Intensive Rotational Grazing of Steers on Highly Erodible Land at the Adams County CRP Project

Grazing yearling steers is one way to utilize the forages required for participation in the Conservation Reserve Program (CRP) after CRP contracts expire. In 1995, a stocker-steer intensive-rotational grazing study was conducted at the CRP Research and Demonstration Project near Corning, Iowa. A similar study was carried out in 1994. Seventy-five yearling crossbred steers grazed a 65- acre pasture that had been divided into 27 paddocks using electric fencing from May 4, 1995 to September 14, 1995. During this period, the 65-acre pasture system produced 9,975 animal-days of grazing and 11,403 pounds of gain. On a per-acre basis, this translates to 153.5 animal-days of grazing and 175.4 pounds of gain. The stocking rate was constant for the entire 133- day grazing season at 1.15 steers per acre. On May 4, 1995, the beginning of the grazing season, the average weight of the steers was 495.7 pounds. By the end of the grazing trial on September 14, 1995, the average weight of the steers had increased to 647.7 pounds. The average gain per steer during the 133-day grazing period was 152 pounds, and the average daily gain per steer was 1.14 pounds. The average bodyweight of the steers during the entire grazing season was 571.7 pounds.

Comparison of Round and Square Cores in the Determination of Beef Tenderness by Warner- Bratzler and Instron

Seven rib-eye rolls, lip on (112A), were each cut into eight 2.54 centimeter thick steaks starting from the blade end. Steaks were randomly assigned to one of four treatment groups; 1) round versus square cores using Instron [inst1], 2) round versus square cores using Warner- Bratzler [inst2], 3) Instron versus Warner-Bratzler using round cores [rdsq1], and 4) Instron versus Warner- Bratzler using square cores [rdsq2]. Subsequently, steaks from each group were broiled in a General Electric industrial broiler grill to an internal temperature of 63 §C. Steaks were held overnight at 2 §C. Two steaks from each rib were placed into each instrument/core treatment group. Steaks were then divided into three sections identified as: a) lateral, b) medial, and c) central. Three 1.27 centimeter cores from each section were taken from each steak for a total of nine cores per steak and sheared once through the center. The results indicated that there was a significant difference ( p> .05) between round and square cores for both Warner- Bratzler and Instron. In all mean groups tested, square cores had higher shear values than did round cores. There was no indication of differences between instruments, and no significant interactions between instruments and core types.

Soil Infiltration and Wetland Treatment of Feedlot Runoff

Treating feedlot runoff using a soil infiltration area followed by a small constructed wetland can significantly reduce contaminants in the runoff. An infiltration/wetland treatment system has been monitored for three years at ISU’s Beef Nutrition Farm near Ames. Overall contaminant concentrations in the wetland effluent are typically 20% or less than the initial runoff concentrations.

Rotational Grazing Demonstrations with Beef Cows on CRP Land in Adams County, 2001

Two rotational-grazing systems, a 13-paddock and a 4-paddock, have been demonstrated on CRP land near Corning, Iowa since 1991 and this report summarizes the 2001 production data. Establishment of this project was to show economically feasible grass alternatives to row crops and CRP for steeply sloping (9% - 14% slope), highly-erodible land (HEL). Stocking rates were 1.57 and 1.72 acres per pair on the 13- and 4-paddock systems, respectively. In a 119 day grazing season calves gained 2.23 and 2.27 lbs/day for the 13- and 4-paddock systems, while cows gained 51.4 and 113.4 lbs, respectively. While some system hay growth was utilized to stave off drought conditions, there was a net hay gain of 11 and 5.5 bales of hay for the 13- and 4-paddock systems, respectively

Intensive Rotational Grazing of Steers on Highly Erodible Land at the Adams County CRP Project, 2001

A steer grazing demonstration was conducted in 2001 at the CRP Research and Demonstration Project farm near Corning, Iowa. Ninety-five steers were delivered to the Adams County CRP farm on April 27, 2001. The steer pasture at the CRP farm was 76 acres, divided into 33 paddocks with electric fence. Cattle were moved 101 times to a fresh paddock during the grazing season. Most of the moves (79.2%) followed 1 day of grazing in a paddock. No paddock was grazed for more than 3 days in succession. Rate of gain on pasture (2.12 lbs./animal/day) was higher in 2001 than in any previous year in the 8-year steer grazing project at the CRP farm. The 95 steers gained a total of 21,056 pounds on pasture, and the cost of the gain on pasture was $51.30/cwt. The 2001 steer grazing project showed a small profit above all costs. The net profit was $4.12/steer or $5.15/acre. Large profits and large losses are possible, primarily depending on the difference between the buying and selling prices.

Rotation Grazing Demonstrations With Beef Cows on HEL - Adams County Conservation Reserve Program (CRP) Project

Two grazing systems were demonstrated on Conservation Reserve Program (CRP) land in southwestern Iowa near Corning in the summers of 1991, 1992, 1993, 1994, and 1995. This report summarizes the 1995 data and compares them to results from the four previous years. The systems, a 13-paddock intensive-rotational grazing system and a 4-paddock more traditional rotation, both established in 1991, are aimed at showing economically sustainable grass alternatives for steeply sloping (9-14% slope), highly erodible land (HEL) once the 10-year CRP ends. In a 147-day grazing season in 1995, nursing crossbred calves with no creep gained 2.36 pounds and 2.38 pounds per day on the 13- and 4-paddock systems, respectively. The rotations were stocked at 1.65 acres per cow-calf pair on the 13-paddock system and 1.72 acres per pair on the 4-paddock system. This produced 210.2 pounds of calf gain per acre on the 13-paddock system and 203.2 pounds of calf gain per acre on the 4- paddock system.. Similar calves gained 2.37 pounds and 2.50 pounds per day for 155 days, yielding a total gain per acre of 222.7 pounds on the 13-paddock system and 224.9 pounds on the 4-paddock system in 1994. Results for 1992 remain the highest from both systems in the five years of grazing, with calf gain per head per day at 2.45 for 155 days netting 241.9 pounds per acre on the 13- paddock system and calf gain per head per day at 2.38 for 154 days on the 4-paddock system yielding 263.6 pounds per acre. Cows maintained both their weight and condition scores in both systems again in 1995. A third system, the 18-paddock intensive-rotational grazing system, was stocked with stocker steers in 1995, and the results are reported in a second article in the 1996 ISU Beef Research Report entitled “Intensive- Rotational Grazing Steers on Highly Erodible Land at the Adams County CRP Project.” Concerning grazing management, paddocks were grazed four, five, or six times in the 13-paddock intensive- rotational grazing system during the 147-day grazing season of 1995. This number of times grazed per paddock was nearly equal to times grazed per paddock in 1994. However, several paddocks were subdivided temporarily to equalize paddock size and increase grazing uniformity. This increased the total number of cattle moves in the 13-paddock system from 78 in 1994 to 109 in 1995. The average length of stay on each paddock or subdivision of a paddock per grazing time was 1 to 2.2 days. This was less than in any of the other four grazing years in this project. The principle of not grazing more than half the standing forage during any one grazing period was closely followed in 1995. All paddocks in the 13-paddock system were also rested approximately the recommended 30 days between each grazing cycle in 1995.

Growth Response and Carcass Characteristics of Yearling Steers Subjected to Differing Implant Strategies

A 106-day demonstration utilizing yearling steers to measure feedlot performance and carcass response to implant strategies was conducted at the ISU Allee Demonstration Farm. Treatments were: 100 mg progesterone + 10 mg estradiol benzoate (ComponentÒ EC) on day 0 followed by 120 mg trenbolone acetate + 24 mg estradiol (ComponentÒ TES) implant 57 days later, or 120 mg trenbolone acetate + 24 mg estradiol (ComponentÒ TES) only on day 0. The control group received no implant. The steers were weighed every 28 days and ultrasound data were collected from demonstration initiation until slaughter. The cattle were marketed as one group on d 106 of the demonstration. Implanted cattle had higher average daily gains, heavier carcass weights, larger rib eye areas, and tended to have improved feed efficiency over control steers. Additionally, the reimplanted steers had higher marbling scores than controls, but no differences existed between once and twice-implanted steers.

Encore® Implant Use in Feedlot Steers

A feedlot demonstration utilizing Encore®, a new longterm implant product, was completed at the Allee Demonstration Farm at Newell, Iowa in 1999. Seventyone steers (697 lbs.) were allotted by weight and hide color and assigned to one of three treatments: 1) Encore® (43.9 mg estradiol = E) on day 0; 2) Encore® plus Component® TS (140 mg trenbolone acetate = ETS0) on day 0; or 3) Encore® on day 0 followed by Component® TS (ETS100) on day 100. Due to wide standard deviation in the weight of steers at the beginning of the demonstration, cattle were harvested in two groups. Approximately half of each treatment group was sorted by visual appraisal as to market readiness. Statistical interactions existed within treatment group between first and second harvest dates, therefore data were split and analyzed accordingly. In the first harvest group, ETS0 steers had higher marbling scores than ETS100 steers, and lower average daily gain than E steers and ETS100 steers. In the second harvest group, ETS0 steers had more fat at the 12th/13 rib than ETS100 steers, but did not differ from E steers. Marbling scores were also higher for ETS0 steers than either ETS100 or E steers in the second harvest group. Pooled data reveal that ETS0 steers had higher marbling scores than ETS100 steers and tended to have higher marbling scores than E steers. First harvest E and ETS100 steers had greater average daily gain than ETS0 steers. In the second harvest group, ETS0 steers had heavier final ending weights than E steers but did not differ from ETS100 steers. Final ending weights, rib eye area, fat thickness at the 12th/13th rib, KPH fat, and calculated yield grades did not differ among treatment groups in the pooled data.

Effects of Feeding Calcium Salts of Conjugated Linoleic Acid (CLA) to Finishing Steers

Thirty crossbred steers were randomly assigned to three treatment groups and fed corn-based finishing diets (88% concentrate) containing 0, 1.0 or 2.5% conjugated linoleic acid (CLA) for an average of 130 days. Steers fed 2.5% CLA consumed less feed and had lower daily gains than control steers. Carcass weights tended to be reduced, and marbling scores were decreased by feeding 2.5% CLA. There were no significant effects of feeding CLA on dressing percentages, yield grades and backfat measurements. The rounds from each animal were physically separated into tissue components. Rounds from steers fed CLA contained a higher percentage of lean tissue and a lower percentage of fat. Feeding CLA increased concentrations of CLA in lipids from fat and lean in rib steaks and rounds. Increasing CLA in beef had no effects on shelf life, tenderness, juiciness, flavor or flavor intensity of rib steaks. Although results indicated that feeding calcium salts of CLA to beef steers decreased performance, concentrations of CLA in tissues could be increased offering the availability of a leaner, more healthful meat product.

Integrating the Use of Spring- and Fall-Calving Beef Cows in a Year-round Grazing System (A Progress Report)

Animal production, hay production and feeding, and the yields and composition of forage from summer and winter grass-legume pastures and winter corn crop residue fields from a year-round grazing system were compared with those of a conventional system. The year-round grazing system utilized 1.67 acres of smooth bromegrass-orchardgrass-birdsfoot trefoil pasture per cow in the summer, and 1.25 acres of stockpiled tall fescue-red clover pasture per cow, 1.25 acres of stockpiled smooth bromegrass-red clover pasture per cow, and 1.25 acres of corn crop residues per cow during winter for spring- and fall-calving cows and stockers. First-cutting hay was harvested from the tall fescue-red clover and smooth bromegrass-red clover pastures to meet supplemental needs of cows and calves during winter. In the conventional system (called the minimal land system), spring-calving cows grazed smooth bromegrass-orchardgrass-birdsfoot trefoil pastures at 3.33 acres/cow during summer with first cutting hay removed from one-half of these acres. This hay was fed to these cows in a drylot during winter. All summer grazing was done by rotational stocking for both systems, and winter grazing of the corn crop residues and stockpiled forages for pregnant spring-calving cows and lactating fall-calving cows in the year-round system was managed by strip-stocking. Hay was fed to springcalving cows in both systems to maintain a mean body condition score of 5 on a 9-point scale, but was fed to fall-calving cows to maintain a mean body condition score of greater than 3. Over winter, fall-calving cows lost more body weight and condition than spring calving cows, but there were no differences in body weight or condition score change between spring-calving cows in either system. Fall- and spring-calving cows in the yearround grazing system required 934 and 1,395 lb. hay dry matter/cow for maintenance during the winter whereas spring-calving cows in drylot required 4,776 lb. hay dry matter/cow. Rebreeding rates were not affected by management system. Average daily gains of spring-born calves did not differ between systems, but were greater than fall calves. Because of differences in land areas for the two systems, weight production of calves per acre of cows in the minimal land system was greater than those of the year-round grazing system, but when the additional weight gains of the stocker cattle were considered, production of total growing animals did not differ between the two systems.

Efficacy of Grazing Stockpiled Perennial Forages for Winter Maintenance of Beef Cows

In a three year study, wintering systems utilizing the grazing of stockpiled perennial hay crop forages or corn crop residues were compared to maintaining cows in a drylot. In the summer of 1992, two cuttings of hay were harvested (June 22 and August 2) from three 10-acre fields containing “Johnstone” endophyte-free tall fescue and “Spreador II” alfalfa, and one cutting of hay was harvested from three 10- acre fields of smooth brome grass. “Arlington” red clover was frost-seeded into the smooth bromegrass fields in 1993 and into tall fescue-alfalfa and smooth bromegrass fields into 1994. Two cuttings of hay were harvested from all fields in subsequent years, and three-year average hay yields for tall fescue-alfalfa and smooth bromegrass-red clover were 4,336 and 3,481 pounds per acre, respectively. Regrowth of the forage following the August hay harvest of each year was accumulated for winter grazing. Following a killing frost in each year, two fields of each stockpiled forage were stocked with cows in midgestation at two acres per cow. Two 10-acre fields of corn crop residues were also stocked at two acres per cow, following the grain harvest. Mean dry matter forage yields at the initiation of grazing were 1,853, 2,173 and 5,797 pounds per acre for fields containing tall fescue-alfalfa, smooth bromegrass-red clover, and cornstalks, respectively. A drylot was stocked with 18 cows in 1992 and 1993 and 10 cows in 1994. All cows were fed hay as necessary to maintain a body condition score of five. During grazing, mean losses of organic matter were -6.4, -7.6, and -10.7 pounds per acre per cow from tall fescue-alfalfa, smooth bromegrass-red clover, and cornstalk fields. Average organic matter loss rates from stockpiled forages due to weathering alone were equal to only 30% of the weathering losses of the corn crop residues. In vitro digestibility of both stockpiled forages and cornstalks decreased at equal rates during grazing each year, with respective annual loss rates of .14, .08, and .06% per day. Cows grazing corn crop residues required an average of 1,321 pounds per cow less hay than cows maintained in the drylot to maintain equivalent body condition during the grazing season. Cows grazing tall fescue-alfalfa or smooth bromegrass-red clover had body weight gains and condition score changes equal to cows maintained in a drylot but required 64% and 62% less harvested hay than cows in the drylot during the grazing season. Over the entire stored forage cows grazing tall fescue-alfalfa and smooth bromegrass-red clover required an average of 2,390 and 2,337 pounds per cow less than those maintained in the drylot. Because less hay was needed to maintain cows grazing stockpiled forages, average annual excesses of 5,629 and 3,868 pounds of hay dry matter per cow remained in the stockpiled tall fescue-alfalfa and smooth bromegrass-red clover systems.

Evaluation of Year-round Forage Management Systems for Spring- and Fall-Calving Beef Cows (A Progress Report)

A year-round grazing system for spring- and fall-calving cows was developed to compare animal production and performance, hay production and feeding, winter forage composition changes, and summer pasture yield and nutrient composition to that from a conventional, or minimal land system. Systems compared forage from smooth bromegrass-orchardgrass-birdsfoot trefoil pastures for both systems in the summer and corn crop residues and stockpiled grass-legume pastures for the year-round system to drylot hay feeding during winter for the minimal land system. The year-round grazing system utilized 1.67 acres of smooth bromegrassorchardgrass- birdsfoot trefoil (SB-O-T) pasture per cow in the summer, compared with 3.33 acres of (SB-O-T) pasture per cow in the control (minimal land) system. In addition to SB-O-T pastures, the year-round grazing system utilized 2.5 acres of tall fescue-red clover (TFRC) and 2.5 acres of smooth bromegrass-red clover (SBRC) per cow for grazing in both mid-summer and winter for fall- and spring-calving cows, respectively. First-cutting hay was harvested from the TF-RC and SB-RC pastures, and regrowth was grazed for approximately 45 days in the summer. These pastures were then fertilized with 40 lbs N/acre and stockpiled for winter grazing. Also utilized during the winter for spring-calving cows in the year-round grazing system were corn crop residue (CCR) pastures at an allowance of 2.5 acres per cow. In the minimal land system, hay was harvested from three-fourths of the area in SB-O-T pastures and stored for feeding in a drylot through the winter. Summer grazing was managed with rotational stocking for both systems, and winter grazing of stockpiled forages and corn crop residues by year-round system cows was managed by strip-stocking. Hay was fed to maintain a body condition score of 5 on a 9 point scale for spring-calving cows in both systems. Hay was supplemented as needed to maintain a body condition score of 3 for fall-calving cows nursing calves through the winter. Although initial condition scores for cows in both systems were different at the initiation of grazing for both winter and summer, there were no significant differences (P > .05) in overall condition score changes throughout both grazing seasons. In year 1, fall-calving cows in the year-round grazing system lost more (P < .05) body weight during winter than spring-calving cows in either system. In year 2, there were no differences seen in weight changes over winter for any group of cows. Average daily gains of fall calves in the yearround system were 1.9 lbs/day compared with weight gains of 2.5 lbs/day for spring calves from both systems. Yearly growing animal production from pastures for both years did not differ between systems when weight gains of stockers that grazed summer pastures in the year-round grazing system were added to weight gains of suckling calves. Carcass characteristics for all calves finished in the feedlot for both systems were similar. There were no significant differences in hay production between systems for year 1; however, amounts of hay needed to maintain cows were 923, 1373, 4732 lbs dry matter/cow for year-round fall-calving, year-round spring-calving, and minimal land spring-calving cows, respectively. In year 2, hay production per acre in the minimal land system was greater (P < .05) than for the year-round system, but the amounts of hay required per cow were 0, 0, and 4720 lbs dry matter/cow for yearround fall-calving, year-round spring-calving, and minimal land spring-calving cows, respectively.

Investigation of the Potential Effects of Epizootic Hemorrhagic Disease Virus on Iowa Cattle

Epizootic hemorrhagic disease virus (EHDV), an arthropod-borne orbivirus, causes significant mortality in white-tailed deer and can also cause disease in cattle. Objectives of this preliminary investigation were 1) to survey cattle at auction markets to determine the prevalence of anti-EHDV antibodies in Iowa cattle, 2) to determine EHDV seroprevalence in herds in which clinical EHD had been diagnosed, and 3) to determine whether EHDV is associated with stillbirths and/or congenital anomalies in calves. There was a 15% seroprevalence in auction market cattle; positive cattle were from southern, central, and western Iowa. Herds in which clinical EHD had been diagnosed had >60% seroprevalence. Viremia was detected in both clinically affected and unaffected cattle during an EHD outbreak. EHDV exposure was not consistently associated with congenital anomalies. Although additional surveillance is warranted, EHDV is unlikely to have a significant effect on the reproductive health of Iowa cattle.