A comparison of 2 vaccination programs in feedlot calves at ultra-high risk of developing undifferentiated fever/bovine respiratory disease

The aim of this study was to compare 2 vaccination programs in feedlot calves at ultra-high risk of developing undifferentiated fever (UF)/bovine respiratory disease (BRD). At feedlot arrival, 3882 calves were enrolled in the study and randomly allocated to 2 groups, which were housed by group in 12 pens. At the time of allocation, 1 group (MLV3-BT2) received a multivalent, modified-live viral vaccine containing infectious bovine rhinotracheitis virus (IBRV) and types I and II bovine viral diarrhea virus (BVDV), as well as a Mannheimia haemolytica (MH) and Pasteurella multocida bacterin-toxoid. The other group (MLV4-BT1) received a vaccine containing IIBRV, type I BVDV, bovine respiratory syncytial virus, and parainfluenza-3 virus, as well as a MH bacterin-toxoid. At an average of 69 days post arrival, the groups received their respective viral vaccines. The initial UF treatment, overall chronicity, overall wastage, overall mortality, and BRD mortality rates were significantly (P < 0.05) lower in the MLV3-BT2 group than in the MLV4-BT1 group. Average daily gain and the proportions of yield grade Canada 3 and quality grade E carcasses were significantly (P < 0.05) higher in the MLV3-BT2 group than in the MLV4-BT1 group. No significant (P > or = 0.05) difference in the dry matter intake to gain ratio was detected between the 2 groups. In economic terms, there was a net advantage of $20.86 CDN/animal in the MLV3-BT2 group. This study demonstrates that it is more cost effective to use an MLV3-BT2 vaccination program than a MLV4-BT1 vaccination program in feedlot calves at ultra-high risk of developing UF/BRD.     

Effects of zilpaterol hydrochloride and days on the finishing diet on feedlot performance, carcass characteristics, and tenderness in beef heifers

British × Continental heifers (n = 3,382; initial BW = 307 kg) were serially slaughtered to determine if increasing days on the finishing diet (DOF) mitigates negative consequences of zilpaterol HCl (ZH) on quality grade and tenderness of beef. A 2 × 3 factorial arrangement of treatments in a completely randomized block design (36 pens; 6 pens/treatment) was used. Zilpaterol HCl (8.33 mg/kg DM) was fed 0 and 20 to 22 d before slaughter plus a 3 to 5 d withdrawal to heifers spending 127, 148, and 167 DOF. Feedlot and carcass performance data were analyzed with pen as the experimental unit. Three hundred sixty carcasses (60 carcasses/treatment) were randomly subsampled, and strip loin steaks were aged for 7, 14, and 21 d for assessment of Warner-Bratzler shear force (WBSF) and slice shear force (SSF) with carcass serving as the experimental unit for analysis. No relevant ZH × DOF interactions were detected (P > 0.05). Feeding ZH during the treatment period increased ADG by 9.5%, G:F by 12.5%, carcass ADG by 33.6%, carcass G:F by 35.9%, carcass ADG:live ADG by 15.6%, HCW by 3.2% (345 vs. 356 kg), dressing percent by 1.5%, and LM area by 6.5% and decreased 12th-rib fat by 5.2% and yield grade (YG) by 0.27 units (P < 0.01). Feeding ZH tended to decrease marbling score (437 vs. 442 units; P = 0.10) and increased WBSF at 7 (4.25 vs. 3.47 kg; P < 0.01), 14 (3.57 vs. 3.05 kg; P < 0.01), and 21 d (3.50 vs. 3.03 kg; P < 0.01). Feeding ZH decreased empty body fat percentage (EBF; 29.7% vs. 30.3%; P < 0.01) and increased 28% EBF adjusted final BW (473.4 vs. 449.8 kg; P < 0.01). Analysis of interactive means indicated that the ZH × 148 DOF group had a similar percentage of USDA Prime, Premium Choice, Low Choice, and YG 1, 2, 3, 4, and 5 carcasses (P > 0.10) and decreased percentage of Select (30.4 vs. 36.6%; P = 0.03) and Standard (0.2 vs. 0.9%; P = 0.05) carcasses compared with the control × 127 DOF group. As a result of ZH shifting body composition, extending the DOF of beef heifers is an effective feeding strategy to equalize carcass grade distributions. This can be accomplished along with sustaining the ZH mediated advantages in feedlot and carcass weight gain.     

The effect of subunit or modified live bovine herpesvirus-1 vaccines on the efficacy of a recombinant Pasteurella haemolytica vaccine for the prevention of respiratory disease in feedlot calves

The efficacy of a Pasteurella haemolytica vaccine (PhV) administered once to calves within 24 hours of arrival at a feedlot was tested for the ability to prevent morbidity and mortality from all bovine respiratory disease (BRD) and specifically from fibrinous pneumonia mortality. The PhV consisted of two immunizing ingredients: outer membrane proteins extracted from P. haemolytica, plus genetically attenuated leukotoxin produced by recombinant DNA technology. This double blind study was conducted at a large Saskatchewan feedlot using 2,324 high-risk calves purchased at auction markets and kept under typical commercial feedlot conditions. The trial design included four vaccine test groups: 1) PhV and a bovine herpesvirus type-1 (BHV-1) subunit vaccine comprised only of the virus glycoprotein IV (gIV); 2) PhV and a commercial modified live vaccine (MLV) containing BHV-1 and parainfluenza-3 viruses; 3) gIV alone; and 4) MLV alone. Calves were assigned to vaccine groups in a random systematic manner, individually identified, and monitored for 90 days after vaccination. The vaccines were given once, on arrival, to reflect common feedlot practice, although vaccination prior to expected risk would be more appropriate.

The PhV in combination with gIV reduced BRD morbidity by 20% (p < 0.05) compared to gIV alone and 24% (p < 0.05) compared to MLV alone, and reduced BRD mortality by 88% (p < 0.05) and fibrinous pneumonia mortality by 100% (p < 0.05) when compared to either gIV or MLV alone. Vaccination with PhV in combination with MLV significantly reduced the efficacy of the PhV in preventing BRD morbidity, BRD mortality, and fibrinous pneumonia mortality and also reduced the antibody response to P. haemolytica leukotoxin. These results suggest that the MLV interfered with the protective capacity of the PhV.

     

A live Pasteurella haemolytica vaccine efficacy trial

A live Pasteurella haemolytica serotype 1 vaccine was used in an efficacy trial conducted on 100 lightweight feeder calves purchased from a Florida ranch. Forty-one calves were inoculated with the vaccine intradermally in the neck. Fifty-nine calves served as nonvaccinated controls. Fourteen days later, the calves were shipped to an order buyer in eastern Tennessee, where the calves were mixed with 60 local calves in a community sale barn for 72 hours. After 3 additional days, the calves were shipped to a research feedlot in Bushland, Tex. They remained in the feedlot for 56 days, and the test was concluded 76 days after vaccination. The P haemolytica vaccine had no significant effect on performance, morbidity, or mortality. There was no significant difference between the vaccinated and nonvaccinated calves in the number of times Pasteurella was isolated. The calves became seropositive to bovine viral diarrhea virus, respiratory syncytial virus, and infectious bovine rhinotracheitis (IBR) virus during the 76-day experiment. All calves initially were seropositive to parainfluenza-3 virus. A virulent outbreak of IBR occurred 30 days after the calves arrived at the feedlot. Before the onset of IBR, the isolation of P haemolytica serotype 1 from nasal turbinates was rare (2 of 500 nasal swabs). After the IBR outbreak, P haemolytica serotype 1 was isolated from 40 of 92 calves.     

A Controlled Field Study Using Live Virus Vaccines and an Antiserum in a Preconditioning Program

Thirty-five vaccinates and 29 control beef calves from five farms were studied. Vaccinates in group 1 received a modified live virus vaccine against infectious bovine rhinotracheitis (IBR) and bovine virus diarrhea (BVD) 30 days after shipment; vaccinates in groups 2, 3 and 4 received live virus vaccines agains IBR and bovine parainfluenza 3 (PI3) seven to 17 days before shipment. Half of group 5 were given bovine origin antiserum containing antibodies against IBR, BVD and PI3. Three weeks later, the animals that had received serum were given a live modified vaccine containing IBR, BVD and PI3. In group 1, WBC counts were lower in the vaccinates than in the controls for two weeks after vaccination. WBC counts in groups 3 and 4 were higher in vaccinates than in controls after addition to the feedlot. Seroconversions to BVD virus occured in all groups. Clinical disease apparently due to BVD affected one vaccinated calf in group 2 and eight calves in group 5. Combined weight gains were significantly higher in three groups of calves vaccinated before shipment compared to unvaccinated control animals after addition to the feedlot. Vaccination with IBR and PI3 live virus vaccines should be given at least 17 days before shipment to feedlots containing infected cattle. Antiserum containing antibodies against the three viruses showed no apparent advantage in preventing clinical respiratory disease over control calves not receiving the serum.     

Comparison of a combination of oxfendazole and fenthion versus ivermectin in feedlot calves

A trial involving 6,169 feedlot calves was conducted under commercial feedlot conditions in western Canada to compare the relative efficacy of treatment with a combination of oxfendazole and fenthion (O/F) versus ivermectin (I) with respect to the outcome variables, final weight, gain, days on feed (DOF), dry matter intake (DMI), average daily gain (ADG), dry matter intake to gain ratio (DM:G), and morbidity, mortality, and carcass grade parameters.

There were no significant differences (p ≥ 0.05) between the treatment groups for final weight, gain, DOF, DMI, ADG and DM:G. In addition, there were no significant differences (p ≥ 0.05) in the carcass grading parameters between the treatment groups. The bovine respiratory disease (BRD) relapse rates, the overall mortality rates, and the cause specific mortality rates were not significantly different (p ≥ 0.05) between the treatment groups. The BRD treatment rate in the O/F group was significantly lower (p ≤ 0.05) than in the I group, but this difference was not economically important.

These data indicate that a combination of oxfendazole and fenthion is comparable to ivermectin with respect to performance, animal health, and carcass grade parameters.

     

The effect of bovine viral diarrhea virus infections on health and performance of feedlot cattle

The aim of this study was to investigate the effect of bovine viral diarrhea virus (BVDV) infections (unapparent acute infections and persistent infections) on the overall health and performance of feedlot cattle. Calves from 25 pens (7132 calves) were enrolled in the study. Overall and infectious disease mortality rates were significantly higher (P < 0.05) in pens categorized at arrival as positive for type I BVDV and lower in pens that were positive for type II BVDV than in negative pens. Mortality attributed to BVDV infection or enteritis was significantly more common (P < 0.05) in the pens containing persistently infected (PI) calves than in pens not containing PI calves (non-PI pens). There were no statistically detectable (P > or = 0.05) differences in morbidity, overall mortality, average daily gain, or the dry matter intake to gain ratio between PI and non-PI pens. Although type-I BVDV infections in feedlots appear to contribute to higher mortality rates, the presence of PI calves alone does not appear to have a strong impact on pen-level animal health and feedlot performance.     

Identification of a mutant bovine herpesvirus-1 (BHV-1) in post-arrival outbreaks of IBR in feedlot calves and protection with conventional vaccination.

Outbreaks of infectious bovine rhinotracheitis (IBR) have recently been observed in vaccinated feedlot calves in Alberta a few months post-arrival. To investigate the cause of these outbreaks, lung and tracheal tissues were collected from calves that died of IBR during a post-arrival outbreak of disease. Bovine herpesvirus-1 (BHV-1), the causative agent of IBR, was isolated from 6 out of 15 tissues. Of these 6 isolates, 5 failed to react with a monoclonal antibody specific for one of the epitopes on glycoprotein D, one of the most important antigens of BHV-1. The ability of one of these mutant BHV-1 isolates to cause disease in calves vaccinated with a modified-live IBR vaccine was assessed in an experimental challenge study. After one vaccination, the majority of the calves developed humoral and cellular immune responses. Secondary vaccination resulted in a substantially enhanced level of immunity in all animals. Three months after the second vaccination, calves were either challenged with one of the mutant isolates or with a conventional challenge strain of BHV-1. Regardless of the type of virus used for challenge, vaccinated calves experienced significantly (P < 0.05) less weight loss and temperature rises, had lower nasal scores, and shed less virus than non-vaccinated animals. The only statistically significant (P < 0.05) difference between the 2 challenge viruses was the amount of virus shed, which was higher in non-vaccinated calves challenged with the mutant virus than in those challenged with the conventional virus. These data show that calves vaccinated with a modified-live IBR vaccine are protected from challenge with either the mutant or the conventional virus.     

Effects of on-arrival versus delayed modified live virus vaccination on health, performance, and serum infectious bovine rhinotracheitis titers of newly received beef calves

Stress commonly associated with weaning, marketing, and shipment of feeder cattle can temporarily compromise immune function, thereby reducing the effective response to vaccination intended to control bovine respiratory disease (BRD). Two vaccination timing treatments were used to evaluate the effect of timing of a multivalent modified live virus (MLV) BRD vaccine on health, performance, and infectious bovine rhinotracheitis (IBR) antibody titers of newly received stocker cattle. Crossbred bull and steer calves (n = 528) were weighed (197 +/- 2.4 kg) and randomly assigned to MLV vaccination treatment: 1) MLV vaccination upon arrival (AMLV), or 2) delayed (14 d) MLV vaccination (DMLV). All cattle were processed similarly according to routine procedures, with the exception of the initial MLV vaccination timing. Subsequently, BW were recorded on d 14, 28, and 42. Blood samples were collected on d 0, 14, 28, and 42 to determine serum IBR titers, and comparisons were made between treatments on a receiving-day basis and an equivalent postvaccination day basis. Daily BW gains were greater (P < or = 0.05) for DMLV calves from d 0 to 14 (1.16 vs. 0.88 +/- 0.22 kg/d) and from d 0 to 42 (0.75 vs. 0.65 +/- 0.09 kg/d). Days to first treatment, total treatment cost, percentage death loss, and pasture ADG after the 42-d receiving period did not differ (P > or = 0.15). Morbidity rates for BRD were high for both AMLV and DMLV (71.5 and 63.5%, respectively) and did not differ (P = 0.12). Positive IBR titer seroconversion was greater (P < or = 0.03) for DMLV calves on d 42 of the study, and for the 28- and 42-d equivalent postvaccination basis. Delaying vaccination by 14 d may increase ADG during the receiving period compared with AMLV, and seroconversion to IBR was greater in DMLV calves, indicating a possible improvement in acquired immune response when MLV vaccination is delayed.     

Evaluation of health status of calves and the impact on feedlot performance: assessment of a retained ownership program for postweaning calves

The objective of this study was to evaluate animal health status at entry to a feedlot against feedlot performance and carcass value. There were 24 herds represented by 417 calves in a retained ownership program. The health status at entry was represented by the levels of serum antibody to infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea viruses 1 and 2 (BVDV1a, BVDV2), parainfluenza 3 virus (PI3V), bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica, and Pasteurella multocida, as well as by the presence of virus in nasal swabs and blood leukocytes and the presence of bacteria in nasal swabs. The presence or absence of viruses or bacteria at entry did not predict subsequent illness. However, there were predictors of illness severity (number of treatments) and performance parameters of feedlot performance. Herds with a low morbidity rate had higher levels of BVDV1a antibodies than herds with a high morbidity rate. On both an individual-animal and a herd-average basis, calves with low levels of antibody to BVDV1a and BVDV2 had increased total treatment costs. Also, for individual animals and the herd as a whole, low levels of antibody to P. multocida, BVDV1a, and BVDV2 were related to decreased net value to owner (carcass value minus total feedlot cost). Calves treated twice or more had lower levels of antibody to BVDV1a than those treated once or not at all. Differences in herd morbidity rate and treatment costs were more related to appropriate timing of vaccine (last dose at or near delivery of calf) or lack of a 2nd dose of killed vaccine. This was best illustrated by the levels of antibody to BVDV1a. The results of this study were used to formulate recommendations for the subsequent year.     

Effect of age at the time of vaccination on antibody titers and feedlot performance in beef calves

OBJECTIVE: To compare antibody responses, feedlot morbidity and mortality rates, feedlot performance, and carcass value for calves vaccinated with 1 of 2 vaccination strategies and for unvaccinated control calves. DESIGN: Randomized controlled clinical trial. ANIMALS: 451 beef steers and heifers. PROCEDURES: Calves were vaccinated with a modified-live infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus types 1 (BVDV1) and 2 (BVDV2), parainfluenza type 3 virus, and bovine respiratory syncytial virus vaccine and Mannheimia haemolytica and Pasteurella multocida bacterin-toxoid at approximately 67 and 190 days of age (group 1; n = 151) or at approximately 167 and 190 days of age (group 2; 150) or were not vaccinated (control; 150). Serum antibody titers were measured at approximately 2, 67, 167, 190, and 232 days of age. Morbidity and mortality rates, feedlot performance, and carcass value were recorded for 361 calves shipped to feedlots. RESULTS: Percentages of calves seroconverting to IBRV, BVDV1, and BVDV2 were significantly higher for groups 1 and 2 than for the control group. Mean treatment costs were significantly lower for vaccinated than for control calves, and mean mortality rate was significantly higher for control calves than for group 1 calves. Feedlot performance and carcass value did not vary significantly among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that vaccination of beef calves with a 5-antigen modified-live virus vaccine at 67 and 190 days of age was as effective in terms of immunologic responses as was vaccination at 167 and 190 days of age.     

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group. In Study 1 and in the combined analysis, the initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) higher in the oxytetracycline group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, third UF relapse, overall chronicity, overall rail, overall mortality, bovine respiratory disease (BRD) mortality, hemophilosis mortality, arthritis mortality, or miscellaneous mortality rates between the experimental groups in either study or in the combined analysis. In addition, there were no significant (P > or = 0.05) differences in initial weight, final weight, weight gain, days on feed, daily dry matter intake, average daily gain, or the dry matter intake to gain ratio between the experimental groups in either study or in the combined analyses. In the economic analysis, there was a net economic advantage of $5.22 CDN per animal in the oxytetracycline group, due to a lower prophylactic cost, even though the UF therapeutic cost was higher.     

A comparison of florfenicol and tilmicosin for the treatment of undifferentiated fever in feedlot calves in western Canada

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of florfenicol and tilmicosin for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feedlot. One thousand and eighty recently weaned, auction market derived, crossbred beef calves suffering from UF were allocated to one of 2 experimental groups as follows: florfenicol, which was intramuscular (i.m.) florfenicol administered at the rate of 20 mg/kg body weight (BW) at the time of allocation (Day 0) and again 48 h later, or tilmicosin, which was subcutaneous (s.c.) tilmicosin administered once at the rate of 10 mg/kg BW on day 0. Five hundred and forty-four animals were allocated to the florfenicol group and 536 animals were allocated to the tilmicosin group. The chronicity, wastage, overall mortality, and bovine respiratory disease (BRD) mortality rates were significantly (P < 0.05) lower in the florfenicol group than in the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, hemophilosis mortality, or miscellaneous mortality rates between the florfenicol and tilmicosin groups. Average daily gain (ADG) from arrival at the feedlot to the time of implanting and ADG from allocation to the time of implanting were significantly (P < 0.05) lower in the florfenicol group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in arrival weight, allocation weight, implanting weight, or ADG from arrival to allocation between the experimental groups. In the economic analysis, there was an advantage of $18.83 CDN per animal in the florfenicol group. The results of this study indicate that florfenicol is superior to tilmicosin for the treatment of UF because of lower chronicity, wastage, overall mortality, and BRD mortality rates. However, interpretation of these observations must take into consideration the fact that these calves received meta-phylactic tilmicosin upon arrival at the feedlot, which is a standard, cost-effective, management procedure utilized by feedlots in western Canada.     

Seroepidemiology of undifferentiated fever in feedlot calves in western Canada.

The relationships between 4 bacterial and 3 viral antibody titers and morbidity (undifferentiated fever (UF)) and mortality were investigated in recently weaned beef calves. Blood samples from 100 animals that required treatment for UF (Cases) and 100 healthy control animals (Controls) were obtained: upon arrival at the feedlot (Arrival), at the time of selection as a Case or Control (Selection), and at approximately 33 d of the feeding period (Convalescent). Seroconversion to Pasteurella haemolytica antileukotoxin was associated with an increased risk of UF (OR = 2.83); however, seroconversion to bovine herpesvirus-1 G-IV glycoprotein was associated with a decreased risk of UF (OR = 0.43). Higher Arrival bovine viral diarrhea virus antibody titer was associated with a decreased risk of UF (OR = 0.83). Increases in Mycoplasma alkalescens antibody titer after Arrival were associated with an increased risk of UF (OR = 1.10). Higher Arrival Haemophilus somnus antibody titer and increases in Haemophilus somnus antibody titer after Arrival were both associated with a decreased risk of UF (OR = 0.76 and OR = 0.78). The odds of overall mortality (OR = 5.09) and hemophilosis mortality (OR = 11.31) in Cases were significantly (P < 0.05) higher than in the Controls. Higher Arrival bovine herpesvirus-1 antibody titer was associated with an increased risk of mortality (OR = 1.30). Protective immunity to Pasteurella haemolytica antileukotoxin, Haemophilus somnus, bovine herpesvirus-1 G-IV glycoprotein, bovine viral diarrhea virus, and Mycoplasma spp. may be necessary to reduce the occurrence of UF. Animals with UF are at an increased risk of overall and hemophilosis mortality.     

A comparison of florfenicol and tulathromycine for the treatment of undifferentiated fever in feedlot calves

The purpose of this study was to compare the relative cost-effectiveness of florfenicol with that of tulathromycin for treatment of undifferentiated fever (UF) in feedlot calves at ultra-high risk of developing UF that receive metaphylactic tulathromycin on arrival at the feedlot. Calves that received therapeutic florfenicol had lower overall mortality (P=.045) and bovine respiratory disease mortality (P=.050) compared with calves that received therapeutic tulathromycin, but no significant differences were detected in feedlot performance, carcass characteristics, or other animal health variables. There was a net advantage of Can$41.19/treated animal in the florfenicol group versus the tulathromycin group. This study demonstrates that it is more cost-effective to use florfenicol than tulathromycin for the initial treatment of UF in feedlot calves at ultra-high risk of developing UF that receive on-arrival metaphylactic tulathromycin.     

Humoral immune response and assessment of vaccine virus shedding in calves receiving modified live virus vaccines containing bovine herpesvirus-1 and bovine viral diarrhoea virus 1a

Susceptible calves were administered modified live virus (MLV) vaccines containing bovine herpesvirus-1 (BHV1) and bovine viral diarrhoea type 1 (BVDV1a) strains intramuscularly, with one vaccine containing both MLV and inactivated BHV-1 and inactivated BVDV1a. There was no evidence of transmission of vaccine (BHV-1 and BVDV1a) strains to susceptible non-vaccinated controls commingled with vaccinates. No vaccinates had detectable BHV-1 in peripheral blood leucocytes (PBL) after vaccination. Each of three vaccines containing an MLV BVDV1a strain caused a transient BVDV vaccine induced viremia in PBL after vaccination, which was cleared as the calves developed serum BVDV1 antibodies. The vaccine containing both MLV and inactivated BHV-1 induced serum BHV-1 antibodies more rapid than MLV BHV-1 vaccine. Two doses of MLV BHV-1 (days 0 and 28) in some cases induced serum BHV-1 antibodies to higher levels and greater duration than one dose.     

The effects of grazing, liquid supplements, and implants on feedlot performance and carcass traits of Holstein steers

In each of 2 yr, 20 Holstein steers (185+/-7 kg initial BW) were allocated to each of three treatments: pastured for 4.5 mo on grass/legume pastures and then fed 80% corn diets (DM basis) until slaughter; pastured for 4.5 mo on grass/legume pastures with ad libitum access to molasses-based protein supplements and fed 80% corn diets until slaughter; and placed in a feedlot and fed only 80% corn diets until slaughter (FEEDLOT). Half of the steers in each treatment were initially implanted with Revalor-S and not reimplanted. Supplemented steers on pasture had greater (P < 0.05) ADG than unsupplemented steers, and FEEDLOT steers gained faster and were fatter (P < 0.05) after 4.5 mo. Implanted steers had greater (P < 0.05) ADG with no significant treatment x implant status effect. Supplement intake was variable and related to ambient temperature. During the feedlot phase, steers previously on pasture had greater DMI and ADG (P < 0.05) but were not more efficient than FEEDLOT steers. Percentage of USDA Choice carcasses, fat thickness, dressing percentage, yield grade, and final weight were greater (P < 0.05) for FEEDLOT steers than for steers on other treatments. Implanting increased ADG of all steers but did not affect carcass traits, carcass composition, or feedlot performance during the finishing phase. Holstein steers consuming supplemented and unsupplemented pasture before slaughter will be leaner, have lower carcass weights, and have generally lower quality grades than those fed exclusively in a feedlot when slaughtered at similar ages.     

Determination of the seroprevalence of Neospora caninum in feedlot steers in Alberta

A study was conducted in Alberta to determine the seroprevalence of Neospora caninum in feedlot calves purchased from various auction markets throughout western Canada. Four feedlots (1 feedlot from each of the Airdrie and High River areas and 2 feedlots from the Strathmore area) were selected for sampling. At each feedlot, a random 10% sample of feedlot steer and bull calves entering the feedlot from September 2001 to December 2001 were enrolled in the study until there were a maximum of 500 animals enrolled per feedlot. Blood samples were collected from 1976 male animals at the time of entry to the 4 study feedlots. The animals represented 375 groups purchased from 70 sale points throughout British Columbia, Alberta, Saskatchewan, and Manitoba. Of the 1976 animals tested, 128 animals tested positive for antibodies to N. caninum. The prevalence and adjusted 95% confidence limits for N. caninum in beef calves on entrance to the feedlot in western Canada were 6.5% (95% CI, 5.1 to 8.2). There were no significant (P > or = 0.05) associations between the risk of treatment, the risk of designation as "chronic," and the risk of death and antibodies to N. caninum either before or after adjusting for feedlot, entry weight, entry date, and clustering of disease within lots at each feedlot. In addition, there was no significant (P > or = 0.05) association between serological status and feedlot entry weight or average daily gain. Note that there was no information available on feed conversion because the calves were mixed within existing commercial feedlot pens and the actual feed intake of each animal could not be determined. Adjustment for the concentration of antibodies to bovine viral diarrhea virus on arrival did not change any of the examined associations between N. caninum status and calf health or performance. The results of this study demonstrated that the prevalence of N. caninum in feedlot calves in western Canada was less than the prevalence reported in the United States. Additional studies are required to determine whether the inferior rate of gain and feed efficiency observed in the southern United States with animals testing positive for antibodies to N. caninum also occurs under the management conditions used in western Canada.     

The relative economics of feeding open, aborted, pregnant feedlot heifers

A 90-day finishing trial involving 144 feedlot heifers was conducted to compare the performance parameters and carcass characteristics of open heifers, therapeutically aborted heifers, and pregnant heifers. In the first 28 days of the trial, the aborted heifers had reduced (p < 0.05) feed intake (FI), average daily gain (ADG), and feed efficiency (FE) compared to pregnant and open heifers. Over the entire trial, on a live weight basis, the aborted group had reduced (p < 0.05) final weight, ADG, and FE compared to pregnant and open heifers. However, when the data were adjusted for total uterine weight, the aborted and open heifers had improved (p < 0.05) final weight, ADG, and FE compared to pregnant heifers. The aborted and open group had a higher (p < 0.05) carcass weight, rib eye area, dressing percentage, and cutability estimate compared to the pregnant heifers. The aborted group had lower (p < 0.05) carcass weight than the open heifers. Over the entire 90-day feeding period, there were no statistically significant differences among the groups with respect to feed intake (FI), average fat, grade fat, and carcass grades. Also, there were no significant health problems or mortality in any of the groups.

In the economic analysis, aborted heifers returned $26.41 per head more than pregnant heifers. Open heifers returned $39.94 per head more than aborted heifers, and $66.35 more than pregnant heifers. Thus, aborting feedlot heifers during the second trimester was determined to be a safe and cost effective management decision.

     

An evaluation of the relative efficacy of tulathromycin for the treatment of undifferentiated fever in feedlot calves in Nebraska

A field trial was performed under commercial feedlot conditions in central Nebraska to assess the relative efficacy of tulathromycin (TULA) to florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in feedlot calves that did not receive a metaphylactic antimicrobial or vaccines/bacterins containing Mannheimia haemolytica or Histophilus somni at feedlot arrival by comparing animal health, feedlot performance, and carcass characteristic variables. Two hundred recently weaned, auction market derived, crossbred beef calves that met the study-specific case definition of UF were randomly allocated in a 1:1 ratio to 1 of 2 experimental groups as follows: TULA, which received tulathromycin administered subcutaneously at the rate of 2.5 mg/kg body weight (BW) once at the time of allocation; or FLOR, which received florfenicol administered subcutaneously at the rate of 40 mg/kg BW once at the time of allocation. In terms of animal health, the first UF relapse (RR = 0.65), overall mortality (RR = 0.33), and BRD mortality (RR = 0.29) rates in the TULA group were significantly (P < 0.05) lower than in the FLOR group. There were no significant (P > or = 0.05) differences between the TULA and FLOR groups for the other animal health variables measured. There was no significant (P > or = 0.05) difference in average daily gain between the TULA and FLOR groups. There were no significant (P > or = 0.05) differences in the overall distributions of quality grade and yield grade between the experimental groups; however, a significantly (P < 0.05) higher proportion of carcasses in the TULA group graded yield grade USDA-4 as compared with the FLOR group. In the economic analysis, the benefits observed resulted in an economic advantage of $52.50 USD/animal in the TULA group due to lower first UF relapse and overall mortality rates, even though the occurrence of yield grade USDA-4 carcasses increased and the initial UF treatment cost was higher.