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Evaluating Alternative Technologies in Forage Production

C. Alan Rotz

US Dairy Forage Research Center,
USDA/Agricultural Research Service,
Agricultural Engineering Department,
Michigan State University, East Lansing, Michigan, USA 48824.
E-mail: rotz@egr.msu.edu

Take Home Message
A computer simulation model of forage production and use provides a tool for evaluating forage technologies. The model, DAFOSYM, simulates alfalfa and corn growth, harvest, storage, feeding and use on a dairy farm. Forage losses and quality changes along with the use and costs of machines, structures, labour, fuel, chemicals, etc. are used to determine the profitability of forage systems. Simulation over many years of weather provides a long term evaluation of the performance and economics of alternative forage technology. This type of information helps direct research toward the more promising technology and aides forage producers in adopting the best technology for their farms.


Large dry matter (DM) and nutrient losses occur during the conservation of forage crops. Development of forage technology continues in an effort to reduce these losses while improving farm profitability. New machines, chemicals and other products promoted to improve forage conservation are introduced each year, but factual information on their affect on losses and profitability are normally not available to the producer.

Quantifying the costs and benefits of alternative technology is not easy. Technology that performs well under one set of crop and weather conditions may not perform well at other times. Long term studies are needed to quantify the benefits and costs over a wide range of conditions. Field studies of this type are costly, impractical and perhaps impossible. Another approach is to use computer simulation. Models developed and validated with limited field experimental work can be used to study system performance over many years of weather. One such model is DAFOSYM, the dairy forage system model. Many alternative technologies and management strategies have been modeled with DAFOSYM to determine their long term performance and economic value to forage producers.


DAFOSYM is a simulation model of alfalfa and corn growth, harvest, storage, feeding and use on dairy farms (4, 6). The dairy forage system is simulated for many years of weather to determine long term performance and economics of alternative technologies and/or management strategies. By modelling several alternatives on the same representative farms, those alternatives which maximize farm production or profit can be determined.

The model is adapted to different locations by changing weather and soil input parameters. The alfalfa growth routine predicts DM accumulation and quality changes on a daily basis throughout the growing season. When the crop is ready for harvest, the harvest routine simulates field machinery operations, drying and rewetting in 3 h increments. Losses and quality changes due to machine operations, plant respiration and rain damage are accounted to predict the quantity and quality of forage stored. A version of the CERES-Maize model is used to predict corn grain and silage yields and a harvest routine accounts for losses and resource requirements during harvest. Storage losses and associated quality changes are predicted for dry hay and silage stored by different methods.

Following storage, feeds are either sold or allocated to a dairy herd. When sold, alfalfa is priced according to its nutrient content. For the dairy farm, balanced diets are fed to each of six animal groups with higher quality forage fed to high producing animals. Supplemental feeds are purchased as needed and extra feeds are sold. Throughout the simulation, costs for machinery, structures, fuel, labour, chemicals and other inputs are totalled along with the value of feeds sold to predict production and total feed costs. Total costs are subtracted from milk income to obtain the net return over feed costs for each simulated year.

To simulate a new technology with DAFOSYM, a submodel is normally required to predict the performance of the technology. Relevant factors such as drying rate, losses, machine parameters, power requirements and chemical and other resource requirements must be modeled based upon field and laboratory experiments. When possible, models are validated by comparing predicted and actual data. In all cases, models are verified to represent the effects experienced under specific conditions of the real world system.

When confidence is established that the model is functioning properly, simulations are made for representative farms. Simulations for 20 to 26 years of historical weather data are required to assure that the systems are evaluated over a full range of weather conditions. Output information includes field curing times, amounts and quality of feeds produced, production costs, and net return to the producer. Results are provided for each year of weather to provide a distribution from best to worst conditions for forage harvest.

Both the mean and variance of simulation results are used to compare forage systems. The mean of production costs and/or the net return over production costs provides an estimate of the long term costs and benefits of one technology versus another. The variance is an indication of the risk of using a given system. Alternative technologies can be compared by their ability to reduce the producers risk in dealing with weather.

DAFOSYM is a FORTRAN program that is compiled for execution on computers using DOS (disk operating system). The latest version includes a package of programs for setting input parameters and viewing simulation results. Overlaying menu and spreadsheet formats are used to view and edit parameters. A plotting package provides bar graphs, pie charts, and other plots of output for rapid evaluation and comparison of simulated systems. The model has been distributed to forage researchers, extension personnel and a few producers to determine its potential as a teaching and management aid.

Alternative Technologies

Several technologies evaluated using DAFOSYM are reviewed here to illustrate the use of the model. These technologies represent a variety of options currently available or proposed for future availability in forage production. Simulation studies conducted with DAFOSYM have predominantly been applied to farms in the northeastern and midwestern US. To better represent Canadian conditions, some model comparisons are included for Ontario weather and prices.

Field Drying Treatments

Chemical conditioning of alfalfa was introduced in the late 70's. Field experiments conducted to develop a practical system for hay producers provided equipment parameters and data required to develop and validate field-curing submodels for DAFOSYM. Simulations of the process on representative farms in the eastern and midwestern areas of the US indicate that the process can reduce field curing time an average of about 12 h on first cutting and 24 h on later cuttings. This results in more high quality hay which reduces feed costs on the dairy farm.

Chemical conditioning can be economical for hay production (2). When the chemical is purchased for $1.80(Can.)/kg and applied to all alfalfa at an appropriate rate, the average cost of the treatment is about $7/t of hay produced. In the midwest, the long-term average gain in feed value is about the same. More selective use of the treatment may improve the economic return, but a greater chemical price makes the process less economical.

Tedding and swath inversion treatments are often used to speed the field drying of forage. Twenty-six year simulations were used to determine the long-term performance and economics of the two processes for a variety of management strategies on representative dairy farms in Michigan and Qu‚bec (10). On the Michigan farm, tedding alfalfa once soon after mowing reduced the average field curing time by 13 h in first cutting and 6 h in subsequent cuttings. Tedding more than once provided little additional benefit through faster drying. Applying inversion once either on the second day of curing or after rainfall reduced the average field time by 5 to 6 h in third cutting and 1 to 4 h in other cuttings.

Mechanical losses caused by tedding were greater than the average rain-induced loss avoided by using the process on alfalfa. With little improvement in the quantity and quality of hay produced, additional machinery and labour costs of tedding decreased farm income. Swath inversion caused less loss, but also provided less drying benefit giving a similar range in the loss of farm income. Simulation of the systems on a similar farm in Qu‚bec with two cuttings of alfalfa gave similar results. The economic value of swath manipulation treatments was not sensitive to any of the major model parameters assumed in the analysis.

Maceration and Mat Drying

Mat drying of hay is a new technology under development in the US, Canada and Europe. Forage is shredded and pressed into a mat that is laid back on the field for rapid drying. The matted forage dries to baling moisture in about one day with minimal loss even in humid climates. Shredding also improves the digestibility and intake of the forage. Simulation has been used to compare the macerated mat harvest system to conventional hay and silage harvest systems under a variety of assumed conditions for the US (7). To better illustrate the use of the model for Canadian conditions, a comparison of the performance and economics of conventional and mat systems for a 100-cow, Ontario dairy farm is listed in Table 1. Further detail on the parameters assumed to describe the farm can be found in reference (3).

Use of the mat process caused a small decrease in preharvest alfalfa production. This occurred because the lower throughput capacity of the mat maker relative to the mower- conditioner slowed the harvesting process. This primarily affected first cutting harvest where heavy alfalfa yields slowed the mowing/mat forming process. Less time was available for regrowth which decreased the alfalfa yield of later cuttings. Even though preharvest yield decreased, harvested yield increased by 30% due to the reduction in field losses with the mat system. Use of the mat system caused a large shift in hay quality with less effect on silage. About twice as much high quality hay was produced.

The higher quality forage produced by the mat system provided more energy so less corn supplement was required to meet the dietary needs of the herd. The requirement for corn dropped 30% for this herd with milk production fixed at a moderate level of 8,200 L/cow/year. For a high producing herd where milk production is limited by forage quality, the feeding of macerated forage can provide a 6% increase in milk production with a 12% decrease in corn use as compared to the feeding of conventional forage.

Use of the mat system has a major effect on machinery, fuel and feed costs. Due to the higher initial cost and higher operating costs of the matting equipment, average annual machinery costs increased about 10%. Fuel costs increased about 25% due to the much greater power requirement for maceration and mat formation compared to conventional mowing and conditioning. Feed costs decreased as less corn and forage were purchased and excess forage was sold. Overall on this farm, the annual net return over feed costs was increased about $60 per cow (Table 1).

Maceration and mat drying can be very economical in hay production, but it is less economical in silage production. In hay production, the reduction in field losses decreases feed costs enough to more than offset the increased costs of production. The increase in farm return is up to $4 per dollar spent on increased machinery, fuel and labour costs. When maceration is used in silage production, the new process, at best, will just pay for itself. On dairy farms which produce both hay and silage, about $2 is returned for each dollar spent on increased machinery costs (Table 1).

Economic studies of the maceration/mat process indicate that this technology is best suited to a forage producer specializing in the production of premium hay.

Dairy farmers may benefit their operations best by purchasing sufficient quantities of this premium forage to feed their high producing animals.

Hay Storage Systems

DAFOSYM can be used to predict DM and nutrient losses during the storage and feeding of large round alfalfa hay bales. Through simulation, the long term performance, costs and return above feed costs for six storage methods, three bale sizes, two feeding methods and two milk production levels were compared on 60 and 400 cow representative dairy farms (1). The value of bale protection was influenced by bale size, amount of hay in the diet, level of milk production and feeding method. Shed storage was usually, but not always, more profitable than unprotected storage.

Round bale size has a large impact on storage and feeding losses and economics. Predicted average annual storage DM losses range from 4% for shed stored bales to 16% and 10% for uncovered small (1.2 m) and large (1.8 m) diameter bales, respectively. When bales are fed ad libitum, average total losses (storage plus feeding) are double the storage losses (8 to 32%). When bales are chopped and fed in a total mixed ration, average total losses range from 7% for shed stored bales to 19% and 13% for small and large uncovered bales, respectively. Handling and storage costs increase as bale diameter decreases. An interaction between bale size and storage method indicates that the value of protection during storage can be $20/cow/year greater for smaller diameter bales compared to larger diameter bales.

The value of hay protection during storage is influenced by the amount of hay used in the ration. As more hay is fed, the impact of lower quality hay on animal performance increases. When all alfalfa forage is fed as hay to a high producing herd, lower quality hay from unprotected bales may cut milk production 5% and decrease farm profitability $200/cow/year compared to hay stored in a shed (1). When only a small amount of hay from unprotected bales is fed along with alfalfa silage to the same herd, milk production may drop less than 1% and farm profitability may decrease only $35/cow/year compared to shed stored hay.

To further illustrate the use of DAFOSYM, a comparison of three storage methods on an Ontario dairy farm is illustrated in Table 1. Compared to shed storage, hay stored without a cover experiences greater DM and nutrient losses. Therefore, a little less hay is produced and more hay is purchased to meet the forage needs of the herd. Purchased feed costs increase, but storage costs are less when hay is stored outdoors. Together these balance to provide only a small increase in the net return over feed costs. When hay bales are wrapped in plastic, the cost of the plastic is greater than the value of the hay saved, so farm net return drops slightly. Overall, the net return is affected little by hay storage method on this farm where relatively large diameter bales were used. Further detail on the assumed parameters of the simulated farm are documented in reference (3).

Hay Preservation

Chemical and biological agents are often used to preserve high-moisture hay. By baling moist hay, field losses are reduced but storage losses are increased. The economic value of preserving high-moisture hay (20-28% moisture, w.b.) was determined using hypothetical hay treatments with three strategies of use and three levels of effectiveness (5). The three strategies of use were defined as limited, moderate and heavy. Under limited use, if a plot of hay was dry enough for harvest as high-moisture hay (<=28% moisture), the model looked ahead to determine if rain was to occur during the remainder of that day or the next. The farmer (decision maker) was given a 60% probability of making the right decision on whether or not to bale the hay wet with a treatment. Using this strategy, limited amounts of treated hay were baled when the probability was high for avoiding rain damage. Moderate use attempted baling all hay as high-moisture hay. Some hay dried enough for stable storage without treatment (below 20% moisture, w.b.) while waiting for other plots to be baled and was not treated with a preservative. For heavy use the same assumptions were followed, but the treatment was applied to all hay regardless of moisture content.

The three levels of effectiveness of hay preservatives were defined as normal, excellent and ideal. Normal effectiveness was modeled to represent preservation with propionic acid. A 60% reduction in the heating of treated hay was assumed compared to untreated hay of similar moisture. The hay remained wetter during storage so a low level of microbial activity occurred over a longer period to give a DM loss equal to that in untreated hay of similar moisture. Loss of CP, gain in acid detergent insoluble protein and gain in fiber concentration were modeled as functions of heating and DM loss. Hay treated with an excellent preservative was assumed to have the same heating, DM loss and quality changes during storage as dry hay (18% moisture). This reflects the goal of current preservatives. For an ideal preservative, all heating, loss and quality change during storage were removed.

Simulation for 26 years of central Michigan weather gave treatment effects on average field-curing time, quantity and quality of hay produced, net returns and breakeven treatment costs. A treatment of normal effectiveness (similar to propionic acid) must cost less than $11/t DM to be economical for limited use on any of the farms studied or less than $5/t DM with moderate or heavy use. As the effectiveness of preservation increases, the breakeven cost increases to a maximum of $28/t DM for an ideal preservative. A sensitivity analysis illustrated that the breakeven costs of a preservative of normal effectiveness could not be greatly improved through realistic changes in the assumed parameters of the analysis. At a typical cost of $18 to 30/t DM, current preservatives are not economically viable. The effectiveness of treatments must be increased considerably and/or the cost must be substantially reduced to provide economic benefit to the dairy producer.

Direct-Cut Silage Systems

DAFOSYM was used to compare the long term performance and economics of direct-cut alfalfa harvest and storage with a treatment such as formic acid to enhance preservation to conventional wilted silage systems (8). Simulation of the dairy forage system showed that reduced harvest losses with direct-cut silage were largely offset by increased effluent losses from the silo. Little difference occurred in the quantity and quality of forage available to the animals when wilted and direct-cut silage systems were compared. Handling of the wetter material increased machinery, fuel and labour costs for transport and feeding.

The economic value of direct-cut silage compared to wilted silage was very poor for dairy farms in central Michigan. With no cost for a preservative treatment of the high-moisture silage, an economic loss was experienced by the producer due to the small difference in system losses and the greater cost of handling and feeding the wetter material. Assuming a wetter climate such as Quebec, the economic value of the direct-cut system improved, but the system remained uneconomical compared to wilted silage systems.

Another issue to consider when comparing systems is the producers' risk of crop and financial loss. This risk is represented by the variances in harvested yield, production costs, and net return across years of weather. Compared to the wilted silage system, the direct-cut system reduced the variance in harvested yield by 15% with a 30% reduction in the variance of silage production costs. When these costs were pooled with other system costs, the variance in the net return over feed costs was reduced 10% indicating a small reduction in overall profit risk.

The economic analysis of direct-cut silage was relatively insensitive to changes in most parameters and functions assumed in the model. A direct-cut silage system could only be justified over a wilted silage system if feeding of direct-cut silage provided at least a 3% increase in milk production; a scenario not supported through feeding trials. Development of a system for direct-cut harvest and preservation of alfalfa for anything less than an extremely wet climate appears infeasible considering known technology.

Grazing Systems

DAFOSYM was used to evaluate the benefits of rotational grazing compared to confined feeding on a Pennsylvania dairy farm (9). The four systems compared included grazing and confined feeding systems which used either custom hire of major operations or owned machinery for all operations. The same hay barn, silage bunker and manure storage were assumed for all systems. Grazing systems required additional investments in fence and watering equipment. Simulations were done for 25 weather years using State College, PA weather data.

Use of rotational grazing greatly reduced the feed supplement requirement on this particular farm. Grazing reduced the annual corn and mineral consumption 30% with a 20% reduction in soybean meal use. Rotational grazing also improved the permanent pasture yield increasing total forage production.

The use of grazing provided good economic benefit. Equipment and material costs increased due to the investment in fence and watering equipment. Fewer harvest and feeding operations, though, reduced fuel use about 25% and labour by 15%. The net of purchased and sold feeds decreased 16% through reduced use of corn and soybean meal. Grazing animals spent up to 70% less time in the barn, so about 30% less bedding was required with 30% less manure hauled each year. Altogether, these effects provided about a 15% reduction in the average feed and manure handling cost. The use of grazing did increase risk. The variation in annual feed and manure handling costs for the grazing system was about double the variation of those costs with confined feeding.

Grazing was a little more economical with custom hired operations than with owned equipment. With custom hire, grazing reduced the total feed and manure handling cost about $3.00/hL of milk. Since milk production was similar among systems, this saving increased the net return over feed and manure costs by $246/cow or $380/ha of land. When all machinery was owned by the farmer, there was a little less benefit for not using those machines. Grazing still reduced costs by $2.56/hL of milk, increasing net return by $217/cow or $337/ha. The economic benefits of grazing are expected to be similar if essentially the same farming systems were compared for other climates.

Current and Planned Modelling Work

DAFOSYM is an evolving model. Submodels of tillage, planting and manure handling have recently been added. This expanded model is being used to evaluate and compare the economics and environmental impact of various manure handling systems on dairy farms. Work is underway for adding grass and small grains as crop options. The emphasis of the modelling work for the next couple years will be to study how different cropping systems and feed supplementation strategies can be used to reduce nutrient loss to the environment while maintaining or improving dairy farm profitability.


1. Harrigan, T.M., C.A. Rotz and J.R. Black. 1994. A comparison of large round bale storage and feeding systems on dairy farms. Appl. Eng. Agric. 10(4):479-491.
2. Rotz, C.A. 1985. Economics of chemically conditioned alfalfa on Michigan dairy farms. Trans. ASAE 28(4):1024-1030.
3. Rotz, C.A. 1994. A comparison of silage systems on Ontario dairy farms. pp. 65-74. In Proc. Quality Forages for Ruminants Symposium, Ontario Ministry of Agric. Food and Rural Affairs, Feed Advisory Program. Fergus, Ontario, Canada.
4. Rotz, C.A., J.R. Black, D.R. Mertens, and D.R. Buckmaster. 1989. DAFOSYM: a model of the dairy forage system. J. Prod. Agric. 2(1):83-91.
5. Rotz, C.A., D.R. Buckmaster, and L.R. Borton. 1992. Economic potential of preserving high-moisture hay. Appl. Eng. Agric. 8(3):315- 323.
6. Rotz, C.A., D.R. Buckmaster, D.R. Mertens, and J.R. Black. 1989. DAFOSYM: a dairy forage system model for evaluating alternatives in forage conservation. J. Dairy Sci. 72:3050-3063.
7. Rotz, C.A., R.G. Koegel, K.J. Shinners, and R.J. Straub. 1990. Economics of maceration and mat drying of alfalfa on dairy farms. Appl. Eng. Agric. 6(3):248-256.
8. Rotz, C.A., R.E. Pitt, R.E. Muck, M.S. Allen and D.R. Buckmaster. 1993. Direct-cut harvest and storage of alfalfa on the dairy farm. Trans. ASAE 36(3):621-628.
9. Rotz, C.A. and J.R. Rodgers. 1993. A comparison of grazing and confined feeding systems on a Pennsylvania dairy farm. p. 252-256. In 1994 Am. Forage Grassl. Council Proc. AFGC, P.O. Box 94, Georgetown, Texas.
10. Rotz, C.A. and P. Savoie. 1991. Economics of swath manipulation during field curing of alfalfa. Appl. Eng. Agric. 7(3):316-323.

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