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© 2009 Plant Management Network.
Accepted for publication 19 December 2008. Published 12 March 2009.

Performance by Fall-Calving Cows Grazing Tall Fescue Pastures With Different Proportions Stockpiled

James D. Caldwell and Kenneth P. Coffey, University of Arkansas, Fayetteville, AR 72701; Wayne K. Coblentz, USDA-ARS, Marshfield, WI 54449; John A. Jennings, University of Arkansas Cooperative Extension Service, Little Rock, AR 72204; Don S. Hubbell, III, University of Arkansas Livestock and Forestry Branch Experiment Station, Batesville, AR 72501; David L. Kreider, University of Arkansas, Fayetteville, AR 72701; Mike L. Looper, USDA-ARS, Booneville, AR 72927; and Charles F. Rosenkrans, Jr., University of Arkansas, Fayetteville, AR 72701

Corresponding author: Kenneth P. Coffey. kcoffey@uark.edu

Caldwell, J. D., Coffey, K. P., Coblentz, W. K., Jennings, J. A., Hubbell, D. S., III, Kreider, D. L., Looper, M. L., and Rosenkrans, C. F., Jr. 2009. Performance by fall-calving cows grazing tall fescue pastures with different proportions stockpiled. Online. Forage and Grazinglands doi:10.1094/FG-2009-0312-01-RS.

Abstract

Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire.] is often stockpiled to reduce winter feed costs for cattle. Over two consecutive years, a total of 158 Gelbvieh × Angus fall-calving cows (1318 ± 13.2 lb) were allocated randomly to one of eight 24-acre tall fescue pastures on 18 August 2004 and 17 August 2005. Treatments consisted of no area stockpiled (0-SP), or 33 (33-SP), or 50% of the total pasture area stockpiled (50-SP); stockpiling was initiated on 10 September of both years. Total hay offered tended (P = 0.07) to be greater for 0-SP than 33-SP and 50-SP. Calf weights at the end of the breeding season were greater (P < 0.05) from 33-SP than 50-SP. Therefore, 33% of tall fescue pasture area can be stockpiled to help meet the nutritional needs of fall-calving cows and reduce winter hay needs.

Introduction

Stockpiling is a management practice in which forage is allowed to accumulate throughout late summer and (or) fall for grazing during late fall and winter. This practice allows grazing to be extended into winter months (2), thereby decreasing winter feed costs (13).

Tall fescue is the most widely used forage for stockpiling in the southeastern USA, because of its high concentrations of nonstructural carbohydrates (5), low concentrations of fiber, high digestibility (4,7), and its ability to produce more autumn growth than other cool-season forages (13). Pregnant beef cows offered stockpiled tall fescue-alfalfa (Medicago sativa) pastures consumed less hay and gained more body weight (BW) than cows offered other forages (8). Stockpiling tall fescue is a viable management practice that can be used for wintering cattle (9); however, little information is available that describes the proportion of the total pasture acreage that should be stockpiled, or the suitability of stockpiled tall fescue for fall-calving beef cows. Our objective was to investigate how autumn-stockpiling different proportions of the total tall fescue grazing area affects forage nutritive value, ergot alkaloid concentrations, and the overall performance of fall-calving beef cows.

Pastures and Treatments

A total of 158 Gelbvieh × Angus pregnant crossbred fall-calving cows (1318 ±  13.2 lb initial BW) were stratified by weight and age and allocated randomly to one of eight 24-acre Neotyphodium coenophialum-infected tall fescue pastures on 18 August 2004, and 17 August 2005. Pastures were subdivided into six 4-acre paddocks and stocked at a rate of one cow per 2.4 acres.

Grazing treatments consisted of no area stockpiled (0-SP), and 33 (33-SP), or 50% of the total area stockpiled (50-SP). Treatments were replicated either three times in both years (0-SP) or two times in one year and three times in the other year (33- and 50-SP). Pastures were allocated randomly to treatments in both years. Cows were reallocated to pasture groups each year. The grazing scheme used for this study is shown in Figure 1. Cows assigned to 0-SP were rotated through all six paddocks at 5- to 6-day intervals followed by 25-to 30-day rest periods. Those assigned to 33-SP and 50-SP were rotated through only two or three paddocks, respectively, until 10 September, removing forage mass on those paddocks to prepare them for subsequent stockpiling. Starting on 10 September, 33-SP and 50-SP treatments were grazed rotationally on the four or three remaining paddocks, respectively, to allow two or three early-grazed paddocks to stockpile until 16 November 2004 and 29 November 2005.

Fig. 1. Grazing scheme illustrating: (A) no stockpiling (0-SP); (B) 33% of the total pasture area stockpiled (33-SP); and (C) 50% of the total pasture area stockpiled (50-SP).

Pastures were located on Clarksville gravelly silt loam soil (loamy-skeletal, siliceous, semiactive, mesic Typic Paleudults) at the Livestock and Forestry Branch Experiment Station near Batesville, AR. Nitrogen was applied at 60 lb/acre as ammonium nitrate (34-0-0) on 16 September 2004 and 15 September 2005. Phosphorus, potassium, and lime were applied annually to meet requirements specified by Arkansas Cooperative Extension Service soil test guidelines (6).

Cattle Management

Calving season started 17 August in both years and continued through 31 October 2004 and 21 October 2005. Any cow that failed to produce a live calf was replaced with a primiparous heifer and calf. An Angus × Gelbvieh crossbred bull that passed a reproductive soundness examination was added to each group of cows in late November of each year and remained for 65-day and 64-day breeding seasons in 2004 and 2005, respectively. Cows were weighed and body condition score (BCS; 1 = emaciated, 9 = obese) (16) were assigned immediately precalving (17 August both years), and at the start (16 November 2004, 29 November 2005) and end (20 January 2005, 4 February 2006) of the breeding season. Cows received vaccinations against seven clostridia strains (Alpha-7; Boehringer-Ingelheim Animal Health Inc., St. Joseph, MO.) and were treated for internal parasites (Ivermectin pour-on; Merial LTD., Duluth, GA) 2 weeks prior to the start of the breeding season.

Cows were offered fescue hay [9% crude protein (CP), 65% in vitro dry matter disappearance (IVDMD)] in their individual pasture groups when forage mass dropped below 1000 lb/acre as measured by disk meter (3). Supplemental corn gluten feed was offered during the breeding season to maintain the cows at their existing BCS (11); this corresponded to 2 lb/cow daily when grazing stockpiled fescue, and 5 lb/head daily when consuming tall fescue hay. All calves where weighed at birth, at the beginning and end of the breeding season, and at the end of trial in both years.

Sample Collection and Analyses

Unless cattle were offered hay, pastures were evaluated monthly for quantity and nutritive value of forage mass. Forage mass was estimated at three random locations/acre using a disk meter (3) calibrated each sampling date. Samples of fescue only were clipped to a 1-inch stubble height, placed in plastic zip-lock bags, and stored in an ultra-low freezer (-112°F) pending lyophilization. Fescue samples were lyophilized and ground through a 1-mm screen, and analyzed for IVDMD using the batch-culture procedures outlined by Ankom Technology Corp. (Fairport, NY) and for total N using rapid combustion (1). Ergovaline and ergot alkaloid concentrations were measured using a modified high performance liquid chromatography procedure (10). Forage species frequency and basal cover were estimated in November of both years using a modified step-point procedure (12).

Statistical Analyses

Forage and cow/calf performance measurements were analyzed statistically using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC.) with pasture or group of cows considered the experimental unit. The random effects were both pasture (treatment) and year. Sampling date was used as a repeated measurement for forage measurements. Four orthogonal contrast statements were used to evaluate forage measurements beginning in September of each year: (i) 0-SP vs. both stockpiled and non-stockpiled areas of the stockpiled treatments; (ii) stockpiled and non-stockpiled areas of 33-SP vs. those of 50-SP; (iii) early-grazed areas within 33-SP and 50-SP vs. the stockpiled area within 33-SP and 50-SP; and (iv) all of the early-grazed areas vs. all of the stockpiled areas. Samples from the August sampling date were analyzed without consideration for the stockpiled and non-stockpiled portions.

Two preplanned orthogonal contrast statements were used for the cow-calf measurements to compare: (i) 0-SP vs. 33-SP and 50-SP; and (ii) 33-SP vs. 50-SP. Sex of calf, and associated interactions were removed from the model if they did not interact with main effects.

Species Composition

Tall fescue represented approximately 70% of the total vegetation for both years, but did not differ (P ≥ 0.16) among treatments. Basal cover and proportions of other cool-season perennials and annuals, warm-season annuals, and broadleaf weeds did not differ (P ≥ 0.11) among treatments and averaged 37, 3, 3, 4, and 7%, respectively. Warm-season perennial forage proportion was greater (P = 0.01) for 0-SP vs. 33-SP and 50-SP, and tended (P = 0.10) to be greater in 50-SP vs. 33-SP pastures. This proportion was primarily bermudagrass [Cynodon dactylon (L.) Pers.] located in areas where hay had been fed in previous years, and is likely a random effect since pastures were reallocated to treatments between years and all pastures were grazed in a similar manner during June through early August.

Forage Mass, Nutritive Value, and Ergot Alkaloids

Initial forage mass (August) did not differ (P ≥ 0.38) among treatments (2750 lb/acre average; Table 1). A sampling date effect was detected (P < 0.01) for forage mass, but interactions of treatment and sampling date were not detected (P = 0.26) from September through December. Therefore, these data were pooled across sampling dates and years. Overall mean forage mass averaged across stockpiled and non-stockpiled areas during the grazing period was 290 lb/acre lower (P < 0.05) in 33-SP vs. 50-SP pastures. Forage mass from the stockpiled portions of each treatment was greater (P < 0.05) than forage mass from all of the non-stockpiled areas including 0-SP (1840 vs. 1580 lb/acre). Although data were pooled across sampling dates, initial forage mass for grazing on the stockpiled areas is of interest to those designing grazing programs. These values averaged across years were 1930 and 2290 lb/acre for 33-SP and 50-SP, respectively. Others have reported forage mass similar to that reported herein when stockpiling began in early August (9).

Table 1. Forage mass, forage nutritive value (DM basis), ergovaline, and total ergot alkaloid concentrations of N. coenophialum-infected tall fescue pastures with different proportions of the total pasture area stockpiled (2-year average).

 ^s 0-SP, 33-SP, and 50-SP represent pastures in which 0, 33, or 50% of the total pasture area was stockpiled, respectively. Early-grazed area refers to the non-stockpiled area grazed beginning 10 September which corresponds to the entire pasture area in 0-SP, 67% of the pasture area in 33-SP, and 50% of the pasture area in 50-SP. Stockpiled areas are those areas in 33-SP and 50-SP that were stockpiled beginning 10 September.

 ^t SEM = Pooled standard error of the mean.

 ^u 33-SP vs. 50-SP (P < 0.05).

 ^v Early-grazed areas of 33-SP and 50-SP vs. the stockpiled areas of 33-SP and 50-SP (P < 0.05).

 ^w Early-grazed areas including 0-SP vs. the stockpiled areas of 33-SP, and 50-SP (P < 0.05).

 ^x 33-SP vs. 50-SP (P < 0.10).

 ^y Total ergot alkaloids represents the means of three ergopeptines (ergocristine, ergovaline, and ergotamine), their isomers, and five lysergic acid derivatives.

 ^z Non-stockpiled treatments (0-SP) vs. stockpiled treatments (33-SP and 50-SP) (P < 0.10).

Forage CP and IVDMD concentrations did not differ (P ≥ 0.25) among treatments on the August sampling date or when pooled across sampling dates and years (Table 1). A sampling date effect was detected (P < 0.01) for these measurements, but interactions of treatments with sampling date were not detected (P ≥ 0.57). Concentrations of CP from September through December were 4 percentage units higher than those reported across accumulation dates beginning in June and ending in September (4), and IVDMD concentrations were comparable with those reported previously (4). Therefore, since the quality of stockpiled fescue is high, winter supplementation required to maintain fall-calving cows may be reduced compared with the amount required to maintain the cows if they were fed a moderate to low-quality fescue hay comparable with that produced commonly throughout the tall fescue region.

Treatment by date interactions were not detected (P ≥ 0.36) for concentrations of ergovaline or total ergot alkaloids (Table 1). Ergovaline concentrations in August tended (P = 0.07) to be greater from 0-SP vs. 33-SP and 50-SP and from 33-SP vs. 50-SP. No differences were detected (P ≥ 0.37) among treatments for ergovaline and total ergot alkaloid concentrations during September through December, but a sampling date effect was detected (P = 0.01). Concentrations of ergovaline averaged across years within sampling dates were greatest (P < 0.05) in mid-November and December (400 ppb) compared with those in mid-October (300 ppb). Others (9) reported declining concentrations of ergovaline beginning in mid-December and suggested that toxic fescue becomes less toxic to livestock as winter progresses. We did not sample beyond our December sampling date because much of the stockpiled fescue had been consumed by early to mid-January. Forage in our study exceeded 150 ppb ergovaline throughout the entire grazing period in both years, which could contribute to fescue toxicosis in livestock through the winter (15). It should be noted that two animals with fescue foot were removed from this trial on 4 January 2006. Other alkaloids should also be considered in assessing the full toxic potential of N. coenophialum-infected tall fescue (17).

Carrying Capacity, Hay Offered, and Cow and Calf Performance

Grazing days/acre did not differ (P ≥ 0.39; Table 2) among treatments, but, the amount of hay offered tended (P = 0.07) to be 620 lb greater for 0-SP vs. 33-SP and 50-SP. Others reported that cattle grazing stockpiled fescue-alfalfa needed less hay to maintain body condition compared with cattle grazing smooth bromegrass, or corn crop residues, or fed hay in a drylot (8).

Table 2. Grazing days/acre, hay offered (as-fed basis), and performance of fall-calving cow/calf pairs grazing N. coenophialum-infected tall fescue pastures with different proportions of the total pasture area stockpiled (2-year average).

 ^s 0-SP, 33-SP, and 50-SP represent pastures in which 0, 33, and 50% of the total pasture area was stockpiled, respectively.

 ^t SEM = Pooled standard error of the mean.

 ^u 0-SP vs. 33-SP and 50-SP (P < 0.10).

 ^v Weights at the beginning of the calving season (17 August for both years), beginning (16 November 2004, 29 November 2005) and end of breeding (20 January 2005, 1 February 2006), and end of trial (16 March 2005, 15 March 2006).

 ^w BCS: 1 = emaciated, 9 = obese (16).

 ^x Analyzed using Chi-square analysis.

 ^y 33-SP vs. 50-SP (P < 0.05).

 ^z 33-SP vs. 50-SP (P < 0.10).

Cow BW and BCS precalving and at the beginning and end of the breeding season, and calving interval and calving rate did not differ (P ≥ 0.15) across treatments (Table 2). Calf BW at the end of the breeding season was 40 lb greater (P = 0.04) from 33-SP vs. 50-SP, but calf BW at the end of the trial did not differ (P ≥ 0.11) among treatments. Calf average daily gain (ADG) during the breeding season tended to be 0.22 lb/day greater (P = 0.08) from 33-SP vs. 50-SP, but calf ADG from birth to the end of the breeding season and to the end of the trial did not differ (P ≥ 0.16) among treatments. Performance by cattle grazing stockpiled cool-season forages has been somewhat variable. Cows grazing tall fescue-alfalfa mixtures or smooth bromegrass during the winter had greater weight gain than those fed hay in a drylot (8), whereas BCS and reproductive measurements from cows grazing stockpiled orchardgrass did not differ from those from cows fed hay or limit-fed corn (14). Therefore, stockpiling tall fescue at 33% of the total pasture area can reduce the amount of hay offered to beef cattle during the winter without causing excessive change in fall-calving cow performance.

Implications

Stockpiled tall fescue is a high-quality forage that can be grazed during the late fall and early winter to reduce both hay and supplemental feed amounts needed for fall-calving cows. The toxicity of endophyte-infected tall fescue may still be greater during the late-fall and early-winter grazing period than the threshold toxicity causing tall fescue toxicocis. It appears producers have considerable latitude in choosing the proportion of the total grazing area to stockpile. This choice may impact both the amount of hay needed and calf performance, and can be modified depending on the goals and objectives of the particular operation.

Literature Cited

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