Effects of Cultivar and Distillers Grains Supplementation on Effects of Cultivar and Distillers Grains Supplementation on Grazing and Subsequent Finishing Performance of Stocker Steers Grazing and Subsequent Finishing Performance of Stocker Steers Grazing Tall Fescue Pasture Grazing Tall Fescue Pasture

Summary Four hundred thirty-two yearling steers grazing tall fescue pastures were used to evaluate the effects of fescue cultivar and dried distillers grains (DDG) supplementation during the grazing phase on available forage, grazing gains, subsequent finishing gains, and carcass characteristics. Fescue cultivars evaluated were high-endophyte ‘Kentucky 31’ and low-endophyte ‘Kentucky 31,’ ‘HM4,’ and ‘MaxQ.’ Steers were either fed no supplement or were supplemented with DDG at 1.0% body weight per head daily in 2009 or 0.75% of body weight per head daily in 2010, 2011, 2012, 2013, and 2014 while grazing. Steers that grazed pastures of low-endophyte ‘Kentucky 31,’ ‘HM4,’ or ‘MaxQ’ gained significantly more ( P < 0.05) and produced more ( P < 0.05) gain/a than those that grazed high-endophyte ‘Kentucky 31’ pastures. Gains of cattle that grazed low-endophyte ‘Kentucky 31,’ ‘HM4,’ or ‘MaxQ’ were similar ( P > 0.05). Subsequent finishing gains were similar ( P > 0.05) among fescue cultivars in 2009, 2012, 2013, and 2014; however, steers that previously grazed high-endophyte ‘Kentucky 31’ had greater ( P > 0.05) finishing gains than those that had grazed ‘HM4’ or ‘MaxQ’ in 2010 and greater ( P < 0.05) finishing gains than those that grazed low-endophyte ‘Kentucky 31’ or ‘HM4’ in 2011. Supplementation of grazing steers with DDG supported a higher stocking rate and resulted in greater ( P < 0.05) grazing gain, gain/a, and overall daily gain and reduced the amount of fertilizer needed by providing approximately 60 lb/a, 50 lb/a


Introduction
Tall fescue, the most widely adapted cool-season perennial grass in the United States, is grown on approximately 66 million acres.Although tall fescue is well adapted in the eastern half of the country between the temperate North and mild South, presence of a fungal endophyte results in poor performance of grazing livestock, especially during the summer.Until recently, producers with high-endophyte tall fescue pastures had two primary options for improving grazing livestock performance.One option was to destroy existing stands and replace them with endophyte-free fescue or other forages.Although it supports greater animal performance than endophyte-infected fescue, endophyte-free fescue has been shown to be less persistent under grazing pressure and more susceptible to stand loss from drought stress.In locations where high-endophyte tall fescue must be grown, the other option was for producers to adopt management strategies that reduce the negative effects of the endophyte on grazing animals, such as diluting the effects of the endophyte by incorporating legumes into existing pastures or providing supplemental feed.In recent years, new tall fescue cultivars have been developed with a non-toxic endophyte that provides vigor to the fescue plant without negatively affecting performance of grazing livestock.
Growth in the ethanol industry has resulted in increased availability of distillers grains, which have been shown to be an excellent feedstuff for supplementing grazing cattle because of their high protein and phosphorus content.Distillers grains contain approximately 4% to 5% N, and cattle consuming them excrete a high percentage of this N in their urine and feces; therefore, feeding dried distillers grains (DDG) to grazing cattle will provide N to the pastures.Objectives of this study were to (1) evaluate two of these new cultivars in terms of forage availability, stand persistence, and grazing and subsequent finishing performance of stocker steers and compare them with high-and low-endophyte 'Kentucky 31' tall fescue; (2) evaluate DDG supplementation of cattle grazing these pastures; and (3) determine the contribution of DDG as a nitrogen fertilizer source.

Experimental Procedures
Seventy-two mixed black yearling steers were weighed on two consecutive days and allotted to 16 5-acre established pastures of high-endophyte 'Kentucky 31' or low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' tall fescue (four replications per cultivar) on March 26, 2009 (569 lb average weight); March 24, 2010 (550 lb); March 23, 2011 (536 lb); March 22, 2012 (550 lb); April 4, 2013 (600 lb); and April 1, 2014 (546 lb).'HM4' and 'MaxQ' are cultivars that have a non-toxic endophyte.Four steers were assigned to two pastures of each cultivar and received no supplementation, and five steers were assigned to two pastures of each cultivar and supplemented with DDG at 1.0% in 2009 or 0.75% body weight per head daily during the grazing phase in 2010, 2011, 2012, 2013, and 2014.All pastures were fertilized with 80 lb/a N and P 2 O 5 and K 2 O as required by soil test on February 5, 2009;February 10, 2010;and January 27, 2011;90 lb/a N on January 25, 2012;85 lb/a N on February 5, 2013;and 74 lb/a N on February 13, 2014.Pastures with steers that received no supplement were fertilized with 60 lb/a N on September 16, 2009;46 lb/a N on August 30, 2010 andSeptember 15, 2011;30 lb/a N on August 10, 2012;and46 lb/a N on September 19, 2013 andSeptember 15, 2014.This was calculated to be approximately the same amount of N from DDG that was excreted on pastures by supplemented steers during the entire grazing season.
Cattle in each pasture were group-fed DDG in meal form in bunks on a daily basis, and pasture was the experimental unit.No implants or feed additives were used.Weight gain was the primary measurement.Cattle were weighed every 28 days; quantity of DDG fed was adjusted at that time.Forage availability was measured approximately every 28 days with a disk meter calibrated for tall fescue.Cattle were treated for internal and external parasites before being turned out to pasture and later vaccinated for protection from pinkeye.Steers had free access to commercial mineral blocks that contained 12% calcium, 12% phosphorus, and 12% salt.Two steers in 2009, one steer in 2012, and two steers in 2013 were removed from the study for reasons unrelated to experimental treatment.Pastures were grazed continuously until October 13, 2009 (201 days);November 3, 2010 (224 days);October 19, 2011 (210 days);August 21, 2012 (152 days);October 17, 2013 (196 days);and October 14, 2014 (196 days) for all pastures except one replicate of low-endophyte 'Kentucky 31,' where grazing was terminated on September 17, 2014 (169 days), when steers were weighed on two consecutive days and grazing was terminated.
After the grazing period, cattle were moved to a finishing facility, implanted with Synovex-S (Zoetis, Madison, NJ), and fed a diet of 80% whole-shelled corn, 15% corn silage, and 5% supplement (dry matter basis).Cattle that received no supplement or were supplemented with DDG while grazing were fed a finishing diet for 119 or 99 days, for 112 or 98 days, for 116 or 102 days, and for 120 or 106 days, respectively, in 2009, 2011, 2013, and 2014; for 106 days in 2010; and for 113 days in 2012.All steers were slaughtered in a commercial facility, and carcass data were collected.
In 2009, subsequent finishing gains and feed efficiency were similar (P > 0.05) among fescue cultivars (Table 1).Steers that previously grazed low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' maintained their weight advantage through the finishing phase and had greater (P < 0.05) final finishing weights, hot carcass weights, overall gains, and overall daily gains than those that previously grazed high-endophyte 'Kentucky 31.' Final finishing weights, hot carcass weights, overall gains, and overall daily gains were similar (P > 0.05) among steers that previously grazed low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ.'Backfat thickness and percentage of carcasses graded choice or higher were similar (P > 0.05) among fescue cultivars.
Average available forage dry matter (DM) is presented for each fescue cultivar and supplementation treatment combination for 2009, 2010, 2011, 2012, 2013, and 2014 in Tables 13, 14, 15, 16, 17, and 18 in Tables 13, 14, 15, 16, 17, and 18, respectively.A significant interaction occurred (P < 0.05) between cultivar and supplementation treatment during all six years.Within each variety, there was no difference (P > 0.05) in average available forage DM between pastures stocked with 0.8 steer/a that received no supplement and those stocked with 1.0 steer/a and supplemented with DDG at 1.0% body weight per head daily in 2009 (Table 13).Average available forage DM was similar (P > 0.05) between supplementation treatments and pastures, with supplemented steers stocked at a heavier rate, which indicates that pastures were responding to the N that was being returned to the soil from steers consuming DDG, cattle supplemented with DDG were consuming less forage, or both.High-endophyte 'Kentucky 31' pastures with or without DDG supplementation had greater (P < 0.05) average available forage DM than 'MaxQ' pastures without supplementation.No other differences in average available forage DM were observed.
In 2010, no difference occurred (P > 0.05) in average available forage DM within variety for high-endophyte 'Kentucky 31,' low-endophyte 'Kentucky 31,' or 'HM4' pastures stocked with 0.8 steer/a that received no supplement and those stocked with 1.0 steer/a and supplemented with DDG at 0.75% body weight per head daily (Table 14); however, 'MaxQ' pastures that were stocked at the heavier rate and grazed by steers supplemented with DDG had greater (P < 0.05) average available forage DM than those stocked at a lighter rate and grazed by steers that received no supplement.High-endophyte 'Kentucky 31' pastures had greater (P < 0.05) average available DM than low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' pastures stocked with 0.8 steer/a that received no supplement.
In 2011, no difference occurred (P > 0.05) in average available forage DM within variety for low-endophyte 'Kentucky 31' or 'HM4' pastures stocked with 0.8 steer/a that received no supplement and those stocked with 1.0 steer/a and supplemented with DDG at 0.75% body weight per head daily (Table 15), but 'MaxQ' pastures that were stocked at the heavier rate and grazed by steers supplemented with DDG had greater (P < 0.05) average available forage DM than those stocked at a lighter rate and grazed by steers that received no supplement.High-endophyte 'Kentucky 31' pastures that were stocked at the heavier rate and grazed by steers supplemented with DDG had lower (P < 0.05) average available forage DM than those stocked at a lighter rate.High-endophyte 'Kentucky 31' pastures had greater (P < 0.05) average available DM than low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' pastures stocked with 0.8 steer/a that received no supplement.
In 2012, a cultivar × date interaction occurred, with similar peak available DM on April 18 (P > 0.05) but lower available DM for 'MaxQ' and 'HM4' (P < 0.05) at the end of the grazing phase on August 17.No difference occurred (P > 0.05) in average available forage DM within variety for low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' pastures stocked with 0.8 steer/a that received no supplement and those stocked with 1.0 steer/a and supplemented with DDG at 0.75% body weight per head daily (Table 16); however, high-endophyte 'Kentucky 31' pastures that were stocked at the heavier rate and grazed by steers supplemented with DDG had lower (P < 0.05) average available forage DM than those stocked at a lighter rate in both 2011 and 2012.This result suggests that supplementation with DDG increased forage intake and utilization by cattle grazing these pastures.High-endophyte 'Kentucky 31' pastures had greater (P < 0.05) average available DM than low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' pastures within each stocking rate and supplementation level in 2012.
In 2013, a cultivar × date interaction occurred, with all cultivars having similar (P > 0.05) available DM at the beginning of the grazing season.On April 30, low-endophyte 'Kentucky 31' had less (P < 0.05) available DM than the other three cultivars.Available DM peaked on June 3 then declined as the grazing season progressed.On June 3, high-endophyte 'Kentucky 31' had more (P < 0.05) available DM than the other three cultivars, and 'MaxQ' had less (P < 0.05) available DM than 'HM4.'By July 31, high-endophyte 'Kentucky 31' had more (P < 0.05) and 'MaxQ' less (P < 0.05) available DM than the other cultivars, a relationship that persisted throughout the remain-der of the grazing season.No difference occurred (P > 0.05) in average available forage DM within variety for low-endophyte 'Kentucky 31' pastures stocked with 0.8 steer/a that received no supplement and those stocked with 1.0 steer/a and supplemented with DDG at 0.75% body weight per head daily (Table 17); however, high-endophyte 'Kentucky 31,' 'HM4,' and 'MaxQ' pastures that were stocked at the heavier rate and grazed by steers supplemented with DDG had lower (P < 0.05) average available forage DM than those stocked at a lighter rate without supplement.This result suggests that supplementation with DDG increased forage intake and utilization by cattle grazing these pastures and/or DDG level was not high enough to substitute for the forage consumed by the additional steer.High-endophyte 'Kentucky 31' pastures had greater (P < 0.05) average available DM than low-endophyte 'Kentucky 31,' 'HM4,' or 'MaxQ' pastures within each stocking rate and supplementation level in 2013.
In 2014, high-endophyte 'Kentucky 31' had more available DM than the other cultivars throughout the season, with no difference among the other three cultivars.On April 7, the initial date, available DM was the lowest for the entire season, whereas the highest available DM did not occur until June 25.This was because of the unusually dry spring followed by abundant rain in June.A cultivar × supplementation/stocking rate interaction occurred in 2014, because average available forage DM was similar for the cultivars, except in 'MaxQ' pastures (Table 18).The unsupplemented 'MaxQ' pastures had less available DM than those where supplement was fed, despite being stocked at a lower rate.

Table 1 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2009

Table 2 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2010

Table 3 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2011

Table 4 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2012

Table 5 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2013

Table 6 .
Effects of cultivar on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural Research Center, 2014

Table 7 .
Effects of dried distillers grains (DDG) supplementation on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural

Table 12 .
Effects of dried distillers grains (DDG) supplementation on grazing and subsequent performance of steers grazing tall fescue pastures, Southeast Agricultural

Table 13 .
Effects of tall fescue cultivar and dried distillers grains (DDG) supplementation on average available forage dry matter, Southeast Agricultural Research Center, 2009 DDG level (% body weight/head per day)

Table 15 .
Effects of tall fescue cultivar and dried distillers grains (DDG) supplementation on average available forage dry matter, Southeast Agricultural Research Center, 2011 Means followed by the same letter do not differ (P < 0.05).

Table 16 .
Effects of tall fescue cultivar and dried distillers grains (DDG) supplementation on average available forage dry matter, Southeast Agricultural Research Center, 2012

Table 17 .
Effects of tall fescue cultivar and dried distillers grains (DDG) supplementation on average available forage dry matter, Southeast Agricultural Research Center, 2013