Use of nonergot alkaloid-producing endophytes for alleviating tall fescue toxicosis in stocker cattle

Grazing studies were conducted to determine cattle growth performance, evaluate toxicosis, and compare grazing behavior in stocker cattle grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup, Georgia-5, and Kentucky-31 tall fescue. Replicated 0.81-ha tall fescue paddocks were established at the Central Georgia Branch Station at Eatonton and the Northwest Georgia Branch Station at Calhoun during October 1998 and were stocked with beef cattle for autumn and spring periods from fall 1999 through spring 2002. Mean ergot alkaloid concentrations were higher (P < 0.01) on E+ pastures than the other treatments at both locations. At Calhoun and Eatonton, post-treatment serum prolactin concentrations were decreased (P < 0.01) on E+ compared with AR542, AR502, and E- tall fescue. Cattle on AR542, AR502, and E- pastures had lower (P < 0.05) post-treatment rectal temperatures than cattle grazing E+ tall fescue during spring at Eatonton and Calhoun. Calf ADG was higher (P < 0.05) on AR542, AR502, and E- as compared with E+ tall fescue during autumn and spring grazing at Eatonton, and at Calhoun, cattle on E+ pastures had lower (P < 0.05) ADG in both autumn and spring. Gain/hectare was higher (P < 0.05) on AR542, AR502, and E- than on E+ during autumn at Eatonton and during spring at both locations. In autumn at Calhoun, gain/hectare was greater (P < 0.05) on AR502 and E- compared with E+ tall fescue. During April, May, and June, cattle grazing E+ pastures at Eatonton spent more (P < 0.01) time idling, more (P < 0.01) time standing, and used more (P < 0.01) water than cattle on AR542 and E- tall fescue. Daily prehensions and biting rate were each higher (P < 0.01) on AR542 and E- tall fescue than E+ tall fescue in both grazing seasons. There were no differences among pasture treatments for bite size in either spring (P = 0.50) or autumn (P = 0.34). Steers grazing E+ pastures had lower DMI than steers grazing AR542 and E- pastures during spring (P < 0.10) and lower DMI than steers grazing E- pastures during autumn (P < 0.05). Daily steer water usage was decreased (P < 0.10) in E+ pastures compared with AR542 and E- pastures during late fall. These results indicate that nonergot alkaloid-producing endophyte technology is a promising option for alleviating tall fescue toxicosis in stocker cattle.     

Use of nonergot alkaloid-producing endophytes for alleviating tall fescue toxicosis in sheep

Nonergot alkaloid-producing endophytes from New Zealand were inserted into tall fescue (Festuca arundinacea) cultivars in an attempt to address the problem of fescue toxicosis in grazing sheep. A 3-yr grazing study was conducted to determine lamb performance and to evaluate toxicosis in lambs grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup tall fescue or nonergot alkaloid-producing endophyte-infected (AR542) Georgia-5 tall fescue. Replicated 0.11-ha tall fescue paddocks were established at the central Georgia Branch Station during September 1997 and stocked with lambs from spring 1998 through autumn 2000. Mean ergot alkaloid concentrations were higher (P < 0.01) in E+ forage than in AR542, AR502, and E- tall fescue, and ergot alkaloid concentrations in E- plants and plants infected with AR542 and AR502 were low. Forage availability did not differ (P = 0.92) across treatments during autumn and was higher (P < 0.05) in Georgia-5 AR542 than in Jesup AR502 and E+ pastures. Initial serum prolactin (PRL) concentrations did not differ (P = 0.58) across treatments during autumn, but were higher on Jesup AR542 than E+ during spring. Post-treatment serum PRL concentrations were depressed (P < 0.01) on E+ compared with AR542, AR502, and E- in both spring and autumn. Signs of heat stress were observed in E+ lambs during periods of high ambient temperatures. Mean post-treatment rectal temperature and mean stocking rate exhibited treatment x year interactions (P < 0.05). Lamb ADG was higher (P < 0.05) on AR542, AR502, and E- than on E+ tall fescue. Similarly, gain/hectare was higher (P < 0.015) on AR542, AR502, and E- than on E+. Tall fescue pastures containing AR542 and AR502 endophytes yielded lamb performance that did not differ from that on E- tall fescue and which was superior to performance on E+ tall fescue. Depressed PRL concentrations and elevated rectal temperatures as indicators of toxicosis were evident only in lambs grazing E+ tall fescue, suggesting that nonergot alkaloid-producing endophyte-infected tall fescue is a viable alternative for alleviating tall fescue toxicosis.     

Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures

A 3-yr study used 16 cows and their spring-born calves (yr 1) and 48 first-calf heifers (yr 2, n = 24; yr 3, n = 24) and their spring-born calves in a completely randomized design. All cows and heifers were Angus x Beefmaster, and calves were sired by Angus bulls. Cow-calf pairs were assigned randomly to one of two management systems: 1) an early-weaning system, in which steer and heifer calves were weaned at 108 d of age and fed a postweaning growing diet (EW), or 2) a normal weaning system, in which calves were weaned at 205 d without supplementation (NW). Before early weaning and within each management system, calves and their dams were maintained in two 1.4-ha, endophyte-infected tall fescue pastures for 35 d (yr 1) or 14 d (yr 2 and 3). Early-weaned calves and cow-calf pairs were then randomly allotted to 1.4-ha, endophyte-infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow-calf pairs per pasture (four pastures per management system). Cow weights and BCS changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG from early to normal weaning did not differ (P = 0.32). Similar to ADG, BW of calves at normal weaning were not different (P = 0.11). Forage intake was greater (P < 0.01) by NW calves during Periods 2 and 3 of yr 1 and Periods 1 and 2 of yr 2 and 3; however, total DM and CP intakes were greater (P < 0.01) for EW calves in Periods 2 and 3 of each year. Intakes of NDF tended (P = 0.11) to be greater by EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2; however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05) than those consumed by EW calves. These results show the condition of cows with EW calves was improved by early weaning and gains by calves weaned at 108 d to pasture plus a commercial grower diet were comparable to those by calves continuing to nurse dams until weaned at 205 d.     

Effect of rotation frequency and weaning date on forage measurements and growth performance by cows and calves grazing endophyte-infected tall fescue pastures overseeded with crabgrass and legumes

A grazing study was initiated in April 2000 and continued through three calving and weaning cycles (ending July 2003) to investigate the effects of rotational grazing management (twice monthly [2M] vs. twice weekly [2W]) and weaning date (mid-April [EARLY] vs. early June [LATE]) on production of fall-calving cow-calf pairs (495 +/- 9.6 kg initial BW) grazing Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.) overseeded with legumes and crabgrass. Secondary objectives of the experiment were to monitor differences in quantity and quality of available forage and to evaluate changes in forage species composition. Pastures were dominated by tall fescue throughout the study, and the proportion of basal cover was greater (P < 0.05) in 2M than in 2W pastures. The percentage of legumes was very low across all treatment combinations, but the percentage of crabgrass continued to increase (P < 0.05) linearly and quadratically across years for both summer and fall sampling periods, regardless of rotation or weaning program. In vitro DM disappearance and mineral concentrations varied minimally because of rotation frequency or weaning date. Rotation frequency did not substantially affect (P = 0.11 to 0.97) cow BW, hay offered, milk production, calving interval, calf birth weight, or actual or adjusted weaning weights; however, 2M cows had 0.3 units higher (P < 0.05) BCS at the time of breeding than 2W cows. Calves weaned late had greater (P < 0.05) actual weaning weight and weighed more (P < 0.05) on the LATE weaning date than on the EARLY weaning date, but 205-d adjusted weaning weights did not differ (P = 0.74) across weaning dates. Therefore, rotation frequency and/or weaning date had little effect on forage species composition or forage quality. In addition, the rapid rotation program offered little advantage with respect to animal performance, and weaning fall-born calves grazing endophyte-infected tall fescue pastures at approximately 189 d of age seemed to be detrimental to calf performance compared with delaying weaning until 243 d of age.     

Performance, forage utilization, and ergovaline consumption by beef cows grazing endophyte fungus-infected tall fescue, endophyte fungus-free tall fescue, or orchardgrass pastures.

Two 120-d trials (May to September, 1988 and 1989) determined the effects of grazing tall fescue (two varieties) or orchardgrass on forage intake and performance by beef cows. Each summer, 48 cow-calf pairs grazed endophyte-infected Kentucky-31 tall fescue (KY-31), endophyte-free Mozark tall fescue (MOZARK), or Hallmark orchardgrass (OG) pastures (16 pairs/treatment). Forage OM intakes and digestibilities were determined during June and August each year. Cow and calf BW and milk production were determined every 28 d. During June of both years, OM intakes did not differ (P greater than .10) among treatments. During August of 1988, intakes were 18% lower (P less than .05) by KY-31 cows (1.6% of BW) than by MOZARK or OG cows (average 1.95% of BW); however, no differences (P greater than .10) were measured in August of 1989. Estimates of ergovaline consumption during June from KY-31 were between 4.2 (1988) and 6.0 mg/d (1989), whereas August estimates were between 1.1 (1988) and 2.8 mg/d (1989). Ergovaline in MOZARK estrusa was below detection limits, except in August of 1989. Cows that grazed KY-31 lost three times (P less than .01) more BW than cows that grazed MOZARK or OG (42 vs 9 and 13 kg, respectively). Milk production by KY-31 cows was 25% lower (P less than .01) than that by cows that grazed MOZARK or OG (6.0 vs average of 8.0 kg/d). Similarly, slower (P less than .01) calf gains were noted for KY-31 than for MOZARK or OG (.72 vs .89 and .88 kg/d, respectively). Cows grazing KY-31 experienced accelerated BW loss and reduced milk production and weaned lighter calves than did cows grazing MOZARK or OG. Decreased performance was not explained by consistently reduced forage intakes; hence, altered nutrient utilization was suspected.     

Allocating forage to fall-calving cow-calf pairs strip-grazing stockpiled tall fescue

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 stockpiled 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 < 0.01) with forage allocation (y = 0.063x + 0.513; R(2) = 0.91). However, calf gain per hectare decreased linearly (P < 0.01) as stockpiled tall fescue allocations increased (y = -26.5x + 212; R(2) = 0.97) such that gain per hectare for cow-calf pairs allocated stockpiled tall fescue at 4.50% BW/d was nearly 40% less (P < 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.     

Genetic x environment interactions on blood constituents of Angus, Brahman, and reciprocal-cross cows and calves grazing common bermudagrass or endophyte-infected tall fescue

Over a 2-yr period, effects of genotype and forage on blood metabolites, enzymes, and minerals were determined in Angus, Brahman, Angus x Brahman (sire x dam), and Brahman x Angus cows, and 129 calves from these cows sired by Hereford bulls. Cows and calves continuously grazed either common bermudagrass or endophyte-infected 'Kentucky-31' tall fescue pastures throughout the year. Blood samples were collected via jugular venipuncture in April, August, October (weaning), and November (after 30 d in a feedlot) of each year. Plasma urea N concentrations of cows and calves were affected by forage (P < 0.01) and breed (P < 0.05). Plasma cholesterol and FFA concentrations of cows were affected by forage (P < 0.01) and breed (P < 0.05). In calves, antibody titers to infectious bovine rhinotracheitis virus were not affected by forage but were affected by breed. Serum inorganic P concentrations of calves and cows were affected by forage (P < 0.05). Serum P concentrations and alkaline phosphatase activity of calves were affected by breed (P < 0.05). Calves grazing bermudagrass had higher (P < 0.05) serum concentrations of Fe and total iron binding capacity (TIBC). There was evidence of maternal heterosis for concentrations of free fatty acids, cholesterol, aspartate aminotransferase, Ca, Mg, alkaline phosphatase, ceruloplasmin, Fe, and TIBC. There was evidence of grandmaternal effects for plasma concentrations of urea N, cholesterol, Ca, P, Mg, and alkaline phosphatase. These results suggest that calves and cows grazing tall fescue are generally on a lower plane of nutrition than those grazing bermudagrass and that Brahman x Angus and Angus x Brahman crossbred cows and their calves seen to be more tolerant of the negative effects of tall fescue than the average of their purebred contemporaries.     

Endophyte infection level of tall fescue stockpiled for winter grazing does not alter the gain of calves nursing lactating beef cows

We examined the effect of endophyte infection level of tall fescue (Festuca arundinacea Schreb.) used for stockpiled forage on the performance of lactating, fallscalving 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.     

Effect of endophyte type on carcass traits, meat quality, and fatty acid composition of beef cattle grazing tall fescue

Fourteen Hereford steers were used to compare carcass traits, meat quality, and fatty acid composition of beef from cattle grazing tall fescue infected with either wild-type (E+; n = 6) or novel, nil ergot alkaloid (AR542; n = 8) endophyte for 209 d. Average daily gain, live weight, and HCW were greater (P < 0.05) for AR542 cattle than for E+. No differences in LM color or pH were observed between AR542 and E+. Steaks from E+ cattle tended (P = 0.10) to have higher L* and b* than those from AR542 cattle at 0 d of display. Ground beef from E+ cattle also had higher (P < 0.05) L* than AR542 cattle, with no differences in a* or b* at 0 d of display. Color changes during display did not differ for both steaks and ground beef from E+ and AR542. Lipid oxidation levels increased (P < 0.05) during simulated retail display, but they did not differ between endophyte treatments. Adipose tissues from E+ cattle had a higher (P < 0.05) percentage of SFA, and a lower (P < 0.05) percentage of MUFA than adipose from AR542 cattle. Ground beef and i.m. fat had higher (P < 0.05) concentrations of SFA, MUFA, and cis-9, trans-11 isomer of conjugated linoleic acid, and lower (P < 0.05) concentrations of PUFA and PUFA:SFA ratio than s.c. fat. The n-6:n-3 fatty acid ratio did not differ among fat depots. Ergot-alkaloids were detected in s.c. adipose tissues, and alkaloid concentration was greater (P < 0.05) for E+ than AR542. Warner-Bratzler shear force values did not differ between endophyte types, but it decreased (P < 0.01) across the postmortem aging period. Conversely, sensory panel evaluation detected greater (P < 0.01) chewiness and lower (P < 0.05) juiciness for AR542 than for E+ steaks aged for 14 d. Although grazing cattle on tall fescue pastures infected with nil ergot alkaloid endophyte improved cattle performance, these results suggest that endophyte type has minor effects on carcass traits and meat quality of pasture-fed beef. Moreover, finishing cattle on tall fescue pastures showed the potential to enhance the fatty acid profile of beef from a human health perspective. Alkaloid concentration was greater (P < 0.05) in s.c. fat from E+ than AR542 (2.81 vs. 0.92 ppb; fresh-tissue basis). This is the first published report demonstrating the presence of alkaloids in beef tissues.     

Cow and calf performance on Coastal or Tifton 85 Bermudagrass pastures with aeschynomene creep-grazing paddocks

Cow and calf performance was determined in a 2-yr, 2 x 2 factorial, grazing experiment using Coastal or Tifton 85 (T85) replicated Bermudagrass pastures (4 pastures each; each pasture 4.86 ha), without or with aeschynomene creep-grazing paddocks (n = 4, 0.202 ha each, planted in May of each year, 13.44 kg/ha). On June 10, 2004, and June 8, 2005, 96 winter-calving beef "tester" cows and their calves were grouped by cow breed (9 Angus and 3 Polled Hereford/group), initial cow BW (592.9 +/- 70.1 kg, 2-yr mean), age of dam, calf breed (Angus, Polled Hereford, or Angus x Polled Hereford), calf sex, initial calf age (117 +/- 20.1 d, 2-yr mean), and initial calf BW (161.3 +/- 30.4 kg) and were randomly assigned to pastures. Additional cow-calf pairs and open cows were added as the forage increased during the season. Forage mass was similar for all treatment pastures (P > 0.70; 2-yr mean, 6,939 vs. 6,628 kg/ha, Coastal vs. T85; 6,664 vs. 6,896 kg/ha, no creep grazing vs. creep grazing). Main effect interactions did not occur for performance variables (P > 0.10; 2-yr means), and year affected only the initial and final BW of the calves and cows. The 91-d tester calf ADG was greater for calves grazing T85 than Coastal (0.94 vs. 0.79 kg; P < 0.01), and for calves creep grazing aeschynomene compared with calves without creep grazing (0.90 vs. 0.82 kg; P < 0.03). Calf 205-d adjusted weaning weights were increased for calves grazing T85 compared with Coastal (252.9 vs. 240.3 kg; P < 0.01) and for calves with access to creep grazing (249.9 vs. 243.3 kg; P < 0.05). The IVDMD of esophageal masticate from pastures had a forage x creep grazing interaction (P < 0.05; Coastal, no creep grazing = 57.4%; Coastal, creep grazing = 52.1%; T85, no creep grazing = 59.1%; T85, creep grazing = 60.0%), and IVDMD was greater (P < 0.05) for T85 than for Coastal pastures. Cows were milked in August 2004, and in June and August 2005, with variable milk yields on treatments, but increased milk protein (P < 0.05) for cows grazing T85 compared with Coastal pastures in August each year, contributing to increased calf gains on T85 pastures. These results complement previous research with T85 and indicate increased forage quality and performance of cattle grazing T85 pastures. Calf gains on T85 pastures and for calves on creep-grazed aeschynomene paddocks were high enough to influence the efficiency of cow-calf operations.     

Forage systems for beef production from conception to slaughter: I. Cow-calf production.

Six year-round, all-forage, three-paddock systems for beef cow-calf production were used to produce five calf crops during a 6-yr period. Forages grazed by cows during spring, summer, and early fall consisted of one paddock of 1) tall fescue (Festuca arundinacea Schreb.)-ladino clover (Trifolium repens L.) or 2) Kentucky blue-grass (Poa pratensis L.)-white clover (Trifolium repens L.). Each of these forage mixtures was combined in a factorial arrangement with two paddocks of either 1) fescue-red clover (Trifolium pratense L.), 2) orchardgrass (Dactylis glomerata L.)-red clover, or 3) orchardgrass-alfalfa (Medicago sativa L.), which were used for hay, creep grazing by calves, and stockpiling for grazing by cows in late fall and winter. Each of the six systems included two replications; each replicate contained 5.8 ha and was grazed by eight Angus cow-calf pairs for a total of 480 cow-calf pairs. Fescue was less than 5% infected with Acremonium coenophialum. Pregnancy rate was 94%. Cows grazing fescue-ladino clover maintained greater (P less than .05) BW than those grazing bluegrass-white clover, and their calves tended (P less than .09) to have slightly greater weaning weights (250 vs 243 kg, respectively). Stockpiled fescue-red clover provided more (P less than .05) grazing days and required less (P less than .05) hay fed to cows than stockpiled orchardgrass plus either red clover or alfalfa. Digestibilities of DM, CP, and ADF, determined with steers, were greater (P less than .05) for the orchardgrass-legume hays than for the fescue-red clover hay. All systems produced satisfactory cattle performance, but fescue-ladino clover combined with fescue-red clover required minimum inputs of harvested feed and maintained excellent stands during 6 yr.     

Calving system and weaning age effects on cow and preweaning calf performance in the Northern Great Plains

A 3-yr study evaluated late winter (Feb), early spring (Apr), and late spring (Jun) calving systems in conjunction with varied weaning strategies on beef cow and calf performance from Northern Great Plains rangelands. Crossbred cows were randomly assigned to one of three calving systems (on average n= 168.calving system(-1).yr(-1)) and one of two weaning times (Wean 1, 2) within each calving system. The Feb and Apr calves were weaned at 190 and 240 d of age, whereas Jun calves were weaned at 140 and 190 d of age. Breeding by natural service occurred in a 32-d period that included estrous synchronization. Cows were managed throughout the year as appropriate for their calving season. Quantity and quality of hay and supplements were provided based on forage and weather conditions, physiological state of the cows, and available harvested feed resources within a year. After weaning, two-thirds of the early weaned steers were fed in confinement in Montana, and one-third were shipped to Oklahoma and were grazed or fed forage. One-half of the early weaned heifers grazed seeded pastures, and the other half was fed in confinement. Early weaned calves were weighed on approximately the same day as late-weaned calves. Birth weight and overall rate of gain from birth to weaning did not differ for calves from the three calving systems. Calf weaning weight differed by weaning age within calving system (P = 0.001), and calves from the Jun calving system that were weaned at 190 d of age tended (P = 0.06) to be lighter than calves of the same age from the Feb or Apr calving systems. Cow BW change and BCS dynamics were affected by calving system, but the proportion of cows pregnant in the fall was not. Cows suckled until later dates gained less or lost more BW during the 50 d between the first and second weaning than dry cows during this period. The previous year's weaning assignment did not affect production in the following year. Estimated harvested feed inputs were less for the Jun cows than for the Feb and Apr cows. We conclude that season of calving and weaning age affect outputs from rangeland-based beef cattle operations.     

Postweaning performance of calves from Angus, Brahman, and reciprocal-cross cows grazing endophyte-infected tall fescue or common bermudagrass

Data from 403 Polled Hereford-sired calves from Angus, Brahman, and reciprocal-cross cows were used to evaluate the effects of preweaning forage environment on postweaning performance. Calves were spring-born in 1991 to 1994 and managed on either endophyte-infected tall fescue (E+) or common bermudagrass (BG) during the preweaning phase. After weaning, calves were shipped to the Grazinglands Research Laboratory, El Reno, OK and stratified to one of two winter stocker treatments by breed and preweaning forage; stocker treatments were winter wheat pasture (WW) or native range plus supplemental CP (NR). Each stocker treatment was terminated in March, calves grazed cool-season grasses, and calves were then moved to a feedlot phase in June. In the feedlot phase, calves were fed to approximately 10 mm fat over the 12th rib and averaged approximately 115 d on feed. When finished, calves were weighed and shipped to Amarillo, TX for slaughter. Averaged over calf breed group, calves from E+ gained faster during the stocker phase (P<.10), had lighter starting and finished weights on feed (P< .01), lighter carcass weights (P<.01), and smaller longissimus muscle areas (P<.05) than calves from BG. Calves from E+ were similar to calves from BG in feedlot ADG, percentage kidney, heart, and pelvic fat, fat thickness over 12th rib, yield grade, marbling score, and dressing percentage. Maternal heterosis was larger in calves from E+ for starting weight on feed (P<.01), finished weight (P<.10), and carcass weight (P<.16). These data suggest that few carryover effects from tall fescue preweaning environments exist, other than lighter, but acceptable, weights through slaughter. These data further suggest that the tolerance to E+ in calves from reciprocal-cross cows, expressed in weaning weights, moderated postweaning weight differences between E+ and BG compared to similar comparisons in calves from purebred cows.     

The effect of residual feed intake classification on forage intake by grazing beef cows

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.     

Animal performance and economic comparison of novel and toxic endophyte tall fescues to cool-season annuals

Increased costs of annual establishment of small grain pasture associated with fuel, machinery, and labor are eroding the profitability of stocker cattle enterprises. Interest has therefore increased in development of cool-season perennial grasses that are persistent and high quality. This study occurred on 24 ha (divided into thirty 0.81-ha paddocks) located at the University of Arkansas Division of Agriculture Livestock and Forestry Branch Station, near Batesville. Two tall fescue (Festuca arundinacea Schreb.) cultivars infected with novel endophytes (NE), Jesup infected with AR542 endophyte (Jesup AR542), and HiMag infected with Number 11 endophyte (HM11) were established in September 2002. Jesup AR542 and HM11 were compared with endemic endophyte Kentucky 31 (KY-31) tall fescue; wheat (Triticum aestivum L.) and cereal rye (WR, Secale cereale L.) planted in September 2003, 2004, and 2005; and annual ryegrass [RG, Lolium perenne L. ssp. multiflorum (Lam.) Husnot] planted in September 2004 and 2005. Each year, 3 steers (3.7 steers/ha) were placed on each pasture for fall and winter grazing, and 5 steers (6.2 steers/ha) were placed on each pasture for spring grazing. Animal performance is presented by year in the presence of a year x treatment interaction (P < 0.01). Body weight gain per hectare of steers grazing NE tall fescue was greater (P < 0.01) than those of KY-31 and WR during 2003 to 2004, whereas in 2004 to 2005, BW gain per hectare of steers grazing NE and RG did not differ (P < or = 0.29) and was greater (P < 0.01) than that of WR, which was greater (P < 0.01) than that of KY-31. During 2005 to 2006, BW gain per hectare was greater (P < 0.01) for steers grazing RG than those of NE and WR, which did not differ (P > or = 0.14). Body weight gain per hectare was least (P < 0.01) for steers grazing KY-31. Average net return of NE tall fescue was greater (P < 0.01) than KY-31, but profitability of NE did not consistently differ from cool-season annuals. Across the 3-yr study, NE tall fescue produced net returns per hectare of $219; this level of profitability would require 4 yr for a new planting of NE tall fescue to break even. Novel endophyte tall fescues offer potential benefits related to decreased risk of stand establishment of annual forage crops, longer growing season, and acceptable animal performance.     

Productivity and hay requirements of beef cattle in a Midwestern year-round grazing system

Our objective was to evaluate a replicated (n = 2) Midwestern year-round grazing system's hay needs and animal production compared with a replicated (n = 2) conventional (minimal land) system over 3 yr. Because extended grazing systems have decreased hay needs for the beef herd, it was hypothesized that this year-round system would decrease hay needs without penalizing animal production. In the minimal land (ML) system, two replicated 8.1-ha smooth bromegrass-orchardgrass-birdsfoot trefoil (SB-OG-BFT) pastures were rotationally stocked with six mature April-calving cows and calves and harvested as hay for winter feeding in a drylot. After weaning, calves were finished on a high-concentrate diet. Six mature April-calving cows, six mature August-calving cows, and their calves were used in the year-round (YR) grazing system. During the early and late summer, cattle grazed two replicated 8.1-ha SB-OG-BFT pastures by rotational stocking. In mid-summer and winter, April- and August-calving cows grazed two replicated 6.1-ha, endophyte-free tall fescue-red clover (TF-RC) and smooth bromegrass-red clover (SB-RC) pastures, respectively, by strip-stocking. In late autumn, spring-calving cows grazed 6.1-ha corn crop residue fields by strip-stocking. Calves were fed hay with corn gluten feed or corn grain over winter and used as stocker cattle to graze SB-OG-BFT pastures with cows until early August the following summer. First-harvest forage from the TF-RC and SB-RC pastures was harvested as hay. Body condition scores of April-calving cows did not differ between grazing systems, but were lower (P < or = 0.03) than those of August-calving cows from mid-gestation through breeding. Preweaning calf BW gains were 47 kg/ha of perennial pasture (P < 0.01) and 32 kg/cow (P = 0.01) lower in the YR grazing system than in the ML system. Total BW gains ofpreweaning calf and grazing stocker cattle were 12 kg/ha of perennial pasture less (P = 0.07), but 27 kg/cow greater (P = 0.02) in pastures in the YR grazing system than in the ML system. Amounts of hay fed to cows in the ML system were 1,701 kg DM/cow and 896 kg DM/cow-stocker pair greater (P < 0.05) than in the YR grazing system. Extended grazing systems in the Midwest that include grazing of stocker cattle to utilize excess forage growth will decrease stored feed needs, while maintaining growing animal production per cow in April- and August-calving herds.     

Effects of pre- and postpartum nutrition on reproduction in spring calving cows and calf feedlot performance

Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 x 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 +/- 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%). Calves born to dams fed supplement prepartum had similar (P = 0.29) birth weight (37 vs. 36 kg) but greater (P = 0.02) weaning weight (218 vs. 211 kg). However, steer feedlot DMI (8.53 vs. 8.48 kg), ADG (1.6 vs. 1.6 kg), and carcass weight (369 vs. 363 kg) were not affected (P = 0.23 to P = 0.89) by prepartum supplementation. Allowing cows to graze subirrigated meadow postpartum improved (P < 0.001) BCS prebreeding (5.2 vs. 4.9) but did not affect (P = 0.88) pregnancy rate (92 vs. 91%). Allowing cows to graze subirrigated meadow increased (P = 0.01) calf weaning weight (218 vs. 211 kg) but not (P = 0.62 to P = 0.91) feedlot DMI (8.4 vs. 8.3 kg), ADG (1.6 vs. 1.6 kg), or carcass weight (363 vs. 362 kg) of their steer calves. Increased percentage of live calves at weaning as a result of feeding supplemental protein increased net returns at weaning and after finishing in the feedlot. Net returns were increased by allowing cows to graze subirrigated meadow postpartum regardless of whether calves were marketed at weaning or after finishing in the feedlot.     

Epidemiology and effects of nematode infections on beef cow-calf systems of Argentina's western pampas.

The epidemiology and the effects of nematode infections on cow-calf systems were followed from 3 weeks before calving to 7 months afterwards. Two groups, each of 15 cow-calf pairs grazed on separate lucerne pastures. Group I (GI) were treated monthly with oxfendazole (4.5 mg kg-1), cows being dosed from calving and calves starting 45 days later. Animals in Group II (GII) were not treated. The egg output of the cows was very low. An increase was recorded 2 months after parturition, consisting mainly of Ostertagia spp. The egg output and worm burdens of calves remained low until late summer and reached a peak in autumn. Ostertagia, Cooperia and Haemonchus were the main genera recovered from slaughtered calves. The pasture contamination and tracer calf worm counts remained consistently low until autumn when they began to increase. Inhibited early fourth stage larvae of Ostertagia were recovered during spring. After calving, the live-weight gains (LWG) of treated GI cows were significantly higher (P less than 0.004) than those of GII cows, whereas the LWG of GI calves were significantly higher during December (P less than 0.037) and March (P less than 0.029) than those of GII calves. There were significant (P less than 0.04) cumulative LWG responses between GI and GII calves with no differences in cow cumulative LWG at the end of the trial. For spring-born calves, these results suggest that strategic deworming programs in cow-calf systems may produce benefits.     

Effects of stocking rate and corn gluten feed supplementation on performance of young beef cows grazing winter-stockpiled tall fescue-red clover pasture

A winter grazing experiment was conducted to evaluate the effects of stocking rate and corn gluten feed supplementation on forage mass and composition and the BW and BCS of bred 2-yr-old cows grazing stockpiled forage during winter. Two 12.2-ha blocks containing Fawn, endophyte-free, tall fescue and red clover were each divided into 4 pastures of 2.53 or 3.54 ha. Hay was harvested from the pastures in June and August of 2003 and 2004, and N was applied at 50.5 kg/ha at the initiation of stockpiling in August. On October 22, 2003, and October 20, 2004, twenty-four 30-mo-old Angus-Simmental and Angus cows were allotted by BW and BCS to strip-graze for 147 d at 0.84 or 1.19 cow/ha. Eight similar cows were allotted to 2 dry lots and fed tall fescue-red clover hay ad libitum. Corn gluten feed was fed to cows in 2 pastures to maintain a mean BCS of 5 (9-point scale) at each stocking rate and in the dry lots (high supplementation level) or when weather prevented grazing (low supplementation level) in the remaining 2 pastures at each stocking rate. Mean concentrations of CP in yr 1 and 2 and IVDMD in yr 2 were greater (P < 0.10) in hay than stockpiled forage over the winter. At the end of grazing, cows fed hay in dry lots had greater (P < 0.05) BCS in yr 1 and greater (P < 0.10) BW in yr 2 than grazing cows. Grazing cows in the high supplementation treatment had greater (P < 0.10) BW than cows grazing at the low supplementation level in yr 1. Cows in the dry lots were fed 2,565 and 2,158 kg of hay DM/cow. Amounts of corn gluten feed supplemented to cows in yr 1 and 2 were 46 and 60 kg/ cow and did not differ (P = 0.33, yr 1; P = 0.50, yr 2) between cows fed hay or grazing stockpiled forage in either year. Estimated production costs were greater for cows in the dry lots because of hay feeding.     

Winter-annual pasture as a supplement for beef cows

In each of two experiments, 120 pregnant beef cows were stratified by body condition score, BW, breed, and age, randomly divided into six groups of 20, and assigned to one of six 5.1-ha bermudagrass (Cynodon dactylon [L.] Pers.) pastures (two replicates/ treatment) in early January to evaluate the use of winter-annual pasture as a supplement. All cows in Exp. 1 and 2 had ad libitum access to bermudagrass/dallisgrass (Paspalum dilatatum Poir.) hay plus three treatments: 1) a concentrate-based supplement fed 3 d/wk, 2) limit grazing on winter-annual pasture 2 d/wk (7 hr/ d; 0.04 ha x cow(-1) x grazing d(-1)), or 3) limit grazing on winter-annual pasture 3 d/wk (7 hr/d; 0.04 ha x cow(-1) x grazing d(-1)) sod-seeded into a portion of the pasture until mid-May. The seeded portion of pastures in Exp. 1 was planted with a mixture of wheat (Triticum aestivum L.) and rye (Secale cereale L.), but annual ryegrass (Lolium multiflorum Lam.) was added to the seed mixture in Exp. 2. In mid-May, cows were blocked by treatment and the previous sorting factors, randomly assigned to six new groups of 20, and placed on the six perennial pastures until calves were weaned. Groups of cows were exposed to a bull for 60 d beginning in mid-May. In Exp. 1 and 2, limit-grazing winter-annual pasture compared to the concentrate-based supplement or limit grazing 2 vs 3 d/wk did not affect (P > 0.15) cow BW. In Exp. 1, cows limit grazed on winter-annual pasture had a lower (P = 0.05) body condition score than cows fed the concentrate-based supplement in the early spring. However, in Exp. 2, cows limit grazed on winter-annual pasture had higher (P < or = 0.07) body condition score than cows fed the concentrate-based supplement. The conception rate of cows in Exp. 1 and 2 did not differ (P > 0.22) between cows fed concentrate-based supplements and cows limit grazed on winter-annual pasture. In Exp. 2, cows limit grazed 2 d/wk tended to have a greater (P = 0.10) conception rate than cows limit grazed 3 d/wk. In Exp. 1 and 2, birth weight, total gain, BW, and ADG of calves were not affected (P > 0.15) by treatment. We conclude that wheat and rye pasture is a marginal supplement for lactating beef cows. However, cows limit grazed 2 d/wk on winter-annual pasture of wheat, rye, and annual ryegrass as a supplement maintained BW and body condition score as well as cows fed the concentrate-based supplement. But, grazing pasture 3 vs 2 d/wk did not seem to affect performance of cows.