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FORAGE & GRAZING LANDS

Cultivar and Environment Effects on Annual Ryegrass Forage Yield, Yield Distribution, and Nutritive Value

^a Oklahoma State Univ., Plant and Soil Sci. Dep., Stillwater, OK 74078
^b LSU AgCenter, Southeast Res. Stn., Franklinton, LA 70438
^c LSU AgCenter, Rosepine Res. Stn., Rosepine. LA 70659
^d LSU AgCenter, Macon Ridge Branch, Winnsboro, LA 71295

* Corresponding author (dredfearn{at}mail.pss.okstate.edu)

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Differences among annual ryegrass (Lolium multiflorum Lam.) cultivars for weight gain of grazing steers have been reported, even though plot experiments suggest that forage dry matter yield among cultivars should not be a limiting factor. Likewise, forage nutritive value differences among cultivars have not been assessed. The objectives of this research were to evaluate differences in cumulative forage yield, yield distribution, and nutritive value among ‘Gulf’, ‘Jackson’, ‘Marshall’, ‘Rio’, ‘Rustmaster’, and ‘Surrey’ annual ryegrass. Plots were harvested six times beginning in December at approximate 30-d intervals during the 1997–1998 and 1998–1999 growing seasons. Nutritive value measurements included crude protein (CP), neutral detergent fiber (NDF), in vitro true digestibility (IVTD), and digestible NDF (DNDF). There were no differences among cultivars for cumulative forage yield (P = 0.99). However, for the January harvest, Surrey and Gulf averaged 1030 (±65) kg DM ha^-1, whereas Marshall yielded only 672 (±79) kg DM ha^-1. For the March harvest, yields of all varieties were similar and averaged 1350 (±95) kg DM ha^-1. At the May harvest, Marshall and Jackson yielded 1232 (±123) kg DM ha^-1, whereas Gulf yielded only 929 (±74) kg DM ha^-1. Crude protein concentration differed significantly among harvests with a general decrease from 260 to 120 g CP kg^-1 as the growing season progressed. Similar declines in nutritive value occurred for NDF, IVTD, and DNDF. Trends in yield distribution and forage quality may indicate a need for cultivar specific recommendations based on intended forage need and season of use.

Abbreviations: CP, crude protein • DM, dry matter • DNDF, digestible neutral detergent fiber • IVTD, in vitro true digestibility • NDF, neutral detergent fiber • NIRS, near infrared reflectance spectroscopy

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
BEEF AND DAIRY CATTLE PRODUCERS require a consistent supply of high-quality forage to maintain economical levels of animal production. Beef and dairy cattle producers in the southeastern USA rely primarily on annual ryegrass to meet their pasture needs for winter and spring. During the past 50 yr, the use of annual ryegrass has expanded significantly. In the Coastal Plain region, annual ryegrass can produce high-quality forage from late fall through late spring.

Many cultivars of annual ryegrass are currently marketed. Where winter temperatures are milder, Gulf annual ryegrass is the preferred cultivar because of lower seed cost. Conversely, in areas where winter temperatures are below freezing for several consecutive days or weeks, cultivars with demonstrated cold tolerance such as Marshall are preferred. Gulf was released in 1958 as a crown rust (caused by Puccinia coronata Corda) resistant cultivar and since then, many cultivars have been released through public and private breeding programs.

To date, most studies on annual ryegrass have focused on critical establishment factors, such as sod-suppression and tillage (Cuomo and Blouin, 1997; Cuomo et al., 1999; Lang, 1989). There have been few studies conducted to determine animal performance (Hafley, 1996; Hoveland et al., 1991) and these have evaluated a minimal number of cultivars due to the expense of conducting these studies. Recent reports indicate annual ryegrass cultivar differences for gains by growing cattle (Bransby et al., 1997; Wyatt and Granger, 2001). The increased animal gain on Marshall versus Gulf pasture has ranged from 77 to 27% in Alabama (Bransby et al., 1997) and 16% to essentially no difference over 3 yr in Louisiana (Wyatt and Granger, 2001). Gains were similar for cattle grazing Marshall and Jackson (Wyatt and Granger, 2001) and for cattle grazing Marshall and Surrey (Hafley, 1996). Animal performance advantages appear to be associated with forage mass as suggested by plant height differences (Bransby et al., 1997) and measurements using a rising plate meter (Wyatt and Granger, 2001). Possible contributions of nutritive value differences among annual ryegrass cultivars to differences in animal performance have not been assessed.

The most extensive review of annual ryegrass nutritive value was recently completed by Lippke and Ellis (1997), but the majority of this review was qualitative with minimal comparisons among annual ryegrass cultivars for nutritive value. A study was conducted to elucidate and quantify the factors responsible for previously observed differences in the agronomic performance of annual ryegrass cultivars grown in diverse environments. The objectives of this research were to quantify differences in forage yield, yield distribution, and nutritive value among Gulf, Jackson, Marshall, Rio, Rustmaster, and Surrey annual ryegrass.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Gulf, Jackson, Marshall, Rio, Rustmaster, and Surrey annual ryegrass cultivars were grown at four locations in the 1997–1998 and 1998–1999 growing seasons. These six cultivars were chosen on the basis of their past variety trial performance. Gulf is considered an intermediate-maturing cultivar (Weihing, 1963). Marshall was released as a late-maturing cultivar (Arnold et al., 1981). Rustmaster was described as an early-maturing cultivar by a private company in 1985. Surrey (Prine et al., 1989) and Jackson (Watson et al., 1990) were described as intermediate-maturing cultivars. Rio was described as an intermediate-maturing cultivar by a private company in 1991.

Soil type at the study sites was Dexter loam (fine-mixed, thermic Ultic Hapludalf) at the Idlewild Research Station located near Clinton, Tangi silt loam (fine-silty, mixed thermic Typic Fragiudult) at the Southeast Research Station located near Franklinton, Bowie fine sandy loam (loamy, siliceous, thermic Plinthic Paleudult) at the Rosepine Research Station located near Rosepine, and Jigger silt loam (fine-silty, mixed, thermic, Typic Fragiudalf) at the Macon Ridge Research Station located near Winnsboro. Experimental design at each location was a randomized complete block with three replications. All trials were established within 7 to 10 d during October of each year with a mean plot area of 9.3 m². Plots were seeded at the rate of 34 kg seed ha^-1 into a prepared seedbed. Phosphorus and potassium fertilizer was applied at all locations according to soil test recommendations. Total nitrogen applied was 280 kg N ha^-1 in multiple applications of equivalent amounts of ammonium nitrate at planting and following the second and fourth harvests.

Plots were mechanically harvested six times to an 8-cm stubble height at approximate 30-d intervals beginning in mid December and ending in mid May. The harvested material was weighed in the field and sampled for dry matter (DM) determination. These samples were oven-dried at 60°C for approximately 72 h and subsequently ground through a 1-mm screen for forage quality analyses. Near infrared reflectance spectroscopy (NIRS) spectra were collected for each sample with a Model 6500 near infrared reflectance spectrophotometer (NIRSystems, Silver Spring, MD). A library data set was developed from samples analyzed previously at the LSU AgCenter Forage Quality Laboratory at the Southeast Research Station. The library file consists of approximately 625 samples analyzed for CP, NDF, and IVTD from previous research experiments.

Samples from this experiment were centered and selected by means of the CENTER and SELECT programs in the NIRS2 (version 3.0) system software (Infrasoft International, 1992). Selected samples were compared with the library by the MATCH program to determine if the spectra of the selected samples from this experiment matched the spectra of any samples in the library. Two matched samples from the library for each selected sample were used if available. If selected samples from this experiment were not matched by at least two samples in the library file, then wet chemistry values were used for these samples. Matched samples from the library file and wet chemistry values for annual ryegrass samples not matched to the library were used to make the calibration data set. The samples in the library file and from this experiment were analyzed for CP colorimetrically (AOAC, 1990), and the NDF was measured by the methods described by Goering and Van Soest (1970), which were modified by excluding decalin. Additonally, 2 mL of a 2% (w/v) -amylase solution was added at the beginning of the NDF procedure (Van Soest and Robertson, 1980). In vitro true digestibility was measured by the methods described by Goering and Van Soest (1970). Digestible NDF (DNDF) was calculated as

Reflectance data were related to the calibration data by means of a modified partial least squares regression procedure to develop the prediction equation (Shenk and Westerhaus, 1991). Samples identified as outliers from the calibration data set were analyzed by traditional wet chemistry methods described above. Prediction equations had standard errors of calibration of 0.73, 1.86, and 2.94 g kg^-1 for CP, NDF, and IVTD, respectively. Prediction equations had standard errors of cross validation of 1.01, 2.22, and 3.41 g kg^-1 for CP, NDF, and IVTD, respectively. The 1 - V/R value (where V/R is the ratio of unexplained variance to total variance) had a value of 0.98 for CP, 0.97 for NDF, and 0.91 for IVTD.

Following the December harvest, a randomly selected 61-cm interior section of a drill row was marked and used visually to determine seedhead development between harvests on a weekly basis. Following each harvest, a different 61-cm section was selected and used to determine seedhead development for that harvest. A seedhead was considered exerted when its length exceeded 2 to 3 cm.

The experiment was designed as a randomized complete block across locations. The locations, blocks within locations, and years were analyzed as random effects and cultivars as fixed effects. Data on the cumulative forage yield, seasonal distribution of forage yield, and nutritive value were used to evaluate the effects of year, location, and cultivar plus the two- and three-way interactions. When differences in yield, yield distribution, and nutritive value were detected among main effects, these differences were assessed by Fisher's least significant difference (Steele and Torrie, 1980). Maturity data were analyzed as repeated measures. All multivariant analyses were performed with the GLM procedure of SAS to evaluate year, location, and cultivar plus the two- and three-way interactions (SAS, 1991). All tests of significance were made at the 0.05 level of probability unless otherwise noted.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Environmental Conditions
The 1998 growing season temperature was atypically warm (temperature data not shown) with precipitation ranging from below average to above average (Table 1) . However, the 1999 growing season temperature was more moderate with near normal precipitation at Clinton and Franklinton and above average precipitation at Rosepine and Winnsboro. The rainfall distribution patterns during this study were characteristic of the short periods of drought that can occur in the region during annual ryegrass establishment in September and October and during periods of rapid growth during March through May.

View larger version (21K): [in this window] [in a new window]   Fig. 1. Year x location interaction for total forage yield of six annual ryegrass cultivars. Bars represent one standard error of the mean.

View larger version (47K): [in this window] [in a new window]   Fig. 2. Distribution of forage yield by month for six annual ryegrass cultivars averaged cross 2 yr and four locations. Bars represent one standard error of the mean.

A closer comparison of Gulf and Marshall confirmed the apparent differences in monthly yield distribution of these two cultivars. Gulf had 302 kg ha^-1 more early-season forage production than Marshall. Conversely, Marshall had 449 kg ha^-1 more late-season forage production than Gulf. On the other hand, Marshall and Rustmaster had virtually identical early- and late-season forage yield.

Maturity
The week x cultivar interaction for seedhead emergence was significant for both the April (Fig. 3) and May (Fig. 4) harvest dates. This indicated that maturity differences existed among these six annual ryegrass cultivars. No seedheads were observed on any cultivar at any location in either year prior to the April harvest. Although no seedheads emerged in March, Rustmaster and Gulf both had a few stems beginning to elongate just prior to the March harvest. By Week 3 of April, seedheads of most cultivars were just beginning to emerge and differences in seedhead number were already apparent. In April, Rustmaster and Gulf had the greatest seedhead emergence at Week 4 with 15 and 12 seedheads m^-1 of drill row, respectively. Although the number of exposed seedheads in May for all cultivars was greatest during Week 4, Rustmaster and Gulf had a greater portion of seedheads fully exerted, whereas Jackson, Marshall, Rio, and Surrey had fewer fully exerted seedheads.

View larger version (24K): [in this window] [in a new window]   Fig. 3. Weekly seedhead emergence for six annual ryegrass cultivars during the month of April averaged across four locations and 2 yr. Bars represent one standard error of the mean.

View larger version (26K): [in this window] [in a new window]   Fig. 4. Weekly seedhead emergence for six annual ryegrass cultivars during the month of May averaged across four locations and 2 yr. Bars represent one standard error of the mean.

Nutritive Value
Similar to the analysis for forage yield distribution, there was a year x location x cultivar interaction for a few nutritive value measurements and no significant location x cultivar interaction. Thus, the year x location interaction for CP and IVTD concentrations (Table 2) and the cultivar effects for CP, NDF, IVTD, and DNDF concentrations (Table 3) were more consistent and meaningful. Therefore, all discussion is focused on these latter effects. McCormick and Fales (1985) reported that well-managed annual ryegrass had in excess of 200 g kg^-1 CP and 700 g kg^-1 total digestible nutrients from mid-November through April. Hafley (1996) concluded that nutritive value of both Marshall and Surrey annual ryegrass was equivalent on the basis of animal performance and laboratory analyses. Data for the 2-yr experiment was collected for 71 d beginning on 8 February in Year 1 and 84 d beginning on 30 January in Year 2.

Crude protein differences among cultivars were observed in April with a range in values of 14 g CP kg^-1 DM (Table 3). Although similar ranges in CP concentration were observed among cultivars during other harvests, these differences were not significant. The differences in plant maturity first observed in April may have been manifested in the CP concentration since Rustmaster and Gulf with the lowest CP values were also the earliest maturing.

Averaged across cultivars and locations, there were large CP concentration differences among months. The obvious inference would be that N applications were inconsistent across locations. However, every attempt was made to ensure that all management practices were completed as close as possible to the same date at each location during each year. Although differences in CP concentration existed, it appears that CP concentration had a more narrow range among locations during the middle portion of the growing season. The most extreme differences occurred in December and May of the 1998 and 1999 growing season at Winnsboro and Rosepine (Table 2). This suggests that differences in precipitation patterns may have affected N uptake and assimilation during the fall and late-spring when rainfall patterns were erratic.

Fiber, Digestible Fiber, and True Digestibility
There was a significant cultivar x harvest date interaction for NDF, DNDF, and IVTD (Table 3). Even though there were differences in NDF among cultivars for the harvest dates, the differences were considered to be nutritionally meaningless because all values were so low. From December through February, and to some extent March, the lower NDF values observed in this study do not necessarily mean that a particular cultivar had greater nutritive value. Typically, lower NDF concentration equates to greater nutritive value, but excessively low forage NDF concentration can result in digestive problems (NRC, 2001). This would suggest that 406 g NDF kg^-1 DM observed for Gulf may actually be nutritionally more acceptable than 371 g NDF kg^-1 DM observed for Marshall during the early part of the growing season. However, the NDF values observed in this study were not excessively low. High NDF is negatively correlated with digestible energy and usually becomes the first limitation to animal production (NRC, 1996, 2001). Although the upper range of NDF values observed in this study was not excessively high, decreased digestible energy would likely become the first limitation to increased animal production. This would be especially true for the early maturing annual ryegrass cultivars such as Rustmaster and Gulf following initiation of internode elongation.

There were differences among cultivars for DNDF from December through March. These differences coincided with the observed NDF and IVTD nutritive value characteristics. In vitro true digestibility, which is defined as the theoretical maximum digestibility, was consistent among cultivars for the December through March harvest dates (Table 3). Similar to NDF concentration, the observed differences in DNDF and IVTD are likely nutritionally meaningless because all values are extremely high.

Nutritive value declined rapidly following seedhead emergence. A similar trend was noted for annual ryegrass nutritive value by Ballard et al. (1990) and Griffith (1992). Growing a late-maturing cultivar such as Marshall and Rio, and to some extent Jackson and Surrey, would allow producers to extend the production of high-quality forage into late-spring. However, the disadvantage to using late-maturing cultivars would appear to be the sacrifice of some early-fall or possibly mid-season production.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
There were no differences among cultivars across locations for forage yield. Since annual ryegrass cultivar yield performance is not consistent across years and locations, cultivar selection should be based on other factors such as seed cost, rust resistance, or cold tolerance. Bransby et al. (1997) suggested that Marshall was superior to Gulf in grazing tolerance. Our results suggest that seasonal yield distribution in response to maturity and nutritive value may contribute to differing animal responses among annual ryegrass cultivars. Advantages of late-maturing cultivars would primarily be expected from April through the end of the growing season. Despite very high nutritive value of all cultivars before April and the theoretical benefits of low NDF at these levels as mentioned previously, the lower NDF and higher IVTD of Marshall compared with Gulf correspond with previously reported superior gains on Marshall, which is likely due to its later maturity. Other cultivars were generally intermediate between Marshall and Gulf in NDF and IVTD. Intake of digestible nutrients by grazing livestock is difficult to measure precisely. However, intake based upon NDF and IVTD could be greater for Marshall and further enhance animal performance compared to Gulf. Animal response to the other cultivars would be expected to be intermediate between Gulf and Marshall due to observed differences among cultivars in NDF and IVTD. A chronological analysis of animal performance throughout the growing season is needed to compare adequately the effects of the seasonal yield and quality differences observed in this study among annual ryegrass cultivars.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Published as Journal Series no. 02-88-0033, Louisiana Agric. Exp. Stn.

Received for publication January 10, 2002.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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• Lippke, H., and W.C. Ellis. 1997. Forage quality of annual ryegrass. p. 71–79. In F.M. Rouquette, Jr. and L.R. Nelson (ed.) Ecology, production, and management of Lolium for forage in the USA. CSSA Spec. Publ. 24. CSSA, Madison, WI.
• McCormick, M.E., and S.F. Fales. 1985. Ryegrass for silage: Stage of maturity and varietal influence on quality. Univ. Ga. Res. Rep. 465:1–15.
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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Related articles in Crop Science Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Redfearn, D. D. Articles by Ward, J. D. Search for Related Content PubMed Articles by Redfearn, D. D. Articles by Ward, J. D. Agricola Articles by Redfearn, D. D. Articles by Ward, J. D. Related Collections Forage Management Other Forage Crops