Theoretical Length Of Cut Research Articles

Effects of barley silage particle size and concentrate level on rumen kinetic parameters and fermentation patterns in steers

Four Hereford steers (471 ± 31 kg) fitted with ruminal cannulae were used in a 4 × 4 Latin square design to evaluate the effects and possible interactions between silage particle size and concentrate level on digestion and ruminal fermentation parameters. Diets were designed with two forage to concentrate ratios [low forage, 20:80, high forage, 50:50 on a dry matter (DM) basis], combined with two theoretical chop lengths of barley silage; short (SBS) = 4.7 mm and long (LBS) =18.8 mm. Results showed that steers fed diets with SBS consumed more DM than those fed LBS. An interaction (P < 0.05) between particle size and concentrate level was noted for molar proportion of acetate. At the higher concentrate level, feeding SBS diets reduced the molar proportion of acetate but increased the molar proportion of propionate. An interaction (P < 0.05) between particle size and concentrate level was noted for ruminal pH. When compared to LBS, the daily mean rumen pH was lower (P < 0.05) for steers fed SBS with 80% concentrate but not for those fed the 50% concentrate diet. Ruminal ammonia concentration was higher (P < 0.05) for those steers fed the 50% concentrate diets than for those fed the 80% concentrate diets. With high concentrate levels, SBS greatly reduced (P < 0.05) ammonia concentration. Passage rates for particulate matter and the retention time were decreased (P < 0.05) when SBS was fed. Feeding SBS reduced (P < 0.05) total tract digestibility of dry matter, crude protein (CP) and neutral detergent fiber (NDF) (65.5 vs. 68.5%, 66.5 vs. 73.4% and 39.4 vs. 45.9%), respectively. These results suggest that barley silage with a theoretical cut length of 18.8 mm can promote higher rumen pH, ammonia nitrogen, and reduced particulate passage rates. These changes in rumen fermentation parameters should favor optimum rumen function and digestion when high concentrate diets are fed. Key words: Barley silage, particle size, steers, concentrate level, rumen fermentation

Corn Silage Management: Effects of Hybrid, Chop Length, and Mechanical Processing on Digestion and Energy Content

Two experiments were conducted to evaluate the effects of chop length and mechanical processing of two hybrids of whole plant corn on digestion and energy content of the total mixed ration (TMR). The experimental designs in experiments 1 and 2 were 6×6 and 4×4 Latin squares, respectively. In the first experiment, Pioneer hybrid 3845 was harvested at three theoretical lengths of cut: 11.1, 27.8, and 39.7mm. At each chop length, corn was harvested with and without mechanical processing using a John Deere 5830 harvester with an onboard kernel processor. In the second experiment, Pioneer hybrid Quanta was harvested at two theoretical lengths of cut: 27.8 and 39.7mm, with and without mechanical processing. In both experiments, the increase in the theoretical length of cut of corn silage increased the average length of cut and tended to increase the percentage of particles greater than 19mm and lower the percentage of particles between 8 and 19mm. In experiment 1, apparent total tract dry matter, organic matter, and neutral detergent fiber (NDF) digestibilities were lower for cows fed diets containing corn silage harvested at a short chop length (11.1mm) than for corn silage harvested at a long chop length (39.7mm). The lower total tract digestibility of nutrients may have contributed to the lower TDN, metabolizable energy (percentage of digestible energy), and NEL concentration of diets containing the short chop length corn silage (experiment 1). In experiment 2, total tract starch digestibility was greater for cows fed medium chop (27.8mm) corn silage diets, and total tract NDF digestibility was greater for cows fed long chop (39.7mm) corn silage diets. The opposing effect of total tract starch and fiber digestibilities between chop lengths may have contributed to the lack of difference in energy content of the diets in experiment 2. The TDN and NEL concentrations of the processed corn silage diets were greater than the unprocessed corn silage diets in experiment 1. The increase in energy concentration for the processed corn silage diet was due to greater total tract digestibility of organic matter and ether extract. Total tract starch digestibility was greater, and total tract NDF digestibility was lower for cows fed processed corn silage diets than unprocessed corn silage diets in experiment 2. The opposing effect of total tract starch and fiber digestibilities between processed and unprocessed corn silage may have contributed to the lack of difference in energy content of the diets.

DEVELOPMENT OF AN AUTOMATED SYSTEM FOR SAMPLING CROP MATERIAL FROM A FORAGE HARVESTER

A modular, computercontrolled sampling system was developed to directly sample chopped forage material froma forage harvester spout. Pneumatic cylinders powered a deflector flap to redirect crop material from the spout. A hydrauliccylinder compressed deflected forage material into 35.6cm long, 10.2cm diameter PVC pipes, which served as miniaturetest silos. Timing of the pneumatic and hydraulic actuators was controlled by a programmable microcontroller. The controlsystem included three operator inputs: travel speed, row length, and number of samples along the row for each silo; thisprovided flexibility to adapt to different harvesting situations. In two experiments, testsilo samples fermented for 48 daysand then were separated into six size fractions. In the first experiment, a sidebyside comparison with a selfpropelled plotharvester, statistically significant differences in the mass fractions of medium and small particles (indicated by low pvaluesin the range of 0.1 to < 0.001) were found between samples collected by both machines and their respective controls. Nodifferences in the mass fractions of large particles were found. In the second experiment, the performance of the modularsampling system in sampling corn chopped at two theoretical lengths of cut (6.35 and 19.1 mm) and two wholeplant moisturelevels (approximately 70 and 60% w.b.) was evaluated. Some significant statistical differences between automatic samplingand manual sampling were present; however, trends were inconclusive. The magnitudes of mass percentage and characteristicparticle size differences were at most 8% and 1.6 mm, respectively.

Corn Silage Management II: Effects of Hybrid, Maturity, and Mechanical Processing on Digestion and Energy Content

Two experiments were conducted to evaluate the effects of maturity and mechanical processing of two hybrids of whole plant corn on starch, fiber, and ether extract digestibilities and energy content of the total mixed ration fed to lactating Holstein cows. In the first experiment, Pioneer® hybrid 3845 whole plant corn was harvested at hard dough, one-third milkline, and two-thirds milkline with a theoretical length of cut of 6.4mm. At each stage of maturity, corn was harvested with and without mechanical processing. In the second experiment, Pioneer® hybrids 3845 and Quanta were harvested at one-third milkline, two-thirds milkline, and blackline stages of maturity with and without mechanical processing. The theoretical length of cut was 12.7mm. The measured TDN and NEL concentrations were lower for diets containing processed corn silage in experiment 1 and greater for diets containing processed corn silage in experiment 2, compared with diets containing unprocessed corn silage. The lower energy content for diets containing processed corn silage in experiment 1 can be explained by the lower total tract NDF, ether extract, and CP digestibilities. The greater energy content for diets containing processed corn silage in experiment 2 can be attributed to greater total tract starch and NDF digestibilities for cows fed processed corn silage diets. In experiment 2, diets containing processed corn silage (1.59 Mcal/kg) had approximately 2.6% more energy available per kilogram of DM consumed compared with diets containing unprocessed corn silage (1.55 Mcal/kg). For hybrid Quanta in experiment 2, the TDN and NEL concentrations of diets containing corn silage harvested at two-thirds ML were greater than at other maturities.

Effects of barley silage of different theoretical cut length on digestion kinetics in ruminants

Two studies were conducted to determine the effects of two theoretical lengths of cut (TLC) (short = 4.7 mm and long = 18.8 mm) on the feeding value of barley silage to steers fed an all-forage diet. In the first study, six steers were used to determine intake of dry matter, total tract digestibility of dry matter (DMD), neutral detergent fiber (NDFD), and acid detergent fiber (ADFD) in a replicated switchback design. In the second study, six steers equipped with rumen cannulas were used to determine the effects of barley silage particle size on ruminal kinetic and fermentation parameters. Feeding short barley silage to steers increased (P &lt; 0.05) dry matter intake (DMI), DMD, NDFD, and ADFD compared with feeding long barley silage. The results of the second study showed that reducing barley silage particle size decreased (P &lt; 0.05) ruminal retention time and increased (P &lt; 0.05) passage rate of particulate matter. Ruminal pH was lower (P &lt; 0.05) at 1000, 1200, 1800, 2000, and 2200 h for steers fed the short barley silage compared with those fed the long barley silage. However, the effects of barley silage particle size on ruminal ammonia nitrogen and volatile fatty acid (VFA) concentrations were minimal. Eating rate was similar in both dietary treatments (average 40.3 g min-1). However, steers fed the long silage produced more (P &lt; 0.05) saliva per kg DMI compared with those fed the short barley silage diets. It was concluded that reducing TLC of barley silage increased feed intake and improved total tract utilization of cell wall components by steers. Results of the metabolism study also showed changes in fermentation parameters, but no adverse physiological changes were noted when cattle were fed all forage diets. Key words: Barley silage, particle size, fermentation patterns

Effects of processed corn silage on its digestibility and production of growing beef replacement heifers

A study was conducted to determine effects of processing whole crop chopped corn prior to ensiling on diet digestibility and growth of beef replacement heifers. Corn silage (CS) was harvested using two identical six-row self-propelled choppers, one of which was adapted with a roller-processing unit. Corn was chopped to either 13.3 mm (unprocessed; UP) or 10.6 mm (processed; PR) theoretical length of cut (TLC) and ensiled in silage bags. Over the 56-day feedlot study, 90 growing British-cross replacement heifers were randomly assigned to UP or PR CS with three pens per treatment. The diet initially consisted on a dry matter (DM) basis of 55.4% UP or PR CS, 22.3% alfalfa hay (AH), 19.6% wheat middling (WM) and 2.7% supplement (SUPP). Whole plant particle size was estimated from three sub-samples per treatment. Whole cob fraction as a percent of total dry mass was 0.0% for PR and 6.4% for UP ( P<0.05). Undamaged kernels as a percent of the total dry kernel mass were 17.3 for UP and 1.8 for PR ( P<0.05). There was no difference in average daily gain (ADG; 0.96 kg per day versus 1.00 kg per day), DM intake (DMI; 7.55 kg per day versus 7.59 kg per day) or feed to gain ratio (8.12 versus 7.70) between heifers fed UP or PR silages, respectively. Processing of CS did not alter ruminal pH but total VFAs and acetate concentrations were higher in heifers fed the UP treatment ( P=0.04). Treatment had no affect on whole tract DM or acid detergent fiber (ADF) digestibility ( P>0.05) but neutral detergent fiber (NDF) digestibility was higher in heifers fed the PR treatment ( P<0.008). Processing substantially reduced the number of whole kernels in CS and increased NDF digestibility, but did not improve heifer performance on diets containing 55% of DM as CS.

Crop Processing and Chop Length of Corn Silage: Effects on Intake, Digestion, and Milk Production by Dairy Cows

Effects of corn silage crop processing and chop length on intake, digestion, and milk production were evaluated. Corn silage treatments were harvested at one-half milkline stage of maturity (65% whole-plant moisture content) and at 0.95-cm theoretical length of cut without processing (control) or 0.95-, 1.45-, or 1.90-cm theoretical length of cut with processing at a 1-mm roll clearance. Twenty-four multiparous Holstein cows averaging 71 d in milk at trial initiation were in a replicated 4 × 4 Latin square design with 28-d periods; one square was comprised of ruminally cannulated cows for rumen measurements. Corn silage treatments were fed in total mixed rations containing 50% forage (67% corn silage and 33% alfalfa silage) and 50% corn and soybean meal based concentrate (dry matter basis). Dry matter intake (25.9 vs. 25.3 kg/d) and milk (46.0 vs. 44.8 kg/d) and fat (1.42 vs. 1.35 kg/d) yields were higher for the processed corn silage treatments compared with the control corn silage. Within the processed corn silage treatments, there were no chop length effects on intake, milk production, or milk composition. Chewing activity was not different among the four corn silage treatments averaging 12 h/d. Total tract digestion of dietary starch was lower for control corn silage (95.1%) compared with fine, medium, and coarse processed corn silage treatments, which averaged 99.3%. Total tract digestion of dietary NDF was reduced for fine-processed corn silage compared with control corn silage and coarse-processed corn silage (28.4% vs. 33.9 and 33.7%, respectively). Processing corn silage improved dry matter intake, starch digestion, and lactation performance. Under the conditions of this study and with theoretical lengths of cut ranging from 0.95 to 1.90cm, length of chop effects were minimal in processed corn silage.

PROCESSING WHOLE-PLANT CORN SILAGE WITH CROP PROCESSING ROLLS ON A PULL-TYPE FORAGE HARVESTER

Whole-plant corn silage (WPCS) was harvested with a pull-type forage harvester equipped with crop processing rolls. Variables considered were crop maturity, theoretical length-of-cut (TLC), processor roll speed difference and roll clearance. Whole-plant particle size, whole cob and coarse fiber fractions, level of kernel breakage, and kernel fraction particle-size were used to quantify crop physical properties. Compared to unprocessed WPCS cut at 9.5 mm TLC, WPCS cut at 19 mm TLC and then processed had greater whole-plant particle size, less whole cob fraction, fewer unbroken kernels, smaller kernel fraction particle size, and greater estimated surface area of the kernel fraction. The processed treatments at 19 mm TLC and 3 or 5 mm roll clearance required similar specific energy and produced similar harvesting rates compared to the control unprocessed treatment at 9.5 mm TLC. Feeding dairy cattle WPCS (~33% of DMI) increased fat-corrected milk yield by about 4% and fat yield by about 2%. Compared to unprocessed WPCS cut at 9.5 mm TLC, WPCS cut at 19 mm TLC and processed with 1 mm roll clearance increased in situ DM disappearance by seven percentage units. Based on crop physical properties, harvester energy requirements and dairy cattle lactation performance, the recommended settings when harvesting WPCS with an on-board crop processor would be 19 mm TLC and 1 to 3 mm roll clearance.

Physical Effectiveness of the Neutral Detergent Fiber of Whole Linted Cottonseed Relative to that of Alfalfa Silage at Two Lengths of Cut

The effectiveness of the neutral detergent fiber (NDF) of whole linted cottonseed to stimulate chewing was examined relative to the effectiveness of the NDF of alfalfa silage at two lengths of cut. Twelve Holstein cows (125 d of lactation) were fed diets containing alfalfa silages differing in theoretical length of cut, with or without cottonseed substituted for alfalfa silage at 27% of alfalfa NDF. The experiment was a replicated (n = 3) 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Length of cut had no effect on milk production or composition, and substitution of cottonseed increased milk production but did not affect milk composition. An interaction was observed between treatment effects for dry matter intake, total chews per day, and total chewing time (minutes per day). Physical effectiveness of cottonseed NDF was calculated by dividing the total chewing time per unit of cottonseed NDF by total chewing time per unit of alfalfa silage NDF. Physical effectiveness of cottonseed NDF was calculated to be 50% of long-cut and 127% of short-cut alfalfa silage NDF. The interaction observed between main effects for total chewing time per day indicated that the physical effectiveness of whole linted cottonseed was relative and depended on the characteristics of the forage that it replaced.

Effect of length of cut on quality of stack silage and milk production

Wilted grass at moisture contents ranging between 62 and 76% was chopped at 6.3, 12.7, 25.4 and 38.1 mm theoretical length of cut (TLC) and conserved in large stack silos during 2 consecutive years (1986, 1987). Average real lengths of cut were 11, 21, 37 and 47 mm for the four TLC, respectively. Dry matter losses in the silos containing forage cut at 12.7 and 25.4 mm TLC (15.6 and 16.2%, respectively) were higher (P = 0.016) than losses in the silos containing forage cut at 6.3 and 38.1 mm TLC (12.1 and 12.9%, respectively). Within the range of TLC used, there was no evidence of improved silage quality to favor shorter chop length in stack silos. In both years, silage of each TLC was mixed with high-moisture barley and protein supplement and fed to a group of 16 dairy cows. There was no consistent effect of TLC on dry matter intake. The shortest length produced slightly more milk which was offset by a slightly lower percentage of milk fat. A TLC of 6.3–38.1 mm is adequate for silage fed to dairy cows producing between 20 and 28 kg of milk per day. Key words: Particle length, stack silos, silage, grass, dairy

Reducing Forage Harvester Peak Power with a Flywheel

A flywheel was installed on the main axis of a cylinder type forage harvester in order to evaluate power reduction potential for silage harvesting. A three factor factorial experiment, including two theoretical lengths of cut, two types of windrow (regular and irregular density) and two flywheel settings (engaged and disengaged), was designed to evaluate the performance of the flywheel.

Forage Chopping Energy vs. Length of Cut

ABSTRACT Acylinder type forage harvester was used to cut forage at 6.3, 12.7, 25.4 and 38.1 mm theoretical length of cut. Experimental data was used to develop a predictive model of energy versus length of cut and moisture content. Energy savings of 22% at the power take-off shaft were predicted at the longest length. Additional energy savings up to 31% were observed in drier crops at 62% moisture compared with 83% moisture. Chopping at 38 mm theoretical length required 15% less tractor power than chopping at 6 mm length to meet peak power demand. Actual fuel savings at the longest length of cut under normal field operations were not as much as the average power reduction measured at the PTO shaft and were confounded with operating speed, yield and moisture content.

In Situ Particle Size Reduction of Alfalfa and Timothy Hay as Influenced by Form and Particle Size

Our objectives were to characterize particle size reduction of alfalfa and timothy hay by in situ incubation. Alfalfa and timothy hay were chopped at .64-cm theoretical length of cut. Subsamples were dry sieved through a 3.2-mm screen, yielding particles>3.2 and<3.2mm, and another subsample ground (5.0mm). Each forage treatment was placed in polyester bags and ruminally incubated for up to 100h. Original and residues were wet sieved. Change in geometric mean diameter (initial to lowest) with time for both forages was less as particle size decreased from chopped to ground; however, percent change was similar between chopped and ground and between sieved>3.2 and<3.2mm. Regression of geometric mean diameter on time for alfalfa exhibited quadratic relationships for all particle categories. For timothy, ground and sieved>3.2mm exhibited linear, whereas chopped and sieved<3.2mm exhibited quadratic relationships with time. Large particle fractions for both forages were reduced proportionately more than particle fractions that were small initially. Particle size distribution showed particles>1.18mm accounted for 63.0 to 98.4% of the initial DM, which was reduced to 14.9 to 24.1% by 100h. Microbial fermentation and detrition associated with ruminal movements appear to contribute substantially to particle breakdown.

Initial Particle Form and Size on Change in Functional Specific Gravity of Alfalfa and Timothy Hay

In situ techniques were employed to characterize functional specific gravity change of alfalfa and timothy in the rumen. Alfalfa and timothy hay were chopped at .64-cm theoretical length of cut. Subsamples of each forage were dry sieved through a 3.2-mm screen, yielding particles >3.2 and <3.2mm, and another subsample was ground through a 5.0-mm screen. Each forage treatment was placed in polyester bags and ruminally incubated for up to 100h. Functional specific gravity was determined on the original and residues. Mean functional specific gravity increased with time in the rumen for all treatments. Change in mean functional specific gravity was affected by initial particle size of the sample; however, no differences could be attributed to sieving. Mean functional specific gravity increased rapidly for timothy during the first hour of ruminal incubation, an effect not evident for alfalfa. Regardless of whether forages were ground or sieved, distribution of organic matter dramatically shifted from low to high functional specific gravity with time in the rumen. Microbial fermentation and ruminal movement caused considerable increase in organic matter functional specific gravity.

Theory of Particle Size Distributions for Chopped Forages

ABSTRACT AN analytical model of chopping of forage crops is presented. The model predicts the size distribution of chopped particles based on the random influences of initial particle length, particle orientation relative to the direction of feeding, and particle placement relative to the succession of cuts made by the blades. Initial particle length is assumed to follow a gamma distribution, and orientation angle is assumed to be uniformly distributed within a given range. The model's results are compared with literature data and suggest the use of the Weibull distribution for describing reduced forage crops. The effects of theoretical length of cut, mean and variability in initial particle length, leaf fraction, and allowable orientation angle on the predicted size distribution are studied.

Melting points and thermoelectric behavior of lead isotopes

Inhibiting the growth of Escherichia coli O157:H7 (EC) in feeds may prevent the transmission or cycling of the pathogen on farms. The first objective of this study was to examine if addition of propionic acid or microbial inoculants would inhibit the growth of EC during ensiling, at silo opening, or after aerobic exposure. The second objective was to examine how additives affected the bacterial community composition in corn silage. Corn forage was harvested at approximately 35% dry matter, chopped to a theoretical length of cut of 10 mm, and ensiled after treatment with one of the following: (1) distilled water (control); (2) 1 × 105 cfu/g of EC (ECCH); (3) EC and 1 × 106 cfu/g of Lactobacillus plantarum (ECLP); (4) EC and 1 × 106 cfu/g of Lactobacillus buchneri (ECLB); and (5) EC and 2.2 g/kg (fresh weight basis) of propionic acid, containing 99.5% of the acid (ECA). Each treatment was ensiled in quadruplicate in laboratory silos for 0, 3, 7, and 120 d and analyzed for EC, pH, and organic acids. Samples from d 0 and 120 were also analyzed for chemical composition. Furthermore, samples from d 120 were analyzed for ammonia N, yeasts and molds, lactic acid bacteria, bacterial community composition, and aerobic stability. The pH of silages from all treatments decreased below 4 within 3 d of ensiling. Escherichia coli O157:H7 counts were below the detection limit in all silages after 7 d of ensiling. Treatment with L. buchneri and propionic acid resulted in fewer yeasts and greater aerobic stability compared with control, ECCH, and ECLP silages. Compared with the control, the diversity analysis revealed a less diverse bacterial community in the ECLP silage and greater abundance of Lactobacillus in the ECLP and ECA silages. The ECLB silage also contained greater abundance of Acinetobacter and Weissella than other silages. Subsamples of silages were reinoculated with 5 × 105 cfu/g of EC either immediately after silo opening or after 168 h of aerobic exposure, and EC were enumerated after 6 or 24 h, respectively. All silages reinoculated with EC immediately after silo opening (120 h) had similar low pH values (<4.0) and EC counts were below the detection limit. The ECCH and ECLP silages reinoculated with EC after 168 h of aerobic exposure had relatively high pH values (>5.0) and EC counts (5.39 and 5.30 log cfu/g, respectively) 24 h later. However, those treated with L. buchneri or propionic acid had lower pH values (4.24 or 3.96, respectively) and lower EC counts (1.32 log cfu/g or none, respectively). During ensiling, EC was eliminated from all silages at pH below 4.0. During aerobic exposure, the growth of EC was reduced or prevented in silages that had been treated with L. buchneri or propionic acid at ensiling, respectively.