Dietary alteration of particle breakdown and passage from the rumen in lactating dairy cattle

To evaluate the effect of dietary alteration on the rates of ruminal small particle passage or large particle breakdown, six ruminally cannulated Holstein cows 90 d postpartum were used in a 3 X 3 Latin square design. Experimental diets were 1) control: 60% concentrate, 40% corn silage; 2) bicarbonate: 60% concentrate (containing 2% sodium bicarbonate), 40% corn silage; and 3) hay: 60% concentrate, 30% corn silage, and 10% long alfalfa hay on a DM basis. Dry matter intake (kg/d), milk production (kg/d), percentage milk fat, rumination (min/d), ruminal fluid outflow (L/d), small particle (150 to 850 micron) passage rate (%h), and large particle (greater than 4.25 mm) breakdown rate for diets control, bicarbonate, and hay were 20.2, 20.9, 22.4; 26.6, 27.7, 26.8; 3.5, 3.6, 3.2; 405, 350, 370; 167, 184, 185; 6.5, 7.6, 7.4; and 7.2, 6.8, 7.4, respectively. Rumen DM content and digesta particle size were reduced at the end of a 24-h feeding period. Data suggested that small particle passage may be more closely related to ruminal fluid outflow and DM intake than large particle breakdown rate.     

The passage of lactic acid bacteria from silage into rumen fluid, in vitro studies

Inoculated silages sometimes improve cattle performance, possibly because of probiotic effects of lactic acid bacteria (LAB) silage inoculants. The cause of improved animal performance following feeding with inoculated silage is unclear. One issue in studying this phenomenon is to find out whether LAB pass from silage into the rumen fluid and survive in it. The purpose of the present study was to determine whether LAB from inoculated and uninoculated silages pass into the rumen fluid in vitro. Wheat and corn silages, uninoculated or inoculated with 1 of 10 commercial silage inoculant LAB, were prepared in glass jars. After ensiling, a 2.5-g silage sample was added to 25 mL of heat-sterilized or strained rumen fluid together with 5 g/L glucose, and incubated for 48 h at 39 degrees C. Analysis of the incubated rumen fluid included pH measurement, enumeration of LAB, and determination of lactic acid and volatile fatty acids (VFA). The pH of the rumen fluid decreased during incubation; both heat-sterilized and strained rumen fluid contained large numbers of LAB. The heat-sterilized rumen fluid contained lactic acid in addition to VFA, whereas the strained rumen fluid contained only VFA. The results indicate that LAB pass from silage samples into the rumen fluid in vitro and survive there. Their interactions with rumen microorganisms should be studied further to understand how some silage inoculant LAB exhibit probiotic effects in dairy cattle.     

影响麦麸膳食纤维得率的因素分析

以麦麸为原料,采用生物法制备膳食纤维。正交实验结果表明,提取膳食纤维的最佳工艺参数为:混合酶制剂的用量为0.2%,α-淀粉酶∶糖化酶=1∶3,酶解时间30min,混合酶解温度65℃;蛋白酶用量为0.3%,酶解时间60min,酶解温度60℃。在此工艺条件下,纤维素得率为66.26%,成品呈淡黄色,气味淡。其溶胀性达6.88ml/g,持水力为7.3581%。     

Role of rumen fungi in fiber degradation

Anaerobic fungi inhabit the rumen and actively degrade plant cell walls. Rumen fungi produce high levels of cellulases and hemicellulases and are particularly proficient in producing xylanases. These enzymes are regulated by substrate (especially soluble sugars) available to the organisms. Fungi degrade unlignified (i.e., no histochemical reaction for phenolics) plant walls totally, indicating that enzymes are able to hydrolyze or solubilize the entire plant wall. These organisms are better able to colonize and degrade the lignin-containing tissues than are bacteria; phenolics are solubilized but not metabolized from the plant wall by fungi. Anaerobic fungi are unique among rumen microorganisms in that they penetrate the cuticle. Residues after incubation with fungi are physically weaker than those incubated with whole rumen fluid or with rumen bacteria, suggesting that fungi could alter the fibrous residue for easier mastication by the animal. Data indicate that cocultures of anaerobic fungi with methanogenic bacteria stimulate cellulose degradation; other data suggest that fungi are inhibited by certain rumen microorganisms. The interaction of rumen fungi with other organisms in relation to fiber degradation in the rumen requires additional study. Rumen fungi have the potential to degrade the more recalcitrant plant walls in forages, but this potential is not always reached in the rumen.     

Release of ‘soluble’ lignin fragments from orchardgrass during its passage through the rumen

Soluble lignin fractions were isolated with 90% (v/v) aqueous dioxane from the rumen digesta and faeces of a heifer fed on orchardgrass harvested at the pre-heading stage. Chemical analysis, UV and IR spectra indicated that the soluble lignin fractions were composed mostly of lignin components. The two solube lignin fractions showed wide distributions of molecular weight and had number-average molecular weights of 650–690 and weight-average molecular weights of 1450–1480. The results showed that, part of the orchardgrass lignin fed was released in the rumen as soluble lignin fragments with different molecular weights and excreted in the faeces possibly without further significant modifications.     

A meta-analysis of passage rate estimated by rumen evacuation with cattle and evaluation of passage rate prediction models

A meta-analysis of studies using the flux/compartmental pool method with indigestible neutral detergent fiber (iNDF) as internal marker was conducted to study the effect of extrinsic characteristics and forage type on particle passage rate (k(p)) in cattle. Further, the k(p) prediction equations in the National Research Council (NRC) and the Cornell Net Carbohydrate and Protein System (CNCPS) were evaluated. Data comprised 172 treatment means from 49 studies conducted in Europe and the United States. In total, 145 diets were fed to dairy cows and 27 to growing cattle. A prerequisite for inclusion of an experiment was that dry matter intake, neutral detergent fiber (NDF), proportion of concentrate in the diet, body weight, and diet chemical composition were determined or could be estimated. Mixed model regression analysis including a random study effect was used to generate prediction equations of k(p) and to investigate the relationships between NRC and CNCPS predictions and observed k(p) of iNDF. Prediction equations were evaluated by regressing residual values on the predicted values. The best-fit model when forage type was not included was k(p) (%/h) = 1.19+0.0879 × NDF intake (g/kg of body weight)+0.792 × proportion of concentrate NDF of total NDF+1.21 × diet iNDF:NDF ratio (adjusted residual mean square error = 0.23%/h). The best general equation accounting for an effect of forage type was as follows: k(p) (%/h) = F+1.54+0.0866 × NDF intake (g/kg of body weight) (adjusted residual mean square error = 0.21%/h), where F is the forage adjustment factor of the intercept. The value of F for grass silage, fresh grass, mixes of alfalfa and corn silage, and dry or ensiled alfalfa as sole forage component were 0.00, -0.91, +0.83, and +0.24, respectively. Relationships between predicted and observed k(p) were y = 0.53(± 0.187)+0.41( ± 0.0373) × predicted k(p) and y = 0.58(± 0.162)+0.46(± 0.0377) × predicted k(p) for the NRC and CNCPS models, respectively. Residual analysis of the NRC and CNCPS models resulted in both significant mean biases (observed--predicted) of -2.40 and -1.70% and linear biases of -0.59 and -0.53, respectively. The results from this meta-analysis suggest that ruminal particulate matter k(p) is affected by forage type in the diet. Further, the evaluation of NRC and CNCPS models showed that passage rate equations developed from marker excretion curves markedly deviated from observed k(p) of iNDF derived using the rumen evacuation technique.     

Effects of dietary protein on milk, rumen, and blood parameters in dairy cattle fed low fiber diets

Eighteen multiparous and 9 primiparous Holstein cows were used to determine the effects of a 13 and 23% crude protein concentrate on milk fat depression during early lactation. Beginning on d 22 postpartum, cows were fed a high fiber diet (27% acid detergent fiber) for 3 wk and then switched to a low fiber diet (9 to 10% acid detergent fiber) for 6 wk. Crude protein percentages calculated from dry matter consumption were 13.5 and 17.9% during the high fiber period and 12.7 and 22.3% during the low fiber period. Daily milk and fat yields for both primiparous and multiparous cows were greater for the high protein treatment. The magnitude of decline in milk fat percentage (from high to low fiber) was greater for the low protein treatment, as determined by nonlinear regression. The high protein treatment was more effective in reducing the severity of milk fat depression in primiparous cows than in multiparous cows. Dietary crude protein had no effect on milk protein or solids-not-fat percentages, rumen volatile fatty acid molar proportions, or serum acetate concentration. The mechanism by which the high protein ration minimized the fat depression response to low fiber rations by primiparous cows is unknown.     

Rates of particle size reduction and passage are faster for legume compared with cool-season grass, resulting in lower rumen fill and less effective fiber

Effects of forage family on rates of particle size reduction in, and passage from, the rumen and the relationship of these effects with preliminary dry matter intake (pDMI) were evaluated using 13 ruminally and duodenally cannulated Holstein cows in a crossover design with a 14-d preliminary period and two 18-d treatment periods. During the preliminary period, pDMI of individual cows ranged from 19.6 to 29.5 kg/d (mean = 25.9 kg/d). Experimental treatments were diets containing either a) alfalfa silage (AL) or b) orchardgrass silage (OG) as the sole forage. Silages were chopped to 10-mm theoretical length of cut and contained 42.3 and 58.2% neutral detergent fiber (NDF) for alfalfa and orchardgrass, respectively. Both diets contained approximately 25% forage NDF and 30% total NDF. Feed, orts, rumen, and duodenal samples were wet sieved to fractionate particles above (large) and below (small) 2.36 mm. Indigestible NDF (iNDF) was used as a flow marker. Preliminary DMI, an index of nutrient demand, was determined during the last 4 d of the preliminary period when cows were fed a common diet and used as a covariate. Main effects of forage family and their interaction with pDMI were tested by ANOVA. Approximately 75% of the NDF consumed was large and 25% was small for both treatments, but cows fed AL consumed more iNDF and less potentially digestible NDF (pdNDF) than cows fed OG. The AL diet increased the reduction rate (large to small) compared with OG despite less rumination per unit of forage NDF for AL than OG, suggesting alfalfa NDF was more fragile than orchardgrass NDF. Over 55% of particles in the rumen were below 2.36 mm for AL and OG, indicating that particle size was not a limiting constraint to passage. Passage rates (k(p)) of large iNDF and large pdNDF were similar for AL and OG, but AL increased k(p) of large pdNDF and OG decreased it as pDMI increased. The AL diet increased k(p) of small iNDF and small pdNDF compared with OG, resulting in lower rumen fill for AL than OG. The k(p) of small iNDF and small pdNDF were similar within forage family, suggesting buoyancy was not limiting passage. The OG diet increased rumen pool size of large NDF compared with AL, which likely retained small NDF, contributing to the slower k(p) of small iNDF and small pdNDF observed for OG. Particle size reduction was a prerequisite to ruminal passage but not a constraint. Selective retention of small particles was less for alfalfa than orchardgrass, resulting in lower rumen fill and less effective fiber.     

影响麦芽溶解度的关键制麦参数及参数优化

麦芽溶解度是衡量麦芽酿造性能的重要指标,针对影响该指标的关键制麦参数即浸麦度、发芽温度、凋萎温度、干燥温度,以进口大麦为原料,进行了单因素试验,并分别采用荧光染色法和冷场发射扫描电子显微镜观察麦芽胚乳溶解情况来确定麦芽溶解度。并在此基础上采用响应面设计优化制麦工艺。结果表明,各因素对麦芽溶解度影响程度的大小顺序为B(发芽温度)D(干燥温度)C(凋萎温度)A(浸麦度)。优化制麦工艺条件为:浸麦度为46%,发芽温度为16℃,凋萎温度为48℃,干燥温度为78℃。优化制麦工艺后,麦芽溶解度从81%提高到87%。     

Bovine milk composition parameters affecting the ethanol stability

The objective of the present work was to identify the compositional parameters of raw milk that affected ethanol stability at natural pH when natural milk conditions were not modified. Heat stability, measured as coagulation time (CT), was included in the analysis to verify relation to alcohol test. Statistical models were proposed for alcohol and heat (CT) stabilities. Milk samples of good hygienic quality from dairy farms were classified in two groups according to their alcohol stability. Unstable samples to ethanol (72%, v/v) presented lower values of pH, somatic cells count, casein and non-fat-solids relative to ethanol stable samples (ethanol at 78%, v/v or more); whereas freezing point, chloride, sodium and potassium concentrations were higher in the unstable group. Logistic regression and multiple regression were applied to modelling alcohol and heat stability behaviour respectively. Chloride, potassium, ionic calcium and somatic cell count were included in the alcohol regression model, whereas calcium, phosphorous, urea, pH and ionic calcium were part of CT model. Ionic calcium was the only measured variable that contributed to both models; however coagulation time was noted to be more sensitive to ionic calcium than alcohol. The relation between ionic strength and casein was found to contribute to the alcohol model but not to the CT model. However, the interaction calcium plus magnesium plus phosphorous and casein contributed only to CT model.     

Generating cotton fiber length probability density function from fiber length parameters by finite mixture model

This paper generated the fiber length probability density function of different cotton samples on the basis of Finite Mixture Model. With the mixture of two Weibull distributions, the commonly used and discrete fiber length parameters were employed to obtain the function. Curve fitting of fiber length frequency histograms was carried out and the differences between the model proposed by this paper and previous model were compared. The results show that when fiber length measures were modified by the related linear relational expressions, this model, compared with other models, could fit the test data very well with the errors all less than 0.0045.     

Niacin absorption from the rumen.

Absorption of niacin from the rumen was tested in vivo using a buffer solution that contained either nicotinic acid or nicotinamide. The experimental design was a 3 X 3 Latin square with three midlactation, ruminally cannulated Holstein cows. Orthogonal comparisons were control versus niacin and nicotinic acid versus nicotinamide. Nicotinamide was more rapidly absorbed from the rumen than nicotinic acid; this may have been caused by differences in the dissociation constants of the compounds. The effects that differential absorption may have on ruminal fermentation and animal metabolism require further study.     

Effects of corn processing on growth characteristics, rumen development, and rumen parameters in neonatal dairy calves

Neonatal Holstein calves were fed texturized calf starters containing 33% whole (WC), dry-rolled (DRC), roasted-rolled (RC), or steam-flaked (SFC) corn to investigate how corn processing method affects intake, growth, rumen and blood metabolites, and rumen development. In the first experiment, 92 Holstein calves (52 male and 40 female) were started at 2 +/- 1 d of age and studied for 42 d. Starter dry matter (DM) intake was measured and fecal scoring conducted daily. Growth and blood parameter measurements were conducted weekly. A subset of 12 male calves (3/treatment) was euthanized at 4 wk of age and rumen tissue sampled for rumen epithelial development measurements. Experiment 2 consisted of 12 male Holstein calves ruminally cannulated at 7 +/- 1 d of age. Rumen fluid and blood samples were collected during wk 2 to 6. In the first experiment, postweaning and overall starter and total DM intake were significantly higher in calves fed starter with DRC than RC or SFC. Postweaning and overall starter and total DM intake were significantly higher in calves fed starter with WC than SFC. Postweaning average daily gain was significantly greater in calves fed starter with DRC than SFC. Blood volatile fatty acid concentrations were significantly higher in calves fed starter with SFC than in calves fed all other treatments. Papillae length and rumen wall thickness at 4 wk were significantly greater in calves fed starter with SFC than DRC and WC, respectively. In experiment 2, calves fed starter with WC had higher rumen pH and lower rumen volatile fatty acid concentrations than calves fed all other starters. Rumen propionate production was increased in calves receiving starter with SFC; however, rumen butyrate production was higher in calves fed starter with RC. Results indicate that the type of processed corn incorporated into calf starter can influence intake, growth, and rumen parameters in neonatal calves. Calves consuming starter containing RC had similar body weight, feed efficiency, and rumen development but increased structural growth and ruminal butyrate production when compared with the other corn processing treatments.     

影响甲壳素和甲壳胺纤维质量的因素

甲壳素纤维作为21世纪的新型绿色纤维，在服装以及医疗卫生领域都有很大的应用潜力。通过对甲壳素和甲壳胺纤维生产工艺的分析，概述了影响甲壳素和甲壳胺纤维质量的主要因素，诸如甲壳素和甲壳胺的品质、溶剂的选择、纺丝液浓度和凝固浴的确定等。     

Dietary fiber and early weaning on growth and rumen development of calves

Holstein calves were assigned to treatments of 1) pelleted prestarter (22% protein and 12% fat) and starter containing 10% alfalfa; 2) prestarter and starter containing 20% alfalfa; 3) no prestarter and starter containing 10% alfalfa; and 4) no prestarter and starter containing 20% alfalfa. Calves assigned to treatments 1 and 2 were fed 3.64 kg milk/d for 2 wk and calves assigned to treatments 3 and 4 were fed 3.64 kg milk/d for 3 wk and 1.82 kg milk/d for wk 4. Calves on treatments 2 and 3 were heavier at 10 wk but body weights and heights were similar by 6 mo. Rumen fluid and plasma measures were similar among treatments. Bull calves were assigned to treatments 1 and 3 and necropsied at 3 or 6 wk. Dry feed intakes to 3 wk and volatile fatty acid concentrations were greater for calves on treatment 1 than those on treatment 3. Wet weights of the empty reticulorumens were greater for calves on treatment 1 than those on treatment 3. Papillary development was not affected by weaning system. Calves weaned at 17 d and fed a prestarter have earlier rumen development than calves fed no prestarter and weaned later.     

竹原纤维抑菌性能影响因素探究

对竹原纤维抑菌性能的影响因素做了系统研究.采用吸收法对所制取的竹原纤维进行单因子实验,并通过计算抑菌率来评价其抑菌效果,研究对抑菌性能产生影响的因素.实验得出:回潮率、接种后培养时间及竹屑都对竹原纤维的抑菌性能有影响,为竹原纤维在纺织领域的开发应用提供了理论指导.     

Effects of urea and starch on rumen fermentation, nutrient passage to the duodenum, and performance of cows.

Four midlactation, multiparous Holstein cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design to determine the effects of supplementing urea or starch or both to diets containing fish meal on passage of nutrients to the small intestine and performance of lactating cows. The treatments (in a 2 x 2 factorial arrangement) were 1) control and control plus 2) urea, 3) starch, or 4) starch and urea. Supplementing diets with urea did not affect DMI; ruminal, postruminal, or total tract digestibilities of DM, starch, ADF, or NDF; ruminal fluid VFA concentrations or molar percentages; or ruminal fluid or particulate dilution rates. Feeding additional starch depressed DMI but did not alter ruminal or postruminal digestion of OM or VFA concentrations and molar percentages in ruminal fluid. Ruminal fluid ammonia concentration was increased by feeding urea and decreased by feeding additional starch. Passage of nonammonia N, nonammonia nonmicrobial N, or microbial N to the small intestine and efficiency of microbial CP synthesis were not affected significantly by supplying either urea or additional starch. Feeding urea increased passage of methionine to the small intestine, whereas feeding additional starch increased passage of methionine and arginine. Passage of other amino acids to the small intestine was not altered significantly by feeding urea or additional starch. Production of milk and milk protein was increased, but yields of fat and SNF were not altered by feeding diets supplemented with urea. Production of milk and milk fat was not affected, but yields of CP and SNF were decreased when additional starch was fed to cows.