Promoción de raigrás anual naturalizado (Lolium multiflorum L.) en la cuenca del río Salado. Evaluación de la producción invernal de forraje en pastoreo

Effective operation of grazing production systems needs control the production of forage at farm level. A nine year old stand of enhanced tame native ryegrass (Lolium multiflorum L.) (RGE) and an annual crop of Italian ryegrass (Lolium multiflorum L. cv Tama) (RGT) were monitored to test the hypothesis that: (i) herbage biomass in such pastures can be assessed by Ration Calculation methodology as accurately as by more exhaustive procedures, and (ii) enhancement increases amount and quality of forage winter supply. Enhancement includes fertilization with NH4 NO3 and (NH4 ) 2 HPO4, and weed control with Glyphosate (N- (phosphonomethyl glycine)). The Ration Calculation method estimates available herbage dry matter assuming that «one herbage ration» equal to one cow equivalent (CE), consisting of 10 kg DM day-1 with 77.57 MJ of ME. Herbage samples were taken from each paddock, representing harvestable biomass. Grazing harvest efficiency and herbage DM intake (HDMI) were estimated through difference between initial (IHA) and final (FHA) herbage available (kg DM ha-1), before and after grazing, corrected by losses due to grazing. Eight grazing cycles of RGE produced 16 041 kg DM/ha year-1, (2 001 ± 79.3 rations/ha year-1) while ration calculation estimates 9 775 kg DM/ha year-1. The RGT allowed seven grazing cycles, yielded 12 269 kg DM/ha year-1 or 1 144 ± 87.1 rations/ha year-1 compared to 8 688 kg DM/ha year-1 estimated by calculating ration. The ration calculation method did not accurately assess the enhanced cumulative herbage DM produced. Enhancement technology improved production and quality of tame ryegrass in winter time.El manejo de sistemas ganaderos de producción requiere controlar la producción de forraje a nivel de unidad de pastoreo. Con una pastura naturalizada y promocionada durante nueve años de raigras (Lolium multiflorum L.) (RGE) y un cultivo de raigras anual (Lolium multiflorum L. cv. Tama) (RGT) se probaron las hipótesis de que la biomasa forrajera aerea puede ser estimada correctamente por el método del cálculo de raciones como mediante los atributos del forraje, y que la promoción permite aumentar la producción invernal de forraje. La promoción involucra fertilizaciones con NH4 NO3 y (NH4 )2 HPO4 y control de malezas con Glifosato (N- (phosphonomethyl glycine). La estimación de materia seca disponible mediante el calculo de raciones asume que «una ración de forraje» son 10 kg MS día-1 que contienen 77.57 MJ de EM que representan un equivalente vaca (CE). La eficiencia de cosecha y consumo en pastoreo (HDMI) fueron estimados por diferencia entre disponibilidad forrajera inicial (IHA) y final (FHA) antes y después del pastoreo, corregido por pérdidas debidas al pastoreo. El período de crecimiento de la RGE permitió ocho pastoreos produciendo 16 041 kg MS/ha año-1 ó 2 001± 79.3 raciones/ha año-1 comparado con 9 775 kg MS/ha año-1 estimados por cálculo de raciones. En siete pastoreos el RGT produjo 12 269 kg MS/ha año-1 ó 1 144 raciones/ha año-1, comparado con 8 688 kg MS/ha año-1 estimados por el cálculo de raciones. Se concluye que el cálculo de raciones no estima correctamente la biomasa producida por una promoción y que, efectivamente, la tecnología de promoción aumenta la producción y calidad invernal del pastizal natural.Fil: Danelon, Jose Luis. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Magaz, Santiago Horacio. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Magaz, Hernan Miguel. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Colombatto, Dario. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Pré-incubação de inóculo ruminal para avaliação da produção de gases e digestibilidade in vitro

In vitro gas production techniques represent a valuable tool to describe the kinetics of ruminal degradation of food. However, the ruminal liquor used as a microbial inoculum has been a great source of variation and error. A standardization of this factor should contribute to assure the independence of food fermentation parameters from those of the inocula. In this research it was hypothesized that a controlled pre-incubation treatment of ruminal liquor could contribute to stabilize and homogenize the undigested residues of blanks and as a consequence, of the production of residual cumulative gas production (CGP). A pre-incubation (i.e. previous real incubation) of rumen inocula was developed with a simple substrate similar to the diet offered to donors at 1% w/v for 0, 1, 2 and 4 h (Control, Prei-1, Prei-2 and Prei-4 treatments respectively). Once the pre-incubation hours were completed, they were incubated with contrasting substrates and without substrate (i.e. blanks) in order to evaluate the CGP, in vitro digestibility of the DM and fermentation products. Although, the fermentative activity of the pre-incubated inoculums worked satisfactorily in the in vitro system, contrary to what was speculated, residues of the pre-incubation increased the variability and heterogeneity of variances among blanks. Consequently, it was concluded that the pre-incubations did not work to generate more homogeneous and less variable ruminal liquor for the in vitro gas production system.Técnicas de produção de gás in vitro representam uma ferramenta valiosa para descrever a cinética de degradação ruminal dos alimentos. No entanto, o líquido ruminal utilizado como inóculo microbiano tem sido uma grande fonte de variação e erro. A padronização deste fator deve contribuir para garantir a independência dos parâmetros de fermentação dos alimentos a partir dos inóculos. Neste trabalho, hipotetizou-se que um tratamento controlado de pré-incubação do líquido ruminal poderia contribuir para estabilizar e homogeneizar os resíduos não digeridos dos brancos e, como conseqüência, da produção de produção cumulativa de gás residual (CGP). Uma pré-incubação (ou seja, incubação real prévia) dos inóculos do rúmen foi desenvolvida com um substrato simples semelhante à dieta oferecida aos doadores a 1% p/v por 0, 1, 2 e 4 h (Controle, Prei-1, Pré- 2 e Prei-4 tratamentos respectivamente). Uma vez completadas as horas de pré-incubação, elas foram incubadas com substratos contrastantes e sem substrato (ou seja, brancos) para avaliar o CGP, a digestibilidade in vitro da MS e os produtos de fermentação. Embora a atividade fermentativa dos inóculos pré-incubados tenha funcionado satisfatoriamente no sistema in vitro, ao contrário do que foi especulado, os resíduos da pré-incubação aumentaram a variabilidade e heterogeneidade das variâncias entre os brancos. Consequentemente, concluiu-se que as pré-incubações não funcionaram para gerar um líquido ruminal mais homogêneo e menos variável para o sistema de produção de gás in vitro.Fil: Cantet, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Wawrzkiewicz, Marisa. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Jaurena, Gustavo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentin

Effects of exogenous enzymes on nutrient digestibility, ruminal fermentation and growth performance in beef steers

Forty crossbred steers (Baladi Friesian, average BW 15375.14 kg) were used to evaluate the effects of exogenous enzyme (ENZ) addition on nutrient intake, digestion, ruminal fermentation and feed conversion in beef steers. Steers were randomly assigned to two groups of 20 animals and fed individually a total mixed ration (TMR) without (CTRL) or with addition of 40 g/hd/d of an enzyme mixture (ZADOs). The ENZ mixture was added for 220 days and in vivo apparent digestibility was measured on days 210–220. Enzyme addition did not affect (P¼0.1) DM intake, whereas it increased (Po0.05) total tract apparent digestibility of all nutrients. The magnitude of improvement in digestibility varied among nutrients, with the highest improvement occurring in digestibility of NDF and ADF (21.8% and 26.7%, respectively). Addition of ENZ also increased (Po0.05) concentrations of rumen ammonia N and total short chain fatty acids (SCFA) before and 3 h post-feeding. Allantoin concentration total purine derivates were increased (P¼0.04) with enzyme addition while uric acid was not affected (P¼0.05). Live-weight gain was also higher (Po0.01) in steers supplemented with ENZ. In conclusion, adding the exogenous enzyme product increased live-weight gain by 16% due to increased nutrient digestibility

Chemical composition and in vitro ruminal degradation of hay and silage from tropical grasses

This study was conducted to evaluate the effects of preservation type on chemical composition and in vitro ruminal degradation of warm-season grasses (WSG). Treatments consisted of two factors (6×2): the first factor was tropical grasses: Cenchrus ciliaris (cv. Biloela, and cv. Molopo), Chloris gayana (cv. Callide and cv. Finecut), Panicum maximum, and Brachiaria bryzanta; and the second factor was preservation type (hay vs. silage). Cell wall, hemicellulose, cellulose, and water-soluble carbohydrate (P<0.05) concentrations were different among WSG. In general, hay or silage altered fiber content compared with fresh. For instance, hemicellulose and cellulose contents were lower in silage than in hay and fresh grass (P<0.05). Gas production rates were higher in silage from 0 to 24 h of fermentation, except at 4 h of incubation. After 24 h, gas production (GP) rate was similar for both preservation types, whilst potential GP was similar between preservation types. However, silage had decreased lag time compared with hay (P<0.01). Silage had greater dry matter disappearance than hay (P<0.05), and gas production yield was similar for grass species and preservation type. Our results indicate that WSG conserved as silage showed beneficial changes in chemical composition and dry matter degradation compared with hay.Fil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estación Experimental Agropecuaria Santiago del Estero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; ArgentinaFil: Cornacchione, M. V.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucuman-santiago del Estero. Estación Experimental Agropecuaria Santiago del Estero; Argentina. Universidad de Buenos Aires. Facultad de Agronomia; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; ArgentinaFil: Kunst, C.. Universidad Nacional de Santiago del Estero. Facultad de Agronomia y Agroindustrias; Argentin

Proposed terminology for animal nutrition laboratory reports

La valoración nutricional de los alimentos constituye un eslabón fundamental para el correcto funcionamiento de la agroindustria asociada con la alimentación de animales. El creciente desarrollo de las técnicas analíticas y la mayor difusión de los controles de calidad sobre los ingredientes y alimentos terminados ha generalizado el uso de términos asociados con la calidad de los alimentos, muchas veces pobremente definidos. Los objetivos de este artículo fueron: resaltar algunos conceptos relevantes para determinar el valor de los alimentos para animales; contribuir a mejorar el uso e interpretación de los resultados analíticos; llamar la atención sobre algunos procedimientos y estimaciones que dan lugar a confusiones o malas interpretaciones. Asimismo se propuso un listado de siglas para identificar algunas de las fracciones analíticas frecuentemente usadas en la evaluación de alimentos para rumiantes.The nutritional evaluation of feedstuffs is a fundamental link to the proper functioning of the agro-industry associated to feeding animals. The growing development of analytical techniques and wider dissemination of ingredients and finished food quality controls have generalized the use of terms associated with the food quality, often poorly defined. The objectives of this article were: highlighting some relevant concepts in determining the value of feedtuffs; contribute to improving the use and interpretation of analytical results; draw attention to some procedures and estimates that give rise to confusion or misinterpretation. It was also proposed a list of acronyms to identify some of the analytical fractions frequently used in the assessment of food for ruminants.Fil: Jaurena, Gustavo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Wawrzkiewicz, Marisa. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentin

Evaluation of in vitro energy distribution and methanogenic potential of two forages with the addition of condensed tannins

The objective of this work was to analyze the effect of the addition of condensed tannins (CT) in the efficiency of digestion, methanogenic potential and energy distribution between the fermentation products of two forages. An assay was carried out using the in vitro gas production technique in which extracts of Quebracho (Schinopsis balansae) and Lotus corniculatus were evaluated with fermentation patterns of derived products from Ryegrass (RG, Lolium perenne) and a tropical forage, Megathyrsus maximus (MM). Tannins were added to the substrate at a concentration of 30 mg g-1. MM presented higher and delayed gas production (GP), and in vitro dry matter, organic matter and fiber digestibilities (ivDMD, ivOMD and NDFD, respectively) were relatively high but lower than RG. In addition, MM presented higher CH4 production (CH4p) than RG in 24 and 48h. Even though CT of Quebracho induced a decrease in the NDFD, contrary to what was expected, CH4p was greater, although this effect could not be attributed to the presence of CT. The stoichiometric evaluation indicated that while the highest CH4p in Quebracho treatments were associated with acetogenic profiles, CH4p with Lotus did not show any relationship with the volatile fatty acids (VFA) profile, but it did show a relationship with the highest total VFA production and the highest GP.Fil: Cantet, Juan Manuel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Martinez, Rocío Soledad. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Barahona Rosales, Rolando. Universidad Nacional de Colombia. Sede Medellin; ColombiaFil: Molina Botero, Isabel Cristina. Universidad Nacional de Colombia. Sede Medellin; ColombiaFil: Jaurena, Gustavo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentin

Comparison of enhanced, tame Italian ryegrass (Lolium multiflorum L.), long established and naturally reseeded, versus an annual ryegrass crop in the flood plain of Río Salado, Argentina: Winter forage production under grazing

Effective operation of grazing production systems requires controlling forage availability at the farm level. A nine-year-old stand of enhanced native ryegrass (Lolium multiflorum L.) (RGE) and an annual crop of Italian ryegrass (Lolium multiflorum L. cv Tama) (RGT) were monitored to test the hypotheses that: (1) herbage biomass in such pastures can be assessed by Ration Calculation methodology as accurately as by more exhaustive procedures, and (2) enhancement increases quantity and quality of the winter forage supply. Enhancement includes fertilization with NH4NO3 and (NH4)2HPO4, and weed control with Glyphosate. The Ration Calculation method estimates available herbage dry matter assuming that «one herbage ration» is equal to one cow equivalent (CE), consisting of 10 kg DM day-1 with 77.57 MJ of ME. Herbage samples were taken from each paddock, representing harvestable biomass. Grazing harvest efficiency and herbage DM intake (HDMI) were estimated through the difference between initial (IHA) and final (FHA) herbage available (kg DM ha-1), before and after grazing, corrected for losses due to grazing. Eight grazing cycles of RGE produced annually 16 041 kg DM/ha, (2 001 ± 79.3 rations/ha) while ration calculation estimated 9 775 kg DM/ha. The RGT allowed seven annual grazing cycles, yielded 12 269 kg DM/ha or 1 144 ± 87.1 rations/ha compared to 8 688 kg DM/ha estimated by calculating rations. The latter method did not accurately assess the enhanced cumulative herbage DM produced. Enhancement technology improved production and quality of tame ryegrass in winter

Effects of chrysotile exposure in human bronchial epithelial cells: Insights into the pathogenic mechanisms of asbestos-related diseases

BACKGROUND: Chrysotile asbestos accounts for > 90% of the asbestos used worldwide, and exposure is associated with asbestosis (asbestos-related fibrosis) and other malignancies; however, the molecular mechanisms involved are not fully understood. A common pathogenic mechanism for these malignancies is represented by epithelial–mesenchymal transition (EMT), through which epithelial cells undergo a morphological transformation to assume a mesenchymal phenotype. In the present work, we propose that chrysotile asbestos induces EMT through a mechanism involving a signaling pathway mediated by tranforming growth factor beta (TGF-β). OBJECTIVES: We investigated the role of chrysotile asbestos in inducing EMT in order to elucidate the molecular mechanisms involved in this event. METHODS: Human bronchial epithelial cells (BEAS-2B) were incubated with 1 μg/cm2 chrysotile asbestos for ≤ 72 hr, and several markers of EMT were investigated. Experiments with specific inhibitors for TGF-β, glycogen synthase kinase–3β (GSK-3β), and Akt were performed to confirm their involvement in asbestos-induced EMT. Real-time polymerase chain reaction (PCR), Western blotting, and gelatin zymography were performed to detect mRNA and protein level changes for these markers. RESULTS: Chrysotile asbestos activated a TGF-β–mediated signaling pathway, implicating the contributions of Akt, GSK-3β, and SNAIL-1. The activation of this pathway in BEAS-2B cells was associated with a decrease in epithelial markers (E-cadherin and β-catenin) and an increase in mesenchymal markers (α-smooth muscle actin, vimentin, metalloproteinases, and fibronectin). CONCLUSIONS: Our findings suggest that chrysotile asbestos induces EMT, a common event in asbestos-related diseases, at least in part by eliciting the TGF-β–mediated Akt/GSK-3β/SNAIL-1 pathway. CITATION: Gulino GR, Polimeni M, Prato M, Gazzano E, Kopecka J, Colombatto S, Ghigo D, Aldieri E. 2016. Effects of chrysotile exposure in human bronchial epithelial cells: insights into the pathogenic mechanisms of asbestos-related diseases. Environ Health Perspect 124:776–784; http://dx.doi.org/10.1289/ehp.140962

Effect of condensed tannins in the methanogenic potential and in vitro digestion efficiency of ryegrass

Los rumiantes son capaces de degradar y fermentar los componentes de la pared celular de forrajeras. En el retículo-rumen, la fermentación microbiana particiona la energía bruta del sustrato en ácidos grasos volátiles, biomasa microbiana (BM) y gases de desecho (e.g. metano, CH4). Estos últimos son eliminados y representan, no solo contaminación ambiental por su efecto invernadero; sino también una pérdida de la energía disponible en el alimento. Numerosas especies vegetales poseen metabolitos secundarios, tales como los taninos condensados (TC), que, aunque tienen propiedades antimicrobianas y astringentes, su uso racional podría generar un mejor aprovechamiento de los forrajes con potenciales efectos mitigadores del CH4 entérico. En este contexto, se evaluó el efecto de cuatro dosis de TC de Quebracho (Schinopsis balansae, 0, 1,5, 3,0 y 4,5 mg TC cada 100 mg de sustrato; correspondientes a los tratamientos Ctrl, TC1, TC2 y TC3) mediante la técnica de producción de gas in vitro (PGiv), en presencia o ausencia de polietilenglicol (inhibidor específico de los TC), para determinar el impacto en la fermentación ruminal del raigrás (Lolium perenne). La digestibilidad disminuyó en TC3, mientras que la PGiv aumentó asociada a las mayores tasas iniciales. No hubo efecto de los TC sobre la producción de CH4, tampoco en la síntesis de BM. Por otro lado, el agregado de TC disminuyó la concentración de ácido propiónico, aumentado la relación acético: propiónico. Se concluye que los TC de Quebracho a las dosis estudiadas, no produjeron un efecto mitigador del CH4, además de modificar los parámetros de fermentación, sobre todo con una inclusión de 4,5 mg de TC/100 mg de sustrato incubado.Ruminants are capable of degrading and fermenting the forage cell wall components. In reticulo-rumen, the microbial fermentation partition gross energy of the substrate into volatile fatty acids, microbial biomass (MB) and waste gases (e.g. methane, CH4). These gases are eliminated and they represent, not only environmental pollution due to its greenhouse effect, but they also represent loss of the energy available in the forage. Numerous plant species have secondary compounds, such as condensed tannins (CT), although they have antimicrobial and astringent properties, their rational use could generate a better use of forages with potential mitigating effects of enteric CH4. In this context, it was evaluated the effect of four doses of Quebracho (Schinopsis balansae, 0, 1.5, 3.0 and 4.5 mg of CT per 100 mg of substrate, correspond to treatments Ctrl, TC1, TC2 and TC3) using the in vitro gas production technique (ivGP), in the presence or absence of polyethylene glycol (specific inhibitor of CT), to determine the impact on ruminal fermentation of ryegrass (Lolium perenne). The digestibility decreased in TC3, while the ivGP increased asociated with the higher initial rates. There was no effect of the CT on the CH4 production, neither in the synthesis of MB. On the other hand, the addition of CT decreased propionic acid concentration, increasing the acetic: propionic ratio. It is concluded that the CT of Quebracho, at the doses studied, did not produce a CH4 mitigating effect, in addition to modifying the fermentation parameters, especially with an inclusion of 4.5 mg of CT/ 100 mg of incubated substrate.Fil: Cantet, Juan Manuel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Neumann Reiter, A. M.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Colombatto, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Unidad Ejecutora de Investigaciones en Producción Animal. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Unidad Ejecutora de Investigaciones en Producción Animal; ArgentinaFil: Wawrzkiewicz, Marisa. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; ArgentinaFil: Jaurena, Gustavo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Animal; Argentin

Evaluación de un modelo de producción de pasturas mediante pruebas empíricas

En el presente trabajo se utilizó un modelo de crecimiento de pasturas desarrollado por McCall y BishopHurley. El objetivo fue evaluar si el modelo es capaz de simular las variaciones en producción primaria neta aérea en la estación húmeda utilizando pruebas empíricas. Se trabajó con una gramínea megatérmica, Chloris gayana. La evaluación empírica se realizó con datos de experimentos realizados en el Instituto de Investigación Animal del Chaco Semiárido (INTA), que incluyeron biomasa seca aérea acumulada durante la estación de crecimiento, y biomasa seca aérea producida entre dos pastoreos. Los estadísticos utilizados fueron raíz cuadrada del cuadrado medio del error, relación RMSE/Media observada, error medio y los coeficientes de la desigualdad de Theil. Los coeficientes de desigualdad de Theil para la producción primaria neta aérea acumulada (Um=0,35, Us=0,1, Uc=0,64) y por cortes (Um=0,08, Us=0,08, Uc=0,84) mostraron que el modelo no presentó errores sistemáticos. El patrón de crecimiento de la producción primaria neta aérea simulado fue 7% oct-nov, 64% dic-ene-feb, 29% mar-abr-may. El trabajo muestra el potencial del modelo de pasturas para simular la dinámica de la producción de Chloris gayana en ambientes del subtrópico argentino, siendo capaz de captar variaciones en el ambiente. En este sentido puede ser útil para estudiar interacciones entre el manejo y la dinámica de las pasturas en climas de alta variabilidad temporal.For this work, a pasture growth model developed by McCall and Bishop-Hurley, was used. The objective was to evaluate the model, using empirical tests. A tropical pasture named Chloris gayana, was used. For the empirical evaluation a database from the Animal Research Institute of Semiarid Chaco (INTA), was used, including information of herbage accumulated during the growing season, and cutting trials based on the difference between pre- and post-grazing herbage. The statistics calculated were root mean square error, relative root mean square error, mean error and Theil coefficients. The Theil coefficients for accumulated herbage (Um = 0.35, Us = 0.1, Uc = 0.64) and cutting trials (Um = 0.08, Us = 0.08, Uc = 0, 84), showed that the model did not present systematic errors. The growth pattern of simulated herbage was 7% Oct-Nov, 64% Dec-Jan-Feb, 29% Mar-Apr-May. The work shows the potential of the pasture model to simulate the forage production of Chloris gayana in subtropical environments, capturing variations in the environment. In this sense, it can be useful for studying interactions between management strategies and dynamics responses of pastures in highly variable climates.Instituto de Investigación Animal del Chaco SemiáridoFil: Nasca, Jose Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Berone, German Dario. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina.Fil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Cesáreo Naredo ArgentinaFil: Feldkamp, C.R. Asociación Argentina de Consorcios Regionales de Experimentación Agrícola; Argentina.Fil: Colombatto, Dario. Universidad de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin