ENDOVAC-BEEF® in Feedlot Beef Steers

Dr. David Hutcheson, Animal Nutritionist and Bovine Consultant, Animal Agricultural Consulting, Inc., P.O. Box 50367, Amarillo, TX 79159

(The 2007-2008 trials were conducted at the Knight Feedlot, Inc., 1768 Ave. J, Lyons, KS 67554)


To evaluate the effects of ENDOVAC-Beef® bacterin-toxoid (manufactured by IMMVAC INCORPORATED, 6080 Bass Lane, Columbia, Missouri 65201) administration to feedlot steers on feedlot performance and carcass quality.


Gram-negative endotoxemia contributes to the signs associated with diarrheal septicemias, and pneumonias in cattle. The classic signs of endotoxemia are depression of the central nervous system, hypernea, dyspnea, anorexia, pyrexia, and leukopenia followed by leukocytosis; recent studies have confirmed that these signs are consistent in response to sub lethal doses of endotoxins.

So a logical approach to formulating an efficacious vaccine would be to use a single vaccine that induces the immune system to produce antibodies that cross- protect against Gram-negative bacteria and their endotoxins. Specific R-mutants of Salmonella and E. coli , although generally poor quality antigens per se, have been found to provide such cross-protection against septicemias from various Gram-negative infections. The antibodies produced by these mutant bacterin vaccines have provided cross-protection to cows, either naturally challenged or arbitrarily challenged in the laboratory. This is especially true when the mutant bacterin is coupled with an effective immune-stimulant such as IMMUNEPlus® incorporated in ENDOVAC-Beef®, that enhances the level of antibodies produced in the host.

An enzyme-linked immunosorbent assay (ELISA) of sera from control and vaccinated calves showed that antibodies produced in response to ENDOVAC-Beef®, a mutant Salmonella typhimurium bacterin-toxoid significantly attenuated the clinical responses to Escherichia coli, Pasteurella multocida, and Mannheimia (formerly Pasteurella) hemolytica endotoxins (Agri. Practice 11:29-34, 1990; Agri. Practice 12:1-4, 1991).

Many clinically evident endotoxemias are associated with Gram-negative septicemias arising from E. coli and Salmonella diarrheas; and/or Pasteurella multocida and Mannheimia hemolytica pneumonias. Veterinarians and Nutritionists have suspected for years that sub-clinical endotoxemia in beef cattle in feedlots on high carbohydrate rations have elevated endotoxins in their blood which somehow hamper maximal feed conversion and optimal weight gain.


Two field trials were conducted with steers from the same source each year. In 2007, there were 300 steers used in 2 pens for the trial and in 2008 there were 128 steers used in the trial. Each year the steers were allotted to two groups, either those vaccinated with two doses of ENDOVAC-Beef® (1-2mL dose at conditioning, and a 2nd -2mL dose on entering the feedlot), or those that did not receive ENDOVAC-Beef® (non-vaccinated). The steers were co-mingled both in the conditioning and feedlot phases of both trials, and fed standard feedlot rations for the duration of the trial. In 2008 carcass data was also collected. Data was collected at the end of each feeding period by pens. Performance and carcass data was analyzed by Analysis of Variance techniques. Performance data was analyzed by pens. Carcass data was analyzed by individual carcasses. Chi Square analysis was used to analyze carcass count data.

Results and Discussion

Data was pooled for the performance data over two years. Table 1 shows the individual years and the pooled means for the field trial.

Table 1 Performance Data 2007-2008

Year Number Days On Feed Weight In, Pounds Weight Out Pounds Dry Matter Intake Average Daily Gain Feed to Gain


2007 147 97 789 1293 26.9 5.19 5.19
2008 91 164 660 1435 24.3 4.38 5.54
Means 119 130 724 1364 25.4 4.76 5.36

Non Vaccinates

2007 153 97 741 1107 22.6 3.77 5.98
2008 37 164 660 1335 24.6 4.11 5.98
Means 95 130 700 1221 23.6 3.84 5.98


Vaccinates 119 130 724 1364 25.4 4.76 5.36
Non Vaccinates 95 130 700 1221 23.6 3.84 5.98
P Value     0.78 0.40 0.40 0.21 0.07

Cattle administer ENDOVAC-Beef® had the best feed to gain ratio (5.36 pounds of dry matter feed per pound of gain) and is significantly different at P =0.07 than the non-vaccinates (5.98). The ENDOVAC-Beef® vaccinates average daily gain was higher (4.76 lbs per day) compared to non- vaccinates (3.84 lbs per day), P=0.21.

Table 2 shows carcass data for the cattle fed in2008.
(Carcass Data for 2008 Trial)

Item Vaccinate Mean Non Vaccinate Mean P Value
Number 90 126  
Stun Weight 1409 1324 0.001
Carcass Weight 915 861 0.001
Dressing Percent 64.9 % 65.1% 0.49
Fat Thickness 0.54 0.52 0.38
Ribeye Square Inches 14.5 13.9 0.005
Yield Grade 3.33 3.26 0.42
  Chi Square analysis    
Prime 3 (3.33%) 8 (6.35%) 0.32
Mid Choice Plus 40 (44.44%) 71 (56.35%) 0.08
Choice 35 (38.89 %) 38 (30.16%) 0.18
Choice and Prime 78 (86.67 %) 117 (92.86%) 0.13
Select 10 (11.11%) 9 (7.14%) 0.31
Standard 2 (2.22%) 0 (0.00%) 0.09

The carcass weight were significantly (P= 0.001) higher for ENDOVAC-Beef® vaccinates by 54 pounds. The ribeye area was significantly larger for ENDOVAC-Beef® vaccinated cattle by 0.6 square inches. The increase in ribeye area may have been due to the significant higher carcass weight for ENDOVAC-Beef® vaccinated cattle.


1. ENDOVAC-Beef® improves feed to gain ratio in finishing steers
2. ENDOVAC-Beef® improves average daily gains in finishing steers
3. ENDOVAC-Beef® vaccinated steers showed increased carcass weights
4. ENDOVAC-Beef® suppressed endotoxemias and improved overall performance