We used chemical composition and in vitro digestibility data from temperate and tropical forages to develop relationships between indices of lignification and forage indigestible NDF. Neutral detergent fiber indigestibility increased nonlinearly as the lignin concentration of the NDF increased. Differences in estimated indigestible NDF using equations developed for a specific forage class (C3 and C4 grasses and legumes) were small and are probably not biologically significant when compared to those estimated from a common equation. Selected equations were compared with the Cornell Net Carbohydrate and Protein System (CNCPS) for the prediction of ADG. The linear equation (2.4 times NDF lignin content) used by the CNCPS and the Beef NRC had some of the largest errors due to mean bias. A log-log model [4.37 x (lignin/NDF)(.84)] provided the best combination of low total prediction error, low mean bias, and minimal error due to regression bias when permanganate lignin was used. A similar equation based on sulfuric acid lignin [6.17 x (lignin/NDF)(.77)] also met the above criteria. These equations then were evaluated with the CNCPS model against animal growth data from diets ranging in forage quality. Regardless of the equation used for predicting unavailable fiber, the CNCPS underpredicted daily gain, with mean biases ranging from -.10 to -.22 kg/d. Regression bias ranged from .13 to .14 kg/d and the coefficients differed from unity (P = .0001). The new equations gave numerically lower energy allowable ADG by steers compared to the linear equation currently used by the CNCPS model. The estimates were lower due to a higher predicted indigestible NDF, which resulted in a lower estimated forage energy value.

No abstract

An experiment was conducted to determine the effect of replacing soybean protein (SBM) with a slow-release urea (SR-U) in control-fed dairy heifers in the tropics. Eight Holstein heifers (237.6±5.45 kg of body weight) were allocated to 2 treatments in a crossover design. Treatments were control (SBM) and SR-U (Optigen II; Alltech Inc., Nicholasville, KY). The forage-to-concentrate ratio was 50:50 [dry matter (DM) basis], and fresh chopped sugarcane was the sole source of forage. Data were analyzed using a mixed-effects model. Compared with the SR-U diet, SBM tended to have greater total tract apparent digestibility of DM and ash. Total tract apparent digestibilities in SBM-fed heifers were greater than in SR-U-fed heifers for organic matter (73.9 vs. 71.3±0.6), crude protein (76.9 vs. 75.2±0.7), hemicellulose (50.5 vs. 43.3±0.9), and starch (98.6 vs. 97.1±0.5). However, total tract apparent digestibility of neutral detergent fiber was similar, and digestibility of acid detergent fiber was higher in SR-U heifers than in SBM (33.3 vs. 27.7±2.6). Water intake and excretion of urine and feces (wet and dry) were similar between treatments. Retained N was similar for all groups, and no differences were observed in the distribution of excreted N. We conclude that when SR-U replaced SBM, it tended to marginally decrease DM and decreased organic matter, crude protein, hemicellulose, and starch total tract apparent digestibility, but did not affect neutral detergent fiber and increased acid detergent fiber digestibility.

Resumen. Se evaluó la producción de Materia Seca (MS), Fibra Neutro Detergente (FND), Fibra Ácido Detergente (FAD), Digestibilidad in vitro de la Materia Orgánica (DIVMO), Proteína Cruda (PC) y absorción de nutrientes de los cultivares Mulato I y II de Brachiaria híbridos en respuesta a la aplicación de los hongos micorriza y Trichoderma harzianum en El Zamorano, Honduras. Se utilizaron 32 parcelas de 3 × 5 m, con cuatro cortes cada 21 días. Se contaron las conidias de T. harzianum cada mes en los tres primeros meses y de esporas e infección de raíces con micorriza al tercer mes. En base a análisis del suelo se fertilizó con 150 kg N/ha/año (Urea) cada dos cortes. Se usó un diseño factorial en el cual el factor principal fue la variedad de pasto (Mulato I o Mulato II) y el factor secundario la aplicación de biofertilizantes (Mycoral . Para analizar las variables de producción de MS y conteo de conidias de T. harzianum se utilizaron medidas repetidas en el tiempo y sin medidas repetidas para esporas y porcentaje de infección de raíces con micorriza. La aleatorización en campo se realizó en un Diseño Completo al Azar (DCA) con cuatro repeticiones por cada combinación de tratamientos. No hubo diferencia (P>0.05) en la producción de MS entre los pastos (117.4 kg/ha/día y 110.9 kg/ha/día para Mulato I y II, respectivamente) ni entre la aplicación del biofertilizante. El tratamiento con micorriza + T. harzianum tuvo el menor rendimiento (107.1 kg/ha/día). El contenido de FND (50.5%), FAD (29.2%) y DIVMO (60.3%) fueron similares en ambos pastos. El contenido de PC fue mayor en Mulato II (15.1%) que en Mulato I (29.2%). La absorción de nutrientes fue similar en ambos pastos, a excepción del zinc y nitrógeno. Palabras clave: Digestibilidad In Vitro de la Materia Orgánica (DIVMO), Fibra Ácido Detergente (FAD), Fibra Neutro Detergente (FND), Materia Seca (MS), Proteína Cruda (PC).Abstract. Dry Matter production (DM), Crude Protein (CP), Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) content, In Vitro Dry Matter Digestibility (IVDMD), and absorption of nutrients of the cultivars Mulato I and II of Brachiaria hybrids in response to the application of the fungi micorriza and Trichoderma harzianum in El Zamorano, Honduras, were evaluated. Thirty two plots of 3 × 5 m were established and harvested every 21 days. Conidia of T. harzianum in the soil were counted once a month during the first three months and the amount of spores and the percentage of infection of the roots with micorriza were evaluated once in the third month after the sowing. According to the soil analysis, urea was applied every second cut to an equivalent of 150 kg N/ha/year. A completely randomized design with four replicates was used. The data was analyzed using a factorial design where the main factor was the variety of the grass (Mulato I vs. Mulato II) and the second factor was the application of biofertilizers (micorriza and T. harzianum). Repeated measurements in time for DM production and the amount of conidia of T. harzianum were used. D...

Con el objetivo de describir el diámetro de fibra y el peso de vellón de vicuñas en la Región Cusco, se evaluaron 302 muestras de fibra de vicuñas crías, juveniles y adultas mediante un equipo OFDA 2000®, colectadas en diferentes capturas programadas (denominadas Chaccus) bajo dos sistemas de manejo: silvestría y semicautividad. Se registró, además, el peso de 633 vellones diferenciados por edad, sexo y tipo de manejo de los animales. El presente estudio estuvo amparado con la Resolución de Dirección General N° 180-2016-SERFOR/DGGSPFFS. Se determinó la finura promedio de fibra de crías (13.24 μm), juveniles (12.03 μm) y adultos (12.72 μm). La finura para machos y hembras fue de 12.99 y 13.53 μm en las crías, 12.06 y 12.02 μm en los juveniles y 12.88 y 12.58 μm en los adultos, respectivamente. El menor diámetro de fibra se presentó en vicuñas juveniles en silvestría (11.88 μm) y en la localidad de Canllini (11.49 μm). El peso de vellón fue mayor en silvestría (165.01 g) y en animales adultos (162.97 g), sin hallar diferencia entre sexos. Se concluye que las mejores características de fibra se encontraron en animales mantenidos en silvestría.