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Beef cattle consume more tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] than any other perennial cool-season grass in North America. Tall fescue forms a mutualistic relationship with the fungus Epichloë coenophiala (Morgan-Jones and W. Cams) C.W. Bacon & Schardl, comb. nov.; these plants are often referred to as endophyte-infected tall fescue. Agronomically, endophyte infection is good; endophyte- infected plants resist biotic and abiotic stresses better than do endophyte-free plants. However, tall fescue plants infected with a common toxic endophyte produce the ergot alkaloids that cause tall fescue toxicosis. Several agronomic practices can eliminate or reduce the effects of tall fescue toxicosis. Renovating tall fescue fields infected with a common toxic endophyte to new cultivars infected with a novel (or nontoxic) endophyte eliminates the problem for that field. Although the cost to renovate currently exceeds US$600/ha, most economic analyses show it to be a good long-term investment, especially on fields with high forage production potential. Less effective, but popular, methods of dealing with tall fescue toxicosis include adding clovers (Trifolium spp.) or other forage species to the pastures to dilute the effects of the toxins, avoiding the use of high rates of nitrogen fertilizers, feeding supplements, and rotating cattle to warm-season forages in summer. Also, the alkaloid concentration in forage can be reduced by making it (drying) into hay. Recent research shows that animal tolerance to tall fescue toxicosis is possible, although there is still much to learn about this topic. Tall fescue toxicosis is likely a reality in the beef industry for some time to come. We contend that renovation of the most productive fields to cultivars infected with a novel endophyte coupled with the prospect of using tolerant livestock in scenarios where renovation is not possible will give innovative producers a competitive edge. [ABSTRACT FROM AUTHOR]

The daily BW gain of stocker steers grazing tall fescue [Lolium arundiriaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor. [ABSTRACT FROM AUTHOR]

A 2–yr production study was conducted to evaluate 3 systems of growing stocker calves under rotational stocking. One group of steers was stocked on pasture from early April to mid August (springstocked steers = SSS), and another group of steers was stocked from early July to late October (fall–stocked steers = FSS). Steers were stratified by BW (n = 72, BW=229±llkgforSSS;n=72,BW=248±18 kg for FSS) and randomly assigned to 1 of 3 treatments. The 3 treatments were 1) rotationally stocked only (control; CON), steers rotated to a new paddock as forage availability dropped below acceptable levels in the occupied paddock; 2) rotationally stocked with distillers grains (DIST); this was the same as CON except steers were supplemented with varying amounts of distillers dried grains with solubles (DDGS) based on forage nutritive value; and 3) rotationally stocked with round–bale silage (SIL); excess forage in spring was harvested and stored as round–bale silage and fed back as needed. Total BW gain/ha over the entire grazing season did not differ between DIST and SIL (P = 0.09) steers, but both were greater thall CON (P < 0.01). Total BW gain/ha for DIST, SIL, and CON was 459 (SEM = 11.5), 402 (SEM = 31.0), and 276 (SEM = 26.2) kg, respectively. For ADG, there was a group x year (P < 0.01) and group x treatment (P = 0.02) interaction. Steer ADG for SSS did not differ between SIL and DIST (P = 0.51), but was greater than the CON (P = 0.01). The ADG for SSS was 0.79 (SEM = 0.04), 0.81 (SEM = 0.05), and 0.62 (SEM = 0.05) kg for DIST, SIL, and CON, respectively. For the FSS, ADG for all 3 treatments was different (P = 0.02). The FSS ADG was 0.72 (SEM 0.03), 0.53 (SEM = 0.04), and 0.29 (SEM = 0.04) kg for DIST, SIL, and CON, respectively. The only treatment with equivalent (P = 0.07) ADG between early and late–stocked steers (SSS vs. FSS) was DIST. Adjusting the amount of DDGS supplemented to steers based on forage nutritive value resulted in consistent BW gains throughout the grazing study, whereas steers in the SIL and CON treatments gained less BW during the latter portion of the season. Controlling forage maturity by removal in the SIL treatment resulted in total BW gains/ha that were not different than the DIST treatment. [ABSTRACT FROM AUTHOR]

A 2–yr production study was conducted to evaluate 3 systems of growing stocker calves under rotational stocking. One group of steers was stocked on pasture from early April to mid August (springstocked steers = SSS), and another group of steers was stocked from early July to late October (fall–stocked steers = FSS). Steers were stratified by BW (n = 72, BW=229±llkgforSSS;n=72,BW=248±18 kg for FSS) and randomly assigned to 1 of 3 treatments. The 3 treatments were 1) rotationally stocked only (control; CON), steers rotated to a new paddock as forage availability dropped below acceptable levels in the occupied paddock; 2) rotationally stocked with distillers grains (DIST); this was the same as CON except steers were supplemented with varying amounts of distillers dried grains with solubles (DDGS) based on forage nutritive value; and 3) rotationally stocked with round–bale silage (SIL); excess forage in spring was harvested and stored as round–bale silage and fed back as needed. Total BW gain/ha over the entire grazing season did not differ between DIST and SIL (P = 0.09) steers, but both were greater thall CON (P < 0.01). Total BW gain/ha for DIST, SIL, and CON was 459 (SEM = 11.5), 402 (SEM = 31.0), and 276 (SEM = 26.2) kg, respectively. For ADG, there was a group x year (P < 0.01) and group x treatment (P = 0.02) interaction. Steer ADG for SSS did not differ between SIL and DIST (P = 0.51), but was greater than the CON (P = 0.01). The ADG for SSS was 0.79 (SEM = 0.04), 0.81 (SEM = 0.05), and 0.62 (SEM = 0.05) kg for DIST, SIL, and CON, respectively. For the FSS, ADG for all 3 treatments was different (P = 0.02). The FSS ADG was 0.72 (SEM 0.03), 0.53 (SEM = 0.04), and 0.29 (SEM = 0.04) kg for DIST, SIL, and CON, respectively. The only treatment with equivalent (P = 0.07) ADG between early and late–stocked steers (SSS vs. FSS) was DIST. Adjusting the amount of DDGS supplemented to steers based on forage nutritive value resulted in consistent BW gains throughout the grazing study, whereas steers in the SIL and CON treatments gained less BW during the latter portion of the season. Controlling forage maturity by removal in the SIL treatment resulted in total BW gains/ha that were not different than the DIST treatment. [ABSTRACT FROM AUTHOR]

Although feed intake and efficiency differences in growing cattle of low and high residual feed intake (RFI) classification have been established, little is known about the difference in grazed forage intake between beef cows of known RFI classification. Two experiments were conducted using Hereford cows for which RFI had been determined as heifers using the GrowSafe 4000E feed intake system, after which heifers had been divided into thirds as low RFI, mid RFI, and high RFI. During Exp. 1, 2 replicates of low and high RFI cows (n = 7/replicate) in mid- to late-gestation were blocked to 1 of 4 non-endophyte-infected tall fescue paddocks (1.8 to 2.4 ha), which they grazed continuously for 84 d during summer. Using grazing exclosures, weekly rising plate meter readings, and forage harvests every 21 d, average forage DMI was calculated. Low and high RFI groups did not differ (P > 0.05) in BW change or BCS change over the trial (19.5 vs. 22.1 kg of BW gain and 0.11 vs. 0.10 BCS gain), but low RFI cows had a 21% numerically lower DMI than high RFI cows (12.4 vs. 15.6 kg/d; P = 0.23). The average area needed per paddock over the trial was similar for low and high RFI cows (1.71 vs. 1.82 ha; P = 0.35), and the average DM on offer over the trial was less for low RFI than for high RFI cows (4,215 vs. 4,376 kg; P = 0.06). During Exp. 2, 3 replicates of low and high RFI cows with their calves (n = 4 pair/replicate) strip-grazed stockpiled and early spring growth tall fescue paddocks (0.7 to 0.9 ha) for 60 d in late winter and early spring. Because of limiting forage availability and quality at trial initiation, cow-calf pairs were also fed 3.31 kg/pair of pelleted soyhulls daily. Pre- and post-grazed forage samples were harvested for 4 grazing periods, and forage growth was estimated using a growing degree days calculation and on-site weather station data. Performance did not differ (P > 0.05) between low and high RFI cows throughout the experiment (18.4 vs. 26.6 kg of BW gain and -0.04 vs. 0.15 BCS gain). Despite the utilization of forage offered being similar for low and high RFI cow-calf pairs (P > 0.05), low RFI cows and their calves had an 11% numerically lower DMI than high RFI pairs (12.5 vs. 14.1 kg/d; P = 0.12). We concluded that either no intake differences existed between low and high RFI cows or that current methodology and small animal numbers limited our ability to detect differences. [ABSTRACT FROM AUTHOR]

In a 2-yr study, we evaluated the effect of different forage allocations on the performance of lactating beef cows and their calves grazing stockpiled tall fescue. Allocations of stockpiled tall fescue at 2.25, 3.00, 3.75, and 4.50% of cow-calf pair BW/d were set as experimental treatments. Conventional hay-feeding was also evaluated as a comparison to grazing stock-piled tall fescue. The experiment had a randomized complete block design with 3 replications and was divided into 3 phases each year. From early December to late February (phase 1) of each year, cows and calves grazed stockpiled tall fescue or were fed hay in the treatments described above. Immediately after phase 1, cows and calves were commingled and managed as a single group until weaning in April (phase 2) so that residual effects could be documented. Residual effects on cows were measured after the calves were weaned in April until mid-July (phase 3). During phase 1 of both years, apparent DMI of cow-calf pairs allocated stockpiled tall fescue at 4.50% of BW/d was 31% greater (P < 0.01) than those allocated 2.25% of BW/d. As allocation of stockpiled tall fescue increased from 2.25 to 4.50% of cow-calf BW/d, pasture utilization fell (P < 0.01) from 84 ± 7% to 59 ± 7%. During phase 1 of both years, cow BW losses increased linearly (P < 0.02) as forage allocations decreased, although the losses in yr 1 were almost double (P < 0.01) those in yr 2. During phases 2 and 3, few differences were noted across treatment groups, such that by the end of phase 3, cow BW in all treatments did not differ either year (P > 0.40). Calf ADG in phase 1 increased linearly (P r< 0.01) with forage allocation (y = 0.063x + 0.513; R² = 0.91). How- ever, calf gain per hectare decreased linearly (P r< 0.01) as stockpiled tall fescue allocations increased (y = -26.5x + 212; R² = 0.97) such that gain per hectare for cow-calf pairs allocated stockpiled tall fescue at 4.5 0% BW/d was nearly 40% less (P r< 0.01) than for those allocated 2.25% of BW/d. Allocating cow-calf pairs stockpiled tall fescue at 2.25% of BW/d likely optimizes its use; because cow body condition is easily regained in the subsequent spring and summer months, less forage is used during winter, and calf gain per hectare is maximized. [ABSTRACT FROM AUTHOR]

We examined the effect of endophyte infection level of tall fescue (Festuca arundinacea Schreb.) used for stockpiled forage on the performance of lactating, fall-calving beef cows and their calves. Treatments were endophyte infection levels of 20% (low; SEM = 3.5), 51%, (medium; SEM = 1.25), and 89% (high; SEM = 2.4; 4 replications/treatment). Five cow-calf pairs grazed in each replicate (n = 60 cow-calf pairs/ yr) for 84 d (phase 1) starting on December 2, 2004 (yr 1), and December 1, 2005 (yr 2). After 84 d of grazing each treatment, the cattle were commingled and fed as a single group (phase 2) until weaning in April of each year. Phase 2 allowed measurement of residual effects from grazing stockpiled tall fescue with varying levels of endophyte infection. Pregrazing and postgrazing forage DM yield, forage nutritive value, and total ergot alkaloid concentrations of forage were collected every 21 d during phase 1. Animal performance data included cow BW, ADG, and BCS, as well as calf BW and ADG. Animal performance was monitored during both phases. Endophyte infection did not affect (P = 0.52) apparent intake (pregrazing minus postgrazing forage DM yield) of stockpiled tall fescue, because each cow-calf pair consumed 16 ± 1.7 kg/d regardless of treatment. Cow ADG during phase 1 was -0.47 ± 0.43 kg for the low treatment, which was greater (P < 0.01) than either the medium (-0.64 ± 0.43 kg) or high (-0.74 ± 0.43 kg) treatments. However, cows that had grazed the high or medium treatments in phase 1 lost -0.43 and -0.57 (± 0.24) kg/d, respectively, which was less (P <0.01) BW loss than the cows in the low (-0.78 ± 0.24 kg/d) treatment during phase 2. By the end of phase 2, cow BW did not differ (528 ± 27 kg; P = 0.15). Body condition score for cows in the low treatment was greater (P = 0.02) than that of the medium and high treatments at the end of phase 1. Body condition scores did not change appreciably by the end of phase 2, and differences among treatments remained the same as at the end of phase 1 (P = 0.02). In contrast to cow performance, calf ADG was unaffected (P = 0.10) by endophyte level and averaged 0.73 ± 0.07 kg during phase 1 and 0.44 ± 0.04 kg during phase 2. Our data suggest that fall-calving herds can utilize highly-infected tall fescue when stockpiled for winter grazing, with little impact on cow performance and no impact on calf gain. [ABSTRACT FROM AUTHOR]

Tall fescue (Lolium arundinaceum Schreb.) is the most predominant forage used in Southeastern United States for cow-calf production. Endophyte-infected tall fescue is easily established, adaptable to different environments and grazing tolerant, however alkaloids produced by the fungus cause metabolic disorders in animals referred to fescue toxicosis. Previous research has demonstrated cows consuming endophyte-infected tall fescue have decreased prolactin concentrations, decreased milk production and reduced growth performance in stacker calves. Animals have been shown to differ in degree of tolerance to endophyte-infected tall fescue. T-Snip is a commercial genetic test developed to identify tolerance of cattle to toxic tall fescue. The objective of this study was to analyze correlation between T-Snip test in cows consuming endophyte-infected tall fescue and 205-d weaning weights of their respective calves. We hypothesized T-Snip test score would be predictive of 205-d weaning weights of calves from cows consuming endophyte-infected tall fescue. Nine herds, with 4 herds tested 2 or more years, consuming endophyte-infected tall fescue were tested for fescue toxicity tolerance using the T-Snip genetic test between yr 2012 and 2015. Cows were scored from 0 to 5 for tolerance to fescue toxicity with zero being intolerant and 5 being most tolerant. Total of 2494 tests were performed and number of animals per herd ranged from 75 to 647. Correlation coefficient between cow tolerance score and 205-d weaning weights were measured for each herd and year data set. Correlation from each data set was significant (P < 0.02). The correlation coefficient averaged 0.63 and ranged from 0.42 to 0.76. Calf weaning weights from cows scored 0, 1, 2, 3, 4, and 5 averaged 212, 218, 226, 233, 240, and 246 kg, respectively. In conclusion T-Snip score from cows consuming endophyte-infected tall fescue was correlated to calf 205-d weaning weight and can be used as an indicator of tolerance to fescue toxicity. Difference in calf weaning weight between tolerant and intolerant cows averaged 28 kg. Tolerance to toxic tall fescue as determined by T-Snip analysis accounts for approximately one-half the effect of toxic tall fescue on calf weaning weight. [ABSTRACT FROM AUTHOR]