The purpose was to evaluate the chemical composition and in situ ruminal dry matter disappearance of four types of grain sorghum silages, one brown midrib sorghum (bmr) and, a corn silage, grown under rainfed conditions in a humid tropical region of Mexico. The crops were established at three sites. At harvest, three minisilos per treatment were filled with forage previously chopped. Minisilos opened at 55 days and samples of silage taken to dry and ground to 1 mm to determine the chemical composition and in situ ruminal dry matter disappearance. The crude protein was higher (p<0.05) in sorghum silages than corn silage. In sorghum silages, bmr sorghum had the lowest (p<0.05) cell wall content, and was equal (p>0.05) in ADF and ADL to corn silage. The degradation parameters (a, b, c ) was higher (p<0.05) in bmr sorghum silage than grain sorghum silages. The effective degradability was equal (p>0.05) in bmr sorghum and corn silages. In the humid tropics, bmr sorghum silages are a good alternative to corn silage, especially in the dry season.

El objetivo fue evaluar la composición química y la degradabilidad ruminal in situ del ensilado de cuatro híbridos de sorgo para grano, uno de nervadura café (bmr) y un híbrido de maíz, bajo condiciones de secano en una región del trópico húmedo de México. Los cultivares se establecieron en tres sitios. A la cosecha, en cada sitio se llenaron tres minisilos de laboratorio por tratamiento. Los minisilos se abrieron a los 55 días y se tomó una muestra que fue secada y molida a 1 mm para determinar la composición química y la degradabilidad ruminal in situ de la materia seca. La proteína cruda fue mayor (p<0,05) en los ensilados de sorgo que en el ensilado de maíz. Entre los sorgos, el sorgo bmr presentó el menor (p<0,05) contenido de pared celular y fue similar (p>0,05) en FDA y LDA al ensilado de maíz. Los parámetros de degradación (a, b, c) fueron mayores (p<0,05) en el ensilado de sorgo bmr en comparación al de sorgos para grano. La degradabilidad efectiva fue igual (p>0,05) en el ensilado de sorgo bmr y el maíz. En el trópico húmedo, el ensilado de sorgo bmr, es una alternativa viable con referencia al ensilado de maíz, especialmente en la época seca.

ABSTRACT The objective was to evaluate the effect of three levels of cull pinto beans (CPB; Phaseolus vulgaris) on ruminal fermentation, kinetics, and nutrient digestibility in hair lambs. Six cannulated lambs averaging 56.6±3.8 kg were used and were randomly assigned to one of three treatments. Treatments were: 0.0 kg kg−1 of CPB in the supplement (control); 0.25 kg kg−1 of CPB in the supplement (CB25); and 0.40 kg kg−1 of CPB in the supplement (CB40). Dry matter intake, ruminal pH, NH3, and volatile fatty acid (VFA) concentration, methane production, Kp (passage rate), MRT (mean retention time), and digestibility of dry matter, crude protein, and neutral detergent fiber were evaluated. Data were analyzed in a Latin square design, repeated in line, by MIXED procedure of SAS. Estimates used for Kp and MRT were obtained by a non-linear regression model (PROC NLIN). Dry matter intake was reduced by supplementation of CPB. No differences were found in ruminal pH or ruminal NH3. During the trial, differences were found for ruminal VFA concentration (mM), which were greater for the CB25 group. The propionate:acetate ratio was greater for the CB40 treatment. Methane production (mM/m) differed among treatments, but it was the greatest for the CB40 group. Passage rate (kg kg−1/h) and MRT (h) were similar among treatments and the digestibility (kg kg−1) of dry matter, crude protein, and neutral detergent fiber was not different among treatments. The inclusion of 0.25 kg kg−1 of CPB in the diet of hair lambs allows for appropriate nutrient digestion without affecting Kp and MRT and increases the molar proportion of the ability of VFA to maintain acetate:propionate ratio without increasing methane production.

ABSTRACT The objective was to evaluate the effect of cull pinto beans (CPB) (Phaseolus vulgaris) on performance of feedlot lambs. Seventy-two crossbred hair-breed lambs (Dorper × Pelibuey and Kathadin × Pelibuey) were used (75±6 days old and 18.7±3.89 kg of initial body weight). Animals were fed twice daily. Diets consisted of 20% alfalfa hay and 80% concentrate based on ground sorghum grain and were formulated to contain 17.9% crude protein and 2.60 Mcal/kg metabolizable energy. Treatments were (dry matter basis): no CPB (0%), 10% CPB, and 20% CPB. Lambs were blocked by body weight and treatments and arranged in a 2 × 3 arrangement of treatments. Body weights were recorded initially and subsequently at 14-day intervals for a total 70 number of days. Dry matter intake was recorded daily. Apparent dry matter digestibility was predicted using insoluble acid detergent fiber. Data were analyzed as a randomized complete block design. Final body weight and average daily gain decreased linearly with increasing CPB level and were greater for males than females. A level × gender interaction was observed for dry matter and crude protein digestibility. Data for hot carcass weight and cold carcass weight decreased linearly as CPB level increased and were greater for males. Carcass yield, longissimus muscle area, and dressing percentage were greater for males. Dressing percentage quadratically increased as CPB level increased. Cull pinto beans are a suitable ingredient for feedlot hair-breed lambs, but the inclusion of more than 10% of CPB level decreases animal performance.

Oat forage (Avena sativa L.) is widely used in livestock feeding systems at the northwestern region of Chihuahua State, México. The effect of variety, planting system, and maturity stage at cutting on yield and chemical composition of oat forage were evaluated on seven varieties planted under rainfed conditions, in furrow diking and plane surfaces, in five locations at the northwestern region of Chihuahua state. Harvest was done at three crop growth stages: boot (BS), dough grain (DS) and physiological maturity of grain (PMS). Yield in kg ha-1 of hay dry matter (DM) and its chemical composition (%) were measured; digestible dry matter (DDM, %) and net energy for lactation (NEL, Mcal kg-1) were estimated. Treatments were distributed into a sub-sub-split experimental arrangement in a completely randomized blocks design; locations were the replications, main plots were planting systems, medium size plots were stages of maturity at cutting, and large plots were varieties. Planting system did not affect hay dry matter yield (P = 0.20) or chemical composition (P > 0.05). As the cutting stage approached PMS, DM yield linearly (P < 0.05) increased (2247, 3120 and 4475 kg ha-1 for BS, DS and PMS, respectively), while crude protein decreased nonlinearly (P < 0.05). A significant effect of the maturity x variety interaction (P < 0.01) on crude protein was detected. As harvest approached PMS, fiber fractions decreased (P < 0.05), while DDM and ENL increased linearly (P < 0.05). Oat hay chemical composition improved towards maturity of grain due to a decrease in fiber, without significant differences among varieties.

El forraje de avena (Avena sativa L.) se usa extensamente en los sistemas de alimentación pecuaria en el noroeste del Estado de Chihuahua, México. Se evaluó el efecto de la variedad, sistema de siembra y estado de madurez al corte sobre el rendimiento y composición química del forraje de avena, en siete variedades sembradas en surco con contras y en plano sin surco, en condiciones de temporal (secano) en cinco localidades del noroeste de esa entidad. La cosecha se efectuó en tres etapas fenológicas: embuche (EMB), grano masoso (MAS) y madurez fisiológica del grano (MF). Se midió el rendimiento de materia seca (MS) en kg ha-1, la composición química del heno (%), y se estimó la materia seca digestible (MSD, %) y la energía neta de lactancia (EN L, Mcal kg-1). Los tratamientos se distribuyeron en un arreglo experimental de parcelas sub-sub-divididas en un diseño de bloques completos al azar, en el que localidad fue la repetición, la parcela grande fue el sistema de siembra, la mediana el estado de madurez al corte, y la parcela chica la variedad. El sistema de siembra no afectó al rendimiento (P = 0.20) ni a la composición química (P > 0.05) del heno. A medida que la etapa de corte fue más cercana a MF el rendimiento de MS (P < 0.01) se incrementó linealmente (2247, 3120 y 4475 kg ha-1 para EMB, MAS y MF, respectivamente), y la proteína cruda disminuyó en forma cuadrática (P < 0.01). En proteína cruda hubo efecto de la interacción de variedad x madurez al corte (P < 0.01). A medida que la cosecha fue más cercana a MF las fracciones de fibra disminuyeron (P < 0.05), e inversamente MSD y EN L aumentaron linealmente (P < 0.05). La composición química del heno de avena mejoró al acercarse a la madurez fisiológica del grano debido a la disminución en su contenido de fibra, sin presentar diferencias importantes entre variedades.