The Costs and Predictive Factors of Bovine Respiratory Disease in Standardized Steer Tests

A retrospective study of 2,146 feedlot cattle in 17 feedlot tests from 1988 to 1997 was conducted to determine the impact of bovine respiratory disease (BRD) on veterinary treatment costs, average daily gain, carcass traits, mortality, and net profit. Morbidity caused by BRD was 20.6%. The average cost to treat each case of BRD was $12.39. Mortality rate of calves diagnosed and treated for BRD was 5.9% vs. .35% for those not diagnosed with BRD. Average daily gain differed between treated and non-treated steers during the first 28 days on feed but did not differ from 28 days to harvest. Net profit was $57.48 lower for treated steers. Eighty-two percent of this difference was due to a combination of mortality and treatment costs. Eighteen percent of the net profit difference was due to improved performance and carcass value of the non-treated steers. Data from 496 steers and heifers in nine feedlot tests were used to determine the effects of age, weaning, and use of modified live virus or killed vaccines prior to the test to predict BRD. Younger calves, non-weaned calves, and calves vaccinated with killed vaccines prior to the test had higher BRD morbidity than those that were older, weaned, or vaccinated with modified live virus vaccines, respectively. Treatment regimes that precluded relapse resulting in re-treatment prevented reduced performance and loss of carcass value. Using modified live virus vaccines and weaning calves 30 days prior to shipment reduced the incidence of BRD.

Effect of Optimum® High Oil Corn on Performance and Carcass Characteristics of Finishing Yearling Steers

Steers fed Optimum® high oil corn had statistically similar live performance as steers fed isogenetic control corn or the control corn + fat. Numerically steers fed high oil corn gained 3% faster during the 107-day study with similar feed conversion. During the first half of the experiment, steers fed high oil corn did not perform as well as those fed control corn. During the second half of the experiment, steers fed high oil corn gained 21% faster and were 17% more efficient. There were no effects of feeding high oil corn on carcass characteristics, except there were more Choice carcasses from the steers fed high oil corn as compared with control corn (57% vs. 43% Choice).

Evaluation of a Mixture of Corn Steep Liquor and Distillers Solubles as a Replacement for Corn and Supplement in Cattle Finishing Diets

Finishing yearling steers fed a corn-based diet containing steep liquor had statistically similar live performance as steers fed the control diet. Numerically steers fed the steep containing diet were 6% more efficient. Steers fed steep liquor tended to contain less carcass fat (as measured by intramuscular marbling) less kidney, heart and pelvic fat, and less backfat thickness. When priced at $50/ton adding steep liquor at 10% of diet dry matter reduced feed cost for gain 9%.

Management Intensive Grazing of Stockers at the Andrew Jackson Demonstration Farm (1996 – 1998)

The Andrew Jackson Demonstration Farm (AJDF) is located in central Jackson County in east central Iowa. A board of directors operates the farm for the purpose of demonstrating different production practices and management strategies. From 1996 to 1998 management intensive grazing practices and the grazing of stockers on a combination of permanent and tillable pasture have been demonstrated. Grazing strategies or practices demonstrated during these years included establishment of Eastern Gamagrass and Big Bluestem, variable density grazing, measuring forage on-offer, estimating dry matter intake, grazing corn, pasture renovation, and fencing and water systems. Production performance data were gathered for the three years stockers that were grazed. During this time the stockers averaged 121 animal days of grazing, a 1.1 head per acre stocking rate, a 1.85 pound average daily gain, and 228 pounds of gain per acre. The financial measures evaluated the value of gain on pasture and the pasture cost of the gain. The value of gain per pound was positive for 1996 and 1997 at $.58 and $.52 whereas in 1998 it was a -$.04. Pasture costs per pound of gain ranged from $.12 to $.16. Production performance is only one part of the profit picture when evaluating a stocker operation. Buysell margins are the other significant part that can greatly impact the profit potential of a summer grazing program.

Correspondence of Gonadotropin-Releasing Hormone and Luteinizing Hormone Secretion during Suckling in Postpartum Cows

The hypothalamus in the lower part of the brain contains neurons that produce a small peptide, gonadotropin- releasing hormone (GnRH, LHRH), that regulates luteinizing hormone (LH) secretion by the anterior pituitary gland. Important functions of LH include induction of ovulation in preovulatory follicles during estrus and the luteinization of granulosa cells lining those collapsed follicles to form corpora lutea that produce progesterone during the luteal phase of the estrous cycle or during pregnancy. The production of progesterone by the corpus luteum conveys a negative feed-back action at the central nervous system (CNS) for further episodic secretion of GnRH and in turn, LH secretion. Gonadal removal (i.e., ovariectomy) allows a greater amount of LH secretion to occur during a prolonged period. The objectives of this study were to characterize the pattern of GnRH secretion in the cerebrospinal fluid (CSF) of the bovine third ventricle region of the hypothalamus, determine its correspondence with the tonic and surge release of LH in ovariectomized cows, and examine the dynamics of GnRH pulse release activity in response to known modulators of LH release (suckling, neuropeptide-Y [NPY]). In ovariectomized cows, both tonic release patterns and estradiol-induced surges of GnRH and LH were highly correlated. A 500-microgram dose of NPY caused an immediate cessation of LH pulses and decreased plasma concentrations of LH for at least 4 hours. This corresponded with a decrease in both GnRH pulse amplitude and frequency. In anestrous cows, GnRH pulse frequency did not change before and 48 to 54 hours after weaning on day 18 postpartum, but GnRH concentration and amplitudes of GnRH pulses increased in association with weaning and heightened secretion of LH. It is clear that high-frequency, highamplitude pulses of LH are accompanied by similar patterns of GnRH in CSF of adult cattle. Yet strong inhibitors of LH pulsatility, putatively acting at the level of the central nervous system (i.e., suckling) or at both the central nervous system and pituitary (NPY) levels, produced periods of discordance between GnRH and LH pulses.

Experience with an Electronic Identification System for Cattle

An electronic identification system involving placement of transponders in rumen boluses was evaluated in thirty feedlot steers. All the devices were retained and remained functional in the steers. Twenty-eight of the devices were recovered at the packing plant. Two of them were lost because of an incomplete understanding that attempts were being made to recover the boluses from rumen contents. Use of rumen boluses is a practical alternative for electronic identification of cattle that is permanent and nearly tamper proof.

Value of High-Oil Corn Grain for Finishing Steers

Rolled high-oil corn in comparison with rolled isogenetic control corn was fed to finishing steers as 33%, 66% and 100% of the corn grain in their diet in a 134-day feeding trial. During the first 75 days of the trial, steers fed highoil corn had numerically lower rates of gain and tended to have poorer feed conversions compared with the control corn. At the end of the trial, there were not statistically significant differences in performance or carcass measurements of the steers fed the different amounts of high-oil or control corns. The results of this study indicated that the steers did not respond to the higher energy content of high-oil corn.

Value of High-Oil and High-Protein Corn Grains for Finishing Cattle

Three specialty corns, high oil, high protein and high oil with high protein, were compared with control corn in a 113-day steer feeding trial. During the first 63 days of the study, steers fed the corns containing more oil had slower gain and poorer feed conversion compared with the control corn. At the end of the trial there were no statistically significant differences in performance of steers fed the different corns. Steers fed the high protein corn tended to have higher grading carcasses compared with those fed the control corn. Otherwise there were no differences in carcass measurements due to source of corn fed the steers. Feed cost of gain was reduced with the high-protein corn and the corn with high fat and high protein compared with the control corn because of similar feed conversions and the reduced amount of soybean meal needed to supplement the specialty corns.

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.

Strategies for Optimizing Value of Finished Cattle in Value-Based Marketing Grids

Performance and carcass data from 624 steers in three experiments were used to evaluate potential strategies that might be used with incoming feeders to remove animals that produce low value carcasses when cattle are sold in a valuebased grid. Removing 10% of the carcasses with the lowest net value from each group increased the overall average net value of the remaining carcasses $17.50 to $21.09. Carcass weight was found to be the most significant factor determining net value of the carcass. Gain of the steers during the first 3 to 5 weeks of the feeding period was significantly related to average final gain and carcass value, but accounted for a small portion of the overall variation in gain or carcass value. Use of initial gain was successful in identifying ten of the sixty-four carcasses with least net value in a value-based grid. Adding frame score and measurement of initial thickness of backfat along with initial gain did not significantly improve identification of the low-value carcasses. Sorting the steers as feeders based on frame score and initial thickness of backfat resulted in differences in performance and carcass measurements. The low-value carcasses tended to be concentrated in the smaller-framed steers.

The Effects of High-Oil Corn or Typical Corn with or without Supplemental Fat on Diet Digestibility in Finishing Steers

Two 3 x 3 latin squares were utilized in an 84-day digestion trial with ruminally- and duodenallycannulated steers. Diets consisted of 73 to 78% whole corn grain, 12.3% corn silage and 2.0% N, with treatment differences being high-oil corn- (HOC), isogenetic typical-corn- (TC), or isogenetic typical-corn + fat- (TC+F) based diets. The HOC and TC+F diets were formulated to provide the same ether extract (EE) content. All diets were fed at 90% of ad libitum intake. Chromic oxide was used as a digestibility marker. Total tract dry matter (DM) (P=.08), organic matter (OM) (P=.08) and nitrogen (N) (P=.06) digestibilities tended to be greater for TC than HOC diets, whereas starch neutral detergent fiber (NDF), acid detergent fiber (ADF), and ether extract digestibilities were similar (P>.10). There were no differences (P>.10) in total tract dry matter, organic matter, starch, NDF, ADF, ether extract, or nitrogen digestibilities between TC+F and HOC diets or TC and TC+F diets. Ruminal digestion of dry matter, organic matter, starch, NDF, ADF, and feed nitrogen was similar (P>.10) among treatments. Microbial-nitrogen flow and efficiencies were also similar (P>.10) among treatments. Results indicate finishing steer diets composed of primarily HOC are equally or less digestible than similar diets composed of TC, and adding fat to TC diets did not affect the digestibility of the diet when fed to finishing steers.

Superovulation of Beef Heifers with Follicle Stimulating Hormone or Human Menopausal Gonadotropin: Acute Effects on Hormone Secretion

The effects of superovulatory treatment (follicle stimulating hormone [FSH] versus human menopausal gonadotropin [HMG]) and of route of administration (intramuscular versus intravenous) of prostaglandin F2a (PGF2a) on hormonal profiles were determined in 32 Angus x Hereford heifers for breeding and subsequent embryo collection and transfer. Heifers were superstimulated either with FSH (total of 26 milligrams) or HMG (total of 1,050 international units) beginning on days 9 to 12 of an estrous cycle and PGF2a (40 milligrams) was administered at 60 and 72 hours after the beginning of superovulatory treatments. Heifers were artificially inseminated three times at 12-hour intervals beginning 48 hours after PGF2a treatment. Blood serum samples were collected immediately before treatments began and at frequent intervals until embryo collection 288 hours later. Concentrations of luteinizing hormone (LH) and FSH were not affected by hormone treatments, route of PGF2a injection, or interactions between them. Estradiol-17ß (E2-17ß) levels were higher in HMG- than in FSH-treated heifers 60 hours after gonadotropin treatment. Peak concentration of E2-17ß occurred earlier in HMGthan in FSH-treated heifers and earlier in heifers injected with PGF2a intramuscularly than those injected intravenously. Progesterone concentrations were not influenced by treatment or route of PGF2a administration. The progesterone:E2-17ß ratio was higher in FSH- than in HMG-treated heifers 24 hours after the LH peak. The high steroid hormone concentrations in superovulated beef heifers before and after ovulation may lead to asynchrony between stages of embryonic development, a situation that may interfere with the pregnancy outcome of superovulated embryos in recipient animals.

Effect of Feeding Procedure and Intake Level on Steer Feedlot Performance and Carcass Composition: A Progress Report

Two feedlot trials were conducted to evaluate the effects of feeding frequency (once daily in the morning, once daily in the afternoon or twice daily) and feeding level (ad libitum, 95% of ad libitum, or 90% of ad libitum) on the feedlot performance and carcass composition of beef steers. Data were collected using 196 yearling beef steers. In both trials cattle fed once daily in the morning tended to have higher gains and better feed efficiencies than cattle fed once daily in the afternoon or cattle fed twice daily. Overall, cattle restricted to 95% and 90% of ad libitum intake levels had better feed efficiencies than cattle with ad libitum access to feed. Cattle fed once daily in the morning tended to have less backfat than cattle fed once daily in the afternoon or cattle fed twice daily.

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.

Jackson County Heifer Development Project Update

The heifer development project took place the past four years on the site of the former Jackson County Farm north of Andrew, Iowa. Heifers arrived around December 1 with 38 heifers delivered for 1992, 44 for 1993, 46 for 1994, and 47 for 1995. After a 30+ day warm-up period, the heifers were put on a 112-day test from early January to late April. They were fed a shelled corn and legume-grass hay ration consisting of between 13% and 14% crude protein and .48, .58, .44, and .54 megacal/pound of NEg respectively for the years 1992 - 1995. During the 112-day test heifers gained 1.86, 1.78, 1.5, and 1.63 pounds per day respectively for years 1992 through 1995. The 1995 heifers averaged 853 pounds at breeding (22 pounds under target weight). This compares with previous years in which the breeding weight was less than target weight in two years by 5 and 12 pounds and exceeded the target weight in one year by 17 pounds. Estrus synchronization used a combination of MGA feeding and Lutalyse injection. Heifers were heatdetected and bred 12 hours later for a three-day period. On the fourth day, all heifers not bred were mass inseminated. Heifers then ran with the cleanup bull for 58 days. The synchronization response rate in 1995 was 83%, which compares with the three year previous average of 77%. The overall pregnancy rates based on September pregnancy exams were 94.6% in 1992, 93% in 1993, 91% in 1994, and 91.5% in 1995. Development costs for the 326 days in 1995 totaled $269.14 per heifer. This compares with the average of $286. 92 for the three previous years. The four-year average total cost per head for heifer development was $282.48, or about $.84 per day. Feed and pasture costs represented 58% of the total costs, or $.49 per day.