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.

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.

Effect of MGA on Performance, Sexual Behavior, Carcass Quality and Tenderness in Mixed-Sex Pens of Cattle

The effect of MGA in mixed pens of steers and heifers was evaluated over a three-year period at the ISU Armstrong Research Farm near Lewis, Iowa. Two pens of approximately 40 head were fed diets with or without MGA in each of three replications. Estrus and riding activity was monitored using the Heat Watchâ system. At slaughter, in addition to routine carcass data collection, a rib sample was collected from each carcass for tenderness evaluation. There was no effect on dry matter intake due to MGA treatment. Mixed-sex pens that were fed MGA were 4% more efficient than controls. MGA-fed steers gained similarly to control steers. MGA fed heifers gained 8% faster than control heifers. MGA highly reduced measures of estrus and riding activity throughout the feeding period. MGA feeding improved marbling and tenderness measured in both steers and heifers. These data suggest that MGA has potential to improve performance, quality grade and tenderness in mixed pens of steers and heifers.

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.

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.

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.

Live Cattle Futures and Options: How Have They Done?

Futures did reduce price risk. Hedging produced a higher minimum return and higher return at the 25th percentile (75% of the returns are better than this figure) than did the cash market. The 50th percentile, or median return, was higher for yearlings in the cash market than hedged cattle, and the calves had mixed results. Although the differences are not great, there have been months when the option strategies performed better than cash or futures, (i.e., January–April and September–October), and there are months when they did not fare well (i.e., June–August).

Estimating the Value of Source Verification in Iowa Feeder Cattle Markets

Source verification and pooling of feeder cattle into larger lots resulted in higher selling prices compared to more typical sales at a southern Iowa auction market. After higher prices due to larger lot sizes were accounted for, cattle that received a specified management program and were source verified as to origin received additional price premiums. The data do not distinguish between the value of the specific management program and the value of the source verification process. However, cow–calf producers participating in the program took home more money.

Profiting from the Cattle Cycle: Alternative Cow Herd Investment Strategies

Beef cow herd owners can benefit from incorporating price signals into their heifer retention decisions. Whereas a perfect forecast of calf prices over the productive life of the heifer added to the herd would be ideal, such information is not available. However, simple decision rules that incorporate current or recent prices and the knowledge that the cattle cycle likely will repeat itself can help producers improve their investment decisions. A dollar cost averaging strategy that retains the same dollar value of heifers each year and a rolling average value strategy that retains a 10-year average value of heifers out performed strategies that sought to maintain a constant herd size or a constant cash flow.

Estimating the Value of Source Verification in Iowa Feeder Cattle Markets

Source verification and pooling of feeder cattle into larger lots resulted in higher selling prices compared with more typical sales at a southern Iowa auction market. After accounting for higher prices due to larger lot sizes, cattle that received a specified management program and were source verified as to origin received additional price premiums. The data do not distinguish between the value of the specific management program and the value of the source verification process. However, cow-calf producers participating in the program took home more money.

Cattle immunized against the pathogenic L-α-glycerol-3-phosphate oxidase of Mycoplasma mycoides subs. mycoides fail to generate neutralizing antibodies and succumb to disease on challenge

The membrane-associated enzyme L-α-glycerol-3-phosphate oxidase (GlpO) of Mycoplasma mycoides subs. mycoides (Mmm), the causal agent of contagious bovine pleuropneumonia (CBPP) has been identified as a virulence factor responsible for the release of toxic by-products such as H2O2 that mediate host cell injury. Since CBPP pathogenesis is based on host inflammatory reactions, we have determined the capacity of recombinant GlpO to generate in vivo protective responses against challenge in immunized cattle. We also investigated whether sera raised against recombinant GlpO in cattle and mice inhibit production of H2O2 by Mmm. Immunization of cattle with recombinant GlpO did not protect against challenge with a virulent strain of Mmm. Further, although both murine and bovine antisera raised against recombinant GlpO detected recombinant and native forms of GlpO in immunoblot assays with similar titres, only murine antibodies could neutralize GlpO enzymatic function. The data raise the possibility that Mmm has adapted to evade potential detrimental antibody responses in its definitive host.

A non-coding genomic duplication at the HMX1 locus is associated with crop ears in highland cattle.

Highland cattle with congenital crop ears have notches of variable size on the tips of both ears. In some cases, cartilage deformation can be seen and occasionally the external ears are shortened. We collected 40 cases and 80 controls across Switzerland. Pedigree data analysis confirmed a monogenic autosomal dominant mode of inheritance with variable expressivity. All affected animals could be traced back to a single common ancestor. A genome-wide association study was performed and the causative mutation was mapped to a 4 Mb interval on bovine chromosome 6. The H6 family homeobox 1 (HMX1) gene was selected as a positional and functional candidate gene. By whole genome re-sequencing of an affected Highland cattle, we detected 6 non-synonymous coding sequence variants and two variants in an ultra-conserved element at the HMX1 locus with respect to the reference genome. Of these 8 variants, only a non-coding 76 bp genomic duplication (g.106720058_106720133dup) located in the conserved region was perfectly associated with crop ears. The identified copy number variation probably results in HMX1 misregulation and possible gain-of-function. Our findings confirm the role of HMX1 during the development of the external ear. As it is sometimes difficult to phenotypically diagnose Highland cattle with slight ear notches, genetic testing can now be used to improve selection against this undesired trait.