Nitrogen fertilization of wheat for forage and grain production in the south west of Buenos Aires province (Argentina)

Cuando del cultivo de trigo (Triticum aestivum) se obtiene forraje y grano, i.e. cultivo doble propósito (DP), la disponibilidad de nitrógeno puede ser un aspecto clave para la expansión de esta alternativa. Se comparó la respuesta al N en trigo DP fertilizado en abril (DPF), en agosto (DPG), en ambas fechas (DPFG) y en el cultivo para grano (TC) en un experimento factorial con las dosis de N: 0, 40, 80, 120, y 160 kg ha-1, aplicado como urea al voleo. Se determinó el rendimiento de forraje y de grano y el contenido de N en cada producto. El rendimiento de forraje se incrementó en promedio en 10,3 kg MS kg-1 de N aplicado, hasta la dosis de 120 kg ha-1. El rendimiento de grano fue menor en los DP, pero tuvo una mayor respuesta a N, incrementándose en 8,3, 7,3, 4,7, y 4,7 kg kg-1 de N aplicado para DPG, DPFG, DPF y TC respectivamente. La eficiencia agronómica de la respuesta a N en el rendimiento de grano fue superior en los manejos de DP y estos resultados muestran una mayor conveniencia de la fertilización nitrogenada en estos que en TC.When forage and grain are obtained from a wheat crop, (Triticum aestivum), i.e. a dual purpose crop (DP), the availability of N can be a key factor for the expansion of this alternative system. The response to nitrogen fertilization of a DP crop fertilized in April (DPF), in August (DPG), in both dates (DPFG) and in wheat grown only for grain (TC) was compared in a factorial experiment with the N levels 0, 40, 80, 120, and 160 N kg ha-1, applied as broadcast urea. Forage and grain yield and N content of each product were determined. Forage yield increased, on average, 10.3 kg dry matter per kg of applied N, up to the 120 kg ha-1 level. Grain yield was lower in DP than TC but had a higher response to N, increasing on average 8.3, 7.3, 4.7, and 4.7 Kg per kg applied N, for DPG, DPFG, DPF and TC respectively. The agronomic efficiency of the response to N in grain yield was higher in DP than in TC and these results show that N fertilization in DP is more convenient than in TC.Fil: Arzadun, M.. Chacra Experimental Coronel Suárez; ArgentinaFil: Laborde, H.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Arroquy, Jose Ignacio. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero; Argentin

Effect of Planting Date, Clipping Height, and Cultivar on Forage and Grain Yield of Winter Wheat in Argentinean Pampas

In Argentinean Pampas, new wheat (Triticum aestivum L.) cultivars are routinely introduced to farmers for dual-purpose production. The objective of this study was to evaluate the effect of planting date, clipping height on forage, and grain yield for wheat cultivars. Treatments were arranged as a 3 × 3 × 3 factorial distributed in a split-split plot within a randomized complete block design. Main plots were planting date (March, April, and May); split-plots were clipping height (3 cm, 7 cm, and no clipping); and split-split plots were a facultative cultivar Pincen, and two nonfacultative cultivars Charrua and Bordenave 223 (Bve223). In 1995 and 1996 forage yield decreased in response to a delayed planting date from March to May, whereas in 1997 it was not affected by planting date. The 3-cm clipping height yielded 21% more forage than plots clipped at 7 cm. Bve223 and Charrua produced significantly more forage than Pincen each year. Grain yield increased as planting date progressed from March to May. Clipping at 3 cm reduced grain yield compared with no clipping, while during 2 to 3 yr, 7 cm produced no significant change in grain yield compared with no clipping. In all years Bve223 produced more grain than Charrua or Pincen. Forage yield lost in response to later planting date ranged between 0 and 81% during the 3 yr; whereas grain yield increased from 40 to 190% for wheat planted in May compared with March. In conclusion, dual-purpose wheat planted during April had both good forage and grain production, and its success was influenced by cultivars.Fil: Arzadún, M. J.. Provincia de Buenos Aires. Ministerio de Asuntos Agrarios; ArgentinaFil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Laborde, Hugo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Brevedan, Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentin

Designing Diverse Agricultural Pastures for Improving Ruminant Production Systems

Pasture-based production systems represent a significant sustainable supplier of animal source foods worldwide. For such systems, mounting evidence highlights the importance of plant diversity on the proper functioning of soils, plants and animals. A diversity of forages and biochemicals –primary and secondary compounds- at appropriate doses and sequences of ingestion, may lead to benefits to the animal and their environment that are greater than grazing monocultures and the isolated effects of single chemicals. Here we review the importance of plant and phytochemical diversity on animal nutrition, welfare, health, and environmental impact while exploring some novel ideas about pasture design and management based on the biochemical complexity of traditional and non-traditional forage sources. Such effort will require an integration and synthesis on the morphology, ecophysiology, and biochemistry of traditional and non-traditional forage species, as well as on the foraging behavior of livestock grazing diverse pasturelands. Thus, the challenge ahead entails selecting the “right” species combination, spatial aggregation, distribution and management of the forage resource such that productivity and stability of plant communities and ecological services provided by grazing are enhanced. We conclude that there is strong experimental support for replacing simple traditional agricultural pastures of reduced phytochemical diversity with multiple arrays of complementary forage species that enable ruminants to select a diet in benefit of their nutrition, health and welfare, whilst reducing the negative environmental impacts caused by livestock production systems.Fil: Distel, Roberto Alejandro. Universidad Nacional del Sur. Departamento de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Arroquy, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Buenos Aires Sur. Estacion Experimental Agropecuaria Cesareo Naredo.; ArgentinaFil: Lagrange, Sebastián. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Bordenave; Argentina. State University of Utah; Estados UnidosFil: Villalba, Juan Jose. State University of Utah; Estados Unido

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

Uso de subproductos de planta de algodón como fuente de fibra en dietas de engorde a corral

Los residuos de cosecha del cultivo de algodón disponibles en el norte argentino son una fuente alternativa de fibra larga (FL) para el reemplazo de forraje voluminoso de mayor costo (ej., heno de alfalfa o ensilajes de gramíneas) en dietas de alta concentración energética. El objetivo de este experimento fue evaluar el efecto de la sustitución de una fuente de FL, heno de alfalfa, por subproducto de planta de algodón (SPA) sobre el aumento medio diario (AMD), el consumo diario de materia seca (CMS) y la conversión (CMS/AMD) en dietas de engorde a corral. Se utilizaron 104 animales (Cruza Braford; 220 ± 4 kg PV) asignados al azar a 12 corrales (8 o 9 animales/corral) durante 68 días. El experimento se dividió en dos etapas de evaluación: adaptación (días 0 a 19), y terminación (días 20 a 68). Los tratamientos (4) consistieron en el reemplazo de heno de alfalfa (12,9% PB, 65,5% FDN) por SPA (7,2% PB, 71,4% FDN): 100% Alfalfa (SPA0), 66% Alfalfa: 33% SPA (SPA33); 33% Alfalfa: 66% SPA (SPA67); y 100% SPA (SPA100). El peso promedio inicial (día 0; P = 0,92), al final de la adaptación (día 19; P = 0,26) y final (día 68; P = 0,37) no difirió significativamente entre tratamientos. El AMD (P > 0,43), CMS (P >= 0,23) y CMS/AMD (P = > 0,50) no fueron afectados por los tratamientos en ninguna de las etapas evaluadas. Los resultados obtenidos en este experimento demuestran que el reemplazo total o parcial de heno de alfalfa de mediana calidad por SPA en dietas altas en concentrados (>89%) no afecta negativamente la ganancia de peso ni la conversión de la ración.Cotton fibre co-products available in northern Argentina are a source of effective fiber to replace high cost roughage (e.i., alfalfa hay or silage or grasses) in finishing diets. This experiment was conducted to evaluate the effect of replacing roughage sources (alfalfa hay) by cotton plant byproduct (SPA) on average daily gain (ADG), dry matter intake (DMI) and feed efficiency (DMI/ADG) in feedlot diets. One hundred and four (220 ± 4 kg PV) were assigned to 12 pens (8 or 9 head/per pens) for 68 days on feed. The experiment was divided in two feeding periods: adaptation (days 0 to 19) and finishing (days 20 to 68). Treatments consisted of replacing the roughage portion of the diet (alfalfa hay; 12.9% CP, 65.5% NDF) by SPA (7.2% CP, 71.4% NDF): 100% alfalfa (SPA0); 66% alfalfa: 33% SPA (SPA33); 33% alfalfa: 66% SPA (SPA67); and 100% SPA (SPA100). Initial (day 0; P = 0.92), adaptation (day 19; P = 0.26) and final (day 68; P = 0.37) average live weight did not significantly differ among treatments. Moreover, ADG (P > 0.43), DMI (P > 0.23) and DMI/ADG (P > 0.50) were not affected by treatments for both feeding periods. Results show that total or partial replacement of alfalfa roughage by SPA in high concentrate diets (>89%) do not adversely affect live weight gain and feed efficiency.EEA Santiago del EsteroFil: Arroquy, Jose Ignacio. 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; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; ArgentinaFil: Lopez Fernandez, C.J. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: López, Agustín. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; Argentin

Suplementação de grãos de destilação secos com solúveis melhora a utilização de grama tropical de baixa qualidade para novilhos de corte

This study was designed to evaluate the effect of corn dried distiller´s grains (DDGS) supplementation on feed intake, total tractdigestibility, and ruminal fermentation of beef steers fed low-quality Guinea grass (Megathyrsus maximus, cv. Gatton panic). TwelveBraford crossbred steers were housed in individual pens (n = 4 steers/treatment), provided with three levels of DDGS supplement: 0%, 0.6%,or 1.2% BW. Steers were blocked by live weight and randomly assigned to treatments within the block. Corn DDGS supplementation increasedtotal OM intake (21.55, 40.23, and 56.69 g/kg BW0.75) and tract OM digestibility (46.33, 49.03, and 72.39 % DM). Total tract digestible OM,CP, NDF and EE intake also increase in response to DDGS supplementation. Forage OM intake decreased when supplementation level reached1.2 % BW. Also, ruminal pH decreased with DDGS supplementation level (6.88, 6.47, and 6.27). No differences were observed in total volatilefatty acids (VFA) concentration; however, the molar proportion of acetate decreased (77.98, 73.90, and 67.29 % Total VFA) as well as acetate:propionate ratio (4.38, 3.48, and 2.74). On the contrary, propionate proportions increased (18.32, 21.86, and 24.81 % Total VFA). Levels ofammonia and lactate were within suggested values for optimal fermentation and bacterial growth. Low-quality grass supplementation withcorn DDGS increased total OM intake and digestibility. Also, DDGS inclusion favorably altered volatile fatty acids profile by reducing theacetate to propionate ratio regarding forage-only diets.O objetivo deste estudo foi avaliar o efeito da suplementação com grãos de destilação secos de milho com solúveis (DDGS) no consumo, digestão e fermentação ruminal de novilhos de corte alimentados com capim-da-índia de baixa qualidade (Megathyrsus maximus, cv. Gatton panic). Doze novilhos mestiços Braford foram alojados em baias individuais (n = 4 novilhos / tratamento), fornecidos com três níveis de suplemento de DDGS: 0%, 0,6% ou 1,2% PV. Os novilhos foram bloqueados pelo peso vivo e atribuídos aleatoriamente aos tratamentos dentro do bloco. A suplementação com DDGS de milho aumentou o consumo de matéria orgânica total (21,55, 40,23 e 56,69 g / kg PV0,75), a digestibilidade da matéria orgânica (46,33, 49,03 e 72,39% MS) e o consumo de todos os nutrientes digestíveis. O consumo de matéria orgânica da forragem diminuiu quando o nível de suplementação atingiu 1,2% PV. Além disso, o pH ruminal diminuiu com o nível de suplementação com DDGS (6,88, 6,47 e 6,27). Não foram observadas diferenças na concentração de ácidos graxos voláteis totais, no entanto, a proporção molar de acetato diminuiu (77,98, 73,90 e 67,29% de AGV total), bem como a relação acetato: propionato (4,38, 3,48 e 2,74). Pelo contrário, as proporções de propionato aumentaram (18,32, 21,86 e 24,81% Total de AGV). Os níveis de amônia e lactato estavam dentro dos valores sugeridos para fermentação ideal e crescimento bacteriano. A suplementação de gramíneas de baixa qualidade com DDGS de milho aumentou o consumo e a digestibilidade da MO total. Além disso, a inclusão de DDGS alterou favoravelmente o perfil de ácidos graxos voláteis, reduzindo a proporção de acetato para propionato em relação às dietas apenas com forragem.Fil: Hernández, Olegario. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: López, Agustín. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: García, Elisa Mariana. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nazareno, Mónica Azucena. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Cesáreo Naredo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; 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

Effect of discontinuous roughage delivery on digestion, rumen metabolism, feed efficiency and live weight gain of beef steers fed a concentrate diet

Two experiments were carried out to study the effect of feeding a total mixed ration (TMR) compared to feeding the roughage portion of the diet once every two days and separated of the daily delivered concentrate mixture on dry matter intake, nutrient digestibility, ruminal metabolism, feed efficiency and liveweight gain. In Trial 1, thirty beef steers (Braford and Braford × Criollo; initial BW = 259 ± 27 kg) were used in a 69-d feeding trial. Treatments were: total mixed ration (TMR), and the same proportion of ingredients for the ration but roughage offered once every 2-d and separated from the daily delivered concentrate portion of the diet (REOD). Treatments were arranged in a completely randomized design (three pens/ treatment). In both treatments, daily offered ration had on dry matter basis 90% concentrate and 10% grass hay (Setaria italica). Average daily gain (ADG) did not differ among treatment (1013 vs. 1080 g/d for TMR vs. REOD respectively; SEM = 95 g/d). Dry matter intake was greater in TMR compared to REOD (P < 0.01). Gain to feed ratio tended to be better for REOD than TMR (P = 0.07). In Trial 2, four rumen cannulated steers (Braford) were used in an experiment with a crossover design. Treatments were arranged as a 2*2 factorial design, where the first factor consisted of roughage level (RL): (R14) 14% roughage: 86% concentrate and (R7) 7% roughage: 93% concentrate. The second factor was roughage delivery system (RDS; as it was described for Trial 1): TMR and REOD. There were no RL*RDS interactions for intake and digestion (OM, CP, NDF and starch). Both RL were similar for intake and digestion. Roughage delivery system did not significantly affect intake and digestion of OM, CP, NDF, and starch measured by total fecal collection. Total organic acids (TOA), acetate to propionate ratio (A:P), pH, and rumen ammonia concentrations were not affected by RL and RDS. In conclusion, under the conditions of these trials, steers fed a separated roughage source once every 2-d had similar ADG, and tended to be more efficient compared with TMR. Total tract digestibility and rumen environment traits (pH, VFA, and ammonia) were not affected in response to discontinuous roughage delivery.Fil: Arroquy, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Nazareno, Mónica Azucena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias. Instituto de Ciencias Químicas; ArgentinaFil: García, Elisa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias. Instituto de Ciencias Químicas; ArgentinaFil: Cervetto, Juan Jose. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Avila, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Saravia, J. J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Distel, Roberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Discontinuous roughage delivery on digestion, rumen metabolism, feed efficiency and liveweight gain of beef steers fed a concentrate diet

Two experiments were carried out to study the effect of feeding a total mixed ration (TMR) compared to feeding the roughage portion of the diet once every two days and separated of the daily delivered concentrate mixture on dry matter intake, nutrient digestibility, ruminal metabolism, feed efficiency and liveweight gain. In Trial 1, thirty beef steers (Braford and Braford × Criollo; initial BW = 259 ± 27 kg) were used in a 69-d feeding trial. Treatments were: total mixed ration (TMR), and the same proportion of ingredients for the ration but roughage offered once every 2-d and separated from the daily delivered concentrate portion of the diet (REOD). Treatments were arranged in a completely randomized design (three pens/ treatment). In both treatments, daily offered ration had on dry matter basis 90% concentrate and 10% grass hay (Setaria italica). Average daily gain (ADG) did not differ among treatment (1013 vs. 1080 g/d for TMR vs. REOD respectively; SEM = 95 g/d). Dry matter intake was greater in TMR compared to REOD (P < 0.01). Gain to feed ratio tended to be better for REOD than TMR (P = 0.07). In Trial 2, four rumen cannulated steers (Braford) were used in an experiment with a crossover design. Treatments were arranged as a 2*2 factorial design, where the first factor consisted of roughage level (RL): (R14) 14% roughage: 86% concentrate and (R7) 7% roughage: 93% concentrate. The second factor was roughage delivery system (RDS; as it was described for Trial 1): TMR and REOD. There were no RL*RDS interactions for intake and digestion (OM, CP, NDF and starch). Both RL were similar for intake and digestion. Roughage delivery system did not significantly affect intake and digestion of OM, CP, NDF, and starch measured by total fecal collection. Total organic acids (TOA), acetate to propionate ratio (A:P), pH, and rumen ammonia concentrations were not affected by RL and RDS. In conclusion, under the conditions of these trials, steers fed a separated roughage source once every 2-d had similar ADG, and tended to be more efficient compared with TMR. Total tract digestibility and rumen environment traits (pH, VFA, and ammonia) were not affected in response to discontinuous roughage delivery.Fil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; 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: Nazareno, Mónica Azucena. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; 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: Avila, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Garcia, M.. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Cervetto, J.. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Distel, Roberto Alejandro. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Saravia, J. J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentin

Effects of deferred forage as winter cover on spring growth of the tropical grasses Chloris gayana and Panicum coloratum = Efectos del forraje diferido como cobertura de invierno en el crecimiento primaveral de las gramíneas tropicales Chloris gayana y Panicum coloratum

This pot study assessed the effects of deferring forage during autumn and leaving as winter cover on reducing cold damage to plants of 2 tropical (C4) grasses (Chloris gayana and Panicum coloratum) in a temperate environment in La Plata, Buenos Aires, Argentina. Mature plants were subjected to the following treatments: (i) autumn-deferred forage retained (DF) as control; and (ii) autumn-deferred forage removed (DFR) cutting at 15 cm from soil level at beginning of winter. This experiment had 10 replicates per treatment and 1 plant per pot (experimental unit). Plants of both species were extracted from a commercial beef farm and transplanted into an experimental garden in pots where they grew outdoors from 2 February to 23 May (111 days) when treatments were applied. After winter, both grasses were cut to 15 cm in early spring (27 September) and spring growth was measured in November. Shoot biomass was harvested at ground level and separated into lower and upper layers (above and below 15 cm), leaf blades, sheaths and stolons. Daily air temperature, relative humidity and frost events were registered. Allometric analysis of shoot biomass was performed to determine the stress incidence by cold. DF plants achieved 55‒80% higher shoot biomass than DFR plants during spring in both species. The allometric analysis revealed for P. coloratum significant relationships between shoot biomass from plant compartments (lower and upper layers, leaf blade and sheath) and total shoot biomass in both treatments, indicating good cold tolerance. However, for C. gayana, unlike DF plants, DFR plants were strongly stressed, showing a lack of shoot biomass fit. These results suggest that deferring autumn forage growth and retaining as winter cover may improve survival during winter and productivity during spring of these two tropical grasses in temperate pastoral systems. However, the study needs to be repeated under field conditions and under grazing or cutting over a number of years in different situations to verify these preliminary results.En La Plata, Buenos Aires, Argentina, en un experimento en macetas a aire libre (condiciones de luz y temperatura naturales) se evaluó el efecto del forraje diferido como cobertura invernal en 2 gramíneas tropicales C4 (Chloris gayana y Panicum coloratum). Plantas adultas fueron extraídas de un establecimiento ganadero, trasplantadas a macetas en un jardín experimental y, después de crecer durante 111 días, sometidas el 23 de Mayo a los tratamientos: (1) control [sin remoción del forraje diferido de otoño (DF)]; y (2) remoción del forraje diferido de otoño (DFR) después de un corte a 15 cm del suelo. Se utilizaron 10 repeticiones por tratamiento y una planta por maceta (unidad experimental). Las plantas fueron cosechadas el 27 de Septiembre (después del invierno) y nuevamente en Noviembre, mediante corte a ras del suelo, para medir la biomasa del rebrote primaveral en los estratos superior (>15 cm) e inferior (<15 cm sobre el suelo), láminas, vainas y estolones. Se realizó un análisis alométrico para dilucidar la incidencia del estrés por frio y se registraron la temperatura del aire, la humedad relativa y la ocurrencia de heladas. Las plantas con forraje diferido alcanzaron una mayor biomasa (55‒80%) que aquellas con remoción del forraje. Panicum coloratum mostró un ajuste significativo entre la biomasa total y la biomasa de los diferentes estratos para ambos tratamientos, mostrando buena tolerancia al estrés por frio. Por otro lado, C. gayana mostró falta de ajuste de la biomasa y un mayor estrés por la remoción del forraje, mientras que las plantas sin remoción presentaron menor daño por frío y un mayor ajuste. La cobertura invernal del forraje diferido podría mejorar la productividad y supervivencia de estas especies forrajeras cuando son utilizadas en sistemas pastoriles templados. Estos resultados preliminares deben ser evaluados en condiciones de campo durante un mayor número de años, considerando diferentes estrategias de pastoreo.Instituto de Investigación Animal del Chaco SemiáridoFil: Imaz, José Augusto. University of Sydney. Faculty of Agriculture and Environment. Centre for Carbon, Water & Food; Australia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Merani, Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Dos Santos, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto de Biodiversidad Neotropical. Universidad Nacional de Tucuman. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Biodiversidad Neotropical. Instituto de Biodiversidad Neotropical; ArgentinaFil: Benvenutti, Marcelo A. University of Queensland, Gatton Campus; AustraliaFil: Gimenez, Daniel Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Hernandez, Olegario. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Investigación Animal del Chaco Semiárido; ArgentinaFil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santiago del Estero; Argentin