Heat Stress In Feedlot Cattle: Producer Survey Results

The weather on July 11 and 12, 1995 was a deadly combination of high temperature, high relative humidity, no cloud cover and no wind. The combination of heat and humidity has been matched only five times in Iowa’s 101 years of weather records. Estimated cattle death loss in a 13-county area of West Central Iowa was 3,750 head or 2.32% of the cattle on feed. A survey of 36 beef producers with 9,830 head of cattle on feed in 81 lots was summarized. Thirty-five lots with shade (24 square feet per head) reported an average death loss of .2% as compared to 46 lots without shade with losses of 4.8%. Producers reported a disproportionately higher death loss in dark-hided cattle. Non-shaded lots facing south, southwest, or west had higher death loss than lots facing east or southeast. Heavier animals were more susceptible to heat stress. Lots containing heifers that were fed MGA had lower death loss ( 3.8% vs. 6.2% ) as compared to lots with heifers but not receiving MGA.

Antibiotic Susceptibility of Mycoplasma bovis Strains Recovered From Mycoplasmal Pneumonia and Arthritis in Feedlot Cattle

Mycoplasmal pneumonia and arthritis is a problem of increasing significance in Midwestern feedlots. The disease presentation cannot be prevented by vaccination or successfully treated with antimicrobials. Due to the reported difficulty in treating these outbreaks, in-vitro antimicrobial susceptibility was tested on isolates of Mycoplasma bovis recovered from cases of pneumonia or pneumonia and arthritis where the mycoplasma was involved as a causative agent. Using a broth microdilution method, 36 M. bovis isolates from cases of pneumonia and 9 from cases of pneumonia and arthritis were tested for susceptibility to antimicrobials currently used in cattle with respiratory disease (ampicillin, tilmycosin, spectinomycin, tylosin, lincomycin, tetracycline, ceftiofur, and erythromycin). Among the isolates from cases with pneumonia, resistance to more antimicrobials was shown in recent isolates than in isolates from earlier years. Tetracycline and lincomycin were the drugs of choice for these isolates, although 3 of 36 isolates were resistant to all drugs tested. Isolates from cases of pneumonia and arthritis were from recent accessions. A majority of these isolates (5/9) were resistant to all antimicrobials tested. Lincomycin, spectinomycin, and tetracycline were antibiotics usable with 4/9 of the isolates. Overall, the results indicate that antimicrobial therapy in cases of mycoplasmal feedlot pneumonia and arthritis may be unrewarding.

An Evaluation of Effective Fiber in Beef Feedlot Finishing Diets

A study was designed to collect a database of Iowa feedlot rations for determination of effective neutral detergent fiber (NDF) in complete diets from fiber analysis and particle size determination of individual feed ingredients and compare this with particle size determination of mixed wet rations. Seventy-one beef finishing total mixed rations were collected by ISU Extension Beef Field Specialists across Iowa. Producers were asked to complete a form assessing the acidosis risk associated with each ration. The average NDF of these diets was 25.9%. Of the total mixed rations 1.33 % remained in the top tray (>.75 in.), 47.27 % remained in the middle tray (>.31 in.), and 50.88 % was smaller than the .31 in screen. The effective NDF (eNDF) calculated from the eNDF of the ingredients averaged 10.56%. Estimated eNDF from total diet NDF and the percentage of the total diet in the top and middle trays averaged 12.47%. The calculated eNDF from non-grain sources alone averaged 3.6%. The percentage of digestive deads was weakly related to the percentage of the ration in the bottom tray (r=.19), the percentage in the top tray (r=- .46) and the effective NDF of the ration (r=-.23). The percentage of bloat was related to the total NDF of the diet (r=.28) and the effective fiber from non-grain sources (r=-.23). The number of off-feed incidences was related to the dry matter of the ration (r=.38), the apparent eNDF (r=-.28) and the percentage of ration in the bottom tray (r=.24). This study confirms that there is some relationship between effective NDF of the diet, effective NDF from non-grain sources or diet particle size; and acidosis indicators. These relationships are weak, however, indicating that other factors such as feedbunk management, feed processing, feed presentation and feed mixing likely also play a role in the incidence of acidosis in feedlot cattle.

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.

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.

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.

Effects of Sorting Steer Calves on Feedlot Performance and Carcass Value

Three groups of steer calves totaling 480 head were sorted into smaller and larger frame sizes, and those groups were sorted into groups with more and less backfat. There was no difference in age among the four sorted groups. The larger steers and steers with less fat had faster rates of gain and tended to have superior feed efficiencies. Steers with more initial fat were fed fewer days. The larger framed steers and steers with less fat had heavier carcasses, less carcass backfat, more yield grade 1 carcasses and a lower percentage of Choice carcasses, but they also had greater value per carcass when evaluated using a grid paying premiums for quality and yield grades. The greatest profit to the feedyard was realized from the smaller framed steers and those with less initial backfat. For similar profit it was calculated that the larger steers should have been discounted as feeders $3.50 per hundred compared with the smaller steers and the steers with more fat discounted $5.00 per hundred compared with those having less initial fat. The results of this study suggest that sorting based on initial fat thickness may have more potential for enhancing the value of finished cattle than sorting based on frame score.

The Effect on Meat Quality of Integrating Pasturing Systems into Cattle Finishing Programs

The effect on meat quality of integrating pasturing systems into cattle finishing programs was observed over a two-year period. Year one consisted of 84 fall born calves and 28 spring born calves and year two consisted of 116 fall born calves. The effect of using Rumensinâ for cattle on bromegrass pasture was incorporated into year one. In year two cattle on pasture received bromegrass pasture, and one treatment group received switchgrass during the warm season. In both years there was a control group of calves that went directly to the feedlot with the remaining calves going to pasture for varying periods of time before being finished in drylot. At the conclusion of the feeding trial, cattle were processed into beef, and a ribeye steak was removed from each carcass for sensory evaluation. In year one cattle that were on pasture the longest had the lowest (P<0.05) average quality grades. In year two this trend was reversed, and cattle placed directly into drylot had the lowest (P<0.05) average quality grades. In both years cattle carcasses in all treatments averaged yield grade 2. Warner Bratzler shear force values were not affected by treatments. Sensory panel evaluations indicated tenderness was unaffected by treatments, and in year two flavor and flavor intensity were unaffected by treatments. In year one flavor intensity was lowest (P<0.05) for steaks derived from cattle that were on pasture the longest and received Rumensinâ. Inclusion of Rumensinâ for cattle on pasture did not influence yield and quality grades or affect tenderness, juiciness, and flavor. Results of this study indicate that steer calves placed on cool and warm season pastures prior to being finished in drylot, can produce carcasses with acceptable yield and quality grades and that the meat eating qualities will be largely unaffected by the inclusion of pasture.

The Effects of Feeding a Live Microbial Product on Feedlot Performance and Carcass Value of Finishing Steers Fed Wet Corn Gluten Feed

This experiment was conducted to evaluate the efficacy of daily feeding a live microbial preparation containing two live organisms to finishing cattle. One organism was a lactobacillus, and the other was a propionibacterium, thought to work in concert to improve fermentation in the rumen and overall digestion. The study was conducted with Angus steers with an average initial weight of 550 lbs that were fed a finishing ration containing 50% wet corn gluten feed on a dry basis for 184 days. Feeding the microbial product improved daily gain and feed efficiency 1.7% and 2.4%, respectively, but the differences were not statistically significant. The microbial preparation increased carcass weights 1% but had no effects on quality or yield grades. It is concluded that potential benefits of this product are more likely to be greater when cattle are fed high grain rations rather than diets containing high concentrations of corn gluten feed.

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.

Integration of Pasturing Systems for Cattle Finishing Programs

A 3-year study, using 84 fall-born and 28 spring-born calves of similar genotypes, was conducted to integrate pasturing systems with drylot feeding systems. Calves were started on test following weaning in May and October. Seven treatments were imposed: 1) fall-born calves directly into feedlot; 2 and 3) fall-born calves put on pasture with or without ionophore and moved to the feedlot at the end of July; 4 and 5) fall-born calves put on pasture with or without ionophore and moved to the feedlot at the end of October; 6 and 7) spring-born calves put on pasture with or without ionophore and moved to the feedlot at the end of October. A bromegrass pasture consisting of 16 paddocks, each 1.7 acre in size, was available. Each treatment group had access to 1 paddock at a time and was rotated at approximately 3-day intervals. In the feedlot, steers were provided an 82% concentrate diet containing whole-shelled corn, ground alfalfa hay, and a protein, vitamin and mineral supplement containing ionophore and molasses. As pens of cattle reached about 1150 lb. average live weight, they were processed and carcass traits were evaluated. Pasture daily gains were highest for cattle on pasture for the longest duration (P < .03), and overall daily gains were highest for drylot cattle (P < .01) and decreased with increased time spent on pasture. Although differences among treatments existed in numerical scores for yield and quality grades (P < .05 and P < .03, respectively), all treatments provided average yield grade scores of 2 and quality grades of low Choice or higher. Use of four production costs and pricing scenarios revealed that fall-born calves placed on pasture for varying lengths of time were the most profitable (P < .04) among the treatments. Furthermore, employing a 5% price sensitivity analysis, indicated that fed-cattle selling price had great impact on profit potential and was followed in importance by feeder purchase price and corn grain price. Overall, these findings should provide significant production alternatives for some segments of the cattle feeding industry and also lend substantial credence to the concept of sustainable agriculture.

Integration of Pasturing Systems for Cattle Finishing Programs: A Progress Report

A three-year study was conducted to integrate pasturing systems with drylot feeding systems. Each year 84 fall-born and 28 spring-born calves of similar genotypes were used. Fall-born calves were started on test in May, and spring-born calves were started in October. Seven treatments were imposed: 1) fall-born calves directly into the feedlot (28 steers); 2 and 3) fall-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of July (14 steers in each treatment); 4 and 5) fall-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of October (14 steers in each treatment); and 6 and 7) spring-born calves put on pasture with or without an ionophore and moved to the feedlot at the end of October (14 steers in each treatment). Cattle on pasture receiving an ionophore gained faster (P=.009), but lost this advantage in drylot (P>.10). Overall, cattle started directly in the feedlot had higher gains (P<.001). Cattle receiving an ionophore on pasture had lower KPH than those that did not receive an ionophore (P<.01). Treatment influenced yield grade (P<0.001), although all treatments were YG 2. The percentage of cattle grading Prime and Choice was 75 % or higher for all treatment groups. The results show that using an ionophore improved pasture gains and that pasture treatments did not adversely influence yield and quality grades.

Integration of Pasturing Systems for Cattle Finishing Programs: A Progress Report

This progress report presents the findings of the first two years of a multi-year study. Each year 84 fall-born and 28 spring-born calves of similar genetic background were used to evaluate the incorporation of rotational pasturing systems into cattle finishing programs. The fall-born calves were started on test on May 7, 1996, and May 8, 1997, whereas the spring-born calves were started on test on October 1, 1996, and September 13, 1997. A total of seven treatments were imposed: 1) fall-born calves directly into the feedlot; 2) fall-born calves put on pasture and receiving an ionophore and moved to the feedlot on July 30, 1996, and July 29, 1997 in the first and second years, respectively; 3) fall-born calves put on pasture without an ionophore and moved to the feedlot on July 30, 1996 and July 29, 1997, in the first and second years, respectively; 4) fall-born calves put on pasture and receiving an ionophore and moved to the feedlot on October 22, 1996, and October 21, 1997, in the first and second years, respectively; 5) fall-born calves put on pasture without an ionophore and moved to the feedlot on October 22, 1996, and October 21, 1997, in the first and second years, respectively; 6) spring-born calves put on pasture and receiving an ionophore and moved to the feedlot on October 22, 1996, and October 21, 1997, in the first and second years, respectively; and 7) spring-born calves put on pasture without an ionophore and moved to the feedlot on October 22, 1996, and October 21, 1997, in the first and second years, respectively. Cattle receiving an ionophore on pasture gained more rapidly; however, cattle without access to an ionophore gained more rapidly in drylot thus negating the advantage obtained on pasture. Overall daily gains and feed conversions in drylot only, improved with increasing numbers of days fed in drylot; however, this may not be very cost effective. At similar end weights no real differences were observed in yield grades among the treatments; however, for fall-born calves the percentage grading Prime and Choice was higher for cattle fed longer in drylot.

Integration of Pasturing Systems for Cattle Finishing Programs: A Progress Report

In this study, 84 fall-born and 28 spring-born calves of similar genetic background were used to evaluate the incorporation of rotational pasturing systems into cattle finishing programs. Because the second-year trial is not complete, this report will include only the first year of the five-year study. Seven treatments were imposed: 1) fall-born calves put directly into the feedlot on May 7, 1996; 2) fall-born calves put on pasture and receiving an ionophore and moved to the feedlot on July 30, 3) fall born calves put on pasture on May 7 and not receiving an ionophore and moved to the feedlot on July 30; 4) fall-born calves put on pasture on May 7 and receiving an ionophore and moved to the feedlot on October 22; 5) fall-born calves put on pasture on May 7 and not receiving an ionophore and moved to the feedlot on October 22; 6) spring-born calves put on pasture on October 1 and receiving an ionophore and moved to the feedlot on October 22; and 7) spring-born calves put on pasture on October 1 and not receiving an ionophore and moved to feedlot on October 22. Performance data showed that cattle on pasture receiving an ionophore had higher gains than those not receiving an ionophore on pasture. This trend was reversed in the feedlot period. Yield grades were not greatly influenced by treatment, although quality grades tended to be higher for older cattle and those cattle that were in drylot for a longer period of time.

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.