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The aim of this study was to evaluate the effect of urea (46% N) on the nutritional quality of corn stover from the areas of Chilampa, La Villa, Miramar and La Querencia of the Cattle Association Irrigación San Felipe, located in Huaura, Lima (Peru). Three levels of urea (0, 3 and 6%) in an aqueous solution over a period of 14 days were applied and the forage was stored in sealed plastic bags. The variables evaluated were crude protein content (CP%), neutral detergent fiber content (NDF%), in vitro digestibility of dry matter (IVDDM%), in vitro digestibility of neutral detergent fiber (IVNDFD%), intake potential of dry matter (%PV DM) and relative feed value (RFV). Randomized complete block design with three replications was used. The results for 0, 3 and 6% urea were: 84.66, 70.01 and 67.78% DM; 5.08, 8.02 and 12.92% CP; 77.31, 76.89 and 74.84% NDF; 59.90, 61.17 and 66.59% IVDMD; 48.15, 50.97 and 55.41% IVNDFD; 1.55, 1.56 and 1.60% potential intake of dry matter; and 72.09, 74.03 and 82.81 FRV respectively. The results of the analysis showed no difference between the source of corn stover or for IVNDFD between the urea levels; however, there was significant difference (p

Páginas 31-37, Se estudió la digestibilidad in situ de la matriz fibrosa de rastrojo de maíz tratado con un complejo enzimático, utilizando dos toros suizos (700 kg PV) con cánula ruminal, en un diseño de bloques al azar, donde cada animal constituyó un bloque, y los tratamientos fueron tres niveles de enzimas: 0 g (TC), 1 g (T1) y 2 g (T2) de Fibrozyme® kg forraje-1 MS. Las muestras (5 g de materia seca en bolsas de nailon) se incubaron en el rumen, y se extrajeron a las 6, 12, 24, 48 y 72 horas posfermentación. La degradabilidad se analizó mediante regresión no lineal, con la utilización del modelo P=a+b*(1-e-c*(t-to)). La porción soluble de la matriz fibrosa, determinada por lavado de las bolsas, resultó similar en ambas fracciones de fibra (FDN y FDA), y fue de 0.50, 0.59 y 0.68 % para sus tres tratamientos, respectivamente. Los valores de degradabilidad de la fracción insoluble, pero degradable, fueron: 37.28, 36.64 y 37.30 % para FDN y 33.85, 35.07 y 41.19 % para la FDA, con sus respectivos tratamientos. El T2 (FDN) y el TC (FDA) registraron los mayores valores de velocidad de degradación (c %/h). La fase Lag fue, aproximadamente, de 3.80, 4.90 y 4.80 h para FDN y 5.30, 5.30 y 4.90 h para la FDA, con sus tres respectivos tratamientos. La degradabilidad efectiva (DE) de la FDN osciló entre 19.70-14.40, 21.30-15.90 y 22.10-16.60 % y la de la FDA, entre 20.30-15.30, 21.10-15.80 y 23.40-17.30 %, en cada uno de los tratamientos, al utilizar diferentes constantes de recambio ruminal. El rastrojo de maíz mostró buen potencial de degradación, superior al 39 % en FDN y de 44 % en FDA, cuando fue tratado con los niveles más altos de enzimas fibrolíticas (T2). Los resultados demostraron que puede hacerse un uso óptimo de la matriz fibrosa como fuente energética para el animal cuando se utilizan complejos enzimáticos en esquilmos agrícolas como el rastrojo de maíz mediante su fermentación ruminal., In situ digestibility of corn stover fiber matrix treated with an enzymatic complex was studied by using two Swiss bulls (700 kg PV) with ruminant cannula. We used a randomized block design, where each animal constituted a block, and three enzyme levels: 0 g (TC), 1 g (T1), and 2 g (T2) of Fibrozyme® kg fodder-1 MS. The samples (5 g of dry matter in nylon bags) were incubated in the ruminant, and were extracted at 6, 12, 24, 48 and 72 hours after fermentation. Debasement was analyzed by a none lineal regression, using the P=a+b* (1-e-c* (t-to)) model. The soluble portion of the fibrous matrix, determined by washing the bags, resulted similar in both fiber fractions (FDN and FDA), with values of 0.50, 0.59 and 0.68 % respectively for each treatment. The degradability values of the insolvent, but degradable, fraction were: 37.28, 36.64 and 37.30 % for FDN, and 33.85, 35.07 and 41.19 % for FDA, with their three respective treatments. The T2 (FDN) and the TC (FDA) registered the highest degradation speed values (c %/h). The lag phase was approximately of 3.80, 4.90 and 4.80 h for FDN and 5.30, 5.30 and 4.90 h for FDA, with their three respective treatments. The FDN effective degradability (DE) oscillated between 19.70-14.40, 21.30-15.90 and 22.10-16.60 %; and the FDA, between 20.30-15.30, 21.10-15.80 and 23.40-17.30 %, in each one of the treatments, by using different ruminant exchange constants. The corn stover showed good degradation potential, over 39 % in FDN and 44 % in FDA, when treated with the highest levels of fibrolytic enzymes (T2). The results showed that an optimal usage of the fiber-matrix as energy source for the animal can be achieved, when enzymatic complexes are used in agriculture products and residues such as corn stover through its ruminal fermentation., Bibliografía y webgrafía: 36-37, Artículo revisado por pares.

espanolSe evaluo la amonificacion con urea de la panca de maiz del hibrido Trueno NB-7443 (a 8 dias de la cosecha de la mazorca) y su efecto sobre la composicion nutritiva. Los tratamientos consistieron en un control sin amonificar y tres tiempos de amonificacion a 21, 28 y 35 dias, distribuidos en un diseno completamente aleatorizado. Los analisisbromatologicosserealizaronmediante la metodologia de la AOAC (2006). La amonificacion aumento significativamente el contenido de Proteina Bruta con respecto al control y entre los tratamientos fue significativamente favorable para los 28 y 35 dias. La Fibra Bruta fue menor en el control. El Extracto Etereo y las cenizas en Base Humeda no difirieron entre tratamientos, pero si con el control. La Fibra Neutra Detergente y Fibra Acida Detergente disminuyeron con el tiempo de amonificacion. El tratamiento mejoro la composicion nutritiva de la panca de maiz, en tanto que los tiempos de amonificacion de 28 y 35 dias tuvieron los mejores resultados. EnglishThe ammonification with urea of corn stover of the Hybrid Thunder NB-7443 was evaluated –after 8 days of harvested corn- and its effect on the nutritional composition. The treatments on a control without ammonification and 3 times of ammonification to 21, 28 and 35 days distributed in a totally randomized design. The bromatological analyses were conducted using the methodology of AOAC (2006). The ammonification significantly increased the Crude Protein content according to the control and among the treatments it was significantly favorable for the 28 and 35 days. Crude fiber was lower in the control. The ether extract and ashes on a wet basis did not differ among the treatments, but it did with the control. Both, the neutral detergent fiber and the acid detergent fiber decreased with the ammonification time. The treatments improved the nutritional composition of corn stover and the ammonification times of 28 and 35 days had better results

Two experiments were conducted to determine the effects of steam explosion (STE) on chemical composition and digestibility of the following forages (F): sorghum stover (SOS), corn stover (COS) and sugarcane bagasse (SUB). The Exp 1 was conducted to determine the effects of STE on pH, fiber fractions (FF) and in vitro digestibility (IVDMD). Fifty four samples were generated using a RCB design with a 3*3*3 factorial treatment arrangement, where the factors were: pressure (P: 10.3, 13.8 and 17.2 kg/cm2), time (T: 5, 10 and 15 min) and F (SOS, COS and SUB). In Exp 2, changes in the digestion kinetics were determined when using the combinations of P and T that maximized IVDMD; thus, SOS and COS were treated at 13.8 kg/cm2 for 10 min, and SUB at 17.2 kg/ cm2 for 15 min. The treated and non-treated samples were incubated in rumen for up to 120 h. Data were fitted to a nonlinear model. No significant interactions T*P or F*P*T were detected on pH or FF; however, as P or T increased, pH, NDF and hemicellulose decreased. Lignin or ADF were not affected by P or T. As for IVDMD concerns, P*F and F*T interactions were significant. STE increased soluble fraction and degree of F digestion. Only lag time of SUB was reduced by STE. The potential digestible fraction was reduced in SOS and COS. It was concluded that the changes in chemical composition and digestion kinetics are related mainly to cell wall solubilization by stem explosion.

The nutrient release from organic residues depends on the chemical and physical properties, as well as the environmental conditions and microbial population in the soil system. The objectives of the present study were to determine the enzymatic activities related to N mineralization, and to estimate the contribution of crop residues on soil N under different tillage practices using corn residues in the Central Plains, Venezuela. In a field experiment, corn residues labelled with 15N were incorporated in soil to evaluate three tillage practices: Direct planting (SD), direct planting after a chisel pass (CSD), and conventional tillage (LC). The amount of N released from crop residues and the deltaN were larger with the LC treatment than with SD and CSD treatments. Enzymatic activity was concentrated in the topsoil layer (0 to 10 cm), and there were significant differences between the two enzymes (protease and urease) in soil at 10 to 20 cm deep, where LC treatment had more enzymatic activity. These results suggest that the application of crop residues with low lignin:N and C:N ratios in a soil with a low C:N ratio, the decomposition rate of crop residues will be faster, probably because of the increase in biological activity of the soil (larger proliferation of urealytic and proteolytic organisms), which could have shown up through an increase in soil N with N released from crop residues.