Percentage Of Neutral Detergent Fiber Research Articles

DEGRADABILIDAD in situ DE LA MATERIA SECA DE Tithonia diversifolia (Hemsl.) A. Grey EN TRES ÉPOCAS DEL AÑO

<p><strong>Background. </strong>Forage trees and shrubs are an alternative that improve dry matter intake and digestibility in ruminants, due to their high ruminal degradation rate, higher nitrogen contribution for rumen microorganisms, low percentage of neutral and acid detergent fiber.<strong> Objective</strong>. To estimate the availability, nutritional quality and degradability for <em>Tithonia</em> <em>diversifolia</em> (Hemsl.) A. Gray were estimated at different cutting age, in three seasons of the year. <strong>Metodology</strong>. Forage production and nutritional quality were measured every 14 d, from cutting to 84 d of age. Leaf and stem samples were taken to determine crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and the "<em>in situ</em>" degradability of dry leaf matter (DM). <strong>Results</strong>. Total DM production was similar in autumn and winter, and both were greater than for spring. In autumn, at 56 d and in winter at 70 d after cutting, DM production was 9 t ha<sup>-1</sup>, while in spring at 84 d it was close to 3 t ha<sup>-1</sup>. Crude protein content increased linearly with days after cutting. <strong>Implications.</strong> In autumn and winter, the highest percentages of NDF and ADF were observed. Plants at 42 d of regrowth had a lower percentage of ADF. <strong>Conclusions</strong>. The DM production and the nutritional quality of <em>T. diversifolia</em> differ according to the season of the year and the age of regrowth, at 42, 70 and 84 days of regrowth in autumn, winter and spring, respectively, under the agroecological conditions of the growing area. study, the best conditions for growth occur in Autumn. The DM degradability is similar between the ages of 42, 56 and 70 days of regrowth. However, harvesting plants at 42 days could sacrifice biomass yield at a very early age.</p>

PSXI-27 Live Yeasts Enhance Ruminal Fermentation of Fibrous Feedstuffs

Abstract Since the beginning of the present century, research results have shown that ruminant researchers have explored the idea of manipulate ruminal fermentation, trying to improve a much better metabolism of nutrients in the rumen, all of this with the aim to increase the productivity of ruminants. The main goal of this experiment was to evaluate the potential use of a savage yeast strain (Pichia guilliermondii) on the ruminal fermentation of maize stover. To accomplish the objective two in vitro treatments were examined: a) filtered rumen liquid + powdered maize stover + yeast-free culture medium, and b) filtered rumen liquid + powdered maize stover + culture medium inoculated with yeast. Samples were collected at different time, 0, 6, 12, and 24 h and examined for effects on culture pH, ammonia nitrogen (NH3-N), the fiber digestibility percentages of neutral detergent fiber (NDFD) and acid detergent fiber (ADFD), as well the digestibility of dry matter (DMD), and the concentration of volatile fatty acids (VFAs). The results showed that the addition of Levica 27 had no effect on the ruminal pH, NH3-N or the digestibility indicators (P > 0.05). However, at 12 h, the inclusion of Levica 27 increased (P < 0.05) the molar total of VFAs, and acetic and propionic acids in ruminal fluid and decreased (P < 0.05) the C2:C3 ratio. Our conclusion was that Pichia guilliermondii had a stimulating effect on the in vitro ruminal fermentation over a range within 6 and 12 h, a result that should be taken into account when in vivo studies are replicated with this yeast strain.

Effect of Live Yeasts (Pichia guilliermondii) on In Vitro Fermentation of Corn Stover as a Fibrous Substrate

The objective of the present study was to examine the potential utilization of the yeast strain Pichia guilliermondii (Levica 27) on the ruminal fermentation of corn stover. Two in vitro treatments were evaluated: (A) filtered rumen liquid + powdered corn stover + yeast-free culture medium and (B) filtered rumen liquid + powdered corn stover + culture medium inoculated with yeast. Samples were collected at 0, 6, 12, and 24 h and examined for effects on culture pH, ammonia nitrogen (NH3-N), the fiber digestibility percentages of neutral detergent fiber and acid detergent fiber, the digestibility of dry matter, and the concentration of volatile fatty acids (VFAs). The results showed that the addition of Levica 27 had no effect on the ruminal pH, NH3-N or the digestibility indicators (p > 0.05). However, at 12 h, the inclusion of Levica 27 increased (p < 0.05) the molar concentrations of total VFAs and acetic and propionic acids in ruminal fluid and decreased (p < 0.05) the C2:C3 ratio. It is concluded that Levica 27 seems to have a stimulating effect on ruminal fermentation over a range within 6 and 12 h, a result that should be taken into account when in vivo studies are performed with this yeast strain.

Use of Chelex-100 for the molecular diagnosis of five animal pathogens

The goal of this work was to evaluate the nutritional quality in 3 cultivars of alfalfa, belonging to different winter dormancy (GRI), subjected to two cutting frequencies during one year of cultivation, based on the abundant information existing in studies carried out in productivity, coverage and persistence, not so in the determination of quality of forage subjected to different frequencies of cuts and contrasting GRI. Three cultivars (GR6-Verzy), (GR9-Mecha) and (GR10-Ruano) were tested. The experimental design was a complete split plot with four repetitions. Two treatments defined by the cutting intervals were established: T1: 25 days and T2: 35 days. These were specified for spring, summer and fall seasons. For winter the interval was 45 and 55 days in T1 and T2, respectively. The evaluated variables were: percentage of dry matter (% DM), percentage of crude protein (% PB), percentage of neutral detergent fiber (% FDN) and percentage of acid detergent fiber (% FDA). Significant differences were found for all the nutritional variables studied, for both treatment with p <0.05 with InfoStat program. Interaction between cultivars and treatment was observed for % PB. The 35 days cutoff frequency of yielded the lowest percentages of PB and the highest percentages of FDN and FDA. Hence the forage resulting from this frequency is of a lower quality, leading to decreased digestibility and lower performance of pasture for livestock.

Chemical Composition and Energy Yield of Elephant-Grass Biomass as Function of Five Different Production Ages

Elephant grass has high biomass production, with qualities suitable for conversion into bioenergy, but has long been used exclusively for animal feed and only in recent years has it become an energetic alternative. Therefore, it is necessary to select genotypes with potential for energy production. This study evaluated the effect of five harvest times (8, 12, 16, 20, and 24 weeks) on the yield and chemical composition related to biomass quality through combined polynomial regression analyses of the following elephant grass genotypes: Cubano Pinda, Mercker 86-México, Pusa Napier n°1, Mole de Volta Grande, P-241-Piracicaba, and King Grass. A completely randomized design with three replicates, in a split-plot arrangement, was adopted, including two factors (plots = genotypes, subplots = harvest times). The evaluated variables were whole-plant dry matter yield, in t ha-1 (DMY), percentage of neutral detergent fiber (%NDF), and percentage of acid detergent fiber (%ADF). The elephant-grass genotypes Cubano de Pinda, Mercker 86-México, and P-241-Piracicaba showed a linear first-degree effect as a function of the harvest intervals, indicating that they did not reach their maximum production potential. Genotypes Pusa Napier n°1, Mole de Volta Grande, and King Grass, in turn, had a linear second-degree effect. For the NDF variable, all genotypes showed a significant linear second-degree effect as a function of the harvest intervals, except P-241-Piracicaba, for which no regression was observed. For this genotype, there was a significant linear first-degree effect on the %ADF variable.

English

The elephant grass has gained prominence as one of the main forage species used for biomass production. Therefore, the aim of this study was to identify elephant grass genotypes with high energy biomass production potential by evaluating morpho-agronomic and biomass quality. The following traits were evaluated in this study: dry matter yield (DMY), percentage of whole-plant dry matter (%DM), percentage of neutral detergent fiber (%NDF), percentage of acid detergent fiber (%ADF); percentage of cellulose (%CEL), percentage of lignin (%LIG), percentage of carbon (%C), percentage of nitrogen (%N), and carbon: nitrogen ratio (C: N). Five different production ages were evaluated, and significant differences were observed for the variable DMY. The harvests performed at 20 and 24 weeks of age, provided the best response for biomass energy production (DMY) from elephant grass, averaging 20.50 and 23.77 t.ha−1. The genotypes that most stood out during the evaluation period at the five production ages were King Grass, Mole de Volta Grande, and Mercker 86 - Mexico. Genotypes Mole de Volta Grande and King Grass are the most suitable for elephant grass breeding programs aimed at biomass energy production in the conditions of Campos dos Goytacazes - RJ, Brazil. Key words: Bioenergy, biomass quality, carbon: nitrogen ratios, Pennisetum purpureum Shum, yield.

Use of elephant grass for energy production in Campos dos Goytacazes-RJ, Brazil.

Elephant grass is a tropical forage plant widely distributed throughout Brazil. It was first exclusively used in the livestock sector as cattle feed. The grass is characterized by its high productivity and photosynthetic capacity and is considered as an alternative source of renewable energy. Here, we estimated the general combining ability of the parents and specific combining ability of the hybrids based on morpho-agronomic biomass-quality traits. The experiment was conducted in a randomized block design with 3 replicates. The diallel was composed of 16 hybrids and 2 groups of genitors. In the diallel analysis of variance, we observed a significant difference among treatments. A significant difference was observed among genitors for dry matter production (DMP). For the general combining ability of group 1, the traits leaf blade width, DMP, height, percentage of neutral detergent fiber, percentage of hemicellulose, percentage of lignin, percentage of acid detergent fiber, and percentage of cellulose were significant. For the estimates of general combining ability of DMP, parents Porto Rico 534-B, Vruckwona, Taiwan A-146, and Mercker S. E. A. were 0.4748, 3.2819, 1.1659, and 0.4317. The parents of Mercker S. E. A. and Porto Rico 534-B produced the highest percentage of detergent fiber and percentage of lignin with values of 0.1482 and 0.0856. Thus, parents Vruckwona, Porto Rico 534-B, and Taiwan A-146 are promising for integration into breeding programs. The best hybrid combinations for DMP were 1 x 5, 1 x 8, 2 x 6, 3 x 7, and 4 x 5.

Diferimento de pastos de Brachiaria decumbens adubados com nitrogênio no início e no final do período das águas

O objetivo com este trabalho foi avaliar a massa de matéria seca forragem e de seus componentes morfológicos, a altura e o índice de tombamento do pasto, a densidade volumétrica e o valor nutritivo da forragem em pastos de Brachiaria decumbens diferidos por 95 dias sob quatro estratégias de adubação nitrogenada. Foram estudadas quatro estratégias de aplicação de nitrogênio no início e no final do período chuvoso, respectivamente (0-0, 100-0, 50-50, 0-100 kg de N.ha-1), avaliados em três estratos verticais a cada 20 cm, num delineamento experimental de blocos casualizados em esquema de parcelas subdivididas com quatro repetições. Os pastos adubados com 100 kg de N no final do período chuvoso apresentaram maiores massas de matéria seca de forragem total, lâmina de folha e de colmo verde, bem como altura, altura estendida e densidade volumétrica da forragem total, lâmina de folha e de colmo verde em todos os estratos estudados. Os índices de tombamento foram maiores para os pastos adubados no final do período chuvoso (0-100 e 50-50). Os percentuais de fibra em detergente neutro foram menores no estrato A (acima de 40 cm do solo) e os teores proteína bruta (PB) maiores em todos os estratos para os tratamentos 0-100 e 50-50. Embora a adubação com 100 kg de N no final do período chuvoso permita aumentar a massa de forragem total e de lâminas de folhas e melhorar a qualidade desta forragem, a maior densidade de colmos nos estratos superiores e o elevado índice de tombamento podem caracterizar dificuldades na seleção da forragem e redução no consumo e desempenho animal.

Valor nutritivo de perfilhos e componentes morfológicos em pastos de capim-braquiária diferidos e adubados com nitrogênio

Este trabalho foi realizado com o objetivo de avaliar o valor nutritivo de perfilhos e componentes morfológicos em pastos diferidos e adubados com nitrogênio de Brachiaria decumbens cv. Basilisk. Dois experimentos foram realizados em delineamento de blocos casualizados com três repetições e esquema de parcela subdivida. No primeiro experimento, foram realizadas combinações entre doses de nitrogênio (0, 40, 80 e 120 kg/ha) com os componentes morfológicos (folha verde, colmo verde, folha morta e colmo morto) ou com as categorias de perfilhos (vegetativo e reprodutivo) do pasto. No segundo experimento, estudaram-se as combinações entre períodos de diferimento (73, 95 e 116 dias) com categorias de perfilhos (vegetativo e reprodutivo). A adubação nitrogenada aumentou o percentual de fibra em detergente neutro (FDN) nos colmos verdes e o teor de proteína bruta (PB) nas folhas verdes e mortas e no colmo verde. Elevou também os percentuais de PB nos perfilhos vegetativos e reprodutivos, assim como o teor de FDN do perfilhos vegetativos. Maior período de diferimento causou acréscimo no percentual de FDN e redução no percentual de proteína bruta nos perfilhos vegetativos e reprodutivos. A dose de nitrogênio e o período de diferimento alteram o valor nutritivo dos componentes morfológicos e dos perfilhos dos pastos de B. decumbens cv. Basilisk. No diferimento da pastagem, ações de manejo que resultem em maiores percentuais de lâmina foliar verde e perfilho vegetativo no pasto contribuem para melhorar o valor nutritivo da forragem diferida.

Effect of rumen-protected methionine on feed intake, milk production, true milk protein concentration, and true milk protein yield, and the factors that influence these effects: A meta-analysis

A meta-analysis of published studies was used to investigate the effect of rumen-protected methionine (RPM) added to the diets of lactating dairy cattle on dry matter intake, milk production, true milk protein (TMP) production, and milk fat yield. Differences in responses between 2 commonly used RPM products, Mepron (Evonik Industries, Hanau, Germany) and Smartamine (Adisseo, Antony, France), were investigated as well as dietary and animal factors that could influence responses. Diets were coded with respect to the amino acid (AA) deficiency of the control diet as predicted by the AminoCow model (version 3.5.2, http://www.makemilknotmanure.com/aminocow.php; 0=no AA deficiency, 1=Met deficiency, 2=Met and Lys deficiency, 3=Met and Lys plus at least 1 other AA deficiency) to test the effect of AA deficiencies on RPM response. Thirty-five studies were identified, 17 studies evaluating Mepron, 18 studies evaluating Smartamine, and 1 study evaluating both. This permitted 75 dietary comparisons between control and RPM-added diets. Diets were entered into the AminoCow and the 2001 National Research Council models to compare predictions of Met, Lys, and metabolizable protein (MP) flow. Mean Met and Lys in diets where RPM was fed were estimated to be 2.35 and 6.33% of MP, respectively. Predictions of flows between models were similar. Overall, RPM addition to diets increased production of TMP, both as percentage (0.07%) and yield (27 g/d). Dry matter intake and milk fat percentage were slightly decreased, whereas milk production was slightly increased. Differences between products were detected for all production variables, with Mepron-fed cows producing less TMP percentage but greater milk production, resulting in twice as much TMP yield. Milk protein response to RPM was not related to predicted AA deficiency, calculated Met deficiency, or Met as a percentage of MP. Other dietary factors, including Lys flow (g/d), Lys as percentage of MP, neutral detergent fiber percentage, crude protein percentage, or energy balance, had no detectable effects on TMP response. When cows with a predicted positive AA balance were fed RPM, milk production increased, but when AA balance was negative, milk production decreased. Amount of RPM added to the diet was not correlated to TMP response. This study does not support the necessity of a high Lys level as a prerequisite to obtaining a TMP response to feeding RPM or the MP requirement suggested by the National Research Council model (2001). However, more dose–response studies over a wide range of milk production and dietary regimens will be required to more clearly establish AA requirements and to predict responses to RPM supplementation.

Influence of Transition Diets on Occurrence of Subclinical Laminitis in Holstein Dairy Cows

Pre- and postpartum diets varying in energy and fiber were studied for effects on subclinical laminitis in Holstein cows. Also, ruminal acidosis was examined relative to sole hemorrhages and ulcers. Cows (n = 98) were assigned to a 2 x 2 factorial arrangement of treatments in a randomized complete block. Diets high in net energy of lactation (NE(L)) and low fiber were classified as high NE(L), whereas low NE(L) and higher fiber were defined as low NE(L). Two diets were fed for 3 wk before calving and 2 others fed for 3 wk postpartum resulting in 4 treatment combinations: high NE(L), low NE(L); high NE(L), high NE(L); low NE(L), low NE(L); and low NE(L), high NE(L). Levels of NE(L) (Mcal/kg DM), percentage of acid detergent fiber, and percentage of neutral detergent fiber for low NE(L) vs. high NE(L) prepartum diets, were 1.51, 30.2, 47.2 vs. 1.65, 23.4, 39.8, respectively, and 1.70, 22.4, 36.8 vs. 1.77, 17.5, 31.4 for low NE(L) vs. high NE(L) lactating diets, respectively. A single diet was fed after 21 d in milk (DIM). Measures of hoof discoloration, hemorrhage, and/or ulcer formation were done at about 45 d before calving, and near 28 and 70 DIM. Rumenocentesis was performed 14 d before calving and at 8, 22, and 70 DIM. Hoof scores among treatments were similar at 28 DIM. The low NE(L), high NE(L) group had less desirable hoof scores than high NE(L), high NE(L), or low NE(L), low NE(L) groups from 55 to 75 DIM. Rumen pH did not differ by treatment before calving. The lowest postpartum rumen pH was significantly lower and rates of ruminal acidosis (pH < or = 5.8) at 8 and 22 DIM were higher for groups fed high NE(L) after calving. No direct relationship between low postpartum rumen pH and hoof scores on individual cows was found. Low NE(L) before calving and high NE(L) right after calving may increase risk of subclinical laminitis if not carefully managed.

Predicting Average Feed Intake of Lactating Holstein Cows Fed Totally Mixed Rations

A dry matter intake (DMI) prediction equation was estimated by using a data file that contained 124 treatment means collected from published studies. Animal factors considered for inclusion in the prediction model were body weight (BW) and its natural logarithm, BW0.75, milk yield (MY) and its natural logarithm, milk fat and protein yields, month of lactation and its square, as well as its natural logarithm. The dietary factors considered were the percentages of neutral detergent fiber, acid detergent fiber, crude protein and hemicellulose in the ration dry matter together with the square of all these predictors. The multiple regression model selected by using the maximum R2 method include both animal and dietary factors as independent variables. The accuracy of this DMI prediction equation was evaluated and compared with that of five other equations previously published by using three independent datasets also containing treatment means collected from literature. Even though the latest NRC equation was slightly more accurate than the equation proposed in this study with the three evaluation datasets, the latter can be used for some applications for which the NRC equation is not appropriate.

Efeito da mistura da planta de girassol (Helianthus annuus L.), durante a ensilagem do capim-elefante (Pennisetum purpureum Schum.) no valor nutritivo da silagem

O girassol foi misturado ao capim-elefante (Pennisetum purpureum Schum) na ensilagem. A colheita do capim-elefante foi realizada manualmente após 70 dias do corte de uniformização, à altura de 10 cm da superfície do solo. Para confecção da silagem, foram utilizados os híbridos de girassol M-742 e M-92007. As misturas capim-elefante e girassol foram feitas nas seguintes proporções de matéria verde: 100 e 0%, 75 e 25%; 50 e 50%; 25 e 75%; 0 e 100% de capim e girassol, respectivamente. As plantas foram picadas mecanicamente em partículas de 2,0 a 3,0 cm de tamanho, ensiladas por 30 dias, em silos de "PVC" de dez centímetros de diâmetro e quarenta centímetros de altura. Foram avaliadas as porcentagens de matéria seca (MS), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN), digestibilidade in vitro da matéria seca (DIVMS) e valores de pH das silagens. O delineamento experimental empregado foi o inteiramente casualizado, com quatro repetições. Concluiu-se que as silagens de capim-elefante com mistura da planta de girassol apresentaram maiores porcentagens de MS, PB, EE e valores de pH, aumentos na DIVMS e menor porcentagem de FDN na matéria seca com o aumento dos níveis de substituição.

한우 수소의 건물섭취량 추정

본 시험은 한우수소 24두를 이용하여 성장단계별 증체량 및 건물 섭취량을 측정하고, 그에 대한 추정식을 유도하기 위하여 수행되었다. 시험구는 조사료 3종류(볏짚, 건초, 옥수수사일리지)와 조사료 급여비율 4수준(100, 60, 40 및 20%)의 3<TEX>${\times}$</TEX>4요인시험으로서 공시축은 incomplete turnover design에 의해 처리당 4두씩 배치되었다. 조사료의 종류 및 급여비율에 따른 한우수소의 일일 증체량은 옥수수사일리지 급여구 및 조사료 20% 급여구에서 각각 가장 많았다. 한우수소에게 건초 혹은 옥수수사일리지만 전량 급여하였을 경우에도 전 기간동안 증체가 지속되었지만, 볏짚구에서는 체중 350kg대 이후부터 체중이 감소하였다. 대사체중당 건물 섭취량은 체중이 증가할 수록 줄어들었으며, 조사료 공급원과 조사료 급여비율에 따른 건물 섭취량은 옥수수사일리지 및 조사료 20%구에서 각각 가장 높았다. 대사체중당(<TEX>$BWkg^{0.75}$</TEX>) 건물 섭취량(DMI, kg/ day)에 따른 한우수소의 일일 증체량(DG, kg) 추정공식은 다음과 같이 유도되었다. DG = －0.842 + 17.5DMI/<TEX>$BWkg^{0.75}$</TEX>체중(BW, kg)과 일일 증체량(DG, kg)을 고려한 사료의 NDF 함량(NDF, %)과 건물 섭취량(DMI, kg/day)과의 관계식은 다음과 같이 유도되었다 DMI = 4.125 + 0.013BW + 1.075DG － 0.045NDF Twenty four Hanwoo bulls(mean initial body weight 162<TEX>$\pm$</TEX>8.1kg) were employed to induce the regression equations on body weight gain and dry matter intake. The diets were fed in a 3<TEX>${\times}$</TEX>4 factorial arrangement; three roughage sources(rice straw, hay, corn silage) and four roughage ratios in ration(100, 60, 40, 20%). Bulls were alloted by incomplete turn over design with four replications. Daily body weight gain was greatest in bulls fed the corn silage as a roughage source and the 20% of roughage ratio, respectively. Bulls fed hay or corn silage only as feed kept in their body weight gain during the whole experimental period, however those fed rice straw only were in a negative body gain hereafter fatteningⅠperiod(350kg of body wt.). Dry matter intake per metabolizable body weight was decreased with increasing body weight. Dry matter intake was greatest in bulls fed the corn silage as a roughage source and the 20% of roughage ratio, respectively. The regression equations on daily body weight gain(DG, kg) and dry matter intake(DMI, kg/day) according to body weight(BW, kg) of Hanwoo bulls were derived as follows; DG = －0.842 + 17.5DMI/<TEX>$BWkg^{0.75}$</TEX> DMI = 4.125 + 0.013BW + 1.075DG － 0.045NDF where, NDF is the percentage of neutral detergent fiber in ration.

Modeling Ruminal Digestibility of Carbohydrates and Microbial Protein Flow to the Duodenum

Carbohydrates are the major source of energy for dairy cows and for microbial protein synthesis in the rumen. The prediction of ruminal carbohydrate digestibility and of the flow of microbial protein to the small intestine is difficult because of the variability among various feeds in the kinetics of digestion and passage of neutral detergent fiber and starch. Disappearance of fiber and starch in vitro or in situ and gas production in vitro have been extensively evaluated, improved, and reviewed. Similarly, markers and models to measure ruminal passage rate have been extensively researched and improved. Sources of variation and decreased accuracy for these techniques are discussed. Variation and potential errors also remain for the prediction of microbial protein flow to the duodenum using in vivo procedures. However, when in vivo results were accumulated into a database, microbial N flow to the duodenum over a wide range of conditions could be predicted accurately by intake of net energy for lactation or by dry matter intake and percentage of neutral detergent fiber in the diet. Although evaluation of feeding interactions and specific dietary limitations for microbial protein production in the rumen are possible with some models but not with this regression approach, mechanistic models need further validation and more accurate rate constants for improved accuracy over a wide range of conditions.

Minimum Versus Optimum Concentrations of Fiber in Dairy Cow Diets Based on Barley Silage and Concentrates of Barley or Corn

Six primiparous and 6 multiparous lactating Holstein cows were used in a double 6 × 6 Latin square to determine the effects of the percentage of forage fiber in diets containing concentrates based on barley or corn. Cows received one of six diets that provided three percentages of neutral detergent fiber (NDF) from barley silage [19.5, 25.0, and 40.9% of dry matter intake (DMI)] combined with concentrates based on either barley or corn.The DMI (18.6 vs. 18.3kg/d) and net energy for lactation (27.2 vs. 26.8Mcal/d) were similar for cows fed barley and corn diets, respectively. Consequently, milk yield (25.7 vs. 25.0kg/d) and fat-corrected milk yield (22.3 vs. 21.7kg/d) were not affected by type of grain. Milk yields were similar for cows fed low and medium NDF diets, but yields declined when NDF from forage exceeded 25% of DMI because of declining intake of net energy for lactation. Effects of increased fiber from forage on milk fat content differed depending on diet; the low NDF diet based on barley caused milk fat to decline. Rumination time was higher for diets based on barley than for diets based on corn (516 vs. 469 min/d), and, as the percentage of forage fiber in the diet increased from low to high, rumination time increased more for cows fed diets based on corn than for cows fed diets based on barley.The minimum amount of forage fiber necessary in diets to avoid milk fat depression appeared to be higher for barley diets than for corn diets, although milk fat depression may not be a valid criterion by which to assess minimum fiber concentrations. Further research is needed to determine the minimum concentration of forage fiber needed to ensure healthy ruminal function and cow longevity.

Effects of Feeding Nonforage Fiber Sources on Site of Fiber Digestion

Although many nonforage fiber sources have high extents of neutral detergent fiber (NDF) digestion, most have rates of digestion similar to or slower than the rates of forage NDF digestion. Rates of NDF digestion vary considerably among and within sources of by-products. Digestion kinetics also vary because of the technique used (in vitro versus in situ) and because of high amounts of dietary concentrate. Based on available data for passage rate and specific gravity measurements, rates of passage of nonforage fiber sources from the rumen of high producing cows appear to be faster than those of forages. Therefore, the potential to shift NDF digestion to the hindgut has been discussed. To account for variability in ruminal and total tract digestibility of NDF, multiple regression analysis was used to indicate that nonforage NDF percentage in the diet had about two-thirds the positive response on total tract NDF digestion that forage NDF percentage did. Although the loss of potentially digestible NDF may occur, DMI does not appear to decrease much until forage NDF is below 14 to 16% of dietary DM. Conversely, replacement of starch with nonforage NDF appears to increase digestibility of fiber, mostly in diets with high concentrations of nonfiber carbohydrates, apparently because of reduced negative associative effects. Increasing the concentration of total NDF above 35% also can decrease DMI with little improvement in NDF digestibility. Increased knowledge of the kinetics of digestion and the passage of various nonforage fiber sources used to replace forage or concentrate should increase the accuracy and precision of dynamic models, thereby increasing the flexibility and utility of nonforage fiber sources in dairy rations.

Enhancement of 1,2-dimethylhydrazine-induced large bowel tumorigenesis in Balb/c mice by corn, soybean, and wheat brans.

This study was designed to determine the effects of four well-characterized dietary brans on large bowel tumorigenesis induced in mice with 1,2-dimethylhydrazine (DMH). Eight-week-old barrier-derived male Balb/c mice were fed a semisynthetic diet with 20% bran added (either corn, soybean, soft winter wheat, or hard spring wheat) or a no-fiber-added control diet. Half of each group was given DMH (20 mg/kg body weight/week, subcutaneously for 10 weeks) beginning at 11 weeks of age. Surviving mice were killed 40 weeks after the first DMH injection. Tumors were not found in mice not subjected to DMH. In DMH-treated mice, tumors were found almost exclusively in the distal colon. Tumor incidences were as follows: controls, 11%; soybean group, 44%; soft winter wheat group, 48%; hard spring wheat group, 58%; and corn group, 72%. Tumors per tumor-bearing mouse ranged from 1.4 to 1.6, except in the corn group, which had 2.1. A positive correlation was found between percentage of neutral detergent fiber in the brans and tumor incidences but not between the individual components of cellulose, hemicellulose, or lignin. The enhancement of DMH-induced large bowel tumorigenesis by all four bran types may reflect a species and/or mouse strain effect that is bran-source related. These data emphasize the importance of using well-defined bran in all "fiber" studies.

Assessing Minimum Amounts and Form of Roughages in Ruminant Diets: Roughage Value Index System

Ruminants require adequate amounts of coarse-textured feeds to avoid metabolic disorders and, in the case of dairy cows, reduced milk fat production. Coarse-textured feeds help to maintain both proper muscle tone in the digestive system and proper rumen pH, both of which contribute to productivity and health. Texture of feeds is quantitatively reflected in the chewing activity of ruminants, and chewing stimulates saliva secretion. Saliva contains bicarbonates and other buffers that alter rumen environment and help avert disorders. Because chewing time reflects feed texture, a series of experiments were conducted in which feed intake, chewing time and milk and fat production were measured. Roughage value indexes (RVI) were partitioned for feed ingredients from regression equations. In addition, an equation was developed that predicts RVI from sieving and chemical data: RVI = 10.86 + PS (21.59) − DMI (1.91) + NDF (.541), where RVI is minutes/kilogram, PS is particle size in mean diameter, DMI is dry matter intake in kilograms and NDF is neutral detergent fiber percentage. The minimum RVI for the production of 3.5% fat milk was determined. By coupling an RVI requirement of 31 min/kg with feed RVI, one can formulate, by computer, diets for lactating cows that not only are nutritionally adequate, but also are adequate in roughage value, and thus avert metabolic disorders. The RVI procedure is ready for field testing.

Título en español.

Ciento una muestras de yerbas tropicales de 30 días de edad se evaluaron con respecto a sus componentes químicos. Estas ya estaban establecidas en parcelas de 10 m.2 en la colección de gramíneas del Colegio de Ciencias Agrícolas de la Universidad de Puerto Rico, localizada en Mayagüez. Las yerbas se abonaron ligeramente con nitrato amónico a razón de 350 kg./Ha. El contenido de proteína cruda varió de 9.8 a 23.8% mientras que el de lignina varió de 2.6 a 7.9% Se obtuvieron variaciones amplias en contenidos de fibra neutrodetergente (45.7 a 79.2%), fibra ácidodetergente (30.9 a 45.3%), hemicelulosa (11.7 a 37.5%) y sílice (0.4 a 5.5%). Los estimados de digestibilidad obtenidos por el metodo de Tilley y Terry y la digestibilidad de la fibra neutrodetergente presentaron variaciones amplias: 42.6 a 66.0 y 22.0 a 62.0%, respectivamente. El coeficiente de desaparici6n de la materia seca total vari6 de 44.3 a 78.2%. Los estimados de digestibilidad a base de ecuaciones de predieción variaron de 74.0 a 94.5% para la materia seca digestible estimada, de 67.3 a 91.7% para la materia seca real digestible estimada y de 54.4 a 78.8% para la materia seca parente digestible estimada. El análisis de varianza presentó variaciones significativas entre y dentro de los géneros, indicando la posibilidad de mejoramiento genético por selección de ciertos géneros a base del alto valor nutritivo. La correlación de la sílice con la digestibilidad varió entre los géneros. La fibra ácidodetergente aparentemente es más importante que la lignina para determinar los valores de digestibilidad. La contribución de la razón lignina a fibra ácidodetergente al estimar la digestibilidad, incluyendo todos los datos, fue mucho menor para los estimados in vitro que para los estimados calculados de ecuaciones predictivas. Esto tiende a indicar que la lignificación de la celulosa tiene una menor influencia en la digestibilidad de los forrajes tropicales que en los de zonas templadas. Los coeficientes de digestibilidad basados en los componentes fibrosos no estuvieron bien correlacionados con los coeficientes de digestibilidad in vitro, lo cual indica que las ecuaciones de predicción desarrolladas para los forrajes de zonas templadas no son necesariamente las más adecuadas para los forrajes tropicales. Se observó una gran variación en los coeficientes de correlación obtenidos entre los correspondientes parámetros evaluados en cuatro géneros: Paspalum, Pennisetum, Digitaria y Panicum.