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J. Anim Sci. 2007. 85:536-544. doi:10.2527/jas.2006-489
© 2007 American Society of Animal Science
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ANIMAL PRODUCTION

Effect of species of cool-season annual grass interseeded into Bermudagrass sod on the performance of growing calves1

P. A. Beck*,2, C. B. Stewart*, J. M. Phillips*, K. B. Watkins{dagger} and S. A. Gunter*

* University of Arkansas, Division of Agriculture, Southwest Research and Extension Center, Hope 71801; and and {dagger} Department of Agricultural Economics, Rice Research and Extension Center, Stuttgart 72160


   Abstract
Top
 Abstract
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS
 LITERATURE CITED
 
Two experiments were conducted to evaluate the effect of species of cool-season annual grass on the growth of stocker cattle over 3 yr. In Exp. 1, the small grains (SG) oat (O), rye (R), and wheat (W), or combinations of SG and annual ryegrass (RG), were interseeded into Bermudagrass sod in a completely randomized design with a 3 x 2 factorial arrangement of treatments. In Exp. 2, RG was planted alone or with O, R, triticale (T), or W in a completely randomized design. Pastures were planted in late October of each year, and seeding rates were 134.4 and 22.4 kg/ha for SG and RG, respectively. In Exp. 1, grazing was initiated on December 18. In Exp. 2, grazing was initiated on December 23 for SG pastures and January 21 or February 16 for RG pastures in yr 1 and on December 8 for all pastures in yr 2. Grazing was managed using the put-and-take method, in which additional calves were added as needed to maintain equal grazing pressure among pastures. In Exp. 1, no interactions (P ≥ 0.28) were detected, so the main effects of SG species and RG addition are discussed. From December 18 to March 12, there were no differences in ADG (P ≥ 0.17), whereas during the spring (from March 12 to May 7), addition of RG increased (P = 0.05) ADG. Using RG increased (P ≤ 0.01) animal grazing-days/hectare and BW gain/hectare. Wheat tended (P = 0.08) to increase BW gain/hectare compared with the other SG, and O tended (P = 0.09) to produce less BW gain/hectare than the other SG. The treatment x year interaction was significant (P ≤ 0.05) in Exp. 2. In yr 1, no differences (P = 0.25) were observed for ADG from December 23 to March 8, but during the spring grazing period (from March 8 to May 5), ADG of calves grazing TRG was less (P ≤ 0.04) than that of those grazing RG, RRG, or WRG. The RRG combination produced more (P ≤ 0.03) BW gain/hectare than ORG, RG, or TRG and tended (P = 0.06) to produce more BW gain/hectare than WRG. The WRG combination produced more (P ≤ 0.05) BW gain/hectare than TRG and RG, and ORG tended (P = 0.09) to produce more BW gain/hectare than RG alone. Pastures planted to R or W produced more (P ≤ 0.05) BW gain/hectare than RG alone or T. During yr 2, there were no differences (P ≥ 0.44) in ADG, BW gain/hectare, or grazing-days/hectare. In conclusion, the choice of cool-season annual to establish is highly weather-dependent, but R and W are generally superior to other small grains, and RG is a necessary complement to SG when interseeding cool-season annuals into Bermudagrass sod.

Key Words: cattle • economics • grazing • ryegrass • small grain


   INTRODUCTION
Top
 Abstract
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS
 LITERATURE CITED
 
Approximately 840,000 calves are produced annually in Arkansas, most of which are sold in the fall. A $0.33/kg difference exists between the average low market price for calves in the fall and the high market price in the spring (Troxel et al., 2002Go). Arkansas production budgets indicate net losses of approximately $111/cow (Hogan et al., 2006Go). Retained ownership of calves by the producer could improve the profitability if calves can be grown economically at a high rate of gain. In the fall and early spring, small-grain (SG) pasture has been extensively used to improve net farm income in the High Plains. This improved net income results from the availability of high-quality forage at a time when it is usually scarce and weaned calves are available at a seasonally low price. Coulibaly et al. (1996)Go stated that grazing stocker cattle on wheat pasture in Oklahoma is one of the most profitable cattle enterprises available to beef producers.

Because much of the land is not suited for cultivation as well as the low machinery requirements, interseeding of SG into warm-season grass sod is common throughout the southeastern United States. The amount and timing of forage production varies by species and location (Kee et al., 1988Go, West et al., 1988Go, Nelson et al., 1993Go). Beck et al. (2005)Go reported that over a 3-yr period ADG and BW gain/hectare did not differ among calves grazing wheat (Triticum aestivum L), ryegrass (RG; Lolium multiflorum Lam. or Lolium perenne L. ssp. multiflorum [Lam.] Husnot, also known as Italian ryegrass), or combinations of cereal rye (Secale cereale L.) with RG or wheat with ryegrass in clean-tilled fields.

Thus, the following experiments were designed to determine the effects of 1) 3 species of SG interseeded into Bermudagrass (Cynodon dactylon [L.] Pers.) sod with or without annual RG, and 2) RG with or without 4 species of SG interseeded into Bermudagrass sod on performance of growing calves, BW gain/hectare, and the economics of cool-season pastures in the southeastern United States.


   MATERIALS AND METHODS
Top
 Abstract
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 IMPLICATIONS
 LITERATURE CITED
 
All animal procedures in the following experiments were conducted in accordance with the recommendations of the Consortium (1999)Go and were approved by the University of Arkansas Institutional Animal Care and Use Committee.

Exp. 1
Twenty-four 0.81-ha Bermudagrass pastures were grazed to reduce the biomass height ( < 5.0 cm) and seeded on 21 to 30 October 2002 to common oat (cv. Bob; University of Arkansas, Fayetteville; Avena sativa L.; O), cereal rye (cv. Wintergrazer 70, Pennington Seed Inc., Madison, GA, R), or soft-red winter wheat (cv. ARLA 85411, University of Arkansas; W), with and without RG (cv. Marshall, Wax Seed Co., Amory, MS) at the University of Arkansas Southwest Research & Extension Center near Hope (33 ° 42' N, 93 ° 31' W), in a 3 x 2 factorial arrangement of treatments (n = 4 pastures/treatment).

Soils in these pastures are primarily Smithdale fine sandy loam but also include areas of Sawyer loam, which are deep, moderately well-drained, and are low in native fertility, with low soil pH and organic matter. The cool-season annual grass treatment combinations were randomly assigned to pasture, before planting at a rate of 134.4 and 22.4 kg/ha for SG and RG, respectively, using a no-till drill (Sukup Mfg, Jonesboro, AR) with 17.8-cm row spacing. All pastures were fertilized with 57 kg of N, P, and K/ha in November after the emergence of seedlings. Ammonium nitrate (57 kg of N/ha) was applied to all pastures in mid January, and SG/RG pastures received an additional 57 kg of N/ha in early March.

Pastures were stocked with 3 calves (2 heifers and 1 steer, with an average BW = 212 ± 5.1 kg) per pasture for fall-winter grazing (3.7 calves/ha). Grazing was initiated on 18 December, when > 1,250 kg of forage DM/ha was accumulated, and was managed using the put-and-take method, as described by Sollenberger and Burns (2001)Go. The 3 original calves were used as tester animals to measure performance, and additional calves were added as needed to maintain an equal grazing pressure among pastures. The calves were offered 0.91 kg/d of a supplement designed to supply 2.58 Mcal of ME, 114 g of mineral premix, and 200 mg of lasalocid (Bovatec; Alpharma Inc., Fort Lee, NJ) prorated for feeding 3 times weekly. The mineral premix (Sunbelt Custom Minerals Inc., Sulphur Springs, TX) contained 14% Ca and 7% P from CaCO3 and Ca2PO4, 5% Mg from MgO, and 14% NaCl, as well as vitamins (661,500 IU of vitamin A/kg, 221 IU of vitamin E/kg, and 66,150 IU of vitamin D/kg), and trace minerals (1,000 ppm of Mn from MnSO4; 2,355 ppm of Fe from FeSO4; 1,250 ppm of Cu from CuSO4; 3,000 ppm of Zn from ZnSO4; 20 ppm of Co from CoCO3; and 25 ppm of I from ethylenediamine dihydroiodide).

At the initiation and end of each grazing period and at 28-d intervals, the calves were weighed after a 16-h fast that was imposed by withholding feed and water. Forage availability was estimated at the beginning of grazing (December 18), at the end of the winter grazing period (March 10), and at the end of the spring grazing period (May 7), using a calibrated rising-plate meter (Michell and Large, 1983Go). Twenty height measurements were taken from each pasture; rising-plate readings were calibrated by clipping the forage within two 30.5 x 30.5-cm quadrants in each pasture. Calibration samples were dried to a constant weight at 50 ° C in a forced-air oven.

Exp. 2
To determine if the addition of SG improves performance and carrying capacity of grazing programs compared with RG alone when interseeding cool-season annual grasses into warm-season perennial grass sod, twenty 0.81-ha Bermudagrass pastures were interseeded with RG or in combination with O (cv. Bob, ORG), R (cv. Wintergrazer 70, RRG), triticale (cv. 2700, x Triticosecale rimpaui Wittm., TRG), or W (cv. Roane, WRG). Pasture establishment, soil fertility, and animal management were the same in Exp. 2 as described for Exp. 1. Winter-annual grasses were seeded each October (average date October 22) into closely grazed Bermudagrass sod, as described in Exp. 1.

Grazing was initiated when 1,250 kg of forage DM/ha was accumulated to support 3 calves/pasture (3 steers, with initial BW = 261 ± 2.4 kg in yr 1; and 2 heifers and 1 steer, with initital BW = 223 ± 5.1 kg in yr 2). Grazing was initiated on December 23 for SG pastures and January 21 or February 16 for RG pastures in yr 1 and on December 8 for all pastures in yr 2. Grazing was managed using the put-and-take method, as described in Exp. 1. Pastures were fertilized with 57 kg of N, P, and K/ha in November after the emergence of seedlings. An additional 57 kg of N/ha was applied as ammonium nitrate in mid January and early March. Calves were offered 0.91 kg/d of the supplement described in Exp. 1. At the initiation and end of each grazing period and at approximately 28-d intervals, the calves were weighed after a 16-h fast that was imposed by withholding feed and water.

During yr 2, forage availability was estimated monthly using a calibrated rising-plate meter (Michell and Large, 1983Go), as described in Exp. 1. To characterize forage quality, samples were collected monthly by hand plucking to mimic the forage consumed by grazing. Samples were dried to a constant weight at 50 ° C in a forced-air oven and ground to pass a 2-mm screen in a Thomas Wiley Laboratory Mill (model 4, Thomas Scientific, Swedesboro, NJ). Forage quality samples were analyzed for DM and ash (AOAC, 1990Go), and NDF and ADF were assayed by the batch procedures outlined by Ankom Technology Corp. (Fairport, NY). Concentration of N was determined by rapid combustion (FP-528, Leco Corp, St. Joseph, MI), and CP was calculated as the percentage of N x 6.25.

Economic Analysis
Net returns of the stocker cattle enterprise were analyzed by assuming retained cattle ownership, with a spring calving cow herd. Price and profitability scenarios were constructed using Arkansas prices from 1991 to 2000 (Cheney and Troxel, 2004Go) of 240 kg of BW, medium-framed, number 1 steers in October and 350 kg of BW steers in May. Values of BW gain were determined by subtracting the initial cost per steer from the sales price per steer and dividing by the amount of BW gain. The value of BW gain averaged $1.49/kg.

The cost of establishing the SG and RG pastures for this study was based on enterprise budgets compiled by the Mississippi State Budget Generator (Agricultural Economics Department, Mississippi State University, Starkville) using input and field operations data from this research site. Actual seed costs from the fall of 2005 were used, which included wheat at $0.34/kg, rye at $0.39/kg, oats at $0.35/kg, triticale at $0.62/kg, and RG at $1.10/kg. Fertilizer costs were based on the actual fertilizer costs during the 2005 to 2006 production year and included ammonium nitrate at $0.32/kg ($0.94/kg N), and 17-17-17 at $0.33/kg ($1.94/kg of N, P, and K). The direct tractor and equipment costs were $27.49/ha, fixed tractor and equipment costs were $16.22/ha, and labor was $11.04/ha.

Costs incurred during weaning were based on the actual costs over the 3-yr period using protocols at the University of Arkansas Southwest Research & Extension Center. Calves were weaned in early October of each year, and standard vaccination protocols were followed. Processing at weaning included treatment for internal and external parasites (Ivomec, Merial, Iselin, NJ), vaccination with 7-way Clostridial antigen plus tetanus (Covexin-8, Schering-Phlough Animal Health Inc., Elkhorn, NE), and vaccination against infectious bovine rhinotracheitis, bovine viral diarrhea, parainfluenza-3, and bovine respiratory syncytial virus (Bovishield-4, SmithKline Beecham Animal Health, Exton, PA). No treatment costs for bovine respiratory disease or losses due to death were incurred during this period. Costs of vaccines and deworming treatment were $7.00 per calf, and the cost of supplement and hay was estimated to be $0.38/d from weaning until the calves were placed on pasture. Supplement and mineral fed while the calves were on pasture was $0.12 and $0.62/kg, respectively.

Statistical Analysis
In Exp. 1, pasture was considered the experimental unit; thus, individual animal performance and BW were analyzed using the MIXED procedure (SAS Inst. Inc., Cary, NC) as a completely randomized design with a 3 x 2 factorial arrangement of treatments; pasture within SG x RG was included in the random statement and was used as the error term (Lentner and Bishop, 1986Go). Body weight gain/ha was calculated using ADG, grazing-days, and stocking rates for each pasture. Body weight gain/hectare was divided into the total cost of pasture production/hectare to determine the pasture cost of gain. Because BW gain/hectare, grazing-days/hectare, pasture cost of gain, and gross return/hectare were calculated based on pasture averages, they were analyzed using the GLM procedure of SAS, using residual error as the error term. Main effects of SG species and RG addition, as well as the interaction, were analyzed. In the event of a nonsignificant (P ≥ 0.10) SG x RG interaction, contrasts (O vs. other SG, R vs. other SG, and W vs. other SG) were used to test the main effects of SG species (Steel and Torrie, 1980Go).

In Exp. 2, the effects of species of winter annual grass and the treatment x year interaction on individual animal performance and BW were analyzed with the MIXED procedure of SAS as a completely randomized design using pasture within treatment x year in the random statement (Lentner and Bishop, 1986Go). In the presence of a year x treatment interaction (P ≤ 0.04), animal performance data were analyzed by year using the MIXED procedure of SAS as a completely randomized design, and pasture within treatment was included in the random statement (Lentner and Bishop, 1986Go). Body weight gain/hectare and pasture cost of gain were calculated as described for Exp. 1. Body weight gain/hectare, grazing-days/hectare, pasture cost of gain, and net return/hectare were analyzed using the GLM procedure of SAS, using residual error as the error term. When a significant (P ≤ 0.05) treatment effect was present, least squares means were separated using predicted differences (Steel and Torrie, 1980Go).

Forage availability prediction equations for the rising-plate data were generated using the REG procedure of SAS using the clipping data for each pasture and collection period. Forage DM/hectare during Exp. 1 was analyzed using the GLM procedure of SAS, using residual error as the error term. The main effects of SG species and RG addition, as well as the interaction, were analyzed; in the event of a nonsignificant (P ≥ 0.10) SG x RG interaction, contrasts (O vs. other SG, R vs. other SG, and W vs. other SG) were used to test the main effect of SG species (Steel and Torrie, 1980Go). Forage DM/hectare and quality constituents of forage collected during Exp. 2 were analyzed as repeated measures using the MIXED procedure of SAS; in the presence of a significant date effect (P < 0.01), least squares means were separated using polynomial contrasts.


   RESULTS AND DISCUSSION
Top
 Abstract
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
IMPLICATIONS
 LITERATURE CITED
 
Exp. 1
No SG x RG interactions (P ≥ 0.28) were detected for animal performance, grazing-days/hectare, BW gain/hectare, or net return/hectare; therefore, main effects of SG species interseeded into Bermudagrass pasture are presented in Table 1Go. Initial BW did not differ (P ≥ 0.69) due to SG species, whereas final BW of W tended (P = 0.09) to be greater than the average of O and R. Species of SG did not affect (P ≥ 0.17) ADG during the winter or spring grazing periods. The number of animal grazing-days/hectare was also not affected (P ≥ 0.24) by species of SG. Total BW gain/hectare of W tended (P = 0.08) to be greater than the average of O and R, whereas BW gain/hectare of O tended (P = 0.09) to be less than the average of R and W, but BW gain/hectare of R pastures did not differ (P = 0.98) from the average of O and W. Pasture cost/kilogram of gain was less (P = 0.05) for W than the average of R and O, and cost of gain was greater (P = 0.03) for O than the average of R and W, whereas cost of gain for R did not differ (P = 0.70) from W or O. Net return/hectare of O tended (P = 0.09) to be less than the average of R and W, whereas net return/hectare of W tended (P = 0.06) to be superior to the average of R and O.


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  		Table 1. Main effects of species of small grain interseeded into Bermudagrass sod on the performance of calves in Exp. 11
 
Climatic conditions can have a large impact on the growth of winter annual grasses and may affect species differently. During the 2002 to 2003 grazing season, precipitation was considerably below normal during September, November, January, February, and March (Figure 1Go), and temperatures were below normal during November and February (Figure 2Go). Residual forage DM did not differ (P ≥ 0.13) due to SG species on March 10 (average 884 ± 43.5 kg/ha across SG) or on May 7 (average 1,464 ± 65.8 kg/ha across SG), which indicates that stocking rate was equalized across treatments in proportion to forage production.


Figure 1
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  		Figure 1. Actual and normal (30-yr average) precipitation by year from September through May at the University of Arkansas Southwest Research & Extension Center near Hope, AR.

 

Figure 2
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  		Figure 2. Actual and normal (30-yr average) average daily temperature by year from September through May at the University of Arkansas Southwest Research & Extension Center near Hope, AR.

 
Based on animal performance, the ranking of SG observed in this experiment is similar to previous reports. In clean-till crop fields, Beck et al. (2005)Go found that calves grazing O did not perform as well as calves grazing W or R over a 3-yr grazing study, but calves grazing R or RRG had greater performance during cool, dry years compared with W, O, and RG alone. During winters with milder temperatures, RG, W, and WRG were superior to R (Beck, et al., 2005Go). Beck et al. (2005)Go also reported that pastures planted to W or containing W in forage blends produced equivalent or greater net returns in 2 yr of the 3-yr study and were superior to R across the 3-yr study.

The effect of addition of RG to SG interseeded into Bermudagrass is presented in Table 2Go. Initial BW did not differ (P = 0.97), whereas addition of RG increased (P < 0.01) final BW. Average daily gain during the winter did not differ (P = 0.25), whereas ADG of calves grazing RG during the spring was greater (P = 0.05) than ADG of calves grazing SG only. Addition of RG to SG also increased (P = 0.01) the number of animal grazing-days/hectare and increased (P < 0.01) BW gain/hectare. Pasture cost of gain was numerically (P = 0.15) less for RG than SG alone, and net return/hectare was increased (P = 0.02) by the addition of RG to SG pasture. Forage DM yield did not differ due to RG addition (P = 0.41) on March 10. At the end of the spring grazing period (May 7), addition of RG to SG pastures increased (P < 0.01) forage DM production by 17% from 1,350 ± 52.3 for SG alone to 1,582 ± 52.3 with addition of RG to SG.


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  		Table 2. Main effect of ryegrass (RG) addition to small grains interseeded into Bermudagrass sod on the performance of calves in Exp. 11
 
Advantages offered by RG addition to grazing programs has also been noted by Coffey et al. (2002)Go and Beck et al. (2005)Go. Annual RG produces a high percentage of its growth later in the spring, extending the grazing season normally associated with SG-based pastures. If climatic conditions are mild and wet there can also be large amounts of forage growth throughout the winter (Beck et al., 2005Go). Coffey et al. (2002)Go reported that over a 3-yr period BW gains of growing calves were similar when grazing RG or blends of RG and wheat or rye.

Exp. 2
Considering results of Exp. 1, RG appears to be an essential addition for grazing programs to produce the highest possible animal performance, BW gain/hectare, and enterprise profitability. Experiment 2 was designed to determine if addition of SG when interseeding cool-season annual grasses into warm perennial grass sod improves performance and carrying capacity of grazing programs compared with RG alone. Because year x treatment was significant (P ≤ 0.04) for initial BW, ADG, grazing-days/hectare, and BW gain/hectare, data from Exp. 2 are shown by year in Tables 3Go and 4Go. During the 2003 to 2004 grazing season (Table 3Go), initial BW of calves grazing RG was heavier (P < 0.01) than ORG, RRG, TRG, and WRG. The difference in initial BW was caused by the 29- to 55-d delay in initial stocking of the RG pastures in relation to pastures containing SG because precipitation was below normal during November and December 2003 (Figure 1Go) and cool-weather encountered during the fall (Figure 2Go). Precipitation was near normal during January, February, and March but below normal during April (Figure 1Go). Temperatures were below normal during February and above normal during March (Figure 2Go). Final BW of calves grazing RG and RRG was heavier (P ≤ 0.05) than calves grazing WRG or TRG, whereas RG tended (P = 0.07) to have greater final BW than ORG. Winter ADG did not differ (P = 0.25) among ORG, RRG, TRG, and WRG. Average daily gain during the spring grazing period was less (P ≤ 0.04) for TRG than RG, RRG, and WRG, whereas ORG was intermediate and did not differ (P ≥ 0.11) from the other treatments. Adding SG to RG pastures increased (P < 0.01) grazing-days/hectare. The RRG combination produced more (P = 0.03) than TRG, whereas ORG and WRG were intermediate and did not differ (P ≥ 0.25) from RRG or TRG. The RRG combination produced more (P ≤ 0.03) BW gain/hectare than ORG, RG, and TRG and tended (P = 0.06) to produce more BW gain/hectare than WRG. The WRG combination produced more (P ≤ 0.05) BW gain/hectare than TRG and RG, and ORG tended (P = 0.09) to produce more BW gain/hectare than RG alone. Triticale planted with RG did not produce more (P = 0.90) BW gain/hectare than planting RG alone. In clean-tilled crop fields, Beck et al. (2005)Go reported that RG planted by itself did not perform as well as W and R grown alone or in combination with RG during a cold grazing season, but pastures planted to R or combinations including R produced more BW gain/hectare than fields that were planted to O, RG, W, and WRG.


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  		Table 3. Effect of species of cool-season annual grass interseeded into Bermudagrass sod on performance of calves in Exp. 2, yr 11
 

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  		Table 4. Effect of species of cool-season annual grass interseeded into Bermudagrass sod on performance of calves in Exp. 2, yr 21
 
The failure of T to provide additional animal gains or increase carrying capacity of pastures compared with RG alone was not expected. Drake and Orloff (2005)Go reported that increasing the defoliation interval of triticale increased cumulative forage production, indicating that repeated defoliation by grazing calves may have affected forage production of the triticale component of pastures.

Cost of BW gain in TRG pastures was greater (P ≤ 0.05) than the average of the other treatments, and this was due to the higher seed cost of triticale ($0.62/kg) and lack of increased forage or animal production compared with RG alone. Net return/hectare was least (P < 0.01) for RG, due to the lack of fall forage production resulting in increased cost of feeding calves from weaning until initiation of grazing. The combinations ORG and WRG produced greater (P ≤ 0.03) net return/hectare than TRG. Wheat planted with RG and ORG tended (P ≤ 0.12) to be more profitable than RG alone. Profits produced by RRG were greater (P ≤ 0.04) than ORG and tended (P = 0.07) to be greater than WRG. Beck et al. (2005)Go reported BW gain during the fall and winter grazing period were more valuable than gain during the spring grazing period ($1.39 and 0.52/kg value of gain for ownership of cattle from October to March and March to May, respectively), and cattle ownership during the fall and winter was more profitable than during the spring (average profit over the reported 3-yr period $101 and $– 40/calf, respectively). In the spring, additional forage is usually available and stocking rates must be increased to efficiently utilize the abundant growth during this season. Clary and Rouquette (2004)Go compared the profitability of purchasing cattle in the fall to purchasing calves in the spring. These researchers found that purchasing calves in the fall for spring grazing was more profitable than waiting to purchase these calves in the spring even though this would require considerable feed expenses. In clean-till fields in northern Arkansas, Beck et al. (2005)Go reported that profitability of grazing pastures containing R were greater when cold weather limited growth of W, RG, and O forage, but R alone was not as profitable as RG, W, and WRG during years with a mild winter. In Alabama, Kouka et al. (1994)Go reported that O were more profitable than a blend of R and RG, which was more profitable than R planted alone.

During the 2004 to 2005 grazing season (Table 4Go), no differences were observed (P = 0.90) in initial BW. All pastures were stocked on the same date because timely rainfall patterns (Figure 1Go) and mild temperatures (Figure 2Go) during the fall allowed adequate forage growth for all treatments. Final BW did not differ due to treatment (P = 0.89), averaging 378 ± 8.3 kg. Forage growth was adequate during the winter grazing period to produce average gains of 0.69 ± 0.07 kg/d, which did not differ (P = 0.80) across treatment. Spring ADG also did not differ (P = 0.31), averaging 1.24 ± 0.08 kg/d. Residual forage DM/hectare was not affected (P = 0.22) by treatment but followed a quintic (P < 0.01) relationship with harvest date, indicating that stocking rate was equalized across treatments in proportion to forage production. Pastures contained an average of 2,272 ± 175.6 kg of forage DM/hectare in December and 2,221 ± 175.6 kg/ha in January; forage DM increased to 4,462 ± 175.6 kg/hectare in February but decreased to 3,636 ± 175.6 and 3,637 ± 175.6 kg/ha in March and April, respectively, and increased once again to 5,502 ± 175.6 kg/ha in May.

Forage diet samples did not differ (P ≥ 0.25) in CP, NDF, or ADF due to treatment. Although quality of the winter annual forages can be considered adequate for growing calves throughout the grazing season, seasonal changes were observed in CP, NDF, and ADF. Crude protein exhibited a quintic (P < 0.01) relationship with harvest date; forages collected in December, January, February, March, April, and May contained 26, 24, 27, 25, 29, and 22 ( ± 0.60)% CP, respectively. Neutral detergent fiber exhibited a quartic (P < 0.01) relationship with harvest date; forages collected in December, January, February, March, April, and May contained 40, 52, 49, 43, 45, and 47 ( ± 0.59)% NDF, respectively. Acid detergent fiber exhibited a quintic (P < 0.01) relationship with harvest date; forages collected in December, January, February, March, April, and May contained 19, 27, 24, 23, 21, and 22 ( ± 0.45)% ADF, respectively. The reduced CP during January and increased fiber content during January and February can be attributed to senescence of leaves due to reduced forage growth during cooler weather. This senescence was followed by the increased CP and decreased fiber content associated with the initiation of spring forage regrowth in March and April, leading to the increased maturity of forages causing reduced CP and increased fiber content in May.

During the 2004 to 2005 grazing season, grazing-days/hectare did not differ (P = 0.44) due to treatment (Table 4Go). Because neither animal performance nor carrying capacity differed, BW gain/hectare did not differ (P = 0.59) due to treatment. In southern Georgia, Utley et al. (1976)Go reported no differences in ADG or BW gain/hectare for calves grazing oats or RG over a 3-yr period. In the current study, because performance and production/hectare was not affected by treatment, cost/gain of RG planted alone was less (P < 0.01) than when planted in combination with O, R, and W. Cost/gain of the TRG combination was greater (P < 0.01) than ORG, RRG, and WRG. Net return/hectare was not affected (P = 0.13) by forage treatment. Over a 3-yr period, ADG and BW gain/hectare were reported by Beck et al. (2005)Go to be greatest for RG and W planted alone, as well as RRG and WRG combinations. Cleere et al. (2004)Go reported that planting RRG combinations resulted in gains/hectare ranging from 426 kg with set stocking to 884 kg when stocking rates were increased in the spring.

Winter ADG by calves in these experiments are generally lower than performance of calves grazing cool-season grasses planted into dedicated crop fields reported by Horn et al. (1995)Go, Cleere et al. (2004)Go, and Beck et al. (2005)Go, but are similar to performance of calves grazing interseeded forages reported by Coffey et al. (2002)Go and Gadberry et al. (2004)Go. Utley et al. (1976)Go reported that calves grazing interseeded RG or oats gained 0.07 kg less/d and produced 254 kg of BW gain/ha less than calves grazing RG or oats grown in a prepared seedbed. Beck et al. (2005)Go reported that ADG during the winter ranged from 0.85 to 1.56 kg/d for calves grazing cool-season annual grass pastures grown in a prepared seedbed. Cleere et al. (2004)Go reported that steers grazing a RRG gained from 1.01 to 1.28 kg/d from December to May across 2 stocking rates and grazing systems. Horn et al. (1995)Go reported BW gains of unsupplemented steers grazing wheat pasture in Oklahoma ranged from 0.80 to 0.97 kg/d over a 3-yr period during the fall/winter grazing period. In southeastern Arkansas, BW gains reported by Coffey et al. (2002)Go ranged from 0.20 to 0.89 kg/d during the December to January grazing period over a 3-yr period for calves grazing cool-season annual pastures interseeded into Bermudagrass. Gadberry et al. (2004)Go reported that ADG of heifers grazing WRG interseeded into Bermudagrass pastures averaged 0.74 kg/d from December to March, even though corn and de-oiled rice bran were supplemented at 1% of BW.

When cool-season annual grasses are high in quality and can support high performing cattle through the winter if adequate forage allowance is maintained, performance < 0.91 kg/d by calves grazing cool-season annuals during the winter is also a common occurrence. Although forage allowance of pastures in the current study were adequate to support growing calves at the initiation of grazing (averaging 132 kg of forage DM/100 kg of BW), it is evident that forage allowance or forage mass during the winter in Exp. 1 and yr 1 of Exp. 2 fell below the threshold identified by Redmon et al. (1995Go; forage allowance of 20 to 24 kg of DM/100 kg of BW and forage mass of 1,243 to 1,339) for optimal forage DMI, OM digestibility, and ADG of wheat pasture in Oklahoma. This restriction in forage allowance during the fall and winter grazing period is commonly encountered with grazing programs based on cool-season annual grasses interseeded into warm-season grass sod and is a classic opportunity to utilize supplementation programs such as that designed by Horn et al. (1995)Go where grain- or by-product-based energy supplements were offered to growing calves at 0.75% of BW, increasing stocking rate by 22 to 44% and increasing ADG by 0.15 kg.

During spring, ADG observed in this study ranged from 0.89 to 1.33 kg/d across treatments and years and were similar to performance of growing calves grazing interseeded cool-season annual grasses in the spring reported by Beck et al. (2002)Go, Coffey et al. (2002)Go, and Gadberry et al. (2004)Go. During spring, performance of calves grazing interseeded cool-season annual grasses was also similar to performance of calves grazing cool-season grasses planted into dedicated crop fields reported by Beck et al. (2005)Go, Gunter et al. (2005)Go, and Phillips et al. (2005)Go.


   IMPLICATIONS
Top
 Abstract
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS
LITERATURE CITED
 
This research was conducted to compare gains of growing cattle grazing small grains, annual ryegrass, or combinations of small grains and annual ryegrass interseeded into Bermudagrass sod in Arkansas. The selection of which cool-season annual combination to interseed into Bermudagrass sod is dependent on climatic conditions. However, interseeding rye or wheat is generally superior in animal performance and profitability to other small grains. In southern Arkansas, there appears to be little advantage in utilization of oats in the interseeding program, and triticale offered no benefit compared with planting annual ryegrass alone. Annual ryegrass is a necessary addition when interseeding cool-season annuals into Bermudagrass sod for grazing programs to produce the highest possible animal performance, BW gain/hectare, and profit-ability.


   Footnotes
 
1 This project was conducted with funding from the Univ. of Arkansas Agric. Exp. Sta., Hatch Project No. AR001735. The authors wish to express their appreciation to Pat Capps, Josh Loe, and Clint Cornelius for technical assistance in completing this project. Back

2 Corresponding author: pbeck{at}uaex.edu

Received for publication July 21, 2006. Accepted for publication September 14, 2006.


   LITERATURE CITED
Top
 Abstract
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS
 LITERATURE CITED
 


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