (NDF), crude potein (CP), lignin, dry matter (DM), ash, ether extract (EE) and in vitro digestibility of dry matter obtained by measurement of gas production. The profile of gas production was adjusted to the logistic bicompartimental mathematical model. The variables and the parameters of the adjusted gas production curves were analyzed as repeated measurements through the PROC MIXED of SAS (version 9.0) and the restricted maximum likelihood (REML) as the method of estimation of parameters. Regression analysis was performed for the variables: DM, CP, EE, NDF, ash, and for the parameter k2 of the bicompartimental model. DM and NDF concentrations increased linearly, CP, ash, and the estimations of the parameter k2 reduced linearly and the EE concentration showed a cubic behavior in function of the age of harvest. Lignin and other parameters of the Schofield model were not influenced by the age of harvest. The harvest interval influenced some chemical components and degradation rate of fiber carbohydrates, but do not interfere in lignin concentration. The forage with 21 days of cutting interval has the high nutritional value.

O objetivo com este estudo foi determinar a qualidade nutricional da aveia (Avena sativa L.) IPR 126, a fim de produzir forragem para ruminantes. Foram utilizados quatro períodos entre os cortes: 14, 21, 28 e 35 dias, distribuídos em blocos casualizados com quatro repetições para cada tratamento. As variáveis avaliadas foram: a concentração de fibra insolúvel em detergente neutro (FDN), lignina, matéria seca (MS), cinzas, extrato etéreo (EE) e digestibilidade in vitro da matéria seca obtida pela medição da produção de gás. O perfil de produção de gás foi ajustado ao modelo logístico bicompartimental. As variáveis e os parâmetros ajustados às curvas de produção de gás foram analisados como medidas repetidas através do PROC MIXED do SAS (versão 9.0) e a máxima verossimilhança restrita (REML) como o método de estimação de parâmetros. A análise de regressão foi realizada para as variáveis: MS, PB, EE, FDN, cinzas, e para o parâmetro k2 do modelo bicompartimental. As concentrações de MS e FDN aumentaram linearmente, PB, cinza, e as estimativas do parâmetro k2 diminuíram de forma linear e a concentração de EE apresentou comportamento cúbico em função da idade de colheita. A lignina e outros parâmetros do modelo de Schofield não foram influenciados pela idade de colheita. O intervalo de colheita influenciou alguns componentes químicos e taxa de degradação de carboidratos de fibra, mas não na concentração de lignina. A forragem com 21 dias de intervalo de corte apresentou maior valor nutricional.

Chemical composition and ruminal degradation kinetics of white oat (Avena sativa L. ) IPR 126 / Composição química e cinética da degradação ruminal de aveia branca (“Avena sativa” L. ) IPR 126

The present study aiming to determine the nutritional quality of oat (Avena sativa L.) IPR 126 in order to produce forage for ruminants. Four periods between harvests were used: 14, 21, 28 and 35 days, distributed in randomized blocks with four replicates for each treatment. The variables evaluated were: the concentration of dry matter (DM), neutral detergent insoluble fiber (NDF), crude potein (CP), lignin, dry matter (DM), ash, ether extract (EE) and in vitro digestibility of dry matter obtained by measurement of gas production. The profile of gas production was adjusted to the logistic bicompartimental mathematical model. The variables and the parameters of the adjusted gas production curves were analyzed as repeated measurements through the PROC MIXED of SAS (version 9.0) and the restricted maximum likelihood (REML) as the method of estimation of parameters. Regression analysis was performed for the variables: DM, CP, EE, NDF, ash, and for the parameter k2 of the bicompartimental model. DM and NDF concentrations increased linearly, CP, ash, and the estimations of the parameter k2 reduced linearly and the EE concentration showed a cubic behavior in function of the age of harvest. Lignin and other parameters of the Schofield model were not influenced by the age of harvest. The harvest interval influenced some chemical components and degradation rate of fiber carbohydrates, but do not interfere in lignin concentration. The forage with 21 days of cutting interval has the high nutritional value.(AU)

O objetivo com este estudo foi determinar a qualidade nutricional da aveia (Avena sativa L.) IPR 126, a fim de produzir forragem para ruminantes. Foram utilizados quatro períodos entre os cortes: 14, 21, 28 e 35 dias, distribuídos em blocos casualizados com quatro repetições para cada tratamento. As variáveis avaliadas foram: a concentração de fibra insolúvel em detergente neutro (FDN), lignina, matéria seca (MS), cinzas, extrato etéreo (EE) e digestibilidade in vitro da matéria seca obtida pela medição da produção de gás. O perfil de produção de gás foi ajustado ao modelo logístico bicompartimental. As variáveis e os parâmetros ajustados às curvas de produção de gás foram analisados como medidas repetidas através do PROC MIXED do SAS (versão 9.0) e a máxima verossimilhança restrita (REML) como o método de estimação de parâmetros. A análise de regressão foi realizada para as variáveis: MS, PB, EE, FDN, cinzas, e para o parâmetro k2 do modelo bicompartimental. As concentrações de MS e FDN aumentaram linearmente, PB, cinza, e as estimativas do parâmetro k2 diminuíram de forma linear e a concentração de EE apresentou comportamento cúbico em função da idade de colheita. A lignina e outros parâmetros do modelo de Schofield não foram influenciados pela idade de colheita. O intervalo de colheita influenciou alguns componentes químicos e taxa de degradação de carboidratos de fibra, mas não na concentração de lignina. A forragem com 21 dias de intervalo de corte apresentou maior valor nutricional.(AU)

Cinética ruminal de rações com diferentes níveis de glicerina bruta / Ruminal kinectics of rations with different crude glycerin levels

O atual mercado consumidor de glicerol não possui demanda suficiente para consumir todo o glicerol que pode ser gerado pela alta produção de biodiesel, o que poderia ocasionar o descarte irresponsável deste resíduo no ambiente. Uma das alternativas para consumir parte do glicerol produzido é a suautilização na alimentação de animais. Uma importante avaliação a ser feita ao se adicionar qualquer ingrediente na ração de ruminantes é se o novo ingrediente causa alguma modificação na cinética ruminal da matéria orgânica. Neste contexto, teores crescentes de glicerina bruta (0, 30, 60, 90, 120, 150, 180,210 e 240 g kg-1 de matéria seca) foram incluídos em rações isoproteicas e isoenergéticas formuladaspara atender as exigências nutricionais de bovino com 300 kg de peso corporal para ganho de 1,2 kgd -1, com o intuito de avaliar possíveis efeitos na cinética de degradação da matéria orgânica in vitro,no pH e no nível de amônia do líquido ruminal e na produção de proteína microbiana. O delineamento experimental foi inteiramente casualizado com nove tratamentos e três repetições. O volume máximo de gases produzidos pelas frações solúveis e insolúveis, a taxa de produção de gás pela degradação dafração solúvel, a taxa de produção de gás pela degradação da fração insolúvel, a latência, o pH ruminal, a produção de amônia e de proteína microbiana não diferiram estatisticamente dentre os teores de glicerina. Em contrapartida, a digestibilidade in vitro da matéria seca, da matéria orgânica e da fibrasofreram aumento linear com a inclusão de glicerina.(AU)

The current consumption of glycerol is not enough to use all the glycerol that can be generated by high production levels of biodiesel, which could lead to irresponsible disposal of this residue in the environment. An alternative to consuming part of the glycerol produced is itsuse in animal feeding. An important assessment to be made before adding any ingredient in the diet of ruminants is if the new ingredient causes some change in the kinetics of ruminalorganic matter. In this context, increasing levels of crude glycerin (0, 30, 60, 90, 120, 150, 180, 210 and 240 g kg-1 dry matter) were included in isonitrogen and isocaloric diets formulated to meet the nutritional requirements of a 300 kg beef cattle gaining 1.2 kg d -1, in order to evaluate possible effects of glycerol on the in vitro kinetics of organic matter degradation, pH and ammonia ruminal levels, and microbial protein production. The experimental design wascompletely randomized with nine treatments and three replications. The maximum volume of gas produced by soluble and insoluble fractions, the rate of gas production by the degradation of the soluble fraction and insoluble fractions, the latency, the ruminal pH, the production of ammonia and of microbial protein did not differ among levels of glycerin. In contrast, the in vitro digestibility of dry matter, the organic matter and the fiber showed a linear increase with the inclusion of glycerin.(AU)

Cinética ruminal de rações com diferentes níveis de glicerina bruta / Ruminal kinectics of rations with different crude glycerin levels

O atual mercado consumidor de glicerol não possui demanda suficiente para consumir todo o glicerol que pode ser gerado pela alta produção de biodiesel, o que poderia ocasionar o descarte irresponsável deste resíduo no ambiente. Uma das alternativas para consumir parte do glicerol produzido é a suautilização na alimentação de animais. Uma importante avaliação a ser feita ao se adicionar qualquer ingrediente na ração de ruminantes é se o novo ingrediente causa alguma modificação na cinética ruminal da matéria orgânica. Neste contexto, teores crescentes de glicerina bruta (0, 30, 60, 90, 120, 150, 180,210 e 240 g kg-1 de matéria seca) foram incluídos em rações isoproteicas e isoenergéticas formuladaspara atender as exigências nutricionais de bovino com 300 kg de peso corporal para ganho de 1,2 kgd -1, com o intuito de avaliar possíveis efeitos na cinética de degradação da matéria orgânica in vitro,no pH e no nível de amônia do líquido ruminal e na produção de proteína microbiana. O delineamento experimental foi inteiramente casualizado com nove tratamentos e três repetições. O volume máximo de gases produzidos pelas frações solúveis e insolúveis, a taxa de produção de gás pela degradação dafração solúvel, a taxa de produção de gás pela degradação da fração insolúvel, a latência, o pH ruminal, a produção de amônia e de proteína microbiana não diferiram estatisticamente dentre os teores de glicerina. Em contrapartida, a digestibilidade in vitro da matéria seca, da matéria orgânica e da fibrasofreram aumento linear com a inclusão de glicerina.

The current consumption of glycerol is not enough to use all the glycerol that can be generated by high production levels of biodiesel, which could lead to irresponsible disposal of this residue in the environment. An alternative to consuming part of the glycerol produced is itsuse in animal feeding. An important assessment to be made before adding any ingredient in the diet of ruminants is if the new ingredient causes some change in the kinetics of ruminalorganic matter. In this context, increasing levels of crude glycerin (0, 30, 60, 90, 120, 150, 180, 210 and 240 g kg-1 dry matter) were included in isonitrogen and isocaloric diets formulated to meet the nutritional requirements of a 300 kg beef cattle gaining 1.2 kg d -1, in order to evaluate possible effects of glycerol on the in vitro kinetics of organic matter degradation, pH and ammonia ruminal levels, and microbial protein production. The experimental design wascompletely randomized with nine treatments and three replications. The maximum volume of gas produced by soluble and insoluble fractions, the rate of gas production by the degradation of the soluble fraction and insoluble fractions, the latency, the ruminal pH, the production of ammonia and of microbial protein did not differ among levels of glycerin. In contrast, the in vitro digestibility of dry matter, the organic matter and the fiber showed a linear increase with the inclusion of glycerin.