Valor alimenticio comparativo del pasto kikuyo (Pennisetum clandestinum, var. Whittet) en dos estaciones de crecimiento con ryegrass (Lolium multiflorum ) Y sudán (Sorgum sudanense) ofrecido a novillos Holstein

P. 135-139Cuatro novillos Holstein (167kg) con cánulas en rumen y duodeno proximal fueron distribuidos en un diseño Cuadro Latino 4×4 para estimar el valor alimenticio comparativo del pasto kikuyo (Pennisetum clandestinum var. Whittet) cosechado en verano e invierno con el de henos de gramínea de verano (pasto sudán; Sorgum sudanense) e invierno (ryegrass anual; Lolium multiflorum var. Oregon). Las dietas experimentales (88,4% MO, 35,5% FDN y 11,8% PC) fueron formuladas con 70% forraje y 30% suplemento. No hubo efecto de tratamientos (P>0,05) en digestión ruminal de la FDN, N, eficiencia microbial ruminal (g de NM/kg de MO fermentada), ni en eficiencia ruminal del N (N no amoniacal que entra a tracto bajo/N consumido). No hubo efecto (P>0,10) de la estación (cosecha en verano vs invierno) en la digestión ruminal y total de la MO, FDN y N en dietas con kikuyo. La digestión ruminal y total de MO, FDN y N fueron similares (P>0,10) para dietas compuestas por kikuyo y sudán. Sin embargo, la digestión ruminal y total de MO y N fue menor (19, 12 y 9%, respectivamente) para dietas con kikuyo a la observada con ryegrass (P0,05) en la relación acetato-propionato. Se concluye que kikuyo tiene un valor alimenticio similar a sudán y representa una alternativa en la alimentación animal como cultivo perenne con aceptable valor nutricional durante el verano.S

Practical parameters for assessing starch digestion and feeding value of steam-flaked corn in finishing diets for feedlot cattle

ABSTRACTSix Holstein steers (153 kg ± 11) with cannulas in the rumen and proximal duodenum were used in a 6 × 6 Latin square design experiment to compare flake density (FD, kg/L), flake thickness (FT, mm), amyloglucosidase reactivity (AGR, % DM) and faecal starch (FS, % DM) as predictors of ruminal (RSD, %) and total tract (TSD, %) starch digestion. Dietary treatments consisted of a finishing diet containing 77% corn. The six corn processing treatments consisted of dry-rolled corn (DRC) with a density of 0.54 kg/L, and steam-flaked corn (SFC) processed to obtain densities of 0.46, 0.41, 0.36, 0.31 and 0.26 kg/L. Compared with DRC, steam flaking enhanced postruminal (34.2%, P < 0.01) and TSD (7.8%, P < 0.01). Measures of FS were the best single predictor of both ruminal (r2 =  0.97) and TSD (r2 =  0.98). Whereas AGR was a good predictor of RSD (r2 = 0.94), it was less effective than FS for estimation of TSD (r2 = 0.91). We conclude that compared with dry rolling, stream flaking markedly enhances the feeding value of corn. To evaluate the consistency of the flaking process, we recommend in addition to the determinations of FD, measurements of FT, starch enzymatic reactivity and FS are useful indicators

Influence of substituting steam-flaked corn for dry rolled corn on feedlot cattle growth performance when cattle are allowed either or restricted access to the finishing diet

Objective The influence of substituting steam-flaked corn (SFC) for dry rolled corn (DRC) on feedlot cattle growth performance and dietary net energy when cattle are allowed either ad libitum or 2-h restricted access to the finishing diet was evaluated. Methods Treatment effects were tested using 96 crossbred steers (251±2 kg) during the initial 56 d of the finishing phase. Cattle were blocked by weight and randomly assigned within blocks to 16 pens (4 pens/treatment). Bunk space was sufficient (41 cm/head) to allow all steers access to the feed bunk at the same time. Treatments consisted of two finishing diets containing (dry matter basis) 77.1% corn grain processed by dry rolling (density = 0.50 kg/L) or steam flaking (density = 0.36 kg/L). Cattle were fed twice daily at 06:00 and 14:00 h, allowing for approximately 5% residual. In the case of restricted feeding, steers were allowed access to feeders for 1 h following each feeding, after which residual feed was withdrawn. Results There were no treatment interactions on dry matter intake (DMI), average daily gain (ADG), gain efficiency (G:F), or dietary net energy (NE). Restricting feed access time reduced (p <0.01) feed intake, and hence, ADG. Substitution of SFC for DRC increased (p<0.01) ADG, feed efficiency (G:F), and estimated dietary NE, without affecting DMI. Based on tabular net energy of maintenance (NEm) value (2.18 Mcal/kg) for DRC, the estimated NEm value for SFC using the replacement technique, averaged 2.44 Mcal/kg; an improvement of 10.7%. The ratio of observed-to-expected dietary NE was not affected by feed access time. Conclusion Substitution of SFC for DRC in finishing diets for feedlot cattle enhanced ADG, gain efficiency, and the NE value of the diet. Although restriction of feed access time depressed DMI and ADG, it did not affect the comparative benefit of steam flaking toward enhancement of ADG, G:F, and dietary NE

Digestion and energy value of macerated sudangrass hay used in growing-finishing diets for feedlot cattle

Mechanical maceration enhances site and extent of digestion of low-moisture, low-quality forages. Four Holstein steers (172 ± 8 kg) with cannulas in rumen and proximal duodenum were used in 4x4 Latin square design to evaluate the process of mechanical maceration of sudangrass hay on the characteristics of ruminal and total tract digestion. Treatments consisted of a steam-flaked corn-based growing diet supplemented with 21 % forage (DM basis) as: i) wheat straw (Triticum aestivum, STRW), ii) sudangrass hay (Sorghum sudanense, SG), iii) macerated SG at intensity of 4,134 kPa (MAC600) and 4) macerated SG at intensity of 6,200 kPa (MAC900). All forages were ground to pass through a 3.8 cm screen before incorporation into complete mixed diets (21:79 forage to concentrate ratio). Maceration did not affect (p &#8805; 0.17) on site and extent of OM, N and ADF, and DE of sudangrass supplemented diets. Characteristics of ruminal digestion of OM, ADF, starch, as well as, microbial efficiency (microbial N, g kg-1 of OM fermentad) and protein efficiency (nonammonia N, g g-1 of N intake) were not different (p &#8805; 0.11) for wheat straw versus sudangrass supplemented diets. However, total tract digestion of OM, ADF, N, and DE diet were greater (p &#8804; 0.05) for sudangrass than for wheat straw supplemented diets. Using the replacement technique, DE value of SG averaged 9.59 MJ kg-1, very close to the expected value given its chemical composition. Mechanical maceration did not enhance the feeding value of sudangrass hay. Increase the intensity of maceration from 4,134 to 6,200 kPa did not altered ruminal or total tract digestion of OM, NDF or energy value of processed ha