Production and Quality of Forage and Economics of Grazing a Hay Meadow in the Spring

The Professional Animal Scientist 22 (2006):318–324

Production and Quality of Forage and Economics of Grazing a Hay Meadow in the Spring V. NAYIGIHUGU,* A. D. SCHLEICHER,*1 B. W. HESS,*2 PAS, D. W. KOCH,† J. W. FLAKE,†3 and L. J. HELD‡ *Department of Animal Science, †Department of Plant Science, and ‡Department of Agricultural and Applied Economics, University of Wyoming, Laramie 82071

Abstract An experiment was conducted to determine the effects of spring grazing on forage DM production and nutritive value, as well as the economics of spring grazing a flood-irrigated hay meadow. Two vegetation types were present: predominantly ’Garrison’ creeping foxtail (Alopecurus arundinanceus Poir) and a complex mixture with both introduced and native species. With use of cages, samples of ungrazed and grazed treatments were collected before and after grazing and also in August. Eighty-eight Angus × Gelbvieh rotationally-crossed heifers (average BW = 361.3 kg) were allowed to graze from May 27 to June 8 at 5.4 heifers/ha. A sampling date effect (P < 0.0001) occurred for forage DM production. Forage DM production was not different (P = 0.90) between native species and creeping foxtail. Also, grazing treatment did not alter (P = 0.23) forage DM production. Vegetation types were not different (P ≥ 0.19) in ash, NDF, ADF, and CP, but creeping foxtail was greater (P = 0.02) in in vitro DM digestibility than

1

Current address: Rock Port, MO 64482. To whom correspondence should be addressed: [email protected] 3 Current address: McMinneville, OR 97128. 2

the native species group. The loss of 12,025 kg of forage due to early grazing treatment, at a hay price of $0.0772/kg, resulted in a replacement hay value of $928. Forage plants were able to adequately recover from grazing despite atypical environmental conditions; however, expected improvements in quality did not occur with the early grazing treatment. It is concluded that although spring grazing by beef heifers did not affect forage production and most indices of forage quality, less harvestable nutrients in late summer were more costly than feeding harvested forage or renting pasture for the spring-grazing period. Key words: meadow grazing, creeping foxtail, native species

Introduction One of the major costs in cow-calf operations is winter feed (Lankister et al., 1999). In the Intermountain region, harvested grass is fed until green grass in meadows or seeded species such as crested wheatgrass is available. Grazing forage early in the growing season has the potential to reduce dependency on harvested and conserved forages by shortening the feeding period (Baker et al., 1988). Spring grazing shortens the feeding period; however, there have been rela-

tively few studies on the value of spring grazing of irrigated meadows in relation to subsequent production and quality of forage. Another practice that may reduce over-wintering costs is leaving windrowed hay in the meadow until grazing in the winter (Bowman and Sowell, 2003). A delay in peak production, if accomplished with spring grazing, would result in less windrow exposure time and might produce forage of similar nutritive value as traditional harvest in July (Anderson and Scherzinger, 1975). The objectives of this experiment were to examine the effects of spring grazing on forage production and quality, and the economics of grazing a flood-irrigated hay meadow in the spring.

Materials and Methods Forage Sampling and Early Grazing. The effects of early-season grazing was studied on a 16.2-ha irrigated meadow near Laramie, WY. The site is at an elevation of 2250 m and long-term annual precipitation is 36 cm with an average growing season of 75 d in which cool-season forage plants do not become fully vegetative until early June. The greatest amount of precipitation occurs in May and declines steadily until December, the driest month. Irrigation water availabil-

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ity on the study farm is normally limited to 1 or 2 applications in late May and late June. Forage cages, 1.5 m2 in area, were placed throughout the meadow to equally represent the 2 main vegetation types present — predominantly ‘Garrison’ creeping foxtail (Alopecurus arundinanceus Poir) and native species. Included in the native species grouping were unimproved species such as meadow fescue (Festuca pratensis Huds.), Kentucky bluegrass (Poa pratensis L.), rush (Juncus balticus Willd.), and sedge (Carex nebraskensis Dew.), and to a lesser degree plantain (Plantago spp.), dandelion (Taraxacum spp.), fern (Potentilla anserina L.), lovegrass (Eragrostis cilianensis), and foxtail barley (Hordeum jubatum L.), and the introduced species tall fescue (Festuca arundinacea Schreb.), red clover (Trifolium pratense L.), and reed canarygrass (Phalaris arundinacea L.). At each of 6 locations, each species type was represented by 3 cages, where 1 forage cage and an equally sized area of comparable stand characteristics adjacent to the cage were sampled to provide the ungrazed and grazed comparisons, respectively. Forage was sampled before (May 26) and after (June 8) the grazing period. Forage was clipped to a height of 2.5 cm from a 0.25-m2 quadrant. The samples were hand-separated into live and dead portions. No fertilizer was applied to the meadow. Grazing began when the forage was 5 cm in height and when at least 1000 kg/ha was available so as to not limit intake or limit animal performance. Irrigation water was only available for the study site once in mid-June. Our intent was to graze the meadow once forage plants became vegetative and, to avoid negative effects associated with hoof action, grazing was permitted before the meadow received irrigation water. Eighty-eight Angus × Gelbvieh rotationally-crossed heifers (average BW = 361.3 kg) were allowed to early graze this meadow from May 27 to June 8, 1999, in accordance with an approved University of Wyoming (UW) Animal Care

and Use committee protocol. The stocking rate was 5.4 heifers/ha. Heifers were weighed before and after grazing. Average daily gain was 0.5 kg/head per d during the early grazing period. To determine the effects of early season grazing on forage production, final forage samples were clipped on August 24, 1999 (the day before the hay from this meadow was harvested) both in ungrazed and in the cages as described above. Laboratory Analyses. Forage samples were dried in a forced-air oven at 55°C for 48 h, weighed, and ground in a Wiley mill to pass a 1-mm screen. Samples were analyzed for DM, ash, Kjeldahl N (AOAC, 1990), in vitro DM digestibility (IVDMD; Tilley and Terry, 1963), NDF, and ADF by non-sequential methods (Goering and Van Soest, 1970), except that Whatman 541 hardened ashless filter paper was used (Whatman, Hillsboro, OR) rather than fritted disc crucibles. Statistical Analyses. Forage data were analyzed as a split-split-plot in a completely randomized design using the GLM procedure of SAS (Version 4.1, release 7.0, 1998; SAS Inst., Inc., Cary, NC). The main plot was forage species, which was tested with the species within the sampling location as the error term (error a). Grazing, as a subplot, and the species × grazing treatment were tested with species × grazing treatment within the sampling location error (error b). Sampling date and respective 2- and 3way interactions were tested with residual error (error c). After a significant preliminary F-test, least-square means were compared using the LSMEANS option of SAS. Economic Analysis. Production and quality data (specifically, IVDMD to estimate ME) were used to determine the costs of options for the production system in relation to early grazing. Costs were based on those incurred at the UW Experimental Farm, average Wyoming custom rates for different enterprises, and average pasture rental rates. Options included whether meadows were grazed in

spring or not — if grazed, the costs and returns associated, and if not grazed, the spring feeding costs and fall costs and returns (harvest costs and value of hay harvested in August) that resulted. Net costs of each option were summarized for comparison.

Results and Discussion Forage Production. No interactions (P ≥ 0.40) were observed for production values, so only main effects will be discussed. Forage DM production at each sampling date for grazing treatments is presented in Table 1. Average forage DM production for creeping foxtail and native species was 1,533 kg/ha, 1,208 kg/ha, and 4,089 kg/ha on the grazed treatment, and 1,506 kg/ha, 1,681 kg/ha, and 4,831 kg/ha on the ungrazed treatment in May, June, and August, respectively. Forage DM production was influenced (P < 0.0001) only by sampling date (Table 2). The similar amounts of forage in May and June indicate that animals consumed amounts of forage similar to that attributed to growth during the grazing period. Forage DM production was not different (P = 0.90) between native species and creeping foxtail (Table 3). This is unusual, as creeping foxtail has been recommended for flood-irrigated meadows prone to wetness in the Intermountain region because of its increased DM yields (Reece et al., 1994). Improved species, however, require a greater level of management such as high fertility and adequate water. The biological potential of adapted species depends on climate (Nelson and Moser, 1994), especially in arid and semiarid systems (Archer and Smeins, 1991; Brummer, 1997). Four factors may have contributed to less than optimum creeping foxtail yields: less than normal precipitation, limited irrigation water, greater than normal temperatures, and N deficiency. Rainfall is generally the most lim-

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TABLE 1. Forage DM production of creeping foxtail and native species in a flood-irrigated meadow grazed and ungrazed in the spring. DM production,a kg/ha Item May June August

Grazedb

Ungrazed

SEMc

1,533 1,208 4,089

1,506 1,681 4,831

383.6 383.6 383.6

a

Sampled August 24. Grazed May 27 to June 8. c n = 34. b

iting factor determining potential productivity of forages in semiarid climates (Snaydon, 1991). Although precipitation was near normal in May compared to the 30-yr average, it was below normal for the rest of the study period, with the greatest difference occurring in July (Figure 1). Water was not available for a needed July irrigation. Average temperatures in July were greater than normal (Figure 2). Greater temperatures can significantly reduce the productivity of cool-season grasses such as creeping foxtail (Nelson and Moser,

1994). Additionally, N fertilizer was not applied in this experiment. Creeping foxtail is sensitive to N deficiencies (Brummer, 1997), and this may have contributed to the lack of difference in production compared to native species. Grazing treatment did not alter (P = 0.23) forage DM production (Table 4). A numeric difference was observed, however, and could be biologically significant if one considers that total hay production from the meadow was reduced 15.4% (4,831 vs. 4,089 kg/ha) by grazing the forage early in the spring. The

influence of grazing on productivity of species is minor compared to the changes resulting from variations in rainfall (Archer and Smeins, 1991). The trends observed in production in the experiment, where early grazing did not depress forage productivity, agree with some reports (Anderson and Scherzinger, 1975; Gomm, 1979) and disagree with others (Swift and Edwards, 1980; Baker et al., 1988; Clark et al., 1998) that suggest that production decreased. These experiments were conducted under different conditions, however, which make direct comparison of results difficult. Forage Nutritive Values. A significant species × grazing treatment interaction was detected (P = 0.04) for forage NDF content. Native forage had greater NDF than creeping foxtail whether grazed (69.5 vs 63.2 %) or ungrazed (67.5 vs 63.2 %). Whereas NDF content of creeping foxtail was not different between grazed and ungrazed forage, native forage that had been grazed was greater in NDF than that which was not grazed. It would be expected that immediately after grazing NDF should be greater because of leaf removal, and leaves have less NDF

TABLE 2. Forage DM production and nutrient content of a flood-irrigated hay meadow in spring and summer.a Sampling datab Item DM production, kg/ha Nutrient content, % of DM Ash NDF ADF CP IVDMDh a

May

SEMc

June

SEMc

August

SEMd

P

1519e

231.3

1444e

231.3

4460 f

271.2

<0.0001

2.3 2.5 1.3 0.6 1.4

0.11 0.81 0.0002 0.001 <0.0001

17.2 64.9 35.4e 9.3e 68.8e

2.0 2.1 1.1 0.5 1.2

11.5 66.8 32.1e 12.2f 75.7f

Means are averaged over grazing treatments and vegetation types. May 26, June 8, and August 24, 1999. c n = 12. d n = 10. e,f,g Within a row, means without a common superscript letter differ (P ≤ 0.05). h IVDMD = in vitro DM digestibility. b

2.0 2.1 1.1 0.5 1.2

11.8 65.8 41.7f 8.9e 59.2g

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TABLE 3. Forage DM production and nutrient content of creeping foxtail and native species in a flood-irrigated hay meadow on August 24.a Item

Figure 1. Monthly precipitation averages (30-yr and 1999) near Laramie, Wyoming from May to August.

than stems. Additionally, greater than normal temperatures and less than normal precipitation may have reduced plant growth and prevented recovery from grazing, further contributing to increased NDF. Date of sampling did not influence forage ash (P = 0.11) or NDF (P = 0.81) content; however, ADF increased (P = 0.0002) as the sampling date progressed (Table 2). The ADF content increased at the August sampling date (Table 2). This is explained by the decreasing leaf to stem ratio, which occurs as forage matures. As forage grows and enters the reproductive stage, tillers assume a determinate growth pattern and no longer form new leaves. The stem elongates and the inflorescence develops. Because the stem is comprised of highly lignified xylem cells, a high concentration of vascular bundles, and other schlerenchyma cells, the forage has less quality (Nelson and Moser, 1994). Increased stem growth also dilutes the greater quality thin-walled mesophyll cells of leaf material. In-

Figure 2. Monthly temperature averages (30-yr and 1999) near Laramie, Wyoming from May to August.

DM production, kg/ha Nutrient content, % of DM Ash NDF ADF CP IVDMDd

Creeping foxtail 2,496 14.7 63.2 35.7 11.0 70.8

SEMb

Native

SEMc

P

234.8

2,453

210.0

0.90

3.3 2.2 1.7 0.9 1.1

0.65 0.19 0.63 0.24 0.02

3.7 2.5 1.9 1.0 1.2

12.3 68.5 37.1 9.3 64.9

a

Means are averaged over grazing treatments and sampling dates. n = 16. c n = 18. d IVDMD = in vitro DM digestibility. b

creased lignin and hemicellulose-lignin concentrations associated with maturity of stems (Morrison, 1980) equates to greater ADF content of forage. Crude protein content increased significantly (P = 0.001) from May to June (Table 2) as a result of an increased proportion of live material (Table 5). By the August sampling date, forage had decreased to 8.9% CP, reflecting the maturation of the forage, where increases in structural components had diluted out the protein content of the forage. Changes in digestibility of forage (P < 0.0001) mirrored the changes that were observed for ADF (Table 2). Forage increased in digestibility from May 26 to June 8 (68.8 to 75.7% IVDMD), then decreased to 59.2% in August. These results coincide with the relationship between ADF and digestible DM of forages as described by Linn and Martin (1989). Forage must develop structurally as it matures. These structural components, represented in ADF, tend to decrease digestibility, thus explaining the lesser IVDMD in August forage. Using values from this experiment, the regression equation between IVDMD and ADF in the forage was as follows: IVDMD =

112.15303 − (1.21418 × ADF); r2 = 0.69. Species type, which included creeping foxtail and native species, did not influence ash (P = 0.65), ADF (P = 0.63), or CP (P = 0.24). However, IVDMD was different (P = 0.02) for the 2 species types (Table 3). Creeping foxtail had an IVDMD of 70.8%, whereas native species were 64.9% digestible. This reflects numerically lesser ADF with creeping foxtail than with native species (Table 3). A characteristic of creeping foxtail is its indeterminate growth, in which plants will be in various phenological stages at a given time (Brummer, 1997). While some plants may have fully mature seed stalks, others may be newly vegetative. The presence of phenologically younger plants, which have greater leaf to stem ratios (Nelson and Moser, 1994), could have contributed to the greater IVDMD value. Despite greater than normal temperatures and less than normal precipitation during most of the study, grazing did not influence ash (P = 0.17), ADF (P = 0.69), CP (P = 0.52), or IVDMD (P = 0.18); (Table 4). Typically, meadows of this type are harvested in early to mid-July. In this

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TABLE 4. Forage DM production and nutrient content of a floodirrigated hay meadow previously grazed or ungrazed in the spring.a Item

Grazedb

DM production, kg/ha Nutrient content, % of DM Ash NDF ADF CP IVDMDd

2,276

Ungrazed 2,673

13.1 66.4 36.5 10.1 67.2

14.0 65.3 36.3 10.2 68.6

SEMc

P

197.0

0.23

0.4 0.2 0.4 0.1 0.6

0.17 0.03 0.69 0.52 0.18

a

Means are averaged over sampling dates and vegetation types. Grazed represents an early grazing period from May 27 to June 8, 1999. c n = 17. d IVDMD = in vitro DM digestibility. b

experiment, however, harvest did not occur until late August. It would be expected that ungrazed forage was phenologically beyond the “ideal” point for hay harvest, whereas grazed forage should have been at the appropriate phenological stage in August because of the delay in maturity associated with early grazing. As noted by Swift and Edwards (1980), warmer-than-average growing conditions tend to hasten the decrease in digestibility of forages and the maturation process. Similar conditions present during this experimental period may have prevented an increase in quality with early defoliation. Economics. Although grazing did not significantly influence (P = 0.23) forage DM production in this experiment, a numeric difference was observed in August. Grazed forage averaged 4,089 kg/ha, and ungrazed forage averaged 4,831 kg/ha. In vitro DM digestibility was 67.2 and 68.6% for grazed and ungrazed forage, respectively (P = 0.18). These values were used to estimate the loss associated with reduced production and quality from the spring grazing treatment (Table 6). Costs and returns were estimated in this economic analysis from the UW Experimental Farm or Wyoming custom rates.

There was a loss of 12,025 kg of forage on the 16.2-ha meadow due to the early grazing treatment, measured at the time of hay harvest (Table 6). This reduction in hay production, at a hay price of $0.0772/kg (Wyoming Agricultural Statistics, 2000), is valued at $928.35 if replacement hay were to be purchased. The cost savings associated

TABLE 5. Amounts of live and dead forage materiala in forage samples collected before (late May) and after (early June) an early grazing treatmentb on a floodirrigated hay meadow.c Item Grazed, kg/ha Live Dead Ungrazed, kg/ha Live Dead a

May

June

644 889

870 338

633 873

1210 471

Live and dead portions determined by hand-separating and weighing dry plant material. b Meadow was grazed May 27 to June 8, 1999. c Meadow was sampled May 26 and June 8, 1999

with less forage to harvest, windrow, bale, transport, and stack is $428.10, based on UW Experimental Farm data, or $861.01 when Wyoming custom harvest rates are used (Custom Rates for Wyoming Farm and Ranch Operations 199899). As a result, net loss of reduced hay production would be $500.25 using UW Farm data and $67.34 with custom harvesting. Assuming that IVDMD is equivalent to TDN, where 1 kg TDN equals 4.4 Mcal DE, and 82% of DE is ME because of an 18% loss of DE to gas and urine (NRC, 1996), 29,086 Mcal ME were lost by grazing the meadow from May 27 to June 8. In the ungrazed treatment, the forage that would have to be fed in spring would supply 18,350 Mcal ME, so an additional 5,017 kg of forage with 2.13 Mcal ME/kg would have to be fed to make up the difference of 10,736 Mcal ME. This hay would be worth $180.87 using UW data and $392.22 using custom rates. Costs were less for the UW Farm because harvest costs were less than those typically charged by custom harvesters. The loss in ME may not be as significant to a producer if greater-quality forage is not necessary. The worth of the forage will depend on desired production levels. Nonetheless, the net cost of the system associated with early grazing in spring would equal $681.12 with UW farm values and $459.56 using custom rates. Despite reduced forage production, one also must consider the cost savings associated with allowing animals to graze forage in spring versus feeding hay. According to the Nutrient Requirements of Beef Cattle software (NRC, 1996), intake would be approximately 8.12 kg/head per d for a yearling heifer fed meadow hay of similar quality and exposed to similar conditions as present in this experiment. For 88 animals over 12 d, 8,575 kg of meadow hay would be required to produce equivalent BW gains to those observed in the exper-

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TABLE 6. Projected economic analysis for effects of early grazing in spring on the production system.a Grazed Item Spring costs Hay to be fed in spring,b kg Hay harvest or purchase price,c,d,e $/kg Cost of hay to be fed in spring, $ Cost of feeding harvested or purchased hay,f $/kg Cost of feeding harvested or purchased hay,e $ Total spring costs, $ August harvest costs and returns Reduction in harvestable forage, kg Value of reduced hay production,e $ Reduced cost of harvest,c,d $/kg Reduced cost of harvest,c,d $ Net loss of reduced hay production, $ Loss of value associated with reduced nutrient content,g $ Total fall costs, $ Net cost of system, $

Ungrazed

UW Farm (a)

Custom (b)

UW Farm (c)

Custom (d)

Hay (e)

Pasture (f)

— — —

— — —

— — —

8,574.7 0.0356 305.26

8,574.7 0.0716 613.95

8,574.7 0.0772 661.63

—

—

—

0.0062

0.0062

0.0062

— —

— —

— 358.42

53.16 667.11

53.16 714.79

53.16 398.46

12,025 928 0.0356 428.10 500

12,025 928 0.0716 861.01 67

— — — — —

— — — — —

— — — — —

— — — — —

180.87 681.12 681.12

392.22 459.56 459.56

— — 358.42

— — 667.11

— — 714.79

— — 398.46

a Grazed = grazing period with 88 yearling heifers from May 27 to June 8, 1999, and reduced production and quality costs; Ungrazed = costs associated with feeding or grazing cattle during the early grazing period. UW Farm = costs based on University of Wyoming production data; Custom = costs based on Wyoming custom rates (Custom Rates for Wyoming Farm and Ranch Operations 1998-99, UW Coop. Ext. Ser. Agric. Appl. Econ. Bull. B1084); Hay = costs associated with purchasing hay; and Pasture = cost of renting pasture at $11.70/animal unit month (Wyoming Agricultural Statistics, 2000). b Hay required to replace forage estimated to be consumed by heifers during early grazing. Intake estimated at 8.12 kg/head per d, using Nutrient Requirements of Beef Cattle software (NRC, 1996). Hay was similar type and quality as forage harvested from the 16.2-ha experimental meadow in August. c UW Experimental Farm data, 1999. d Custom Rates for Wyoming Farm and Ranch Operations 1998-99 (UW Coop. Ext. Ser. Agric. Appl. Econ. Bull. B1084, 2000). e Wyoming Agricultural Statistics (2000). f Feuz and Kearl (1987); Boehlje and Eidman (1984). g Hay needed to replace the loss of 10,735.9 Mcal ME in forage harvested in August which was early-grazed, assuming 2.13 Mcal ME/kg.

iment (0.5 kg/head per d). If a beef cattle producer purchased hay at a total price of $661.63 (Wyoming Agricultural Statistics, 2000) with associated feed delivery costs of $53.16 (Boehlje and Eidman, 1984; Fuez and Kearl, 1987), net costs would be $714.79 (Table 6). Another option for the livestock and hay producer could be to produce the hay to replace that cost which was lost with the early grazing treatment, assuming that an additional meadow was available for

hay production. In the spring, the purchase expense of the hay is removed so only expenses of feeding occur, totaling $53.16. Producing hay on the ranch costs $305.26 using UW harvest data and $613.95 using custom rates in Wyoming (Table 6). Again, differences in harvest costs are present between UW and Wyoming custom rates. Total spring costs, as well as net costs, would be $358.42 with UW data and $667.11 with custom harvest rates. The greater harvest costs asso-

ciated with custom harvesting result in the difference between the 2 options. A third option for the producer might be to rent pasture in the spring versus grazing meadow forage. At $11.70/animal unit month (Wyoming Agricultural Statistics, 2000), total spring expenses equal $398.46. Costs of early grazing, whether calculated using UW values or custom harvest rates, are greater than pasture rental. Pasture rental rates would have to exceed $20/ani-

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mal unit month before early grazing would be economically competitive with this option in this experiment. Net costs of the production system in this experiment indicate that because of greater harvest costs with custom harvesting, early grazing was more costly on the UW Farm than if custom harvesters were hired in August. By not early grazing in spring, custom harvesting was more expensive; the most viable option was to not graze in spring and incur typical UW costs of production and feeding. However, renting pasture in spring was an economical alternative. Early grazing could be a desirable option if one hires custom harvesters because, at these rates, grazing is more economical than feeding forage. The idea that ‘grazing is cheaper than feeding’ depends on how each is accomplished and the costs associated with each option.

Implications It appears that plants were able to recover adequately from grazing despite atypical environmental conditions. The difficulty in implementing an early grazing regime is the uncertainty of temperature and moisture conditions that will occur after the grazing period. The level of forage production must be considered when evaluating the usefulness of grazing in spring. In years when irrigation water is expected to be short, there may not be enough water later in the season for compensatory growth following early grazing. Also, more intense grazing may have shown a difference between May and June production and may have carried over to Au-

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gust harvest. A loss of 12,025 kg of forage with an estimated loss of 29,086 Mcal of ME on the 16.2-ha meadow due to the early grazing treatment resulted in a net loss of potential income ranging from $67.34 to $681.12.

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