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PubMed2001

Effect of hybrid, maturity, and mechanical processing of corn silage on intake and digestibility by beef cattle.

A study involving a 2 x 2 x 2 factorial arrangement of treatments was conducted to evaluate effects of hybrid (Pioneer 3335 and 3489), maturity (half milkline and blacklayer), and mechanical processing (field chopper with and without on-board rollers engaged) on intake and digestibility of corn silage. Forty Angus steers (322 +/- 5.2 kg BW) were assigned to the eight silage treatments (five steers per treatment) and individually fed using electronic gates. Diets consisted of 60% corn silage and 40% chopped alfalfa hay (DM basis). Following a 5-d adaptation period, intake was measured for 7 d and subsequently fecal samples were collected for 5 d. Chromic oxide (5 g/d) was fed beginning 7 d before fecal sample collection and digestibility was determined by the ratio of Cr in the feed and feces. Steers were reallocated to treatments and these procedures were repeated, providing 10 observations per treatment. In addition, all silages were ruminally incubated in six mature cows for 0, 8, 16, 24, 48, and 96 h to determine extent and rate of DM, starch, NDF, and ADF disappearance. Processing increased DMI of hybrid 3489 but did not affect DMI of hybrid 3335 (hybrid x processing; P < 0.06). Total tract digestibility of DM, starch, NDF, and ADF decreased (P < 0.01) as plant maturity increased. Maturity tended to decrease starch digestibility more for hybrid 3489 than for hybrid 3335 (hybrid x maturity; P < 0.10). Processing increased (P < 0.01) starch digestibility but decreased (P < 0.01) NDF and ADF digestibility, resulting in no processing effect on DM digestibility. There was a numerical trend for processing to increase starch digestibility more for latethan for early-maturity corn silage (maturity x processing; P = 0.11). Processing increased in situ rates of DM and starch disappearance and maturity decreased in situ disappearance rates of starch and fiber. These data indicate that hybrid, maturity, and processing all affect corn silage digestibility. Mechanical processing of corn silage increased starch digestibility, which may have been associated with the observed decreased fiber digestibility.

Adaptation, Physiological↗
PubMed2004

Prediction of nutritive values in grass silages: II. Degradability of nitrogen and dry matter using digestibility, chemical composition, and fermentation data.

One hundred thirty-six perennial rye-grass silages with wide variations in quality were evaluated for N and DM degradability in three beef steers offered grass silage of medium quality ad libitum. The silages were incubated in the rumen of each animal in triplicate for 0, 6, 12, 24, 48, and 72 h, respectively. The disappearance rates of N or DM were used to calculate the readily soluble fraction ("a" value), potentially degradable fraction ("b" value), and the fractional degradation rate of"b" ("c" value). The effective degradability (P) of N or DM was then estimated assuming a ruminal outflow rate of 0.02, 0.05, or 0.08/h (P0.02, P0.05, or P0.08). The objective was to use these data to develop prediction equations for N and DM degradability in grass silages. There were considerable variations in "a," "b," and "c" values and the P0.02, P0.05, or P0.08 of N and DM (e.g., the P0.02 of N ranged from 75.0 to 93.4% and the P0.02 of DM from 51.5 to 82.5%). The P0.02, P0.05, or P0.08 of N and DM were negatively related (P < 0.001) to ADF, NDF, and lignin concentrations but positively related (P < 0.001) to protein fractions (CP, soluble CP, and true protein concentrations) and digestibility of DM, OM, GE, CP, and NDF and digestible OM in the total DM (measured with sheep). The N and DM degradability data were also positively related to silage lactic acid concentration, but the relationships between DM degradability data and pH, ammonia N/total N, and VFA concentration in silages were negative (P < 0.05). Several sets of prediction equations (linear and multiple) were thus developed for N and DM degradability using CP or NDF concentration, "a" value or digestibility data as primary predictors, together with or without other nutrient concentration and silage fermentation variables. All these relationships were highly significant (P < 0.001), and each predictor had a significant effect on the relationship (P < 0.05). The R2 values in multiple regression for N and DM degradability were generally over 0.70 and higher than in linear regression equations. Four equations were also developed to convert N and DM degradability at a given ruminal outflow rate, predicted using the above-mentioned equations, to their counterparts at any ruminal outflow rate (0.02 to 0.10/h), respectively.

Animals↗
PubMed2005

Effect of cutting height and genetics on composition, intake, and digestibility of corn silage by beef heifers.

This research was conducted to determine the effect of corn genetics and cutting height on the composition and nutritive characteristics of corn silage. An in situ study involving eight commercially available corn hybrids indicated main effects and interactions (P < 0.01) of hybrid and cutting height on NDF, ADF, and starch content and on in situ DM and NDF degradablility. Four ruminally cannulated Angus heifers (initial BW = 378 +/- 3 kg) were used in a 4 x 4 Latin square digestion experiment with a 2 x 2 factorial treatment arrangement. Main effects and interactions of hybrid (Pioneer Hi-Bred Int., Inc., hybrids 3335 and 3223) and cutting height (LO = 20.3 cm, and HI = 61 cm) were evaluated. Dietary treatment consisted of 40% chopped alfalfa hay and 60% corn silage. Although corn silage hybrids used were of equivalent maturity at harvest (60% milkline), 3335 treatments had 37.8% starch and 34.8% NDF, whereas 3223 treatments had 33.7% starch and 38.6% NDF. The LO treatments averaged 3.1 percentage units greater in NDF and 3.45 percentage units less in starch content than the HI treatments. Intake of DM was greater for heifers fed 3335-HI than 3335-LO; however, DMI was greater by heifers fed 3223-LO than 3223-HI (hybrid x cutting height interaction, P < 0.05). Starch intake was greater (P < 0.05) and NDF intake was less (P < 0.05) by heifers fed HI vs. LO and fed 3335 vs. 3223 dietary treatments. Digestibility of DM, starch, and NDF was greater (P < 0.05) by heifers fed 3223 than 3335 dietary treatments, but digestibility differences were not observed (P > 0.10) between cutting heights. Rate of in situ DM and starch degradability was not affected (P > 0.10) by hybrid or cutting height; however DM degradability was greater (P < 0.05) for HI than LO corn silage substrates at 8, 16, and 24 h of incubation. Rate of NDF degradability tended (P = 0.08) to be greater for 3223 than for 3335, and for LO compared with HI corn silage. Degradability of NDF was greater (P < 0.05) for 3223 compared with 3335 substrates at 24, 36, and 48 h of incubation. These data suggest fiber may not be an accurate measure of corn silage quality. Whereas cutting height affected chemical composition, we observed genetics to have a greater effect on corn silage quality.

Ammonia↗
PubMed1986

Effect of sulfur fertilization on chemical composition, ensiling characteristics and utilization of corn silage by lambs.

Effects of S fertilization, 0 or 67 kg S/ha, as (NH4)2SO4, as a single or split application on chemical composition, ensiling characteristics and utilization of corn (Zea mays L.) silage by wether lambs was investigated. Corn forages were ensiled at hard-dent stage at 35% dry matter (DM). Sulfur fertilization increased (P less than .01) total S and SO4 but had no effect on N, Mg, Ca or fiber components in silages. Sulfur-fertilized corn silages (N:S = 42 and 43) and non-S fertilized silage (N:S = 62) were fed alone and supplemented with Na2SO4 at two rates to achieve N:S ratios of 12 (high) and 45 (low, to approximate S-fertilized silage), to 30 wether lambs (Suffolk and Dorset crosses) in metabolism and palatability trials. Both trials were randomized complete-block designs. Lambs weighed 36 and 41 kg, respectively. All silages were supplemented with 6.7 g urea/d. Digestibility of DM and cell wall components, and apparent absorption of S and N were increased (P less than .05) by S fertilization and supplementation. Nitrogen retention was increased (P less than .01) by S fertilization and supplementation. Retention was higher (P less than .001) for lambs that were fed S-fertilized silage, compared with supplementation to achieve a similar N:S ratio. It appears that S fertilization was more effective than S supplementation in improving efficiency of N utilization.

Ammonia↗
PubMed2000

Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 1. Feeding behavior and nutrient utilization.

The effects of digestibility of corn silage neutral detergent fiber (NDF) and dietary NDF content on feeding behavior, dry matter intake (DMI), and energy utilization were evaluated with eight multiparous high producing dairy cows in a duplicated 4 x 4 Latin square design with 21-d periods. Experimental diets contained corn silage from a brown midrib (bm3) hybrid or its isogenic normal control at two concentrations of dietary NDF (29 and 38%). Both low NDF diets and bm3 corn silage treatments increased DMI and milk yield. However, an interaction between corn silage treatment and dietary NDF content was observed for meal size and for interval between meals, implying that different mechanisms regulating DMI dominate depending on the fermentation characteristics of diets. The bm3 treatment depressed milk fat concentration when fed in a low NDF diet. The bm3 corn silage increased solids-corrected milk yield, but did not affect daily body weight gain compared with control, whereas low NDF diets increased daily body weight gain, but did not affect solids-corrected milk yield compared to high NDF diets. Both bm3 treatments and low NDF diets reduced ruminal pH, but low NDF treatments increased fluctuation of ruminal pH and bm3 treatments did not. Feeding bm3 corn silage increased the energy utilized for milk production, possibly because of a consistent supply of metabolic fuels from the rumen. The beneficial effects of bm3 corn silage on productivity of lactating cows were greater for the cows fed a high NDF diet.

Animals↗
PubMed2001

Effects of brown midrib corn silage on the energy balance of dairy cattle.

Effects of genotype and level of intake on net energy for lactation values of corn silage were evaluated by indirect calorimetry in two experiments using lactating and dry, nonpregnant dairy cows. In experiment 1, six multiparous Holstein cows in early lactation were fed experimental diets containing either brown midrib (bm3) or isogenic normal corn silage. Dietary treatments were isogenic and bm3 diets fed ad libitum, and the bm3 diets restricted-fed. Dry matter (DM) intake was 2.4 kg/d greater for cows fed the bm3 diet ad libitum compared with cows fed the isogenic diet. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows restricted-fed bm3 than the isogenic diet. In experiment 2, six dry, nonpregnant Holstein cows were fed maintenance diets containing either bm3 or isogenic corn silage. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows fed bm3 compared with isogenic corn silage. Digestible energy and metabolizable energy were greater for maintenance diets containing bm3 compared with isogenic corn silage, respectively. These data indicate increased milk production seen in other studies is a result of increased DMI rather than an increase in energy efficiency. Increased organic matter digestibility of bm3 corn silage resulted in greater digestible energy and metabolizable energy values in cows fed at maintenance energy intake. However, calculated net energy for lactation values of bm3 and isogenic corn silages were similar at both productive and maintenance levels of feeding.

Animals↗
PubMed2001

Feeding value of corn silage estimated with sheep and dairy cows is not altered by genetic incorporation of Bt1376 resistance to Ostrinia nubilalis.

A genetically modified Bt176 corn hybrid (Rh208Bt)--providing control of European corn borer damage--and the conventional isogenic hybrid (Rh208)--harvested as whole plant silage--were evaluated in three separate feeding trials to verify that the in vivo feeding value was substantially equivalent among modified and conventional hybrids. In the first trial, after a week of preexperiment, two sets of six Texel sheep, housed in digestibility crates, were fed silage sources of Rh208 and Rh208Bt hybrids, and silage of three additional control varieties of low, intermediate, and high feeding value (Rh289, Adonis, and Adonis bm3) for 1 wk. Feed offered to sheep was adjusted to maintenance requirements based on metabolic body weight. Agronomic and biochemical traits were similar among the Rh208 and Rh208Bt hybrids. Organic matter digestibility (67.1 and 67.6%), crude fiber digestibility (52.9 and 54.2%), and neutral detergent fiber digestibility (50.2 and 49.0%) were not significantly different among Rh208 and Rh208Bt hybrids. In the second trial, two sets of 24 Holstein cows were fed silage from Rh208 and Rh208Bt corn hybrids for 13 wk, 9 wk after calving, and including 2 wk of preexperiment. Fat-corrected milk yield (31.3 and 31.4 kg/d), protein content (31.7 and 31.6 g/kg) and fat content (36.7 and 37.0 g/kg) in milk of dairy cows were unaffected by hybrid source. Body weight gains of cattle were not different. However, intake was significantly higher in cows fed Rh208Bt silage. In the third trial, five midlactation multiparous Holstein cows were successively fed the silage from Rh208 and Rh208Bt corn hybrids 2 or 3 wk. Data were considered only for the last week of each period. There were no significant effects on protein fractions, fatty acid composition, or coagulation properties of milk between Rh208 and Rh208Bt fed cattle. Cattle and sheep can perform equally well with a conventional or a genetically modified Bt176 corn silage.

Animal Feed↗
PubMed2002

Influence of particle size on the effectiveness of the fiber in alfalfa silage.

The objective was to determine the influence of alfalfa silage particle length on milk yield, milk composition, and chewing activity. Sixteen multiparous lactating Holsteins were used in each of two separate feeding trials over a 2-yr period providing two repetitions. Each trial was based on 4 x 4 Latin squares with 21-d periods. All four diets (2-yr average, dry basis) contained a basal level of 10.7% neutral detergent fiber from corn silage and 2.3% neutral detergent fiber from chopped alfalfagrass hay. One of the diets served as a low forage, low fiber control and contained only the basal forages. The other three diets contained an additional 8.6% neutral detergent fiber from coarser alfalfa silage, finely rechopped alfalfa silage or an equal mixture ofthe two. An increase in the forage content above the basal amount using alfalfa silage increased 4% fat-corrected milk yield, milk fat yield and concentration, eating time, and total chewing time. Dry matter intake was not influenced by diet. Linear increases in rumination and total chewing times were observed as the mean particle size of the alfalfa silage increased from finer to coarser. There was no linear effect of alfalfa silage particle size on milk yield, 4% fat-corrected milk yield, dry matter intake, or milk composition.

Animals↗
PubMed2005

Effects of corn silage particle length and forage:concentrate ratio on milk fatty acid composition in dairy cows fed supplemental flaxseed.

This study aimed to evaluate the effects of length of chop of corn silage and forage:concentrate ratio (F:C) on performance and milk fatty acid profiles in dairy cows supplemented with flaxseed. Our hypothesis was that decreasing forage particle length and F:C ratio would increase unsaturated fatty acid flow to the small intestine and subsequent transfer of these unsaturated fatty acids into milk. Eight Holstein cows (648.1 +/- 71.5 kg body weight; 109.6 +/-43.6 days in milk) were used in a replicated 4 x4 Latin square design with 21-d periods and a 2 x2 factorial arrangement of dietary treatments. Dietary factors were: 1) F:C ratios (dry matter basis) of 55:45 and 45:55; and 2) corn silage particle lengths of 9.52 and 19.05 mm. All experimental cows received 1 kg of flaxseed to substitute for 1 kg of a rolled barley grain-based concentrate daily. Diets were fed twice daily as a total mixed ration. Corn silage particle length and F:C ratio had no effect on dry matter intake, milk yield, and milk composition; however, feeding short cut corn silage depressed milk protein yield. Significant particle size xF:C ratio interactions were observed for milk fat proportions of C(16:0), C(18:1) cis-9, and C(18:2) cis-9, trans-11 (a conjugated linoleic acid isomer). At short corn silage particle size, decreasing F:C ratio depressed milk fat proportion of C(16:0). Conversely, feeding short corn silage at high F:C ratio increased the proportion of C(18:1) cis-9 and C(18:2) cis-9, trans-11 in milk fat. The milk fat proportion of C(18:2) trans-10, cis-12, a conjugated linoleic acid isomer that is associated with milk fat depression, was not affected by dietary treatment. Our results show that corn silage particle length and F:C ratio influence milk fatty acid profiles in dairy cows fed supplemental flaxseed as a source of polyunsaturated fatty acids.

Animal Nutritional Physiological Phenomena↗
PubMed1976

Rumen volatile fatty acids and milk composition from cows fed hay, haylage, or urea-treated corn silage.

Alfalfa-brome hay, haylage, .5% urea-treated corn silage, or .5% urea plus 1% dried whey-treated corn silage was fed as the only forage to one of four groups of 10 lactating cows per group for a lactation trial of 10 wk. Rumen samples were collected via stomach tube 3 to 4 h after the morning feeding. The pH of the rumen samples from cows fed hay was higher than for cows fed haylage, urea-treated corn silage, and urea-whey corn silage, 6.69 versus 6.36, 6.40, and 6.50. Total volatile fatty acids and propionate were highest from cows fed urea-whey corn silage and were higher on all three fermented forages than cows fed hay. Acetate/propionate ratio was highest from cows fed hay and lowest from cows fed corn silages. Butyrate was highest from cows fed haylage or hay. Milk protein composition was not affected by ration although nonprotein nitrogen of milk was highest from cows fed the urea-treated corn silages. Oleic acid and total unsaturated fatty acids were lowest in milk fat from cows fed hay while palmitic acid was highest from cows fed hay and haylage. These results suggest that type of forage fed may cause small changes in rumen fermentation and in milk composition. The importance of these changes is unknown but may affect properties of dairy products produced from this milk.

Animal Feed↗
PubMed1980

Prediction of silage digestibility and intake by chemical analyses or in vitro fermentation techniques.

Chemical analyses and in vitro fermentations were on three corn silages, four legume-grass silages, and four corn-hay crop silage mixtures which had been fed to sheep for 21 days. In vivo data were collected for voluntary silage intake and apparent digestibility of energy. Forage nutritive value was expressed as digestible energy intake. Multiple regression equations were developed to determine the more reliable methods to evaluate voluntary intake, digestibility, and nutritive value of silage. Equations for quadratic response surfaces accounted for 71 to 79% of variation in in vivo data compared to 54 to 70% of variability accountable by simple linear regression equations. Dry matter, crude protein, cell wall, acid-detergent fiber, and acid-detergent lignin contents of silage accounted for greater variability in silage intake, digestibility, and nutritive value than did any in vitro method either alone or in combination with chemical analysis. The results support Crampton's concept of nutritive value index, which is now expressed in the relative feed value system proposed by the American Forage and Grassland Council for differences between forages.

Animal Feed↗
PubMed1985

Effect of additive on alfalfa silage fermentation characteristics and feedlot performance of steers.

In each of two trials four large plastic bags were filled with approximately 72 mt of first cutting, early bloom alfalfa (35% dry matter). Fresh alfalfa in two bags was treated with .5 kg/metric ton of a commercial silage additive (Silo-Best). Two bags were left untreated. When compared with steers fed untreated alfalfa silage, weight gains, intakes, and feed efficiencies were not significantly (P greater than .05) altered for steers fed treated silage. However, laboratory analysis showed silage treatment increased in vitro dry matter digestibility (57.0 versus 60.6%) and decreased silage pH (4.98 versus 4.83). Concentrations of propionic and butyric acid were decreased by the additive. Data suggest that anaerobic fermentation was enhanced with the additive. Slight but significant improvements of silage in vitro dry matter digestibility, obtained by treating alfalfa silage with the inoculant-type preservative, did not result in improved performance in feeding trials.

Animal Feed↗
PubMed1991

Effects of additives and growth environment on preservation and digestibility of wheat silage fed to Holstein heifers.

Wheat grown in two separate years under different environmental conditions was fed as silage to investigate effects of additives on forage preservation and digestibility. Direct-cut wheat was harvested in an early head stage of maturity. Wheat was drought stressed in yr 1 and averaged 41.6% DM, and yr 2 averaged 23.0% DM at harvest. Forage was ensiled in 10 900-kg concrete stave silos; 2 per year were assigned to one of five treatments consisting of control, treatment with an enzyme-chemical product, or treatment with one of three different types of lactic acid bacterial inoculants. Each year, during two 12-d periods, forage from five different silos was fed individually for ad libitum intake, separate from concentrate (1.1% of BW) to 15 Holstein heifers (average BW 228 +/- 32 kg). Wheat forage and silage from yr 1 was lower in CP but higher in NDF, ADF, lignin, and starch than that harvested in yr 2. Silage additives decreased DM and NDF recovery in yr 1 and increased DM, NDF, and neutral detergent solubles recovery in yr 2. Additives increased the ratio of lactic to acetic acid and decreased ammonia in silage both years. Additives increased DM and fiber digestibilities of wheat silage-based rations fed to Holstein heifers in yr 2. In vitro digestibility indicated that these improvements were associated with a reduction in the lag phase of forage digestion. The rate of in vitro DM digestibility was positively correlated with silage DM recovery, suggesting an association with nutrient preservation. Wheat preservation and digestibility both were improved by silage additives when wheat was grown under normal environmental conditions, but losses were greater with additives in drought-stressed forage.

Animals↗
PubMed1994

Effects of alfalfa silage chop length and supplementary long hay on chewing and milk production of dairy cows.

Twelve lactating, multiparous Holstein cows were used to evaluate the effects of silage chop length and proportion of long hay in low and adequate forage fiber diets on chewing activities and productivity of cows fed barley-based concentrates. Diets were designed with two forage:concentrate ratios (low forage fiber, 35:65; adequate forage fiber, 65:35), combined with two theoretical chop lengths of alfalfa silage (fine, 5 mm; coarse, 10 mm), and three proportions of long-stemmed alfalfa hay (0, 10, and 20% of DMI). Increasing the chop length of silage in low forage fiber diets did not affect DMI but increased FCM; in adequate forage fiber diets, it decreased DMI and FCM. Addition of hay to silage diets increased DMI, but not FCM yield. Increasing silage chop length in diets formulated below the recommended minimal amount of NDF from forage promoted rumination and increased milk production while maintaining milk fat content and DMI. Addition of a small amount of hay to low forage fiber diets was less effective than increased particle length of silage. In adequate forage fiber diets, finely chopped silage can be used effectively.

Animal Feed↗
PubMed1995

Performance of lactating dairy cows fed either alfalfa silage or alfalfa hay as the sole forage.

Alfalfa was harvested from alternate windrows as 40% DM silage or hay in small rectangular bales and fed in two 12-wk 4 x 4 Latin square trials, each with 20 multiparous lactating cows (4 with ruminal cannulas). Diets contained (DM basis) 69 (trial 1) or 66% (trial 2) alfalfa, 26 to 33% high moisture corn, 1.3% minerals and vitamins, and about 1.6 Mcal of NEL/kg of DM. In trial 1, second-cutting silage (21.2% CP) and hay (19.7% CP) containing 35% NDF were fed in diets: 1) silage (17.3% CP), 2) hay (16.3% CP), 3) silage with 3% fish meal (19.1% CP), and 4) hay with 3% fish meal (18.1% CP). Cows had lower DMI and lost BW on diet 1. Yields of milk and milk components were similar on diets 1 and 2 and greater on diet 3 than on the other three diets, except that fat yield was greater on diets 1 and 3 than on diets 2 and 4. In trial 2, first-cutting silage and hay containing 19.9 and 16.5% CP and 40 and 41% NDF were fed in diets: 1) silage (16.8% CP), 2) hay (14.6% CP), 3) silage with 3% fish meal (18.2% CP), and 4) hay with 3% fish meal (16.0% CP). Cows had lower DMI and lost BW on diets 1 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Kinetics of cell-wall digestion of orchardgrass and alfalfa silages treated with cellulase and formic acid.

The objectives of this study were to determine the effects of cellulase (from Trichoderma longibrachiatum) combined with formic acid, applied before ensiling, on the subsequent concentration and composition of the cell wall and on the extent and rate of in situ cell-wall digestion of orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.). Treated and control forages of both plant species were ensiled for at least 60 d before being ruminally digested by two fistulated cows. Analyses of NDF, ADF, and acid detergent lignin were conducted sequentially on original and digested samples. Data were fitted with a first-order, nonlinear model to estimate extents and rates of digestion of potentially digestible NDF, cellulose, and hemicellulose. The concentration of indigestible residue and the discrete lag time before digestion were also determined for the cell-wall components. After ensiling, the mean NDF concentration of treated silages was 19% lower than that of control silages; the effect was greater for orchardgrass than for alfalfa. The extent of digestion of NDF, cellulose, and hemicellulose, respectively, was 33, 37, and 27% lower for treated silages than for control silages. Treatment effects on the extent of digestion varied between plant species. Cellulose from treated orchardgrass was digested 19% more slowly than cellulose from the control silage. Indigestible residue concentrations of NDF, cellulose, and hemicellulose, respectively, were 7, 8, and 7% lower in treated silages than in control silages. Thus, extensive cell-wall degradation by cellulase during ensiling resulted in less digestible cell-wall material for ruminal digestion but greater total cell-wall degradation, including that during ensiling and ruminal incubation, especially during early digestion in the rumen.

Cell Wall↗
PubMed1998

Influence of maturity of grass silage and flaked corn starch on the production and metabolism of volatile fatty acids in dairy cows.

An experiment employing a Latin square design was used to quantify the effects of two stages of maturity of grass silage (early cut and late cut) and three concentrations of flaked corn starch (0, 2, and 4 kg) on the molar proportion of rumen volatile fatty acids (VFA), the production of rumen VFA, and the net fluxes of VFA in the splanchnic tissue of cows. The molar proportions of VFA in rumen fluid were similar for cows fed both silages. When the silage diets were supplemented with starch, the proportion of propionic acid increased for cows fed diets containing early cut grass silage, but no effects were found for cows fed diets containing late cut grass silage. Estimated gastrointestinal production of acetate, propionate, butyrate, and branched-chain fatty acids plus valerate was related to intake of metabolizable energy and organic matter fermented into VFA. The portal release of acetate was approximately 14% lower than the estimated production of acetate by cows fed diets containing early cut grass silage, but cows fed diets containing late cut grass silage showed a variable difference between estimated production and portal release (31, 24, and 15%, respectively) as starch supplementation increased. The portal release of butyrate plus beta-hydroxybutyrate and the release of branched-chain fatty acids plus valerate were approximately 70 and 25%, respectively, of the estimated gastrointestinal production. Propionate production was similar to the portal release of propionate. Net flux measurements in splanchnic tissue in combination with gastrointestinal digestion and kinetics provide information that increases the knowledge of pathways and metabolism and quantifies the availability of individual nutrients for milk production in dairy cows.

Animals↗
PubMed1999

Evaluation of the physical structure of fodder beets, potatoes, pressed beet pulp, brewers grains, and corn cob silage.

The physical structure of fodder beets, raw potatoes, ensiled pressed sugar beet pulp, ensiled brewers grains, and corn cob silage was evaluated in diets containing concentrates and either corn silage or grass silage as the roughage source. In one series of experiments, the chewing activity of eight cows was measured over 4 d. The beet pulp and fodder beets were added to the two roughage sources at two ratios [20:80 and 35:65, dry matter (DM) basis]. Potatoes, brewers grains, and corn cob silage were fed in a fixed amount (5 to 6 kg of DM) with corn silage. The chewing indexes (eating and ruminating time per kilogram of DM ingested) for fodder beets and beet pulp averaged 34.3 and 32.3 min/kg of DM, respectively, and were hardly affected by the nature of the roughage or by the inclusion ratio. The chewing indexes for potatoes, brewers grains, and corn cob silage were 23.7, 56.6, and 41.6 min/kg of DM, respectively. In another series of experiments using 8 to 11 cows, the ratio of roughage to concentrates was lowered weekly by 5 percentage units, and the critical rough-age portion of the diet was determined (i.e., the amount just before a lack of physical structure was observed). The roughage source was either fed alone or supplemented with about 4 kg of DM of the experimental feed. The critical roughage portion of the diet decreased when the experimental feeds were added; the decrease was greatest with ensiled pressed beet pulp and was lowest with corn cob silage.

Animal Feed↗