J.C. Henning, G.D. Lacefield, R.F. Spitaleri, and L. Lauriault
The perennial question about using better varieties of alfalfa is whether the extra cost is really worth it. The question is highly valid, and sometimes the answers are taken for granted. However, the value of better varieties of alfalfa come from several areas. These include seed quality, consistent performance, yield, pest resistance, grazing tolerance, and forage quality. However, the most important reason for choosing an improved variety must be yield. The improvement in yield from choosing a better alfalfa variety has been estimated below using data from the past 10 years of the Kentucky Forage Variety Trials.
Choosing a better alfalfa variety has a definite yield advantage (Table 1). A comparison of the top five varieties versus the checks for four different studies found that the better varieties were worth an average of almost 1 ton (0.93 tons) of 15 percent moisture content hay per acre per year for every year of the stand (including the year of seeding). If alfalfa hay is valued at $85 per ton, that makes a better variety of alfalfa worth on average $79 per year or $415 over the life of the stand.
The difference in seed cost between the checks and the best varieties is about $2 per pound. At a 20-pound per acre seeding rate, the extra cost of seeding the best alfalfa compared to the checks would be $40 per acre, which is certainly a significant figure. However, 0.93 tons of hay at $85 per ton equals $79 extra revenue per acre per year from better varieties of alfalfa. Over the average stand life of these four studies, this extra yield was worth $415 per acre. That makes the net return on investment for a better alfalfa variety worth about 938 percent. Are better varieties worth it? Absolutely.
|Table 1. Average annual dry matter yields of top five alfalfa varieties and of check varieties (Arc, Liberty, Saranac AR) for four yield trials across Kentucky.|
|Test Site Seeding Year (length of study)||Lexington 1990 (5 yr)||Lexington 1991 (5 yr)||Bowling Green 1992 (5 yr)||Princeton 1993 (6 yr)||Average|
|Annual Yield, Tons of Hay/Acre (15% moisture content)|
|Top 5 Varieties||5.1||6.44||4.91||5.95||5.61|
|Annual Difference Tons/Acre||1.03||0.85||0.87||0.96||0.93|
|Value, Dollars per Acre (@$85/Ton)|
|Life of Stand||$440||$360||$371||$492||$415|
|Check Varieties||Liberty Saranac AR||Liberty Saranac AR||Saranac AR Arc||Saranac AR Arc|
R.F. Spitaleri J.C. Henning, C.T. Dougherty, G.D. Lacefield, Department of Agronomy; B.T. Larson, Department of Animal Sciences
In the past, farmers made variety choices about alfalfa and tall fescue based on "clip and carry" yield trials. These data are certainly useful for establishing yield potential, resistance to significant diseases of the region, and adaptation. However, yield trials reveal little about persistence under grazing.
Alfalfa is the highest yielding, highest quality forage crop grown in Kentucky. It is produced mainly for hay, but its use as a pasture crop is increasing. Research at the University of Georgia found that persistence among alfalfa cultivars varied when subjected to mowing versus continuous grazing. They subsequently found that selecting for grazing tolerance during the breeding process could result in significantly more grazing tolerance compared to hay-type alfalfas. This selection resulted in the release of `Alfagraze.' Since this release, many varieties of alfalfa have been released with claims of grazing tolerance. However, farmers are concerned that these new varieties (including Alfagraze) may not persist under less-than-perfect pasture management, especially continuous grazing. It is unclear if all claims of grazing tolerance among varieties are equally valid.
Tall fescue is the predominant pasture species in Kentucky. Most tall fescue in Kentucky is infected with a fungal endophyte (Neotyphodium coenophialum Morgan-Jones and Gams). Stand establishment and persistence of initial endophyte-free cultivars of tall fescue in Kentucky was disappointing. As a result, later releases of new endophyte-free tall fescue varieties have been poorly adopted. The prevailing attitude among farmers is that to be truly better, a new endophyte-free variety would have to demonstrate the "toughness" of endophyte-infected Kentucky 31 (the predominant variety). It is unclear if new endophyte-free varieties of tall fescue are as tolerant to close, continuous grazing as endophyte-infected Kentucky 31.
Identifying truly grazing tolerant varieties of alfalfa and endophyte-free tall fescue would greatly encourage their use and would therefore result in higher pasture productivity and quality in Kentucky. The purpose of these studies was to evaluate current varieties of alfalfa and tall fescue under heavy, continuous grazing pressure by cattle.
Varieties of alfalfa and tall fescue were fall-seeded in small (5 ft x 15 ft) plots in 1994 and 1996 and harvested for yield the following spring. After this first cutting, plots were allowed to regrow to approximately 6 to 8 inches in height and then were grazed by cattle continuously for the remainder of the season so as to keep stand heights at 3 inches or less. This procedure was repeated for one or two more grazing seasons, depending on stand survival. Stands were visually rated for stand in the fall and spring.
Alfalfa varieties differed significantly in tolerance to overgrazing (Table 1). There was a fairly clear separation between the grazing type and hay-type alfalfas (denoted with an H) in both the 1994 and 1996 seedings. Alfagraze was numerically the most grazing tolerant cultivar in Study 1 but was significantly different from the top variety (Feast) in Study 2.
|Table 1. Percent stand ratings for alfalfa varieties sown 3 September 1994 (Study 1) and 23 August 1996 (Study 2) at Lexington, Kentucky, and continuously grazed for two growing seasons.|
|Study 1: Grazed 1995-96||Study 2: Grazed 1997-98|
|Variety||Jun 1997 Rating||Variety||Jul 1999 Rating|
|Alfagraze||63 *||Feast||73 *|
|Wintergreen||60 *||Amerigraze 401+Z||66 *|
|ABT205||58 *||WL326GZ||63 *|
|ABT405||45 *||ABT405||59 *|
|Spredor-3||45 *||Spredor 3||53|
|Magnagraze||35||Saranac AR (H)||34|
|Fortress (H)||25||Fortress (H)||28|
|Rushmore (H)||20||Apollo (H)||23|
|Legacy (H)||20||Arc (H)||9|
|CV, %||36||CV, %||28|
|LSD 0.05||21||LSD 0.05||15|
|* Not significantly different from the highest numerical value in the column based on the 0.05 LSD.
(H) = Hay-type alfalfa
Several endophyte-free varieties of tall fescue proved to be as tolerant of overgrazing as endophyte-infected Ky31 (Ky31+), considered the grazing-tolerant check (Table 2). Cattle Club and Richmond in Study 1 and Festorina and Dovey in Study 2 were as tolerant to overgrazing as Ky31+.
In both studies, endophyte-infected varieties were more tolerant of their genetic equal without the endophyte (Ky31+ vs. Ky31-; Ga Jesup+ vs. Ga Jesup-).
Endophyte infection is not a prerequisite for stand survival under grazing stress, at least in the central Kentucky environment (Table 2). However, both 1998 and 1999 could be characterized as drought years in Kentucky (data not shown). The latter half of the growing season in 1998 was dry, as was all of 1999. In fact, 1999 was the driest year in Kentucky since rainfall records have been kept. Therefore, these data are especially indicative of the stress tolerance of some of the newer, endophyte-free tall fescue varieties, especially Study 2 (Table 2).
Plant breeders have successfully selected for grazing tolerance in alfalfa (Table 1). Considering the severity of the grazing pressure, farmers should feel confident that varieties surviving this treatment should well tolerate occasional lapses in proper pasture rotation.
It is very encouraging that at least a few varieties of endophyte-free tall fescue have proven to be as tolerant of close, continuous grazing as Ky31+ (Table 2). Considering the severity of the drought in 1999 and the closeness of grazing of these plots, farmers can expect the top-performing cultivars in these studies to withstand even extreme stress for short periods of time.
|Table 2. Percent stand of tall fescue varieties sown 3 September 1994 (Study 1, grazed two seasons) and 23 August 1996 (Study 2, grazed three seasons) in Lexington, Kentucky, and continuously grazed.|
|Study 1: Grazed 1995-96||Study 2: Grazed 1997-99|
|Variety||Jun 1997 Rating||Variety||Mar 2000 Rating|
|Ga Jesup +||61||Ky31-||47|
|Ga Jesup -||48|
|* Not significantly different from the highest numerical value in the column based on the 0.05 LSD.
1 '+' indicates variety is endophyte infected; '-' indicates variety is endophyte free. All others are endophyte free.
R.F. Spitaleri, J.C. Henning, D. Ditsch, and G.D. Lacefield
Red clover and white (ladino) clover are the primary pasture legumes for Kentucky. Seeding either alone or in binary mixture will improve grass pasture yield and quality. These legumes differ in agronomic characteristics. It is often uncertain which is more important or more useful in pasture renovation situations. Studies were established in the spring and fall of 1998 in Quicksand and Lexington, respectively, to compare the yield of red clover and ladino clover varieties. The occurrence of the severe drought in 1999 enabled some conclusions about survival under drought stress.
Quicksand was about equal in temperature but wetter than Lexington from April through November (data not shown). The yield and persistence data from both locations are shown in Tables 1 and 2. In general, ladino persisted better than red clover in both trials, but this was especially true for Lexington. Yields of red clover were greater than ladino clover in both locations, but the difference was greatest at the drier site, Lexington.
Certified versus Uncertified Red Clover. Three common medium red clovers were included in both trials (Common X, Y, Z) along with uncertified Kenland for comparison. In nearly every case, the uncertified red clovers were inferior to improved, certified varieties of red clover. Uncertified Kenland ranked at or near the bottom for red clover yield and persistence.
Due to the biennial growth habit of red clover, little growth should be expected from these varieties past the first cutting or two in 2000, while the ladino can be expected to persist longer. These studies show that red clover is a higher yielding clover that will produce more summer yield, especially under hotter conditions. During drought, ladino does not yield well but appears to have superior persistence to red clover, especially when red clover is in its second production year.
|Table 1. Dry matter yields (tons/acre) and percent stand of red and white clover varieties sown 13 August 1998 at Lexington, Kentucky.|
|Variety||% Stand 18 Nov 1999||1999 Harvests||1999 Total|
|May 25||Jun 30||Aug 18|
|Commercial Varieties - Available for Farm Use|
|Kenland Certified||27.5||3.09 *||0.67 *||0.33 *||4.10 *|
|Cinnamon||22.5||3.25 *||0.52 *||0.26 *||4.03 *|
|Greenstar||12.5||3.06 *||0.61 *||0.21 *||3.87 *|
|Common Y||12.5||3.11 *||0.52 *||0.17||3.80 *|
|Solid||12.5||3.11 *||0.49||0.19||3.79 *|
|Kenstar||12.5||3.18 *||0.45||0.16||3.78 *|
|Syn 3-92||22.5||3.01 *||0.51||0.16||3.68|
|Common Z||3.00||2.97 *||0.54 *||0.12||3.63|
|Common X||0.00||2.94 *||0.5||0.14||3.58|
|Royal Red||12.5||2.92 *||0.43||0.21 *||3.56|
|Kenland Uncertified||5.00||2.68||0.57 *||0.13||3.39|
|Regal Ladino (white)||45.0 *||1.66||0.2||0.01||1.88|
|California Ladino (white)||32.5 *||1.4||0.17||0.05||1.61|
|Experimental Varieties - Not Available for Farm Use|
|Freedom!||27.5||3.26 *||0.67 *||0.30 *||4.24 *|
|97L381749||17.5||3.11 *||0.41||0.23 *||3.75 *|
|* Not significantly different from the highest value in the column based on the 0.05 LSD.|
|Table 2. Dry matter yields (tons/acre) and percent stand of red and white clover varieties sown 13 April 1998 at Quicksand, Kentucky.|
|Variety||% Stand 2 Sep 1999||1998 Total||1999 Harvests||1999 Total||2-yr Total|
|May 19||Jun 23||Jul 23||Sep 2||Oct 26|
|Commercial Varieties - Available for Farm Use|
|Kenland Certified||71.3||1.34 *||2.22 *||1.68 *||0.97 *||0.88 *||0.81 *||4.87 *||6.21 *|
|Royal Red||67.5||1.08||2.39 *||1.49||1.01 *||0.84 *||0.64||4.90 *||5.98 *|
|Kenstar||58.8||1.24 *||2.1||1.54 *||0.96 *||0.87 *||0.69 *||4.61 *||5.84 *|
|Greenstar||62.5||1.15 *||2.09||1.61 *||0.96 *||0.71||0.65||4.66 *||5.81 *|
|Cinnamon||63.8||1.1||2.16 *||1.42||0.97 *||0.84 *||0.68||4.56 *||5.66|
|Solid||66.3||1.06||2||1.53 *||0.98 *||0.80 *||0.63||4.52 *||5.58|
|Common Y||42.5||0.87||2.38 *||1.36||0.76||0.5||0.49||4.50 *||5.36|
|Common X||18.8||0.92||2.42 *||0.99||0.66||0.49||0.3||4.08||5|
|Kenland Uncertified||15.0||1.01||2.15 *||1.1||0.71||0.48||0.35||3.95||4.96|
|Common Z||12.5||0.75||2.36 *||1.2||0.64||0.4||0.34||4.2||4.95|
|California Ladino (white)||87.5 *||0.95||2.03||0.73||0.6||0.25||0.38||3.37||4.32|
|Regal Ladino (white)||87.5 *||0.99||1.91||0.88||0.52||0.18||0.41||3.32||4.31|
|Experimental varieties - Not Available for Farm Use|
|ZR9701R||72.5||1.02||2.55 *||1.31||0.97 *||0.80 *||0.67||4.83 *||5.85 *|
|Freedom!||73.8||1.25 *||1.72||1.73 *||1.05 *||0.88 *||0.74 *||4.50 *||5.75 *|
|Syn 3-92||17.0||1.06||2.39 *||1.18||0.8||0.38||0.36||4.37||5.43|
|* Not significantly different from the highest numerical value in the column based on the 0.05 LSD.|
N.L. Taylor, M. Collins, and R.E. Mundell
A series of experiments was conducted over several years to elucidate the relationship of pubescence to drying rate and dustiness in red clover (Trifolium pratense L.). Faster drying rates and decreased dustiness are desirable attributes, and it is possible by selection to modify pubescence. Five cycles of recurrent selection reduced pubescence on stems of Kenland red clover, resulting in the development of the experimental strain, Freedom!, so named for its freedom from dustiness.
In forage yield trials at Lexington and Quicksand, Kentucky, Freedom! was not significantly different from Kenland, its parent variety. At Princeton, Freedom! was not significantly different from Kenland in leafhopper resistance, stem diameter, and mildew resistance, but it had less pubescence than Kenland.
In seed yield trials at Lexington, Freedom! yielded 318 pounds per acre compared to 338 for Kenland. This difference was not statistically significant, but, because seed yield is very important to the success of a variety, it was decided to measure seed yields in 2000 before making a decision on release of Freedom!. Sufficient breeder seed should also be available at this time.
D.C. Ditsch and W. Turner
Forage quality is generally improved when forage legumes are part of the livestock diet. Research has proven that the superior nutritive value and intake of legume forage often increases individual animal productivity compared to grass alone. Unfortunately, short-term persistence of legume species such as red clover requires frequent reestablishment, adding to the cost of forage production and complicating pasture management.
One legume species that has shown promise at the research level has been Kura clover (Trifolium ambiguum Bieb.) (Taylor et al. 1998). Kura clover is a long-lived perennial introduced from the Caucasian region of Russia. Kura clover closely resembles white clover but spreads vegetatively by rhizomes (horizontal underground stems). Kura's persistence is due primarily to its ability to spread over substantial distances by way of rhizome growth.
Unfortunately, low seedling vigor has been identified as a major limitation to successful kura clover establishment (Taylor and Henry 1989; Caradus 1994; Ehlke et al. 1994). Attempts to establish kura clover by seeding at the recommended rate of 10 to 12 lb per acre often fails due to extremely limited aboveground growth and subsequent weed pressure during the first growing season. However, research by Scott and Mason (1992) suggested that kura clover could be successfully established by planting rhizome fragments. This technique is more commonly referred to as "sprigging," whereby plant rhizomes and/or stolons (aboveground root system) are mechanically harvested by shallow cultivation, collected, and redistributed over an area that has been prepared by various degrees of tillage.
Objectives of this study were to determine the optimal sprigging rate (plants/ft2) and transplant method for kura clover establishment.
The first year of a three-year field study was initiated at the University of Kentucky Robinson Experiment Station in the spring of 1997. The experimental site was located on a Pope silt loam soil (well-drained, alluvial soil derived from sandstone and shale) that was previously managed for no-till corn production.
All treatments were replicated three times in a split-plot experimental design. Main plot treatments were sprig incorporation methods that consisted of surface broadcast only, cultipack only, disk only, and the combination of disk plus cultipack. Subplot treatments were sprigging rates of one, two, three, and four sprigs per square foot. This rate is equivalent to 190, 380, 570, and 760 lb of sprigs per acre, respectively. Individual plot dimensions were 7 ft x 15 ft. The soil surface was prepared for sprigging with a tractor-driven rotary tiller. Sprigging dates were 13 March 1997; 17 March 1998 and 1999. Each year, a new study area adjacent to the previous year's experiment was prepared. Sprigs for the study were collected from an established source of certified cv. "Rhizo" kura clover with the aid of a tractor-driven Bermuda King sprig digger. Sprigs (average length = 6 inches) were hand broadcast at the appropriate rate and immediately followed by incorporation treatments. Treatment effects on sprig survival were measured by counting the number of live kura clover plants twice during the growing season (early and late) using a 6.25 ft2 (2.5ft x 2.5ft) quadrant.
Kura clover sprig survival was highly dependent on the amount and distribution of rainfall during the growing season and the degree of sprig incorporation as indicated by a highly significant year and tillage effect. Table 1 shows the total rainfall for each growing season and the critical 30-day period immediately following sprigging. In 1998, excellent rainfall conditions resulted in a 90 percent, 134 percent, 126 percent, and 100 percent survival of kura sprigs at the one, two, three, and four sprigs per square foot rate, respectively, followed by the disk-only and disk-plus-cultipack treatments. Survival rates above 100 percent indicate growing conditions were adequate enough to promote spreading and the development of daughter plants. In contrast, maximum sprig survival in 1997 and 1999 was 50 percent and 18 percent, respectively (Tables 2 through 4).
In general, kura clover plant populations, measured at the end of the sprigging year, appeared to reach the 25 to 35 percent groundcover threshold recommended for optimal mixed grass/legume forage production at the 4-sprigs/ft2 (760 lb/A) rate when followed by disking. Therefore, vegetative establishment of kura clover can be highly successful provided adequate rainfall or irrigation follows sprigging and sprigs are placed in good contact with the soil.
Allan, B.E., and J.M. Keoghan. 1994. More persistent legumes and grasses for oversown tussock county. Proceedings New Zealand Grassland Association 56:143-147.
Caradus, J.R. 1994. Frost tolerance of Trifolium species. New Zealand J. Agric. Res. 38:157-162.
Ehlke, N.J., C.C. Sheaffer, D.J. Vellekson, and D.R. Swanson. 1994. Establishment of kura clover for seed or forage production. Proceedings, 13th Trifolium Conference, Charlottetown, Prince Edward Island, Canada, June 22-24, 1994.
Scott, D., and C.R. Mason. 1992. Potential for high country pasture improvement from planting or rhizome fragments of spreading legumes. Proceedings, New Zealand Grassland Association 54:127-129.
Taylor, N.L., R. Spitaleri, J.C. Henning, G.D. Lacefield, D.C. Ditsch, and R.E. Mundell. 1998. The 1998 Kura Clover Report. Kentucky Agricultural Experiment Station Progress Report 419.
Taylor, N.L., and D. Henry. 1989. Kura clover for Kentucky. University of Kentucky Cooperative Extension Service Publication AGR-141.
|Table 1. Rainfall during kura clover growing season and 30-day period immediately following sprigging.|
|Year||Total Rainfall (in.)||30-Day Period (in.)|
|Table 2. Kura clover plant counts+ as affected by sprigging rate and method of incorporation (10-14-97).|
|Incorporation Method||Sprigging Rate (plants/ft2)|
|disk + cultipack||0.5||0.6||2||2|
|+ Sprigging date: 3-13-97. Rainfall for growing season = 17.5 inches.|
|Table 3. Kura clover plant counts+ as affected by sprigging rate and method of incorporation (10-26-98).|
|Incorporation Method||Sprigging Rate (plants/ft2)|
|disk + cultipack||0.9||2.8||3.9||2.9|
|+ Sprigging date: 3-17-98. Rainfall for growing season = 35.9 inches.|
|Table 4. Kura clover plant counts+ as affected by sprigging rate and method of incorporation (10-21-99).|
|Incorporation Method||Sprigging Rate (plants/ft2)|
|disk + cultipack||0.3||0.2||0.4||0.8|
|+ Sprigging date: 3-17-99. Rainfall for growing season = 20.9 inches.|
D.W. Hancock and M. Collins
Silage can be described as forage material that is preserved by storage under airtight conditions. Baled silage is produced by baling a crop at moisture concentrations well above those used in hay production, then excluding oxygen by covering with plastic to achieve near-anaerobic conditions. Currently, a considerable amount of baled silage is produced using the stretch-wrap system that covers the crop with multiple layers of a stretch-wrap, low-density polyethylene plastic.
Achieving adequate coverage of plastic film is essential to success in producing silage using the stretch-wrap system. Therefore, the objectives of this study were to compare the storage of stretch-wrap baled silage with conventional round-baled hay and to determine the effects of two, four, and six layers of stretch-wrap plastic on the quality and palatability of baled silage.
Alfalfa forage from an established stand was baled in 4-ft diameter bales at 40 or 50 percent moisture and wrapped using two, four, or six layers of stretch-wrap plastic. Forage from the same field was baled as hay when it reached 20 percent moisture for comparison with silage. Samples were collected and analyzed for crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) before and after the storage period. Hay was stored outside.
Immediately after baling, hay had reduced levels of CP compared with alfalfa baled at the higher moisture levels suitable for silage production. Legume leaves are more brittle at hay moisture levels and are more susceptible to shattering during raking and baling. The amount of plastic coverage significantly influenced NDF and ADF concentrations measured at the end of the storage period (Table 1). Hay was higher in NDF than silage (46 vs. 41 percent for silage) and ADF (34 vs. 31 percent). In this trial, initial moisture did not influence silage NDF or ADF concentrations. However, silage wrapped with two layers of plastic had 43.0 percent NDF compared with only 39.4 percent in silage wrapped with six layers of plastic.
|Table 1. Quality of alfalfa hay and silage.|
|Moisture (%)||Plastic Coverage (layers)||NDF||ADF||CP|
Elevated storage temperatures are typical of silage exposed to air due to holes or insufficient plastic coverage. In this trial, starting three days after baling, temperatures of the two-layer treatment were significantly higher than temperatures of bales with four or six layers. The level of acidity, or pH, of silage is another indicator of the effectiveness of preservation. In this study, silage with two layers of film had higher pH than silage with four- or six-layer bales for alfalfa near 40 percent moisture.
After storage, hay was higher in both NDF and ADF than silage. Weathering that occurs on the exposed surface of hay stored outside removes more of the soluble sugars, minerals, and other digestible constituents than of the fiber constituents. Silage and hay were fed simultaneously to Angus cows, and silage was consistently consumed to a greater extent than hay. Among silage treatments, bales with four or six layers of stretch film were preferred over those with two layers.
Results indicate that two layers of stretch-wrap plastic film are not sufficient to adequately preserve round bale alfalfa silage at this location. Adequate preservation resulted when either four or six layers of stretch-film were used.
C. Teutsch, M. Collins, D. Ditsch, J. Johns, C. May, and L. Clay
Agricultural production in Appalachia is limited by a lack of suitable land. The primary limitation is the sloping topography associated with this region's landscape. Mountaintop removal is a common method of surface mining in Appalachia resulting in more level land that represents a significant resource for grazing livestock. In Kentucky alone, more than 1 million acres of surface mines have been reclaimed as hay and pastureland. The study reported here was established near Chavies, in Perry County, Kentucky, in 1997 to determine sustainable stocking densities for beef cow-calf enterprises on reclaimed mine-land pastures.
The experimental site was located on reclaimed surface-mined land. The 400-acre mountain-top-removal site was divided into two replicates of 30-, 60-, and 90-acre pastures with adjacent area fenced off and left ungrazed for comparison. Each pasture was grazed by 10 Angus-cross cows and their calves, resulting in allowances of 3, 6, or 9 acres per cow/calf unit. The reclamation mixture included orchardgrass, tall fescue, redtop, red clover, white clover, birdsfoot trefoil, sericea lespedeza, and annual.
Cows and calves were weighed at two-month intervals throughout the grazing season. Cow body condition score was rated at the start and end of the grazing season using a scale from 1 to 9, with 1 being emaciated and 9 being extremely fat. Cows were wintered on their respective pastures with supplemental hay fed as needed.
Cows at the highest stocking density (SD) weighed less than those at the medium and low stocking density at the start of the grazing season. This trend continued at the June weigh date (Figure 1). By October, cows at the highest SD weighed less than those at the medium and low stocking densities. Our observations indicate that this difference resulted from insufficient forage available late in the grazing season at the highest stocking density. Cows at the 9-acre allowance were in better condition in October than those at the medium or high SD (Figure 2). However, condition scores of cows on all stocking treatments were within the acceptable range for rebreeding.
Calf weaning weights were reduced in the 30-acre per cow/calf unit treatment in 1998 and 1999 compared with one or both of the other treatments (Table 1). In 1997, calves at the highest stocking density were heavier in June and August but not in October. In 1998, calves from the medium stocking rate were heavier throughout the grazing season.
Calf growth at the highest stocking rate was limited by reduced forage availability. The difference between the medium and low stocking rates can be attributed to maintenance of higher forage quality at the medium stocking rate. Heavier grazing pressure at the medium stocking rate resulted in a vegetative state later in the season, thereby increasing forage quality compared with the highest allowance treatment that allowed 9 acres per cow/calf unit.
These results indicate that reclaimed surface-mined land can be used to produce beef in a cow/calf system. Results to date suggest that allowances in the range of 5 to 6 acres per cow/calf may be optimal, but data collection will continue during two additional years.
|Table 1. Calf weights for 1997, 1998, and 1999 grazing seasons.|
|Allowance per Cow/Calf Unit (acres)||Calf Weight (lb)|
|30||486 a†||494 b||482 b|
|60||504 a||536 a||502 b|
|90||498 a||510 b||524 a|
|† Means followed by the same letter within a year and month are not significantly different according to LSD (P<0.10).|
Figure 1. Stocking density effects on cow body weight averaged over three years.
Figure 2. Stocking density effects on cow body condition score averaged over years. Bars followed by the same letter are not significantly different according to LSD (P<0.10).
Equal opportunity statement