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ANIMAL PRODUCTION |
* Southwest Research and Extension Center, University of Arkansas, Hope 71801;
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Department of Animal Science, University of Arkansas, Fayetteville 72701;
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Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville 72701;
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Department of Agricultural Economics, Rice Research and Extension Center, University of Arkansas, Stuttgart 72601; and
# Livestock and Forestry Branch Station, University of Arkansas, Batesville 72501
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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0.29) and was greater (P < 0.01) than that of WR, which was greater (P < 0.01) than that of KY-31. During 2005 to 2006, BW gain per hectare was greater (P < 0.01) for steers grazing RG than those of NE and WR, which did not differ (P 
0.14). Body weight gain per hectare was least (P < 0.01) for steers grazing KY-31. Average net return of NE tall fescue was greater (P < 0.01) than KY-31, but profitability of NE did not consistently differ from cool-season annuals. Across the 3-yr study, NE tall fescue produced net returns per hectare of $219; this level of profitability would require 4 yr for a new planting of NE tall fescue to break even. Novel endophyte tall fescues offer potential benefits related to decreased risk of stand establishment of annual forage crops, longer growing season, and acceptable animal performance.
Key Words: cattle • Festuca arundinacea Schreb. • Lolium perenne L. ssp. multiflorum (Lam.) Husnot • Neotyphodium coenophialum • Neotyphodium lolii • Secale cereale L
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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). Chemical composition indicates tall fescue is high quality during the fall and early spring (Beck et al., 2006), but grazing steers exhibit reduced growth rates and elevated body temperatures caused by ergot alkaloids produced by fungal endophytes (Neotyphodium coenophialum, Neotyphodium lolii) present in the forage. These ergot alkaloids enable the tall fescue to persist in harsh conditions. Endophyte-free tall fescue provides excellent animal performance (often >1.8 kg/d; Thompson et al., 1993) but does not tolerate drought and grazing resulting in complete stand loss in <4 yr (Gunter and Beck, 2004). Endophytes have been discovered that produce very little or no ergot alkaloids; these novel endophytes (NE) have been promoted to combine the advantages of plant persistence with increased animal performance of fescues not containing a toxin-producing endophyte (Bouton et al., 2002). Several recent experiments have reported performance of growing cattle grazing NE and toxic endophyte tall fescue (Parish et al., 2003; Nihsen et al., 2004; Hopkins and Alison, 2006); to date there have been no comparisons to cool-season annual grasses. Thus, the following study compared performance and economics of growing cattle grazing cool-season annuals, toxic endophyte-infected KY-31 tall fescue, or tall fescue varieties infected with NE.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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All animal procedures were conducted in accordance with recommendations of FASS (1999) and were approved by the University of Arkansas Institutional Animal Care and Use Committee.
Steers were crossbred (English x Continental) and were stratified by BW and breed characteristics to each forage treatment. Steers were purchased at a local sale barn by a cooperator and received at the research site. At the time of receiving, steers were processed and vaccinated, as described by Beck et al. (2005). Before turn out on pasture, steers were implanted with 40 mg of trenbolone acetate and 8 mg of estradiol (Revalor-G, Intervet Inc., Desoto, KS). While on pasture, a custom- blended mineral mixture (Sunbelt Custom Minerals Inc., Sulfur Springs, TX) was offered ad libitum in weather vane-type mineral feeders located in each pasture. The mineral mixtures contained (as-fed basis) 14% Ca and 7% P from CaCO3 and Ca2PO4, 5% Mg from MgO, and 14% NaCl, as well as vitamins (661,500 IU/kg of vitamin A, 221 IU/kg of vitamin E, and 66,150 IU/kg of vitamin D) and trace minerals (1,000 ppm Mn from MnSO4, 2,355 ppm Fe from FeSO4, 1,250 ppm Cu from CuSO4, 3,000 ppm Zn from ZnSO4, 20 ppm Co from CoCO3, and 25 ppm I from ethylenediamine dihydroiodide) designed to meet the NRC (1996) requirements. Steers were weighed after withholding feed and water for 16 h at the beginning and end of each grazing period and at 28-d intervals. Body weight gain per hectare was calculated using ADG, grazing days, and stocking rate.
Pasture Establishment and Measurements
The study occurred on 24 ha located at the University of Arkansas Division of Agriculture Livestock and Forestry Branch Station located northwest of Batesville (35°50' N, 91°48' W) on Peridge silt loam soil, which is a deep, well-drained upland soil (Ferguson et al., 1982). Novel endophyte tall fescues were Jesup infected with AR542 endophyte (Jesup AR542, MaxQ, Pennington Seed Inc., Madison, GA) and HiMag infected with Number 11 endophyte (HM11, University of Arkansas, Fayetteville). Novel endophyte tall fescues were established in 12 pastures (0.81 ha each) by drilling 22 kg/ha of seed into prepared seedbeds in September 2002. Endemic endophyte Kentucky 31 (KY-31) tall fescue pastures (n = 6), established in 1996, were used for comparison to the NE pastures. This comparison was deemed appropriate, because the normal decision of producers would be whether to replace an existing stand of endemic endophyte-infected tall fescue with NE tall fescue.
A blend (1:1, wt/wt) of soft red winter wheat (Delta King 9027, Triticum aestivum L.) and cereal rye (Wintergrazer 70, Pennington Seed Inc., Secale cereale L.) was planted in 6 pastures at a rate of 136 kg/ha into a prepared seedbed in early September of 2003, 2004, and 2005; these pastures were referred to as wheat-cereal rye (WR). Annual ryegrass (RG, Marshall, Wax Seed Co., Amory, MS) was seeded at 45 kg/ha into a prepared seedbed in early September of 2004 and 2005. Forage treatments were randomly assigned to pastures at the onset of the study. Each fall, pastures were fertilized according to soil test to meet P and K requirements using diammonium phosphate and potash (Chapman, 1998). Tillage operations included offset disking and chisel plowing, followed by use of a finishing disk, cultipacker, and a grain drill for seeding. Pastures received 67 kg of N/ha each fall from ammonium nitrate and were topdressed with 145 kg of urea/ha in mid-February to deliver an additional 67 kg of N/ha.
Visual estimation of forage quality and availability was used for establishing stocking and removal dates during 2002 to 2003. During 2003 to 2004 and 2004 to 2005, stocking date and removal decisions were based on forage availability estimated monthly using a calibrated rising-plate meter (Michell and Large, 1983). Beginning in September each year, 20 height measurements were taken from each pasture monthly; rising-plate readings were calibrated by clipping the forage within a 30.5 x 30.5-cm quadrant in each pasture. Additional forage samples were collected monthly by hand-plucking to mimic forage consumed by cattle to characterize forage quality. Rising-plate calibration and forage quality samples were dried to a constant weight at 50°C in a forced-air oven. Dry weights of rising-plate calibration clippings were used to relate forage mass (kg/ha) to plate height within each forage type using linear regression for forage mass prediction (R2 0.88) using the REG procedure (SAS Inst. Inc., Cary, NC).
Forage quality samples were ground to pass a 2-mm screen in a Wiley Laboratory Mill (model 4, Thomas Scientific, Swedesboro, NJ) and were analyzed for DM and ash (AOAC, 1990). Neutral detergent fiber 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. Forage digestibility was estimated by 48-h, in situ DM degradability (DMD) using 4 ruminally cannulated heifers (BW = 431 ± 53.9 kg) maintained on ryegrass silage. The silage (12.3% CP, 51.2% NDF, and 33.7% ADF; DM basis) and fresh water was offered in quantities sufficient for ad libitum intake. Forage quality samples for each pasture and collection date were weighed (0.5-g aliquots) into nylon bags (7 x 7 cm; 25-µm pore size) and heat-sealed at the top using an impulse sealer (Model CD-200, National Instrument Co. Inc., Baltimore, MD). Samples were soaked in water for 20 min before ruminal incubation for 48 h in a mesh nylon bag. Upon removal, samples were washed in a hand-operated washer (Wonder Clean, Wonder Wash Corp., Bala Cynwyd, PA) 10 times for 2 min each until the rinse water remained clear, then dried at 100°C for 24 h.
Stand counts of tall fescue pastures were based on grid-frame quadrant readings. The quadrant consisted of a 0.76 x 0.76-m, steel-wire frame divided into twenty-five 0.15 x 0.15-m cells. The percentage of cells containing at least 1 live tall fescue crown (or partial crown, not overhanging leaves) was averaged across 50 random throws/pasture during each fall and spring to determine the long-term stand persistence. Endophyte infection levels of pastures were verified during the spring of 2005 by sampling 25 tiller bases from each pasture using a tissue-print immunoblot (Gwinn et al., 1992).
Animal Measurements
Initial stocking date and date of removal from pasture along with the calendar grazing days for each forage treatment are presented in Table 1. The pastures (n = 4/treatment in 2003 to 2004 and n = 6/treatment in 2004 to 2005 and 2005 to 2006) were stocked with 3 steers (3.7 steers/ha) for fall and winter grazing each year (initial BW = 199 ± 2.2, 229 ± 3.7, and 228 ± 2.4 kg, for 2003, 2004 to 2004, 2005, and 2005 to 2006, respectively). Steers were removed from the pastures when the forage allowance became limiting to calf growth using the forage allowance (20 to 24 kg of DM/100 kg of BW and forage mass of 1,243 to 1,339 kg/ha) for cool-season annual grasses defined by Redmon et al. (1995).
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). During the spring of 2006, steers began grazing WR pastures on March 1, RG pastures on March 5, and tall fescue pastures on March 17 (Table 1). Steers were removed from the pasture when the forage allowance (forage mass of <1,243 kg/ha) or quality (<12% CP and <60% TDN; NRC, 1996) became limiting for growth. Two steers were removed from a HM11 pasture on April 4 because of limited forage availability during the spring of 2006. All steers were removed from KY-31 pastures on April 20, 2006, because daily ambient temperatures increased by 8°C, from 22 to 30°C, from the previous week, causing symptoms of heat stress (panting, excessive salivation, and standing in mud by the water source), which resulted in 2 mortalities judged to be associated with clinical signs of fescue toxicosis (Stuedemann and Hoveland, 1988). Grazing was terminated on May 11 for WR, May 26 for RG, June 17 for HM11, and June 22 for Jesup AR542. Economic Analysis
The cost of establishing WR, RG, and NE pastures for this study (Table 2) was based on enterprise budgets compiled by the Mississippi State Budget Generator (Agricultural Economics Department, Mississippi State University, Starkville). The seed costs included the following: wheat, $0.26/kg; rye, $0.42/kg; RG, $0.95/kg; and NE tall fescue, $8.82/kg. Fertilizer costs included the following: ammonium nitrate, $0.24/kg; urea, $0.33/kg; diammonium phosphate, $0.32/kg; and potash, $0.31/kg. The custom rate for fertilizer application was $6.18/ha. Enterprise budgets were generated using input and field operations data from the research site. Direct and fixed tractor costs were $16.82 and 15.76/ha, respectively. Direct and fixed equipment costs were $5.73 and 12.18/ha, respectively. Expenses also included 2.47 h of labor/ha at $8.50/h. An opportunity cost of $197/ha, based on the profitability of WR pastures during a grazing study at the research site (Beck et al., 2005), was charged for establishing NE tall fescue, because the cattle did not graze these pastures for 1 yr after establishment. Hay was harvested from the NE tall fescue pastures during the establishment year, with an average yield of 14,820 kg of hay/ha, which was valued at $3.86/100 kg. The value of the hay ($259/ha) was subtracted from the total cost of pasture establishment to determine the net cost of NE tall fescue establishment.
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) of 204-kg BW, medium-framed, number 1 steers in September for fall grazing and February for spring grazing. Sales prices were based on Arkansas prices from 1991 to 2000 of 295-kg BW, medium-framed, number 1 steers in January and May for the fall and spring grazing period, respectively. The value of gain use in these calculations was $1.40/kg of BW for the fall grazing period and $0.52/kg of BW for the spring grazing period.
Costs incurred during the receiving period were based on actual costs over a 3-yr period using protocols at the University of Arkansas Livestock and Forestry Branch Station, Batesville. Treatment costs for bovine respiratory disease assumed medication costs of $1.10, 0.53, and 0.44/mL for tilmicosin (Micotil, Elanco Animal Health, Indianapolis, IN), enrofloxacin (Baytril, Bayer Animal Health, Monheim, Germany), and florfenicol (Nuflor, Schering-Plough Animal Health Corp., Union, NJ), respectively. Costs of vaccines and medication were $14.27/calf, with 50% morbidity and 0.75 treatments/calf. Cost of receiving supplements and hay was $0.38/d. Cattle interest expense of 10% annual percentage rate and death losses (3.5%) were assessed on the average purchase cost of the cattle for the fall ($201.33/100 kg of BW) and spring ($219.42/100 kg of BW) of the 10-yr period from 1991 to 2000 (Cheney and Troxel, 2004). Mineral was offered free choice, with a projected intake of 114 g/d at a cost of $0.07/d. Total BW gain per hectare was divided into the total annual pasture cost per hectare to determine the pasture cost of BW gain.
Statistical Analysis
Mean forage chemical composition was calculated by collection date and forage treatment using the MEANS procedure of SAS. Animal performance data were analyzed as a completely randomized design using the MIXED procedure of SAS; pasture was considered the experimental unit (Steel and Torrie, 1980) and steer the sampling unit. In the presence of a year x treatment interaction (P < 0.05) for BW, BW gain, ADG, and BW gain per hectare, data were analyzed by year, with forage treatment as the main effect and pasture within treatment in the random statement (Lentner and Bishop, 1986). Because BW gain per hectare and net return per hectare were calculated based on pasture means, sampling unit for these variables was pasture, and thus the effect of forage treatment on BW gain per hectare and net return per hectare were analyzed by ANOVA using the GLM procedure of SAS. Forage treatment effects on BW gain per hectare and net return per hectare were tested using residual error as the error term. In the presence of a treatment effect (P < 0.05), least squares means were separated using the predicted differences option of SAS (Steel and Torrie, 1980).
Forage DM mass per hectare was analyzed by year as a repeated measure using the MIXED procedure of SAS; sampling date was the repeated variable and subject was pasture within treatment. In the presence of a treatment x sampling date interaction (P < 0.01), least squares means were separated using the predicted differences option of SAS.
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RESULTS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Chemical composition of forage samples collected during 2004 to 2005 and 2005 to 2006 is presented in Tables 3 and 4, respectively. A general decline in CP concentration of tall fescue occurred from November through February. A decline in fiber concentration was noted along with a corresponding increase of in situ DMD of tall fescue from November to December of 2004; subsequently, fiber concentrations increased and in situ DMD decreased through February of both years. With the initiation of spring regrowth, CP and in situ DMD increased and detergent fiber concentrations decreased. The CP and in situ DMD declined and detergent fiber increased due to plant maturity. Although changes were observed in CP and in situ DMD over the months of the grazing studies, in most cases, digestibility and protein content were greater than requirements for a 250-kg growing steer to gain in excess of 1.20 kg/d (70% total digestible nutrients and 12.4% CP; NRC, 1996) until the end of the spring grazing season late April or early May of each year. This indicates that these cool-season grasses provide a nutrient-dense diet for grazing cattle, and any differences in animal performance among forages would likely be due to restrictions in forage availability.
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The actual and normal (30-yr mean) temperature and precipitation from September through May for each year at the University of Arkansas Livestock and Forestry Branch Station are presented in Figures 1 and 2, respectively. Forage DM availability for 2004 to 2005 and 2005 to 2006 are presented in Tables 5 and 6, respectively.
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) was inadequate for steers to be placed on WR or RG until December (Table 1), when steers were stocked to WR and RG pastures. Forage DM availability of the tall fescue pastures was adequate for steers to be placed in November (Table 1). Forage DM availability (Table 5) of tall fescue pastures was greater (P 0.05) than annual pastures throughout 2004 to 2005.
Although greater-than-normal precipitation was recorded in September 2005, less-than-normal precipitation was recorded in October, November, and December 2005 and February 2006 (Figure 2). The precipitation during September allowed for establishment of cool-season annuals, and forage DM availability (Table 6) was adequate for grazing initiation in November for all pastures (Table 1). In December, forage DM availability was greater (P < 0.01) for all tall fescue pastures than RG or WR (Table 6). There also was greater (P < 0.01) forage DM available in KY-31 than HM11 pastures. Forage DM availability in January was greater (P < 0.01) in Jesup AR542 and KY-31 than HM11, RG, or WR (Table 6). There was not enough available forage DM (Table 6) for steers in February and early March, so steers were not placed on pasture until mid-March (Table 1). With the initiation of spring growth, there was ample forage DM availability (Table 6) in all pastures up to the time steers were removed. Forage DM availability of Jesup AR542 was greater (P 0.05) then WR and RG during the remainder of the spring of 2006 (Table 6).
When stands were evaluated during the fall of 2005, HM11 had an average stand of 64% (range of 43 to 81%) compared with a 90% stand count for KY-31 and 86% stand count for Jesup AR542. Analysis of the endophyte infection levels indicates infection of KY-31 and Jesup AR542 (93 and 92% infection, respectively) were greater (P = 0.05) than the endophyte infection for the HM11 (60%). The lower infection level of HM11 tillers may explain poor persistence observed. The poor survival of the HM11, as well as stand losses experienced by producers that established NE tall fescue in drought-prone areas, highlights the importance of management factors such as seed handling, grazing management, and site selection when establishing new NE tall fescue pastures.
Animal Performance
Body weight and performance of steers grazing WR and tall fescue pastures during 2003 to 2004 are shown in Table 7. Temperatures recorded at the study site (Figure 1) were warmer than normal during the fall of 2002 and 2003 (October and November) and March 2003. Even though precipitation (Figure 2) during 2002 to 2003 was less than normal during October, January, and February, it was adequate for forage growth, so grazing could be initiated in tall fescue pastures in September (Table 1). Precipitation was greater than normal during April, and average temperature was mild enough to allow steers to remain on tall fescue pasture into early July (Table 1).
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) of steers that had grazed NE tall fescue was greater (P < 0.01) than KY-31 steers. Body weights of steers removed from WR pastures were not different (P > 0.23) from steers grazing NE tall fescue, but steers grazing WR were heavier (P < 0.01) than KY-31. Average daily gain (Table 7) of steers grazing WR was greater (P < 0.01) than steers grazing NE tall fescue. Average daily gain of cattle grazing NE tall fescue was greater (P < 0.01) than for cattle grazing KY-31. Total BW gain/calf did not differ (P > 0.83) among HM11, Jesup AR542, and WR, averaging 77 ± 4.2 kg/calf. Compared with KY-31, BW gains of steers grazing HM11, Jesup AR542, and WR were greater (P < 0.01) per calf during the fall and winter grazing period.
Steers grazing WR in spring 2004 were only able to graze 56 d (until May 12) compared with 113 d (until July 8) for steers grazing tall fescue (Table 1). Body weight at the termination of grazing did not differ (P = 0.57) between steers grazing KY-31 and WR and was less (P < 0.01) than steers that grazed NE tall fescue (Table 7). Average daily gains (Table 7) of steers grazing WR, HM11, and Jesup AR542 were not different (P > 0.23) but were greater (P < 0.01) than ADG of steers grazing KY-31. Body weight gain/calf (Table 7) did not differ (P = 0.51) between WR and KY-31, averaging 49 ± 4.2 kg/calf, and was less (P < 0.01) than BW gain of steers grazing HM11 and Jesup AR542, which did not differ (P = 0.86), averaging 104 ± 4.2.
Tall fescue pastures produced 1,060 ± 11 grazing days/ha (Table 7) during 2003 to 2004 (Table 7), which was greater (P < 0.01) than WR (590 ± 11 grazing days/ha). Body weight gain per hectare (Table 7) did not differ (P = 0.49) between WR and KY-31 (averaging 534 ± 36 kg/ha), which was less (P < 0.01) than BW gain per hectare produced by HM11 and Jesup AR542. The NE tall fescues produced a mean of 924 ± 36 kg of BW gain/ha, made possible because animal performance was held at a high level (0.78 and 0.92 ± 0.05 kg/d for the fall and spring grazing period, respectively) for a long period of time (total grazing season of 211 d).
Body weight at the onset of the fall and winter 2004 to 2005 (Table 8) was greater (P < 0.01) for steers grazing WR and RG than tall fescue pastures, due to the later start of grazing for WR and RG pastures. After removal of steers from pasture, BW of steers (Table 8) grazing NE tall fescue was greater (P 0.01) than BW of steers grazing KY-31, WR, or RG. Average daily gain (Table 8) of steers grazing NE was greater (P < 0.01) than KY-31. Average daily gains of steers grazing KY-31 was greater (P 0.04) than WR and RG.
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) was greater (P < 0.01) than BW of steers from NE tall fescue pastures, which were greater (P 0.03) than BW of steers grazing WR. Steers grazing KY-31 gained less (P < 0.01) than WR. Daily gains of steers grazing RG pastures were greater (P < 0.01) than ADG of steers grazing WR or NE tall fescue pastures, which were greater (P < 0.01) than steers grazing KY-31 (Table 8). Body weight gain/calf (Table 8) of steers on RG was greater (P < 0.01) than steers grazing NE tall fescue. Steers grazing WR gained less (P < 0.01) than steers from NE tall fescue pastures, and steers from KY-31 pastures gained less (P < 0.01) than WR. Grazing days per hectare (Table 8) was least (P < 0.01) for WR, because earlier maturity of the pastures led to earlier removal dates than other pastures. Grazing days per hectare (Table 8) did not differ (P 0.08) among tall fescues and RG, averaging 645 ± 8. Body weight gain per hectare (Table 8) for NE tall fescue and RG did not differ (P 0.29), averaging 564 ± 60 kg/ha, BW gain per hectare of WR was 231 kg less (P < 0.01) than NE and RG, and BW gain per hectare of KY-31 was 424 kg less (P < 0.01) than NE and RG.
Body weight of WR and RG at the end of fall and winter 2005 to 2006 (Table 9) did not differ (P = 0.83) and was greater (P < 0.01) than Jesup AR542, which was greater (P 0.03) than KY-31 and HM11, which did not differ (P = 0.32). Average daily gain (Table 9) of the steers grazing WR and RG did not differ (P = 0.55) and was greater (P < 0.01) than ADG of steers grazing NE tall fescue. The ADG of steers grazing Jesup AR542 was greater (P < 0.01) than ADG of steers grazing KY-31, and ADG of HM11 tended (P = 0.07) to be greater than KY-31. Total BW gain (Table 9) of RG, WR, and Jesup AR542 did not differ (P 0.82), and BW gain of RG was greater (P = 0.04) than HM11. Total BW gain was less (P 0.01) for KY-31 than Jesup AR542, WR, and RG.
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), BW upon removal from pasture, BW gain, and ADG was less (P < 0.01) than other treatments. Steer were removed from K-31 pastures on April 20, because 2 mortalities were found the previous week. Maximum ambient temperatures increased by approximately 8°C from around 22°C to >30°C in the weeks before April 20. Surviving steers in KY-31 pastures were observed with classic symptoms of heat distress (panting, excessive salivation, standing in mud by water source) at this time, whereas steers in other nontoxic pastures (NE tall fescue, RG, and WR) did not appear to be under distress. Body weights (Table 9) of steers from RG pastures at the end of grazing were greater (P = 0.04) than steers from WR pastures, which were greater (P 0.02) than steers grazing Jesup AR542 and HM11. Steers grazing RG gained more (P < 0.01) daily than the steers in WR (Table 9). Steer that grazed WR tended (P = 0.06) to gain more BW per day than HM11 and gained more (P = 0.02) daily than steers grazing Jesup AR542. The ADG of steers grazing Jesup AR542 and HM11 did not differ (P = 0.64). Total BW gain (Table 9) of steers grazing RG was greater (P < 0.01) than Jesup AR542, HM11, and WR, which did not differ (P 0.13).
Jesup AR542 pastures produced more (P 0.02) grazing days per hectare during 2005 to 2006 than other treatments (Table 9). The HM11 variety produced more (P < 0.01) grazing days per hectare than RG, which produced more grazing days per hectare (P = 0.03) than WR. Because of the early grazing termination date of the KY-31 pastures, grazing days per hectare was least (P < 0.01) for KY-31. Total BW gain per hectare (Table 9) was 160 ± 31 kg greater (P < 0.01) for RG than Jesup AR542, HM11, and WR, which did not differ (P 0.14). Total BW gain per hectare was least (P < 0.01) for KY-31.
Economic Analysis
In 2003 to 2004 (Table 7), net return per hectare of NE averaged $388 ± 15/ha; this was greater (P < 0.01) than KY-31 and WR, which averaged a net loss of $45.65/ha. Net return per hectare of Jesup AR542 and HM11 did not differ (P = 0.61) during 2004 to 2005 (Table 8). Pastures containing HM11 were more profitable (P = 0.05) than RG. Pastures containing WR and KY-31 produced net losses of $227 and 251 ± 8.9/ha, respectively. Net return per hectare for 2005 to 2006 (Table 9) did not differ (P = 0.31) between RG and Jesup AR542 or between Jesup AR542 and HM11 (P = 0.19). Pastures planted to RG were more (P = 0.03) profitable than HM11. Net return did not differ (P = 0.16) for HM11 and WR, but Jesup AR542 produced more (P = 0.01) profit than WR. Because of the short grazing season, deaths associated with heat stress, and poor overall performance, KY-31 produced net losses of $235.73 ± 32/ha during 2005 to 2006.
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DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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reported that ADG of steers grazing Jesup AR542 and toxic endophyte- infected Jesup in Georgia averaged 0.82 and 0.48 kg/d, respectively, in the fall and averaged 0.75 and 0.40 kg/d, respectively, in the spring. Nihsen et al. (2004) reported that cattle grazing endophyte-free tall fescue and NE tall fescue in Arkansas and Missouri gained an average of 0.58 kg/d compared with 0.34 kg/d for cattle grazing toxic endophyte KY-31 fescue. Hopkins and Alison (2006) reported that in south central Oklahoma there was no difference between ADG of steers grazing endophyte-free, toxic endophyte, or NE tall fescue during the fall. During the spring, Hopkins and Alison (2006) reported ADG of steers grazing tall fescue infected with NE in Oklahoma averaged 0.66 kg/d compared with 0.47 kg/d for toxic endophyte Georgia-5 and 0.29 kg/d for toxic endophyte-infected KY-31 tall fescue. In northeastern Louisiana, Hopkins and Alison (2006) reported that ADG during the spring was 1.20, 1.12, and 0.76 kg for endophyte-free, Jesup AR542, and toxic endophyte tall fescue, respectively. In the current study, mean ADG across the 3-yr study was 0.86 and 0.64 ± 0.05 kg for NE and KY-31, respectively, during the fall and 0.84 and 0.29 ± 0.03 for NE and KY-31, respectively, during the spring.
Performance of steers grazing the NE tall fescue is also similar to performance of steers grazing endophyte-free tall fescue. McMurphy et al. (1990) reported that gains of steers grazing tall fescue with low endophyte infection (0.7% infection) averaged 0.84 kg/d compared with ADG of 0.62 kg for steers grazing highly infected tall fescue (>76% infection). In a combined analysis of 12 tall fescue grazing studies, the relationship between the level of toxic endophyte infection and animal performance was reported to be ADG (g/d) = 928 - 4.86 (% infection) for spring grazing (Thompson et al., 1993), indicating for every percentage unit increase in endophyte infection, ADG is reduced by 5 g. Using the relationship reported by Thompson et al. (1993), 93% endophyte infection present in KY-31 would lead to a reduction in ADG of 0.47 kg, which corresponds closely with the 3-yr mean of 0.54 kg/d reduction in steers grazing K-31 compared with NE tall fescue observed in the present study.
During the 2003 to 2004 and 2005 to 2006 studies, BW gain of steers grazing WR in the fall and winter were 78 ± 4.2 and 81 ± 5.3 kg, respectively, whereas the steers grazing KY-31 gained 54 ± 4.2 and 60 ± 5.3 kg, respectively. During the fall and winter of 2004 to 2005, BW gains of steers grazing WR were 15 ± 2.6 kg compared with 39 ± 2.6 kg for steers grazing KY- 31. In the spring of 2004, BW gains of steers grazing WR (47 ± 4.2 kg) were not different from KY-31 (51 ± 4.2 kg). During the springs of 2005 and 2006, steers grazing WR gained 45 ± 5.1 and 64 ± 3.4, respectively, compared with 23 ± 5.1 and 5 ± 3.4 for steers grazing KY-31. The performance differences observed during the fall and winters of 2003 to 2004 and 2005 to 2006 and the springs of 2005 and 2006 are similar to results of Gunter et al. (2005), who reported that BW gain of steers grazing small grain or KY-31 tall fescue were 59 and 36 kg/calf, respectively, in the fall and were 61 and 27 kg/calf, respectively, in the spring. The inconsistency of these results observed in the current study is due to the length of the grazing periods. Total BW gain was similar or greater for KY-31 than WR when steers were able to graze the perennial pasture for a longer period of time. If the grazing periods were held constant as they were in Gunter et al. (2005), the greater ADG for WR steers would lead to greater total BW gains.
Across years, mean ADG of steers grazing WR and RG during the fall and winter were 0.88 and 0.84 ± 0.05 kg/d, respectively. Steers grazing WR and RG pastures during the fall and winter grazing period of a 3-yr study from 1999 to 2002 (Beck et al. 2005) had slightly better BW gain (mean ADG of 1.18 and 1.07 kg/d, respectively) than steers in the current study. During the fall of 2004 to 2005, the poor fall grazing performance of the steers grazing WR and RG (0.44 and 0.43 ± 0.06, respectively; Table 8) was due to the short grazing period (35 d) and poor forage growth of the annual pastures and was the cause of the overall reduction in mean ADG across year. Depending on annual forages for a stocker, grazing enterprise can be risky because of possible problems that can occur with stand establishment caused by either drought (delaying emergence until a rainfall event does occur) or too much rain (causing a crust to form on soil surface preventing emergence). Grazing cattle will often gain little to no BW for up to 30 d after being switched from hay-based receiving diets fed in confinement to cool-season pasture. Phillips et al. (2003) reported that Angus steers grazing wheat pasture lost BW during the first 10 d of grazing, BW on d 20 was similar to initial BW, and BW increased only 10.5 kg by d 30. Phillips et al. (2006) reported that steers grazing wheat pasture in Oklahoma lost 1.7 kg during the initial 2 wk of grazing and gained <17 kg over the first 28 d of grazing. In another study reported by Phillips et al. (2006), ADG of calves grazing wheat pasture was –0.74, 0.01, and 0.26 kg for the first 10, 20, and 30 d of grazing, respectively. Lippke et al. (2000) observed a negative relationship between the magnitude of change in the ruminal acetate:propionate ratio and ADG of steers in the first 7 d of grazing immature wheat pasture. These researchers suggested that this decrease in the ruminal acetate:propionate ratio may indicate digestive upset as a cause of poor initial grazing performance. The reduced performance observed during fall and winter of 2004 to 2005 may thus be caused by the short grazing period, which did not allow sufficient time for steers to acclimate to the high quality forage diet.
Small grains produced an average net loss of $67.82 ± 25.3/ha compared with positive net returns of $219 ± 25.3 for NE tall fescue across the 3 yr. Research conducted at the site of the present study (Anders et al., 2007) indicates no-till establishment of small grain pastures can increase profitability by $220/ha compared with the conventional tillage systems used in the present study. The length of the spring grazing season for RG resulted in similar or greater BW gain per hectare compared with NE tall fescue; thus, profitability of RG pastures did not consistently differ from the NE tall fescue.
In an economic analysis of replacing KY-31 tall fescue with NE tall fescue, Gunter and Beck (2004) reported that a stocker cattle enterprise required 3 to 7 yr to cover establishment costs and produce a positive return on the investment. The length of time required to cover establishment costs depended primarily on the effect of the native endophyte on performance of cattle and the discounts received for cattle due to signs of fescue toxicosis. Zhuang et al. (2005) reported that for cow-calf production, toxic endophyte tall fescue stands can profitably be replaced over a 12-yr stand life when infection levels of toxic endophyte tall fescue were >74% at stocking rates of 1.2 AU/ha. Across the 3-yr study, NE tall fescue produced average net returns per hectare of $219. If the profit stream of NE tall fescue over time is converted to current dollars using a 6% discount rate, this level of profitability would require 4 yr for a new planting of NE tall fescue to break even and begin producing positive returns.
Profitability of a stocker enterprise is determined by both animal performance and production per hectare. In this study, NE tall fescue offers greater animal performance than native endophyte tall fescue and greater gain per hectare than either WR or native endophyte tall fescue. Compared with both KY-31 and cool-season annuals, NE tall fescues offer potential benefits related to decreased risk of stand establishment of annual forage crops, longer grazing seasons, and acceptable animal performance.
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2 Corresponding author: pbeck{at}uaex.edu
Received for publication August 16, 2007. Accepted for publication February 27, 2008.
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