Effect of varying the proportion of molasses in the diet on intake, digestion and microbial protein production by steers

The present experiment was conducted to determine the efficiency of microbial protein production in the rumen and intake by cattle fed high-molasses diets. Intake and microbial crude protein (MCP) production were measured along with the concentration of rumen ammonia-nitrogen (N) and volatile fatty acids (VFA), pH and the rate of digestion of roughage in the rumen. Eight Brahman crossbred steers weighing 211 ± 19.3 (± s.d.) kg were used in a double 4 × 4 Latin square design. Steers were allocated to one of four total mixed rations: control (pangola hay only), 25M (25% molasses/urea mix + 75% hay), 50M (50% molasses/urea + 50% hay), and 75M (75% molasses/urea + 25% hay). The production and efficiency of production of MCP (EMCP) of the diet increased quadratically as the level of molasses in the diet increased. The EMCP from the molasses/urea mix was estimated as 166 g MCP/kg digestible organic matter (DOM), a relatively high value. Intake of dry matter (DM) and DOM increased quadratically, reaching a peak when molasses was ~50% (as fed) of the ration. Digestibility of DM increased quadratically and that of neutral detergent fibre decreased linearly with increasing level of molasses in the diet. Molasses inclusion in the diet had no effect on rumen pH, ammonia and VFA concentration in the rumen fluid, plasma urea-N, urine pH or ruminal fractional outflow rate of ytterbium-labelled particles and Cr-EDTA. It was concluded that a diet with a high level of molasses (>50%) and supplemented with adequate N had high EMCP, and that low MCP production was not a factor limiting intake or performance of cattle consuming high-molasses diets.

Effect of varying the proportion of molasses in the diet on intake, digestion and microbial protein production by steers

The present experiment was conducted to determine the efficiency of microbial protein production in the rumen and intake by cattle fed high-molasses diets. Intake and microbial crude protein (MCP) production were measured along with the concentration of rumen ammonia-nitrogen (N) and volatile fatty acids (VFA), pH and the rate of digestion of roughage in the rumen. Eight Brahman crossbred steers weighing 211 ± 19.3 (± s.d.) kg were used in a double 4 x 4 Latin square design. Steers were allocated to one of four total mixed rations: control (pangola hay only), 25M (25% molasses/urea mix + 75% hay), 50M (50% molasses/urea + 50% hay), and 75M (75% molasses/urea + 25% hay). The production and efficiency of production of MCP (EMCP) of the diet increased quadratically as the level of molasses in the diet increased. The EMCP from the molasses/urea mix was estimated as 166 g MCP/kg digestible organic matter (DOM), a relatively high value. Intake of dry matter (DM) and DOM increased quadratically, reaching a peak when molasses was ∼50% (as fed) of the ration. Digestibility of DM increased quadratically and that of neutral detergent fibre decreased linearly with increasing level of molasses in the diet. Molasses inclusion in the diet had no effect on rumen pH, ammonia and VFA concentration in the rumen fluid, plasma urea-N, urine pH or ruminal fractional outflow rate of ytterbium-labelled particles and Cr-EDTA. It was concluded that a diet with a high level of molasses (>50%) and supplemented with adequate N had high EMCP, and that low MCP production was not a factor limiting intake or performance of cattle consuming high-molasses diets.

Programming rumen bacterial communities in newborn Merino lambs

Establishment of the rumen microbiome can be affected by both early-life dietary measures and rumen microbial inoculation. This study used a 2 × 3 factorial design to evaluate the effects of inclusion of dietary fat type and the effects of rumen inoculum from different sources on ruminal bacterial communities present in early stages of the lambs’ life. Two different diets were fed ad libitum to 36 pregnant ewes (and their lambs) from 1 month pre-lambing until weaning. Diets consisted of chaffed lucerne and cereal hay and 4% molasses, with either 4% distilled coconut oil (CO) provided as a source of rumen-active fat or 4% Megalac® provided as a source of rumen-protected fat (PF). One of three inoculums was introduced orally to all lambs, being either (1) rumen fluid from donor ewes fed the PF diet; (2) rumen fluid from donor ewes fed CO; or (3) a control treatment of MilliQ-water. After weaning at 3 months of age, each of the six lamb treatment groups were grazed in spatially separated paddocks. Rumen bacterial populations of ewes and lambs were characterised using 454 amplicon pyrosequencing of the V3/V4 regions of the 16S rRNA gene. Species richness and biodiversity of the bacterial communities were found to be affected by the diet in ewes and lambs and by inoculation treatment of the lambs. Principal coordinate analysis and analysis of similarity (ANOSIM) showed between diet differences in bacterial community groups existed in ewes and differential bacterial clusters occurred in lambs due to both diet and neonatal inoculation. Diet and rumen inoculation acted together to clearly differentiate the bacterial communities through to weaning, however the microbiome effects of these initial early life interventions diminished with time so that rumen bacterial communities showed greater similarity 2 months after weaning. These results demonstrate that ruminal bacterial communities of newborn lambs can be altered by modifying the diet of their mothers. Moreover, the rumen microbiome of lambs can be changed by diet while they are suckling or by inoculating their rumen, and resulting changes in the rumen bacterial microbiome can persist beyond weaning.

Probiotic Bacillus amyloliquefaciens Strain H57 Improves the Performance of Pregnant and Lactating Ewes Fed a Diet Based on Palm Kernel Meal

Probiotic supplements are single or mixed strain cultures of live microorganisms that benefit the host by improving the properties of the indigenous microflora (Seo et al 2010). In a pilot study at the University of Queensland, Norton et al (2008) found that Bacillus amyloliquefaciens Strain H57 (H57), primarily investigated as an inoculum to make high-quality hay, improved feed intake and nitrogen utilisation over several weeks in pregnant ewes. The purpose of the following study was to further challenge the potential of H57 -to show it survives the steam-pelleting process, and that it improves the performance of ewes fed pellets based on an agro-industrial by-product with a reputation for poor palatability, palm kernel meal (PKM), (McNeill 2013). Thirty-two first-parity White Dorper ewes (day 37 of pregnancy, mean liveweight = 47.3 kg, mean age = 15 months) were inducted into individual pens in the animal house at the University of Queensland, Gatton. They were adjusted onto PKM-based pellets (g/kg drymatter (DM): PKM, 408; sorghum, 430; chick pea hulls, 103; minerals and vitamins; Crude protein, 128; ME: 11.1MJ/kg DM) until day 89 of pregnancy and thereafter fed a predominately pelleted diet incorporating with or without H57 spores (10 9 colony forming units (cfu)/kg pellet, as fed), plus 100g/ewe/day oaten chaff, until day 7 of lactation. From day 7 to 20 of lactation the pelleted component of the diet was steadily reduced to be replaced by a 50:50 mix of lucerne: oaten chaff, fed ad libitum, plus 100g/ewe/day of ground sorghum grain with or without H57 (10 9 cfu/ewe/day). The period of adjustment in pregnancy (day 37-89) extended beyond expectations due to some evidence of mild ruminal acidosis after some initially high intakes that were followed by low intakes. During that time the diet was modified, in an attempt to improve palatability, by the addition of oaten chaff and the removal of an acidifying agent (NH4Cl) that was added initially to reduce the risk of urinary calculi. Eight ewes were removed due to inappetence, leaving 24 ewes to start the trial at day 90 of pregnancy. From day 90 of pregnancy until day 63 of lactation, liveweights of the ewes and their lambs were determined weekly and at parturition. Feed intakes of the ewes were determined weekly. Once lambing began, 1 ewe was removed as it gave birth to twin lambs (whereas the rest gave birth to a single lamb), 4 due to the loss of their lambs (2 to dystocia), and 1 due to copper toxicity. The PKM pellets were suspected to be the cause of the copper toxicity and so were removed in early lactation. Hence, the final statistical analysis using STATISTICA 8 (Repeated measures ANOVA for feed intake, One-way ANOVA for liveweight change and birth weight) was completed on 23 ewes for the pregnancy period (n = 11 fed H57; n = 12 control), and 18 ewes or lambs for the lactation period (n = 8 fed H57; n = 10 control). From day 90 of pregnancy until parturition the H57 supplemented ewes ate 17 more DM (g/day: 1041 vs 889, sed = 42.4, P = 0.04) and gained more liveweight (g/day: 193 vs 24.0, sed = 25.4, P = 0.0002), but produced lambs with a similar birthweight (kg: 4.18 vs 3.99, sed = 0.19, P = 0.54). Over the 63 days of lactation the H57 ewes ate similar amounts of DM but grew slower than the control ewes (g/day: 1.5 vs 97.0, sed = 21.7, P = 0.012). The lambs of the H57 ewes grew faster than those of the control ewes for the first 21 days of lactation (g/day: 356 vs 265, sed = 16.5, P = 0.006). These data support the findings of Norton et al (2008) and Kritas et al (2006) that certain Bacillus spp. supplements can improve the performance of pregnant and lactating ewes. In the current study we particularly highlighted the capacity of H57 to stimulate immature ewes to continue to grow maternal tissue through pregnancy, possibly through an enhanced appetite, which appeared then to stimulate a greater capacity to partition nutrients to their lambs through milk, at least for the first few weeks of lactation, a critical time for optimising lamb survival. To conclude, H57 can survive the steam pelleting process to improve feed intake and maternal liveweight gain in late pregnancy, and performance in early lactation, of first-parity ewes fed a diet based on PKM.

Composición quimica y digestibilidad in situ de los pastos angleton (Dichantium aristatum, poir.), Colonial (Panicum maximum, Jacq.) y Taiwan (Pennisetum purpureum, Schum)

Se determinó la digestibilidad de los pastos Angleton, Colonial y Taiwan mediante el método in situ, disponiendo para ello de tres novillos de la raza criolla Reyna cuya edad oscilaba entre 12 y 18 meses y con un peso promedio de 261 kg, los cuales estuvieron provistos de una fístula ruminal. El objetivo propuesto fue obtener y comparar los estimados cuantitativos relativos a la degradación ruminal a diferentes tiempos de incubación (24,48 y 72 horas} tanto de materia seca como de proteína bruta. Los pastos fueron cosechados a los 35 días después del rebrote y se analizaron químicamente según procedimientos de la A.O.A.C (1984) para materia seca (MS), proteína bruta (PB), extracto etéreo (EE), extracto libre de nitrógeno (ELN), fibra bruta (FB) y cenizas (C) (Weende), y según el método de Van Soest (CATIE, 1987) para fibra neutro detergente (FND)y fibra ácido detergente (FAD), así como Hemicelulosa (HC). Se incubaron 10 gr de las muestras de cada uno de los pastos en bolsas de nylon. Para analizar estadísticamente los valores de degradación obtenidos, se utilizaron análisis de varianza dentro de un DCA para determinar la significancia entre pastos en los tiempos medidos y prueba de rango múltiple de Duncan para comparar medias de los pastos dentro de cada tiempo, obteniéndose diferencias altamente significativas entre ellos (P <0.01), y al observar la separación de medias se manifestó la superioridad del Taiwan en todos los tiempos de incubación, sin embargo el Colonial, no presentó diferencias significativas con el Taiwan y el Angleton en el tiempo de 72 horas. Se concluye como resultado de este estudio, que a una edad de rebrote de 35 días, el. Taiwán es superior al Angleton y al Colonial en lo que respecta a solubilidad de materia seca v proteína bruta al mismo tiempo el Colonial. mostró superioridad ante el Angl.eton debido a su mayor solubilidad de materia seca. Las mayores degradaciones de materia seca se presentaron en el. período de 0 a 24 horas de fermentación para los tres pastos; en cambio para proteína bruta ocurrieron para el. Angleton y el Taiwán entra 1as 24 y 48 horas y para e1 Colonia1 entre O y 24 horas. En qenera1, a través de la dinámica de digestión de 1os pastos se observó la influencia negativa que ejerce proporcionalmente a su contenido, la fracción de fibra (fibra neutro detergente y fibra acido detergente).

Caracterizacion morfologica y potencial forrajero del teocinte anual (Zea nicaraguensis ILTIS y BENZ), colectado en la reserva de recursos geneticos de Apacunca, Chinandega, Nicaragua

El teocintle anual (Zea nicaraguensis Iltis & Benz), es una especie silvestre emparentada con el maíz y con alto potencial forrajero, es endémico de la Reserva de Recursos Genéticos de Apacunca (RRGA), Somotillo, departamento de Chinandega. El objetivo de la presente investigación fue contribuir con información científica. El estudio se realizó en el área experimental de la Universidad Nacional Agraria. Se establecieron diseños en franjas, categorización estadísticas según LSD (α=0.05), correlación y análisis multivariado en los tratamientos. El teocintle fue expuesto a períodos de enmalezamiento, distancia de siembra y fertilización nitrogenada. Se evaluó materia seca, proteína total y fibra en diferentes momentos de cortes, y se comparó material vegetal del teocintle con el maíz (Zea mays L.) y sorgo forrajero ( Sorghum spp.). De igual manera se evaluó la degradación ruminal en vacas fistuladas mediante la ecuación de Orskov y McDonald. Los tratamientos evaluados afectaron variables de tallo, hoja y reproductivas. El mejor tratamiento fue la distancia de 0.8 m, tres limpias a lo largo de su ciclo reproductivo, y fertilización. Las variables de hojas, hijos y frutos; así como la altura de planta, ramas laterales, y panoja presentaron alta correlación. Asimismo, variables de tallo y ramas laterales, fueron las variables más representativas. Los valores de análisis proximal fueron mayores en cortes de material vegetal realizado en los mes es de Junio y Julio. Por otro lado, la materia seca en el teocintle fue menor al sorgo forrajero y maíz. En cuanto a la cantidad de fibra, el teocintle mostró valores similares al maíz y mayores al obtenido en el sorgo forrajero. La categorización estadística mostró que la degradación ruminal a los 96 y 72 horas fue significativa, con porcentajes promedios de 39.5 y 34.94%, y la ecuación de d egradación ruminal fue la siguiente: Y= 2.047+40.612*(1- e-0.0249*tiempo).

Potencial forrajero del Teocincle anual (Zea nicaraguensis ILTIS y BENZ)

El teocintle anual ( Zea nicaraguensis Iltis & Benz) es una especie silvestre endémica de la Reserva de Recursos Genéticos de Apacunca (RRGA) en el nor-oeste de Nicaragua. Está emparentado con el maíz y tiene un alto potencial forrajero. En el estudio se evaluaron momentos de cortes en el teocintle, y relacionados con maíz ( Zea mays L . ) y sorgo forrajero ( Sorghum vulgare ). La degradabilidad de materia seca en bovinos fistulados de la raza Reyna fue determinada con la metodología de Orskov y McDonald (1979), así como análisis de varianza y categorización estadística (LSD, α=0.05). Los valores de análisis proximal fueron mayores en cortes realizados en los meses de junio y julio, y la materia seca en el teocintle fue menor al sorgo forrajero y maíz. El teocintle mostró valores similares de fibra al maíz y mayores al sorgo. La mayor tasa de degradación ruminal se da durante las primeras 24h

Degradación de harina de granos de Canavalia (Canavalia ensiformis) con y sin tratamiento térmico

Con el objetivo de determinar la tasa de degradación ruminal de la harina de granos de Canavalia con y sin tratamiento térmico. Se utilizó una vaca fistulada criolla Reyna con un peso corporal de 380 kg y 11 años de edad; Los tiempos de incubación evaluados fueron 3, 6, 9, 12, 24, 48 y 72 horas utilizándose un diseño completamente al azar con arreglo factorial, con 3 repeticiones por tratamiento, donde se consideró el tiempo como factor A y los tratamientos como factor B. La degradabilidad de las harinas de granos de Canavalia se estimó mediante el modelo de Orskov y McDonald (1979); para conocer el efecto del tratamiento térmico sobre la tasa de degradabilidad, se realizó análisis de varianza y la prueba honesta de Tukey para conocer las diferencias entre los tiempos de incubación. En los resultados de la degradación ruminal, se observó diferencias altamente significativas (p <0.01) para las variables de DRMS con 70.67% y 80.4% y DRMO con 71.02% y 80.44%. Mientras que no se encontró diferencia signifi cativa (p>0.01) para la DRPB de 74.47% y 90.65% a las 72 h de incubación respectivamente. Estos resultados sugieren que las harinas de granos de canavalia ensiformis tanto con y sin tratamiento térmico son de fácil degradación en el rumen, tanto para la MS, MO como para la PB, y que representan una alternativa de alimentación sostenible para la ganadería en el trópico

Biofiltração de compostos orgânicos voláteis e gás sulfídrico em estações de despejos industriais de processamento de hidrocarbonetos.

Neste trabalho foi estudado o tratamento simultâneo por biofiltração de emissões de compostos orgânicos voláteis, COV e gás sulfídrico, H2S, em estações de tratamento de despejos industriais, de refinaria de petróleo, ETDI. A biofiltração dos gases emanados da EDTI mostrou ser uma técnica de alta eficiência, atingindo valores de 95 a 99 % para tratamento simultâneo de COV e H2S em concentrações de 1000 e 100 ppmv, respectivamente. Foram realizados testes em 95 dias consecutivos de operação, em uma planta piloto instalada na Superintendência da Industrialização do Xisto, SIX, em São Mateus do Sul, Paraná, de março a agosto de 2006. O biofiltro foi do tipo fluxo ascendente, com 3,77 m3 de leito orgânico, composto de turfa, carvão ativado, lascas de madeira, serragem brita fina além de outros componentes menores. Foi realizada inoculação biológica com lodo filtrado de estação de tratamento de esgoto sanitário. As vazões de gás aplicadas variaram de 85 a 407 m3/h, resultando em taxas de carga de massa de 11,86 a 193,03 g de COV/h.m3 de leito e tempos de residência de 24 segundos a 6,5 minutos, com tempo ótimo de 1,6 minutos. A capacidade máxima de remoção do sistema encontrada, nas condições testadas, foi de 15 g de COV/h. m3, compatível com os valores encontrados na literatura para depuração biológica de COV na escala praticada. Também foi verificada a redução de componentes específicos de BTX, demonstrando boa degradabilidade dos compostos orgânicos. Finalmente o biofiltro demonstrou boa robustez biológica diante dos desvios operacionais intencionalmente provocados, tais como falta de umidade do leito, baixa temperatura, alta vazão, falta de carga de COV e baixo pH do leito. Depois de retomada a condição de operação estável, a biofiltração rapidamente atingiu o estado de equilíbrio, assegurando o uso eficiente e confiável da técnica no tratamento de gases de EDTI na indústria do hidrocarbonetos ou em refinarias de petróleo.

Aspectos práticos da suplementação alimentar de bovinos de corte.

Para ser competitiva, a bovinocultura de corte tropical precisa explorar melhor o pasto, corrigindo, quando necessário, possíveis deficiências nutricionais, isto com muito critério e dentro de uma meta de produção bem estabelecida. Nos trópicos, ao contrário dos países de clima temperado, é possível manter os bovinos em pastejo durante todo o ano, maximizando o conceito do ?boi verde? e preservando as características digestivas do animal ruminante. Tal conceito envolve inúmeros fatores: a energia solar (luz e calor), a planta forrageira (componente sintetizador das substâncias orgânicas via fotossíntese), os bovinos (componente transformador da matéria vegetal em carne/leite por fermentação ruminal), o solo (componente sustentador e fornecedor de elementos nutritivos), a umidade (fornecedora de água) e o ar (fonte contínua de CO2, O2, e N2). Executar uma pecuária precoce, mas racional, é alcançar o equilíbrio biológico entre todos esses componentes, de forma a assegurar sua sustentabilidade. Nesta publicação discutirem-se e sugerem-se medidas corretivas nos pontos de desequilíbrio dos sistemas de produção de carne em pasto, visando a uma pecuária de ciclo curto. Hoje, precocidade é uma demanda de mercado e se o Brasil pretende ampliar e manter sua presença nele, é necessário melhorar o manejo alimentar do seu rebanho.

Cambios en la biodisponibilidad de cromo en un suelo inducidos por la incorporación de materia orgánica

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In vitro evaluation of fibrolytic enzymes as additives for maize (Zea mays L.) silage - III. Comparison of enzymes derived from psychrophilic, mesophilic or thermophilic sources

A completely randomised study was completed to examine the influence of fibrolytic enzymes derived from psychrophilic, (F), mesophilic, (L) or thermophilic (Ta) sources, applied at ensiling, on the chemical characteristics and in vitro rumen fermentation of maize silage, assessed using the Reading Pressure Technique (RPT). Treatments, all in triplicate, consisted of untreated maize forage or treated with preparations F, L, Ta or a mixture (1: 1, v/v) of F and L (FL), at two levels each, and ensiled for 210 days in plastic mini-silos. Addition of enzymes L decreased (P < 0.05) silage pH relative to the control, whereas enzyme Ta tended (P < 0.10) to reduce it. Preparations F, L and Ta tended to reduce (P < 0.10) the fibre contents of the silages, with effects being attributable to a decrease in the cellulose fraction. Starch contents were reduced (P < 0.05) in the treatments including enzyme F. End-point (96 h) gas production (GP) values did not differ among treatments, suggesting that enzymes did not change the total amount of fermentable substrate. However, consistent with the decrease in starch contents, adding enzyme F reduced (P < 0.05) GP at most incubation times. Addition of enzymes increased (P < 0.05) the initial (6 h) organic matter degradation (OMD) levels in all but one treatment (F), with increases of 14, 19, and 26% for preparations L, Ta, and FL, respectively, averaged across levels. Furthermore, the addition of enzymes increased (P < 0.05) the soluble OM losses, however, these increases did not fully account for the initial increase in OMD. The latter suggests that enzymes increased solubility and also altered silage structure, making it more amenable to degradation by ruminal microorganisms. As a result of the increase in OMD, without a concomitant increase in GP, the fermentation efficiency was greatly increased (P < 0.05) in enzyme treatments. Addition of enzymes to maize at ensiling, particularly those from the mesophilic and thermophilic sources used here, have the potential to increase the initial rate of silage OMD. (C) 2003 Elsevier B.V. All rights reserved.

Technical note: A proposed method to determine the extent of degradation of a feed in the rumen from the degradation profile obtained with the in vitro gas production technique using feces as the inoculum

A method is proposed to determine the extent of degradation in the rumen involving a two-stage mathematical modeling process. In the first stage, a statistical model shifts (or maps) the gas accumulation profile obtained using a fecal inoculum to a ruminal gas profile. Then, a kinetic model determines the extent of degradation in the rumen from the shifted profile. The kinetic model is presented as a generalized mathematical function, allowing any one of a number of alternative equation forms to be selected. This method might allow the gas production technique to become an approach for determining extent of degradation in the rumen, decreasing the need for surgically modified animals while still maintaining the link with the animal. Further research is needed before the proposed methodology can be used as a standard method across a range of feeds.

Utilisation by ruminants of nitrogen compounds in silage-based diets

This paper considers the various complex changes that occur to nitrogen (N) containing compounds in forages through the processes of ensiling, rumen degradation and microbial synthesis, post-ruminal digestion and absorption and synthesis into milk protein. Particular emphasis is placed on reviewing recent data on the efficiency of utilisation of N-containing compounds in silages by rumen microbes, since low efficiency here is believed to be a major cause of large N losses to the environment on some silage-based diets. Data are reviewed which show that although rumen degradation of N compounds in silage is rapid and extensive, up to 10% of the soluble N can escape the rumen by being associated with the liquid phase. There is now firm evidence that the composition of the amino acids (AAs) absorbed is heavily dependent on the process of ensiling and that witting or use of certain silage additives conserve the initial amino acid profile of the forage. This provides an opportunity to manipulate the amino acid supply to better match demand thus potentially enhancing utilisation. This review confirms that utilisation of the N fractions in grass and legume silages in particular, is poor and the efficiency of microbial protein synthesis (EMPS) is consistently higher on maize silage-based diets. It is concluded that the way in which grass and legume silages in particular are produced and used in the future needs a radical rethink. New research needs to be aimed at enhancing the utilisation of N in the rumen through a better understanding of N/carbohydrate relationships and the ability of forages to supply degraded carbohydrate. Also more emphasis is needed on understanding of the potentially different role of the different N fractions that exist in silages. (C) 2004 Elsevier B.V. All rights reserved.

In situ degradability of dry matter and neutral-detergent fibre of thorn scrubland forage consumed by goats in the semi-arid region of north Mexico

Three goats provided with oesophageal and ruminal cannulae were used to determine variations in dry matter (DM) and neutral-detergent fibre (NDF) degradability of the forage consumed when grazing thorn scrubland in the semi-arid region of north Mexico, during two consecutive dry and wet periods. Ingesta samples were incubated intraruminally, the data were fitted to the exponential equation P = a + b (1-e(-ct)) and statistically analysed using a randomized-block design. Organic matter and crude protein (CP) contents were higher (P < 0.05) in the wet seasons. Values of NDF were similar in dry and wet season of both years whereas higher numerical values of acid-detergent fibre (ADF), lignin and cellulose were registered in the dry seasons. DM and NDF degradabilities after 24 and 48 h of ruminal incubation were higher (P < 0.05) in the wet seasons. Higher values (P < 0.05) in DM and NDF bag losses at zero time (A fraction) were registered in the two wet seasons. The insoluble but fermentable DM and NDF (B fractions) were higher (P < 0.05) in the 1999 wet season and variable in the rest of the studied period. Numerically higher values of DM and NDF c fraction were found in wet periods, whereas DM and NDF potential degradabilities were higher (P < 0.05) in the wet season in 1999 and similar across seasons in 2000. Lowest (P < 0.05) contents of CP in grazed forage, DM and NDF degradabilities after 48 h of ruminal incubation, and A, and B, and c fractions were observed in the dry seasons. Thus, these results may be related to both the lower feeding value of forage consumed by the animals and lower performance of livestock during this period. Then, the DM and NDF degradability after 48 h, together with the insoluble but fermentable matter and the c fraction permit the nutritive value of the forage consumed by grazing goats to be accurately described.