Antibody Response to Inactivated Viral Vaccines Administered to Calves at Weaning

Respiratory disease in beef calves has been associated with the stress of weaning. Management practices commonly delay vaccination of calves to this time, and weaning stress could potentially suppress the immune response. To reduce this stress we have been experimenting with a procedure termed “pasture weaning” in which the dams are removed and the calves remain on pasture. Observation suggests that calves weaned with this approach adapt to the weaned state much better than those held in drylot. Consequently, one would expect less stress-mediated effects including those on the immune system. Calves were weaned and assigned to groups that were pasture or drylot weaned, and calves within the groups were vaccinated with one of two inactivated virus vaccines by either the intramuscular or subcutaneous route. Weaning placement did not affect antibody responses to the viruses included in the vaccines. The route of administration did not influence responses with subcutaneous injection inducing responses equivalent to the intramuscular site. Utilization of this route for vaccination could be advantageous because it precludes the tissue damage and hidden abscessation that sometimes results from intramuscular injections. A distinct difference was noted in the immunogenicity of the vaccines with the Vira Shield product yielding significantly better responses to all viral entities.

Antibody Responses of Vaccinated and Nonvaccinated Calves to Haemophilus somnus

Respiratory disease resulting from infection of calves with Haemophilus somnus (H. somnus) is an annual occurrence in fall calves at the McNay Farm. Previous observations of skin test reactivity to H. somnus antigens suggested a role for this phenomenon in the pathogenesis of the disease. Groups of calves, about 90 days of age, were vaccinated with four different commercial H. somnus vaccines, and serum levels of H. somnus antibodies were determined. Antibodies of the IgG and IgE classes were detected with ELISA procedures conducted on sera collected before and after vaccination. Most of the calves had detectable H. somnus IgE class antibodies at the start of the experimentation but IgG class antibodies were minimal. Antibodies of both classes increased in nonvaccinated and vaccinated calves during the 30 day period of experimentation. However, the level of IgE class antibodies in vaccinates was lower than in controls suggesting that vaccination may limit the IgE response.

Bovine Respiratory Syncytial Virus Infection in McNay Farm Calves

Clinical respiratory disease occurs almost every year in fall calves in the McNay Farm herd. Diagnostic procedures have implicated Haemophilus somnus (H. somnus) and bovine respiratory syncyial virus (BRSV) as the infectious agents primarily associated with this disease. Therefore, the 1995 calves were closely monitored after weaning and during the course of a respiratory disease. Serologic evidence indicated the involvement of the same two agents in the pathogenesis of the disease. Also, experimental evidence suggested a role for a preexisting immediate hypersensitivity to H. somnus and the development of this type of response to BRSV. We theorize that the pathogenesis of the clinical disease involved infection with H. somnus, establishment of immediate hypersensitivity in the lungs, viral infection with associated pathologic lesions, and viral exacerbation of the immediate hypersensitivity reaction with resultant clinical signs and tissue damage.

Evaluation of Condition Scoring of Feeder Calves as a Tool for Management and Nutrition

Two experiments were conducted to evaluate the effects of body condition scores of beef calves on performance efficiency and carcass characteristics. In Experiment 1, 111 steer calves were stratified by breed and condition score (CS) and randomly allotted to 14 pens. The study was analyzed as a 2 x 3 factorial design, with two breeds (Angus and Simmental) and three initial CS (4.4, 5.1, and 5.6). In Experiment 2, 76 steer calves were allotted to six pens by CS. The resultant pens averaged 3.9, 4.5, 4.7, 5.0, 5.1, and 5.6 in CS. Calves in both studies were fed a corn-based finishing diet formulated to 13.5% crude protein. All calves were implanted with Synovex- SÒ initially and reimplanted with Revalor-SÒ. In Experiment 1, 29-day dry matter intake (lb/day) increased with CS (17.9, 18.1, and 19.1 for 4.4, 5.1, and 5.6, respectively; p < .04). Daily gain (29 days) tended to decrease with increasing CS (4.19, 3.71, and 3.26; p < .13). Days on feed decreased with increasing CS (185, 180, and 178d; p < .07). In Experiment 2, daily gains also increased with decreasing initial CS for the first 114 days (p < .05) and tended to increase overall (p < .20). In Experiment 1, calves with lower initial CS had less external fat at slaughter (.48, .53, and .61 in. for CS 4.4, 5.1, and 5.6, respectively; p < .05). This effect was also noted at slaughter (p < .10), as well as at 57 days (p < .06) and at 148 days (p < .06) as measured by real-time ultrasound. Measurements of intramuscular fat and marbling were not different in either study. These data suggest that CS of feeder calves may be a useful tool for adjusting energy requirements of calves based on body condition. Also, feeder cattle may be sorted into outcome or management groups earlier than currently practiced using body condition and/or real-time ultrasound.

Effect of Early Weaning of Beef Calves on Performance and Carcass Quality

A study was conducted to evaluate early weaning of beef calves at 60-70 days of age on feedlot performance and carcass characteristics. One hundred twenty steer calves sired by either Simmental or Angus sires were weaned at an average age of 67 (early weaned, EW) or 147 (late weaned, LW) days. Calves were allotted to 16 feedlot pens by weaning treatment and sire breed at approximately 750-800 lb. EW calves were heavier (P < .05) in initial feedlot weight. There were no differences due to weaning age on daily gain, dry matter intake, feed efficiency or slaughter weights. Simmental steers required more days on feed than Angus steers (P < .05). Early-weaned calves had a higher percent intramuscular fat (5.7 vs. 5.1%), higher average marbling scores (Small78 vs. Small20, P < .05), a higher percentage of cattle grading average USDA Choice and higher (38% vs. 14%, P < .05) and a higher percentage of USDA Prime (10% vs. 0%, P < .05). These data confirm observations in previous studies that early weaning and placing calves on a higher grain diet improves marbling at slaughter. In this study, the effect was shown in calves weaned at an average of 67 days.

Effect of Yeast Supplement on Performance of Steer Calves

The effect of Prosponse® yeast supplement fed to newly arrived steers was evaluated at the ISU Armstrong Research Farm near Lewis, Iowa. Four pens of approximately 32 head were fed similar diets with 2 pens receiving yeast supplement and 2 pens not. Calves were weighed on delivery to the feedlot and allocated on weight and sire. Calves were on test 34 days. There was no effect on daily gain or feed to gain. Dry matter intake trended higher for the yeast supplemented calves (P=.10). These data suggest that yeast supplement may improve dry matter intake in newly arrived feedlot calves.

Genetic Characterization of a New U.S. Bovine Rotavirus Isolate

We have identified a new group A rotavirus associated with diarrheic calves in the field. The VP7 gene of this virus (designated VMRI-29), appears to differ genetically from that of the reference strain NCDV-Lincoln. Studies are underway to determine the importance of this genetic variant in the etiology of rotavirus-induced calf diarrhea.

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.

Alternative Rotational Grazing Systems at the Beef Teaching Farm

Fifty-six acres of central Iowa corn land were seeded to bromegrass and divided with high-tensile wire into eight seven-acre plots. This bromegrass was fertilized with 70 pounds of nitrogen each spring and fall, 1987-1990. In 1991 – 1995, the nitrogen was increased to 80 pounds both spring and fall. The plots were stocked with 1.3 cow/calf pairs per acre in 1987-1991 and 1993–1995, but in 1992 the plots were stocked with 1.55 cow/calf pairs per acre. The pairs were rotated using two distinct schemes among four cells for about 150 days. The plots averaged 607 pounds of net calf weight per acre per year over nine years. Rainfall was quite variable during the grazing seasons and was reflected in calf performance as well as summer feed costs. This intensive rotational grazing system has greatly reduced both weed population and the need for mechanical clipping.

Prebreeding Immunization of Beef Cows

A number of infectious agents are potential threats to the fetus of a pregnant cow and may result in abortion. These agents include Leptospira sp., Campylobacter fetus and viruses such as infectious bovine rhinotracheitis (IBR) and bovine virus diarrhea (BVD). Maintenance in the cow of a high level of immunity to these agents during pregnancy can insure protection of the fetus. In particular, vaccines against BVD and IBR viruses can establish protective immunity throughout gestation. An appropriate vaccination regimen prior to breeding is required to establish this protective immunity. This can be achieved with a single dose of certain modified live virus vaccines, but those vaccines must be administered at least 30 days prior to breeding to avoid interference with conception. We have evaluated an oil-adjuvanted inactivated virus vaccine in cattle with differing immunological histories. Two doses of the vaccine administered 30 days apart to serologically negative animals induced appreciable levels of BVD and IBR anti-viral antibodies with persisting titers throughout gestation. In other experiments a single dose of the vaccine was administered to: (1) animals given two doses of the vaccine several months earlier, (2) animals previously vaccinated with other inactivated virus vaccines, or (3) animals previously vaccinated with modified live virus vaccine. The vaccine consistently induced marked anamnestic responses in these animals. Not only did mean titers rise, but a vast majority of individual animals responded. This contrasts with efforts to boost titers with modified live virus vaccines where the effect may be erratic among animals. The safety and efficacy of selected inactivated viral vaccines argues for their use in prebreeding immunization of beef cows.

Infectious Bovine Rhinotracheitis Virus Antibody Responses to Vaccines Used in Combination

The objective of this experimentation was to determine if circulating antibody titers to parainfluenza type-3 (PI-3) and infectious bovine rhinotracheitis (IBR) viruses could be enhanced by a combination of vaccines. The vaccines utilized were a modified live virus vaccine administered by the intranasal route and an inactivated virus vaccine injected intramuscularly. Virus neutralization tests were conducted on sera obtained at intervals before and following vaccination. Unfortunately, the calves were apparently exposed naturally to PI-3 virus, and the responses to that virus were inconclusive. However, antibody responses to IBR virus were dramatically enhanced by the combination of the two vaccines.

Antibody Responses of Young Calves to Inactivated Viral Vaccines

Three commercial inactivated virus vaccines were evaluated for immunogenicity in young calves with residual maternal antibodies. Groups of 30 calves were administered each of the vaccines at the start of the experimentation and were administered a second dose 32 days later. Serum was obtained from these calves and 30 calves in a nonvaccinated control group prior to vaccination and at 32, 61, 99 and 125 days thereafter. Antibody responses to viruses in two of the vaccines were extremely limited. The third vaccine overcame suppression by maternal antibodies and elicited responses clearly differentiated from antibody levels in the control group of calves.

The Effects of Low Dose Irradiation and Storage Time on Aroma of Fresh Beef Patties in Anaerobic Packaging

The effects of electron beam irradiation, anaerobic packaging, and storage times on the aroma of raw ground beef patties were investigated. Patties were coarse ground at three days postmortem, and then fine ground and packaged at three, six, and nine days postmortem. Patties were irradiated immediately after packaging, or three days after packaging at 2 kGy, and then stored at 2.5 °C ñ1.5 °C for four days. Non-irradiated controls were held under similar conditions. After four days of storage for each postmortem time (three, six, and nine days), sensory aroma evaluations were performed on all samples. Irradiated and non-irradiated patties with the shortest postmortem storage times had the most desirable aroma scores. Controls had significantly (p £ .05) more desirable aroma scores than irradiated patties.

Experiences with Grid Marketing - Summary of Chariton Valley Beef Sales for Year 2000

Producers in the Chariton Valley Beef organization have marketed more than 10,000 head of cattle into grid markets over the past three years. Data from 134 lots were summarized, with 3,791 head of cattle marketed into four grid markets. Producers averaged $26.05 per head premiums. Premiums and discounts ranged from a positive $79.01 to a negative $40.44 on tots delivered.

Beef Cow Feeding Demonstration

Pregnant mature beef cows were fed one of five rations: tub ground hay, low corn supplementation plus hay, high corn plus hay, low corn gluten feed (CGF) pellets plus hay, and high CGF plus hay. All treatments resulted in weight gains and limited body condition score changes. The hay and high CGF pellet diet resulted in statistically different weight gains compared with the other supplementation programs.