Journal of the NACAA
Volume 14, Issue 1 - June, 2021
Performance of Cattle Grazing Stockpiled Tall Fescue as Late Fall Supplemental Forage in the Upper Southern USA
- Lemus, R. , Extension Forage Specialist, Mississippi State University Extension Service
White, J.A., Forage Variety Testing Manager, Mississippi State University
Stockpiling tall fescue for winter grazing in the upper southern USA has great potential to reduce cow supplementation costs, improve the environmental impact of winter-feeding systems, and potentially improve animal performance. The objective of the study was to determine the impact of nitrogen (N) application on herbage accumulation (HA), nutritive value, and animal performance of two stockpiled tall fescue cultivars. The study was conducted for two seasons at Mississippi State University using three N rates (0, 50, and 100 lb N/ac) and two cultivars (K-31 and Texoma MaxQ II) in a randomized complete block design replicated twice. Herbage accumulation (HA) increased with N application. Average dry matter HA was greater for K-31 during both seasons of the study. Crude protein and other nutritive value components were affected by N application rates rather than cultivars. Despite greater HA and good nutritive value, animal daily gain and gain per acre were lower for K-31 compared to Texoma MaxQ II. This could be related to an increase in tall fescue toxicosis due to drought stress conditions during the second year of the study. Under these adverse conditions, novel endophyte tall fescue led to enhanced animal performance.
Abbreviations: HA, herbage accumulation; N, nitrogen; P, phosphorus; E+, K-31 endophyte-infected; NE, novel endophyte; E-, endophyte-free; ENV, environment; ADG, average daily gain; GAP, gain per acre; CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; LSD, a least significant difference; AU, animal unit.
Keywords: nitrogen, stockpiled grazing, tall fescue, novel endophyte, K-31.
The southern USA is a major region for grazing beef cattle due to the longer growing season and mild temperatures. Beef cattle producers in the upper south are always looking for an alternative to traditional winter-feeding systems such as hay and baleage. Stockpiled forage has become of interest since producing or purchasing hay to feed livestock through the winter represents a considerable expense. Stockpiling tall fescue [Schedonorus arundinaceous (Schreb.) Dumort.] can be used to extend the grazing season and reduce such expense due to its low cost of production compared to providing other feed sources (hay and commodity feed) (Nave et al., 2016). Bishop-Hurley & Kallenbach (2001) indicated that a gestating, mature cow can be maintained by one-fourth the cost of feeding hay while using stockpiled fescue.
Tall fescue is the preferred stockpiled forage because of its excellent fall growth and nutritive value. In addition, winter defoliation has a little subsequent effect on spring regrowth. Despite these advantages, tall fescue is one of the most under-utilized species in the region. However, most tall fescue pastures in the southeastern United States still contain the wild-type endophyte. In Mississippi, there are approximately 174,000 acres of tall fescue with 85% of the area containing K-31 endophyte-infected fescue (E+). Poore et al. (2000) indicated that grazing K-31 infected fescue during the winter has reduced gains despite the good forage nutritive value when compared to endophyte-free or novel endophyte cultivars. The reduced gains can be extremely variable due to the presence of a toxic endophyte (Neotyphodium coenophialum Morgan-Jones and Gams) that can produce ergot alkaloids which negatively influence animal performance by reducing dry matter intake, weight gain, lactation, and reproduction (Stuedemann & Seman, 2005). On the other hand, novel endophyte (NE) cultivars may help to minimize toxicity issues associated with K-31 and increased the potential integration of tall fescue in the upper southern USA.
A primary factor affecting biomass accumulation of tall fescue in the fall is nitrogen (N) fertilization. The response to fall N applications can be highly variable due to environmental conditions, date of fertilization, and N source. Lemus & Walker (2021) indicated that N application in mid-September favored biomass accumulation compared to mid-October application. They also indicated that ammonium nitrate had greater biomass accumulation compared to urea. On the other hand, Teustch et al. (2014) indicated that the yield of stockpiled tall fescue increased linearly with N rate across different N sources, but the rate of increase varied from 5 to 13 lb DM/lb of N. Franzluebbers & Poore (2020) also indicated that forage nutritive value of stockpiled tall fescue was enhanced with N fertilization, but not with P fertilization.
While stockpiled tall fescue has been shown to extend the grazing season in the transition zone, it has not been widely adopted in the upper South. This study was designed to determine the effect of N rate on herbage accumulation (HA), nutritive value, and animal performance of livestock grazing two stockpiled tall fescue cultivars (E+ and NE).
MATERIALS AND METHODS
The protocol for this study was approved by the Institutional Animal Care and Use Committee at Mississippi State University (AICUC-14-092).
The experiment was conducted over two consecutive fall grazing cycles [2014-2015 (ENV1) and 2015-2016 (ENV2)] in well-established tall fescue pastures at the Henry H. Leveck Animal Research Farm at Mississippi State University. Tall fescue pastures were established in October of 2013. The soil types across all pastures were Marietta Sandy Loam (Fine-loamy, siliceous, active, thermic Fluvaquentic Eutrudepts) and Oktibbeha soils (Very-fine, smectitic, thermic Chromic Dystruderts). The experimental design was a randomized complete block in 2 x 3 factorial replicated twice. Treatments consisted of two tall fescue species [K-31(E+) and Texoma MaxQ (NE)] with the application of urea (46-0-0) at three N rates (0, 50, and 100 lb N ac-1). Nitrogen was applied on September 12 and 15 of 2014 and 2015, respectively. Forage was accumulated for late fall grazing. Each pasture was approximately one acre in size. Winter grazing of the stockpiled forage was initiated on December 3 and 9 of 2014 and 2015, respectively.
Two steers were assigned to each pasture and the average initial stocking rate 698 and 644 lb live body weight (BW) per acre in 2014 and 2015, respectively. Cattle were given free-choice access to a mineral supplement. Before the start of the grazing period, all steers were weighed in two consecutive days to determine initial body weight (BW). Steers were stratified by BW and randomly allotted to 6 groups in which groups were randomly assigned to replicate and treatment combination (TF x N). Bodyweight gain per acre (GPA) and the number of grazing days per acre were calculated for each cultivar and N treatment. Gain per acre was calculated using the formula [pasture ADG (lb/animal daily) x animals grazing x length of a grazing period (d)]/total area grazed (ac)] (Drewnoski et al., 2009). Animal grazing days (d/ac) were calculated using the formula [animals grazing x length of a grazing period (d)]/[total area grazed (ac)] (Drewnoski et al., 2009). The grazing periods for determination of pasture animal daily gain (ADG) were 90 d (ENV1) and 74 d (ENV2).
To determine pre-grazing dry matter biomass, five random samples were taken in each pasture using a 2-ft2 quadrat, and samples were clipped to ground level. Samples were dried in an air-forced dryer at 140 °F until reaching a constant weight and used to determine the pound of dry matter herbage accumulation per acre. Herbage offered (lb/animal daily) during the grazing period was determined by using the following formula: [pre-grazing mass (DM/ac) × area offered during the period (ac)]/[number of animals grazing × length of a grazing period (d)] (Drewnoski et al., 2009). Samples were ground to pass a 1-mm screen and analyzed for nutritive value using a Foss 2500 near-infrared reflectance spectrophotometer (NIRS; Foss North America, Eden Prairie, MN) and by applying the 2018 mixed hay equation developed by the NIR Forage and Testing Consortium (Berea, KY). Nutritive values included crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and in vitro true dry matter digestibility (IVTDMD) at 48 h.
Data were statistically analyzed in combined analyses with years treated as repeated measures using PROC GLIMMIX (SAS Institute, 2018). In the mixed model, tall fescue cultivars and N treatments were considered fixed whereas years and replications were considered random. Differences were tested at α = 0.05 unless otherwise stated.
RESULTS AND DISCUSSION
Rainfall and Temperature Data
Total precipitation was 13 and 3% lower during ENV1 and EV2, respectively. Precipitation was below normal in September of both seasons when urea applications occurred. Such lack of precipitation could have increased N losses and decrease plant uptake and utilization. The temperature was above normal in September and October of both seasons. Temperatures also remained above normal in November and December of ENV2.
|Month||Temperature (°F)||Precipitation (inches)|
Stockpiled Herbage Accumulation
Differences in herbage accumulation (HA) were observed across environments due to precipitation lower than normal from the time of N application to the grazing initiation. Differences in HA due to N had a significant tendency at α = 0.10 during ENV1 (P = 0.0666), but not different for ENV2 (P = 0.7216). There was a positive linear response to N application during ENV1 and quadratic response during ENV2 (Fig. 1). Such results were similar to those reported by Teutsch et al. (2014) where HA increased linearly with N rate across different N sources, but the rate of increase was variable. This could be related to the lack of moisture, above-normal temperatures, and humidity that could have increased N losses and reduced efficiency. Average HA was 7 and 25% higher for K-31 than Texoma across both environments (Fig. 2). Kallebach et al. (2017) indicated that for optimum stockpiled forage yields, tall fescue should be fertilized with less than 100 lb N/ac and grazed by mid-January.
Figure 1. Impact of three nitrogen fertilization rates on stockpiled tall fescue across two environments. Data pooled across cultivars. Letters represent significant differences among N rates within Environment 1 at α = 0.10.
Figure 2. Stockpiled tall fescue biomass distribution across two environments (ENV1 and ENV2) before stockpiled grazing initiation.
Forage Nutritive Value
Overall CP was slightly higher for K-31 than Texoma (18.5 vs 17.5%), but both levels were above those required for the livestock grazing the pastures. No differences in ADF, NDF, and lignin concentrations were observed among cultivars and across the environments. This finding is similar to that reported by Kallenbach et al. (2003). Fat concentration was significantly higher for K-31 than Texoma (1.96 vs. 2.73%). A significant Environment x N application was observed for CP (P = 0.0441), ADF (P < 0.0001), NDF (P < 0.0001), fat (P < 0.0010) and lignin (P < 0.0001). Percent CP increased with N application and concentrations were higher in ENV1 than ENV2 within N application rates (Table 1). Compared to average grass hay in Mississippi, stockpiled tall fescue in this study contained greater CP to meet the nutritional requirements of all classes of beef cattle. Acid detergent fiber concentrations declined with N application in ENV1, while concentration was significantly higher at 0N during ENV2 (Table 1). Neutral detergent fiber followed the same trend observed with ADF. Larger differences in NDF concentrations were observed at the 0N application (Table 1). Fat concentration had a linear increase with N application in both environments, with slightly higher concentrations in ENV1. Lignin concentration had a linear decrease with N application in both environments (Table 2). Although tall fescue cultivar differences were small, these data indicate the high nutritive value of stockpiled tall fescue.
|Nitrogen Rate (lb N/ac)|
|Concentration (% DM)|
|Crude Protein (CP)|
|Acid Detergent Fiber (ADF)|
|Neutral Detergent Fiber (NDF)|
1Least significant difference at α = 0.05.
The number of days on pasture was impacted only by the environmental conditions and HA and not by cultivars and N fertilization. Animals spend 90 days on pasture during ENV1 compared to 74 days during ENV2. Despite no N impact, there was a linear increase of days on pasture with N application (Days on Pasture = 0.055N + 38.25, R² = 0.9758). It could be difficult to give a good estimation of the number of grazing days that can be expected from an acre of stockpiled tall fescue due to the climatic variability and the potential for moisture and temperature gradients in the southern USA. The amount of forage offered was affected by cultivars (P = 0.0272). K-31 had a 100% greater consumption of forage compared to Texoma MaxQ II (34 vs. 17 lb DM/day/animal).
Across environments, average daily gain (ADG) was 62% greater in ENV1 compared to ENV2. Texoma MaxQ II had 17% greater ADG than K-31. Our results are opposite to those reported by Drewnoski et al. (2009) and Hopkins & Alison (2006) in which no differences were reported among E+, NE, and E- tall fescue in the fall. There was a significant cultivar x N interaction for ADG (P = 0.0327). Texoma MaxQ II had 13, 7, and 32% greater ADG than K-31 at 0, 50, and 100 lb/ac, respectively (Fig. 3). Across tall fescue cultivars, ADG was 44 and 33% greater with N application of 50 and 100 lb N/ac when compared to the control.
Figure 3. Average daily gain distribution across two stockpiled tall fescue cultivars and three nitrogen rates.
There was a significant Environment x Cultivar interaction (P = 0.0056) for gain per acre (GPA). Gain per acre was not significantly different during ENV1; however, Texoma MAXQ II had 78% greater gain during ENV2 compared to K-31 (Fig. 4). A significant ENV x N interaction (P = 0.0151) also impacted GPA during the study (Fig. 5). There was a positive response of GPA to N application during ENV1. GPA increased 11 and 47% with N applications of 50 and 100 lb/ac compared to the control. ENV2 had a greater GPA at the 50 lb N/ac compared to 0 and 100 lb N/ac. Lower response at the 100 lb N/ac can be attributed to higher N losses due to drought conditions at the time of application compared to ENV1. A cultivar x Nitrogen (P = 0.0420) have a linear impact on GPA. Gains were significantly greater for Texoma MAxQ II across all N treatments compared to K-31. This could be related to the endophyte effect. Stockpiled forage from endophyte-infected K-31 might contain higher ergovaline levels, especially when tall fescue has been fertilized and undergoing drought stress. Despite the possibility of tall fescue toxicosis decreasing later in the fall, animal performance may be impacted.
Figure 4. Animal gain per acre in stockpiled tall fescue as influenced by environment and cultivar. Letters are for comparison of cultivars within an environment.
Figure 5. Animal gain per acre in stockpiled tall fescue as influenced by environment and nitrogen rate. Letters are for comparison of N rates within an environment.
In Mississippi, the current combined costs of producing and harvesting hay are approximately $30 per round bale of mixed-grass hay. The average nutritive value of mixed-grass hay in Mississippi is 8% CP and 50% TDN (Lemus, 2020). Savings from stockpiled tall fescue were estimated based on the cost of fertilizer to grow the stockpiled fescue forage compared to the value of hay and supplement that would have been required to replace the grazing time and animal performance gained from the stockpiled forage. Savings were converted to an animal unit (AU) basis for comparison. One AU represents the daily energy requirement for a mature, non-lactating cow weighing 1,000 lbs. Average savings per AU of stockpiled tall fescue across N treatments was estimated at $15.89 and $12.78 for ENV1 and ENV2, respectively, when compared to days of hay supplementation during the same stockpiling period.
Stockpiling forages can be a useful tool for beef cattle producers in the upper south. Herbage accumulation will be dependent on rainfall, N fertilization, and tall fescue cultivar. Variability in precipitation during the fall can impact tall fescue recovery from the hot summers in the southern USA along with soil moisture content to facilitate N uptake and reduce losses that could affect efficiency. This type of climatic influence can also impact the number of grazing days that can be available to extend the grazing season and may not indicate the true number of grazing days that a producer could depend on to reduce hay supplementation. The average number of grazing days indicates that a producer could eliminate approximately 34 to 41% of the time spent feeding hay when using an average hay feeding season of 110 days. Due to the high quality of the forage, ADG was comparable to those reported in the literature in areas more conducive for tall fescue stockpiling. Although the 100 lb N/ac indicated a higher gain per acre, producers need to be aware of the environmental conditions, the age of the stand, and the grazing management to avoid factors that could pose a significant financial risk. Producers should not apply more than 50 to 70 lb N/ac during stockpiling of tall fescue. This study indicated that stockpiling tall fescue might be a cost-effective strategy to reduce hay supplementation in tall fescue areas of the southern USA and to close the gap until the initiation of grazing cool-season annual forage crops. The stable herbage biomass accumulation and nutritive value suggest that livestock producers can reduce hay supplementation by stockpiling these cultivars for winter grazing. Furthermore, there is still a need to evaluate differences in the efficiency of grazing management systems and stocking rates that can provide a more comprehensive approach to tall fescue management in the upper south. This especially the case with new novel-endophyte and endophyte-free cultivars.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interest.
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch project under accession number 1016223, Project Number MIS-164010. The authors are grateful to undergraduate students W. Mike Hammack, Joey Hessner, and Daniel Newman for their help with data collection and processing.
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