Abstract The objective of the present study was to evaluate the effect of the precut in the yield and quality of guinea grass seed (Megathyrsus maximus) cv. Mombasa. The study was carried out in the experimental field of the University of the Papaloapan Campus Loma Bonita, Oaxaca. Eight treatments were evaluated, which consisted in precuts every 10 days from the court of uniformity, which took place on July 1. The treatments were tested under a design of a randomized complete block with three replications per treatment. We evaluated the total seed yield, pure seed yield, yield of pure germinable seed, germination percentage of harvested seed, plant height, total number of panicles per m2, ripe panicle number per m2, panicle length, number of seeds harvested by panicle, seed weight per panicle, percentage of purity and weight of a thousand seeds. There were significant differences (p< 0.05) between treatments for pure seed yield and yield of pure germinable seed, where the highest values (205.2 and 103.1 kg ha-1, respectively) were obtained with the precut the date July 20, there were also significant difference to the number of seeds harvested by panicle and weight of seeds per panicle. It is therefore concluded that the July 20 is the best date for precut to increase seed yield of Megathyrsus maximus cv. Mombaza.

Resumen El objetivo del estudio fue evaluar el efecto del precorte en el rendimiento y calidad de semilla de pasto guinea (Megathyrsus maximus) cv. Mombaza. El estudio se realizó en el campo experimental de la Universidad del Papaloapan Campus Loma Bonita, Oaxaca. Se evaluaron ocho tratamientos, los cuales consistieron en precortes a cada 10 días a partir del corte de uniformidad, el cual se realizó el 1 de julio. Se utilizó un diseño de bloques completos al azar, con tres repeticiones por tratamiento. Se evaluó el rendimiento de semilla total, semilla pura, semilla pura germinable, porcentaje de germinación de la semilla cosechada, número de panículas totales por m2, número de panículas maduras por m2, longitud de panícula, número de semillas cosechadas por panícula, peso de semillas por panícula, porcentaje de pureza y peso de mil semillas. Se detectaron diferencias (p< 0.05) entre tratamientos para rendimiento de semilla pura y semilla pura germinable, donde los mayores valores (205.2 y 103.1 kg ha-1, respectivamente) se obtuvieron con la fecha de precorte del 20 de julio, también hubo diferencia significativa para el número de semillas cosechadas por panícula y peso de semillas por panícula. Se concluye que el 20 de julio es la mejor fecha de precorte para incrementar el rendimiento de semilla de Megathyrsus maximus cv. Mombaza.

Abstract: The effect of the urea level of the fermented supplement Sacchapulido (SP) on the degradation of elephant grass (Pennisetum purpureum) was evaluated. The pH, N-NH3 and in situ and effective degradation (ID and ED respectively) were determined, as well as the kinetic parameters of dry matter (DM), NDF and ADF of the forage. Five fistulated bovines were used in a 5 x 5 Latin square design. The standard deviation indicated that the supplements have between 0.5 and 1.0% urea; they contributed 10% more biomass due to the increase in size of the potentially degradable fraction of the feed, both in the NDF and cellular content. Due to the cost of urea, the use of SP with 0.5% urea is recommended.

Resumen: Se evaluó el efecto del nivel de urea sobre la degradación del pasto Elefante (Pennisetum purpureum) en el suplemento fermentado, Sacchapulido (SP). Se determinó el pH, N-NH3, la degradación in situ (DI) y efectiva (DE), así como, los parámetros cinéticos de materia seca (MS), FDN y FDA del forraje. Se utilizaron cinco bovinos fistulados en rumen en un diseño cuadro Latino 5x5. La DE indicó que los suplementos que tienen entre 0.5 y 1.0% de urea, aportaron un 10% más de biomasa por el aumento de tamaño de la fracción potencialmente degradable (PD) del alimento, tanto en la FDN, como en el contenido celular. Debido al costo de la urea, se recomienda el uso del SP con 0.5% de urea.

The objective of this study was to use the Turix model (a new mechanistic dynamic model that can be used for feed evaluation under tropical conditions), along with in situ and in vitro sugar cane experimental data from a previous study, to evaluate sugar cane kinetics through estimation of three parameters associated with ruminal bacterial growth: kM,SmL, the substrate uptake; kLM, the bacterial growth from intermediate metabolite; and Y VFAP,FS, the products related to volatile fatty acid yield. Values of these parameters for the whole sugar cane and its neutral detergent fiber (NDF) and acid detergent fiber (ADF) fractions were: a) kM, SmL, 16.20, 50.47 and 21.97 mL h-1 (mg M)-1 ; b) kLM, 96.00, 543.00 and 1,680.00 h-1 ; and, 1.02, 0.40 and 0.23 g g-1 , respectively. Results from the model adjustment showed a slow microbial substrate uptake c) Y VFAP, FS and a low biomass yield for whole sugar cane. The highest substrate uptake was obtained for NDF, while the highest biomass yield was obtained for ADF. The interrelation between the parameters kM, SmL showed to be important for biological and Y VFAP, FS description of microorganism growth and VFAP and biomass production.