Evaluation of Dietary Laidlomycin Propionate and Synovex Plus Implants for Enhancing Performance of Feedlot Steers

One hundred fifty crossbred yearling steers with an average weight of 876 pounds were used in a 111-day experiment. Steers received either 1) no implant and no ionophore, 2) Synovex Plus¨ and no ionophore, 3) Cattlyst¨ and no implant, 4) Synovex Plus¨ and Cattlyst¨, or 5) Revalor S¨ and Rumensin¨. Implanting steers with ) Synovex Plus¨ increased gain and improved feed efficiency compared with control steers. Compared with steers not implanted, steers implanted with Synovex Plus¨ had heavier carcasses and larger ribeye areas, but similar fat thickness and yield grades. Feeding Cattlyst¨ alone did not increase gain or improve feed conversion, but there was some improvement in feedlot performance when Cattlyst¨ was fed to steers implanted with Synovex Plus¨. Steers implanted with Synovex Plus¨ and fed Cattlyst¨ had superior gains to steers implanted with Revalor S¨ and fed Rumensin¨.

Intensive Rotational Grazing of Steers at the Andrew Jackson Demonstration Farm

Fifty head of crossbred steers started grazing 51 acres of pasture on May 1 in a rotational grazing system using a variable density paddock system. Twenty-two head grazed 92 days, 27 grazed 140 days, and one steer died. A total of 11,922 pounds was produced on 5,804 animal-days of grazing. The average daily gain was 2.02 pounds for group 1 and 2.07 for group 2. The stocking rate for the first 92 days was .98 steers per acre and .53 for the final 48 days. The animal days of grazing per acre was 113 and the pounds of gain per acre was 233. Total return for land, labor and management for the demonstration was $2,829.76 or $55.49/acre.

Evaluation of Synovex Plus, Synovex S and Revalor S Implants in Feedlot Steers

One hundred forty-four crossbred yearling steers with an average weight of 841 pounds were used in a 116- day experiment. Steers received either 1) no implant, 2) Synovex S¨, 3) Revalor S¨, or 4) Synovex Plus¨. All implanted groups consumed more feed and gained faster and more efficiently than non-implanted steers. There were no significant differences in gain, feed intake or feed efficiency among implanted groups, though steers with the estrogen + trenbolone acetate combination implants were numerically superior to those implanted with Synovex S¨. There were no differences in feedlot performance between the two combination implants. Implants increased carcass weight with no significant effects on fat thickness or carcass quality grades. The combination implants containing trenbolone acetate increased ribeye area and increased masculinity of the carcasses. These results indicate Synovex Plus¨ is an effective implant for finishing steers.

Effects of Supplementing High or Low Quality Forages with Corn or Corn Processing Co-Products Upon Digestibility of Dry Matter and Energy by Steers

A digestibility trial, utilizing eight crossbred steers weighing initially 741 lbs. was conducted in an 8 x 8 Latin square design. High-fiber corn by-products were compared with corn as energy sources when fed in mixed diets with either lowor high-quality forage. Ground, dry corn stover and ground alfalfa hay were both fed alone or with corn grain, dried corn gluten feed (CGF), and dried corn distillers grains plus solubles (DDG) in a 1:1 ratio (dry basis). Total tract dry matter digestibility (DMD) was increased for both forages when fed with concentrates. Total tract DMD was similar in stover-based and alfalfa-based diets fed with CGF and DDG. However, stover+corn was lower in DMD than either stover+CGF and stover+DDG. Conversely, alfalfa+corn was higher in DMD than alfalfa+CGF or alfalfa+DDG. Feeding stover with corn tended to decrease digestibility of neutral detergent fiber (NDF), while feeding stover with CGF or DDG increased NDFD. There was no effect upon NDF digestion of alfalfa-based diets when fed with any of the concentrates. Feeding either forage with a concentrate increased digestible energy (DE). Stover+CGF and stover+DDG were similar in DE and were both higher in DE than stover+corn. Alfalfa+DDG tended to be higher than alfalfa+CGF and was similar to alfalfa+corn in DE. Alfalfa+CGF was lower in DE compared with alfalfa+corn. Results are interpreted to indicate that stover is more susceptible to negative feed interactions caused by corn grain than is alfalfa. Additionally, highfiber corn co-products fed with stover resulted in a positive associative effect but essentially had no associative effect when fed with alfalfa.

Brain Regulation of Growth in Beef Calves

Small peptide hormones produced in the lower part of the brain (hypothalamus) regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Crossbred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n = 5), HST (n = 5), or SOC (n = 8) at 146 days of age, whereas another group was HST (n = 5) or SOC (n = 7) at 273 days of age. Body weight was determined every 21 days from birth to 1008 days of age. From day 146-1008, growth was arrested (P < 0.001) in HYPOX (0.06 kg/day) compared with SOC (0.50 kg/day) calves. Growth continued but at a significantly lower rate (P < 0.05) in calves HST at 146 days (0.32 kg/day) and 273 days (0.32 kg/day) compared with SOC (0.50 kg/day). Although episodic growth hormone (GH) secretion was abolished and peripheral blood serum GH concentration remained consistently lower in HST calves (2.4 ng/ml) than in the SOC (5.5 ng/ml; P < 0.01), the calves continued to grow throughout 1008 days. Peripheral serum thyroid stimulating hormone (TSH) concentration was less (P < 0.05) in HST compared with SOC calves. There was an abrupt decrease (P < 0.001) in serum thyroxine (T4) (4-fold) and triiodothyronine (T3) (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At sacrifice, pituitary gland weight was markedly reduced (P < 0.001) in HST (0.18 g/100 kg body weight) compared with SOC (0.55 g/100 kg body weight) calves. Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the anterior pituitary gland as SOC calves. Coronal sections of the gland revealed GH and TSH secreting cells in HST calves that were similar to the controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T4, and T3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable.

Forage-Based Beef Production Research at the Armstrong Outlying Research Farm

Fifty-five yearling crossbred steers and 3C cow-calf pairs were used in a forage-based beef production system demonstration project at the Armstrong Outlying Research Farm. From May 11 to June 13, steers rotationally grazed a 41-acre grass pasture that was divided into eight paddocks. From June 13 to August 24, steers were placed in a drylot and fed berseem clover/oat soilage from a strip-intercropping system. Beginning June 5, 36 cow-calf pairs were allowed to rotationally graze the 41-acre pasture until September 18. Calf weight gains for the 110 days were 1.57 pounds per day, and total production from the pasture was 151 pounds per acre. No cow weight change or condition score change was measured. Total steer production was 29 and 580 pounds per acre or average daily gains were .67 and 2.23 pounds while grazing pasture and being fed in a drylot.

Use of Ultrasound Backfat Estimates to Form Marketing Groups Prior to Finishing for Feedlot Steers

An experiment was conducted using 95 Continental crossbred steers. The cattle were sorted by ultrasound 160 days before slaughter into a low backfat group (Low BF) and a higher backfat group (High BF). Half of the Low BF and half of the High BF were implanted whereas the other halves were not. Data from the experiment were used in two hypothetical markets. One market was a high yield beef program (HY) that did not allow the use of implants. The second market was a commodity beef program (CM) that allowed the use of implants. The cattle were priced as an unsorted group (ALL) and two sorted groups (Low BF and High BF) within the HY (non-implanted) and CM (implanted) markets. The CM program had a base price of $1.05/lb hot carcass weight (HCW) with a $0.15/lb HCW discount for quality grade (QG) Select and a $0.20/lb HCW discount for yield grade (YG) 4. The HY program used a base price of $1.07/lb HCW with premiums ($/lb HCW) paid for YG £ .9 (.15), 1.0 - 1.4 (.10), and 1.5 - 1.9 (.03). The carcasses were discounted ($/lb HCW) for YG 2.5 - 2.9 (.03), 3.0 - 3.9 (.15), and ³ 4.0 (.35). This data set provides good evidence that the end point at which to sell a group of cattle depends on the particular market. Sorting had an economic advantage over ALL in the HY Low BF and the CM High BF groups. The HY High BF cattle should have been sold sooner due to the discounts recieved for increased YG. The increased YG was directly affected by an increase in BF. Furthermore, the CM Low BF group should have been fed longer to increase the number of carcasses grading Choice.

Effects of Bovine Somatotropin and Revalor-S® on Growth Performance and Carcass Leanness in Beef Cattle

Twenty crossbred steers were used to evaluate bovine somatotropin (bST) and an anabolic steroid implant, Revalor-S® (REV), to improve growth and increase carcass leanness. During the first 70 days on feed, bST-treated steers tended to improve live weight gains, consume more feed, and numerically improve feed utilization for growth. The implanted steers grew faster and utilized feed better than steers not implanted with REV. The improvement in gain and feed utilization for growth was maintained throughout the feeding period for REV-implanted steers. At slaughter, REV steers had heavier carcasses which resulted in more pounds of muscle, bone, and fat. When adjusted for hot carcass weight, bST increased leanness of the carcass as evident by the increased weight of the semitendinosus muscle, more pounds of dissected lean, and fewer pounds of dissected fat. Thus, REV and bST can be used to improve growth performance and increase carcass leanness.

An Economic Comparison of Rotational Grazing Systems to Eight Crop Alternatives and the CRP Option for Highly Erodible Land in Southwest Iowa

Economic comparisons of income on highly erodible land (HEL) in Adams County were made utilizing five years of grazing data collected from a 13- paddock intensive-rotational grazing system and a four-paddock rotational-grazing system and four years of data collected from an 18-paddock intensive-rotational grazing system, all at the Adams County CRP Research and Demonstration Farm near Corning. Net income from the average grazing weight-gain of Angus-sired calves nursing crossbred cows was compared to the net income from grazing yearling steers, to the net income of eight NRCS-recommended crop rotations, and to the Conservation Reserve Program (CRP) option. Results of these comparisons show the 13-paddock intensive rotational grazing system with cow-calf pairs to be the most profitable alternative, with a net return of $19.86 per acre per year. The second most profitable alternative is the CRP option, with a net return of $13.09 per acre, and the third most profitable option is the fourpaddock rotation with cows and calves with a net return of $12.53 per acre. An 18-paddock system returned a net income of $2.47 per acre per year with cows and calves in 1993, but lost an average of $107.69 per acre each year in 1994 and 1995 with yearling steers. Each year, the steers were purchased high and sold low, contributing to the large loss per acre. The following recommended crop rotations all show net losses on these 9-14 % slope, Adair-Shelby Complex soils (ApD3): continuous corn; corn-soybean rotation; corn-soybean rotation with a farm program deficiency payment; corn-corn-corn-oats-meadow-meadow rotation with grass headlands; continuous corn to “T” with grass headlands and buffer strips; continuous corn to “T” with grass headlands, buffer strips, and a deficiency payment; corn-corn-oats-meadow rotation to “T”; and corn-soybeans-oats-meadow-meadow-meadow-meadow rotation to “T”. Per-acre yield assumptions of 90 bushels for corn, 30 bushels for soybeans, 45 bushels for oats, and four tons for alfalfa were used, with per-bushel prices of $2.40 on corn, $5.50 on soybeans, and $1.50 on oats. Alfalfa hay was priced at $40.00 per ton and grass hay at $33.33 per ton. The calf weight-gain in the cow/ calf systems was valued at $.90 per pound. All crop expenses except land costs were calculated from ISU publication Fm 1712, “Estimated Costs of Crop Production in Iowa - 1995.” Land costs were determined by using an opportunity cost and actual property tax figures for the land at the grazing site. In preparation for the end of the CRP beginning in 1996, further economic comparisons will be made after additional grazing seasons and data collection. This project is an interagency cooperative effort sponsored by the Southern Iowa Forage and Livestock Committee which has special permission from the USDA Farm Service Agency (FSA) to use CRP land for research and demonstration.

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.

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.

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.