Economic Analysis of Forage Mixture Productivity in Pastures Grazed by Dairy Cattle

Matt A. Sanderson, Michael S. Corson, C. Alan Rotz, and Kathy J. Soder, USDA-ARS, Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA, 16802-3702

Abstract

The botanical composition of complex forage mixtures can be unstable and may require frequent re-establishment to maintain the desired mixture. We used a whole-farm model (Integrated Farming System Model, IFSM) to simulate the costs and returns of establishing five types of pasture with stand lives of 3, 5, or 10 years. We compared four mixtures [two, three, six, or nine species of grasses, legumes, and chicory (Cichorium intybus L.)] and an orchardgrass (Dactylis glomerata L.)+N (150 lb/acre) pasture with a 10-year stand life. The whole-farm economic returns of these five pasture types were estimated for a representative 100-cow dairy farm based on actual costs of establishment and pasture production from two published studies. Planting grass-legume or grass-legume-chicory mixtures increased net returns per cow compared with the orchardgrass+N pasture. The increase in net return ranged from $57/cow for the two-species mixture to $191/cow for the six-species mixture with a 3-year stand life. Corresponding values for a 5-year stand life were $107 and $225, respectively, and for a 10-year stand life were $136 and $246, respectively. The greater forage yields of the mixture compared with orchardgrass+N reduced purchased feed inputs and in some instances increased the income from forage sold off the farm. Production risk due to weather influences was up to 24% less for the forage mixtures compared with orchardgrass+N and risk decreased with increased stand life. Even with a shorter stand life, the grass-legume-chicory mixture was more profitable compared with a long-lived and lower-yielding orchardgrass+N pasture.

Forage Mixtures and Pasture Productivity

Forage-livestock operations in the northeast USA often emphasize intensively managed pastures as the primary forage base for three principal reasons: (i) lower production costs (13); (ii) improved animal health (3,17); and (iii) a perceived better quality of life for the farm family (4).

Establishment of new pastures from seed can be expensive and producers often prioritize stand life of the pasture over herbage yield. Nonetheless, we have found that some producers in the Northeast plant complex mixtures of grasses and legumes (9,16) because they believe that maintaining a highly diverse botanical composition in pastures contributes to increased persistence, yield stability, and productivity. In an informal survey of 86 mixed-species pasture plantings on 56 farms, we found that about 30% of the plantings were to four or more forage species (10).

Two pasture-scale studies indicated an herbage production benefit for complex mixed swards compared with a simple grass-legume mixture (11,12). In an on-farm study, an 11-species mixture of several grasses, legumes, and chicory yielded more herbage (average of 4 years) than did an orchardgrass-white clover or orchardgrass-alfalfa (Medicago sativa L.)-chicory mixture (12). Sanderson et al. (11) reported that six- and nine-species mixtures of grasses, legumes, and chicory yielded more herbage than an orchardgrass-white clover mixture in a dry year but not in a wet year. In both studies, the yield benefit resulted mainly from including highly productive, drought-tolerant species (e.g., chicory and alfalfa). Although greater botanical complexity resulted in greater herbage yield, individual animal milk production and herbage intake of lactating dairy cows was similar among the four mixtures (14). A major disadvantage reported in the pasture-scale studies was that nearly one-half of the planted species in the complex swards did not persist beyond three or four years, indicating that species presence was not very stable in these mixtures.

The unstable botanical composition of the complex forage mixtures suggests that more frequent re-establishment of pastures would be necessary to maintain the mixture complexity. The greater herbage production, however, may allow for greater stocking rates and perhaps greater animal production per unit area, which may offset some of the re-establishment costs. Our objective was to determine the whole-farm economic returns from several pasture planting scenarios that varied in stand life. We used the Integrated Farm System Model (IFSM; 6) to simulate the different planting scenarios calibrated to the herbage and animal production results from a previous dairy grazing trial.

Description of the Dairy Grazing Trial

We used the herbage production and animal performance data from Sanderson et al. (11) and Soder et al. (14), respectively, to calibrate the model simulations with IFSM. The pertinent details of the studies are summarized below.

We conducted the pasture research at the Dairy Cattle Research and Education Center of the Pennsylvania State University in University Park. Existing vegetation at the site was killed with glyphosate [N-(phosphonomethyl)glycine] and dicamba (3,6-dichloro-2-methoxybenzoic acid) herbicides both of which were applied at 1 lb/acre active ingredient. Four mixtures of forage species (Table 1) were no-till planted in replicated 2.5-acre pastures (Table 1). The mixtures were: orchardgrass and white clover (Trifolium repens L.); orchardgrass, white clover, and chicory; orchardgrass, tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and chicory; and the six-species mixture plus white clover, alfalfa, and bluegrass (Poa pratensis L.). The experimental design was a randomized complete block with two replicates (pastures) of each mixture.

The pastures were subdivided into smaller paddocks and stocked rotationally with lactating Holstein cows from April through August in 2002 and 2003. Five cows grazed each treatment. Cows were confined to a fresh area of pasture after each milking, which took place each morning at 0500 and afternoon at 1800 h. The herbage allocated (55 lb dry matter/cow/day) was equalized among treatments twice weekly by using temporary electric fencing to adjust the area allotted for grazing. Cows were individually fed a corn-based concentrate at a rate of 1 lb dry matter/4 lb milk (based on pre-trial milk yield with an upper limit of 20 lb/day) split in two equal feedings after milking. The total diet consisted of 40% concentrate and 60% forage in 2002, and 47% concentrate and 53% forage in 2003, with 100% of the forage coming from pasture both years. Milk production was recorded daily.

Total dry matter intake was estimated with Cr₂O₃ as an indigestible fecal marker during Week 3 of each of four grazing periods during May, June, and August. Intake was estimated using the equation dry matter intake = fecal output/(1-in vitro digestibility). Herbage dry matter intake on pasture was estimated by difference between total dry matter intake (based on fecal output) and the known concentrate dry matter intake.

Whole-Farm Simulation Modeling of the Grazing Trial

We used IFSM to simulate 13 different pasture planting scenarios. The IFSM simulates the many biological and physical processes on dairy and beef farms (Fig. 1) (6,7,8). Crop production, feed use, and the return of manure nutrients to the land are simulated over many years of weather. Growth and development of grass, alfalfa, maize, and multi-species pastures are determined on a daily time step as a function of soil and weather conditions. Tillage, planting, harvest, and storage operations are simulated to predict resource use, timeliness of operations, crop losses, and nutritive value changes in feeds. Feed allocation and animal response are related to the nutritive value of available feeds and the nutrient requirements of the animal groups making up the herd (7).

Fig. 1. Illustration of the components of the Integrated Farming System Model.

Simulated performance is used to predict production costs, income, and farm net return or profit for each year of weather. A whole-farm budget is used where investments in equipment and structures are depreciated over their economic life, and the resulting annual costs are added to other annual expenditures and incomes determined for each year. By simulating various production alternatives, the effects of system changes are compared with respect to resource use, production efficiency, environmental impact, and net return. The distribution and standard deviation of annual values predicted by the model is used to assess the risk involved in alternative technologies or strategies as influenced by weather. Further detail on the algorithms and assumptions used in the model can be found in the reference manual (6).

Thirteen scenarios were modeled for a representative grazing dairy farm. The representative farm was based on actual management and production information from dairy farms in the northeast USA. Assumptions for the farm were 100 Holstein cows with 28 other stock on 125 acres of pasture and 125 acres of corn (Zea mays L.) grown for silage and grain. The soil was a Hagerstown silt loam. A conventional year-round calving management was used with the herd housed in a free-stall barn when not on pasture. The herd grazed the pasture in a management-intensive rotational stocking system during April through October. The herd was supplemented as per Soder et al. (14). Milk production was set at 20000 lb/cow/year based on milk yields reported by Soder et al. (14).

The thirteen scenarios included an orchardgrass+N (150 lb/acre) pasture with a 10-year stand life and the two-, three-, six-, and nine-species pastures with a 3, 5, or 10-year stand life. To simulate the different stand lives, 33% of the pastures were replanted each year for the 3-year stand life, 20% for the 5-year stand life, and 10% for the 10-year stand life. The input costs for establishing each pasture are in Table 2. We did not vary the stand life of the orchardgrass monoculture because it persists well on the Hagerstown soil. We chose the three stand life periods for the mixtures because we observed large changes in the botanical composition of various mixtures within 3 to 5 years (11,12). We set the simulated average annual yield to be equal to the 2-year average yields of each mixture reported by Sanderson et al. (11). The average yields of the orchardgrass+N pasture (5700 lb/acre) was based on grazing trial data from the Pennsylvania State University annual forage trials for the same weather years (15).

Summary of Herbage Production and Animal Performance in the Grazing Trial

Detailed results of herbage yield and botanical composition changes of the four pasture mixtures are in Sanderson et al. (11) and animal performance data are in Soder et al. (14). We summarize the results pertinent to the simulation analysis here.

Herbage yield was 36% lower on the orchardgrass-white clover mixture compared with the other mixtures in 2002 (a dry year; Table 3). The mixtures did not differ significantly in herbage yield in 2003 (a wet year); however, the pattern of yields among the four mixtures was the same. By the end of the study in May 2004, the botanical composition of the mixtures had changed greatly. Red clover and chicory proportions decreased by 80% and orchardgrass dominated in all pastures. Thus, to maintain the legume and chicory components in the mixed-species pastures, a producer would need to reseed these species.

Milk production averaged 76 lb/cow/day in both years with no statistically significant differences among treatments (Table 3). Grazed herbage intake averaged 26 lb/cow/day and did not differ among treatments.

Whole-Farm Model Simulation Results

Planting pastures to grass-legume or grass-legume-chicory mixtures increased net returns per cow compared with the orchardgrass+N system (Table 4). The increase in net return ranged from $57/cow for the two-species mixture to $191/cow for the six-species mixture with a 3-year stand life. Corresponding values for a 5-year stand life were $107 and $225, respectively, and for a 10-year stand life were $136 and $246, respectively. Within the four mixtures, the three-, six-, and nine-species mixtures had greater net returns per cow than the two-species mixture. Wedin et al. (18) reported that a simple mixture of one grass and one legume [alfalfa-smooth bromegrass (Bromus inermis Leyss.)] or grass+N (105 to 134 lb/acre) were more economical, in terms of milk production per acre, than a complex mixture of nine grasses and legumes. Our simulation results indicate that all forage mixtures were more economical, on a whole-farm basis, than grass+N pasture. Milk production levels were low (35 lb/cow/day) in the Wedin et al. (18) study and they conducted only a partial economic analysis. Milk production in our study was much higher (76 lb/day) and our economic analysis was more comprehensive and conducted at the whole-farm scale, which may account for differences between the studies. Seed costs per acre were higher for the six- and nine-species mixtures because of the relatively high seeding rates (Table 1 and Table 2). Lower seeding rates would improve the economic advantage of the mixtures compared with orchardgrass+N. Costs could be reduced further by frost-seeding forages instead of no-till planting if the forages successfully establish.

Increasing stand life increased net returns from all mixtures but the increase in net return was greatest with the two-species mixture. However, the greater herbage production and resulting greater net returns per cow for the grass-legume-chicory mixtures offset any disadvantage of shorter stand life compared with the orchardgrass+N or orchardgrass+white clover pastures. For example, the net return per cow from the three- and six-species mixtures with a 3-year stand life had equal or greater net returns compared with the orchardgrass+N or orchardgrass+white clover pastures with a 10-year stand life. Thus, producers who place a premium on stand life of pastures without regard to herbage yield may give up potential profits.

Cuomo et al. (2) reported that renovating cool-season grass pastures with legumes or a complex mixture of grasses and legumes (an eight-species mixture) increased forage production by 46% compared with an unrenovated control. The cost of the increased forage production was only 10% of the cost of purchasing the extra forage as hay, which Cuomo et al. (2) considered a cost-effective practice. The additional economic benefits from renovation did not include any potential forage quality or increased herbage intake benefits associated with an increase in the legume proportion of the pasture. We accounted for this effect in the supplementation of the herd and show a further economic benefit to using mixed-species swards in pasture-based dairy production. Burns and Standaert (1) summarized 24 experiments in the USA and reported that steer daily gain from grass-legume pastures averaged 0.31 lb/day more than from grass+N pastures. They also examined seven experiments conducted with lactating dairy cows and reported that grass-legume pastures yielded more milk than grass+N pastures.

The principal item affected in our simulation analysis was the net purchased feed and bedding cost per cow (Table 4). The greater forage yields of the mixture compared with orchardgrass+N reduced purchased feed inputs and in some instances increased the income from forage sold off the farm. The reduction in feed costs with more efficient forage production on pastures and the generally lower feed costs are the principal benefits of pasture-based dairy systems (5).

Production risk (measured as the standard deviation of net returns across years) was up to 24% less for the forage mixtures compared with the orchardgrass+N scenario (Table 4). This may have been because forage production was more consistent year-to-year with the mixtures and because excess forage harvested as baleage or hay was available to supplement forage shortages during drought years. Production risk for the two-species mixture was higher than for the other mixtures, which accurately reflects the greater fluctuations in actual yields observed among mixtures in dry vs. wet years (Table 3; 11). Increased stand life reduced production risk as well.

Conclusions

Using grass-legume or grass-legume-chicory mixtures for grazing dairy cattle was more economical on a whole-farm basis and less risky than grass+N pastures. The increased forage production from the mixtures reduced purchased feed inputs and sometimes increased income from forage sold off the farm. In all of the pasture scenarios modeled, increasing stand life of the pastures increased economic returns. Even with a shorter stand life, the grass-legume-chicory mixture was more profitable compared with a long-lived and lower yielding orchardgrass+N pasture.

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