ABSTRACT 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).

ABSTRACT 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 β 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.

ABSTRACT 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.

RESUMO 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.

SUMMARY 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.

RESUMO. O manejo da pastagem com níveis de lâminas foliares pode favorecer incrementos significativos na produção, sendo que as folhas representa um papel importante na relação planta-animal, sendo responsável pela eficiência fotossintessintética e substrato de melhor qualidade na dieta animal. Com o intuito de avaliar as massas foliares da estrela africana (Cynodon nlemfuensis var. Nlemfuensis), o presente trabalho teve como objetivo identificar qual massa de lâmina foliar proporciona melhor produtividade e qualidade nutricional. Os tratamentos avaliados foram as diferentes massas de lâmina foliar: 800, 1.200, 1.600 e 2.000 kg de matéria seca ha-1. O delineamento experimental utilizado foi inteiramente casualizado, com quatro tratamentos e três repetições, totalizando 12 parcelas de 100 m2 cada. Os resultados indicaram elevação na produção de colmo, na relação folha: colmo e nos dias de descanso de acordo com o aumento das massas de lâminas foliares. A taxa de acumulo diário de laminas foi semelhante para os tratamentos. Além disso ocorreu decréscimo nos teores de proteína bruta e elevação nos teores de fibra em detergente neutro e ácido. No entanto, as maiores produções de forragem foram observadas nos tratamentos 1.200 e 1.600 kg ha-1 de massa de lâminas foliares.

ABSTRACT. Pasture management with levels of leaf blades may favor significant increase in production, and the leaves indicated an important role in plant-animal relationship, caused by photosynthesis efficiency and better quality in animal diet. Current study identifies which leaf blade mass of the African star (Cynodon nlemfuensis var. Nlemfuensis) provides better productivity and nutritional value. Treatments comprised different leaf blade masses: 800, 1200, 1600 and 2000 kg of dry matter ha-1. The experimental design was completely randomized, with four treatments and three repetitions, totaling 12 plots with 100 m2 each. Results indicated increase in production, in the leaf/stem ratio and in the interval days according to increase in leaf blade mass. Daily accumulation rate was similar to treatments. Crude protein decreased and fiber increased with rise in leaf blade mass and the highest forage productions were reported in the treatments 1200 and 1600 kg ha-1 leaf blade mass.