Bovine Respiratory Disease (BRD) can adversely impact feedlot performance and carcass traits.  In this study, residual effects of BRD from the receiving period were measured.  Following a 42-d receiving period, 406 mixed breed sale barn heifers were placed in commercial feedlots to examine long term effects of diagnosis and treatment for BRD on feedlot performance and carcass measurements.  Heifers were categorized by severity of BRD: those never treated; those treated once; and those treated more than once.  Heifers treated during the backgrounding period had lower average daily gain during the period.  However, daily gain during the feedlot period was not significantly different among BRD classes.  Heifers treated for BRD had lower marbling scores resulting in a 37.9% reduction in the percentage of carcasses grading U.S.D.A. Choice, or above.  Heifers never treated produced a net return (carcass basis) that was $11.48/head more than heifers treated once for BRD, and  $37.34/head more than those treated two or more times.  This negative impact on carcass traits 200 d later illustrates the importance of preventing BRD in calves.

Key Words:  Health, Morbidity, Receiving Period, Carcass Value

Introduction

One of the most common diseases in newly received stocker and feedlot cattle is the Bovine Respiratory Disease (BRD) complex.  BRD accounts for approximately 75% of morbidity and over 50% of mortality in feedlots (Edwards, 1996).  Perino (1992) indicated that BRD is one of the few diseases that manifests its economic losses cumulatively -- through the cost of treatment, the cost of lost production and/or salvage, and the cost of death loss.  These losses make BRD one of the most costly diseases affecting feedlot cattle.  Gardner et al. (1999) reported that respiratory tract lesions at slaughter correlated with feedlot and carcass performance.  The objective of this experiment was to evaluate the effects of health during a 42-d receiving period (appraised by body temperature and visual clinical appraisal) on feedlot performance during finishing and on carcass characteristics.

Materials and Methods

Four hundred-six crossbred heifer calves were followed from receiving at the Willard Sparks Beef Research Center, Stillwater, OK, through finishing in commercial feedlots in the Oklahoma and Texas panhandle to harvest.  Management of the calves during the receiving period were discussed in a previous paper (Stovall et al., 1999). 

Cattle included a sub-sample of 406 head (Trials 1 through 7) from the 906 head used in the previous study (Table 1).  Feedlot gain (LOTADG) was calculated from shrunk body weight at the end of the receiving period (42-d wt) to final live weight.  Overall average daily gain (TOTALADG) was calculated from the start of the receiving period to final live weight.   

Health records from the receiving period were analyzed by frequency of treatment for BRD: 0 medical treatments; 1 medical treatment; and >1 medical treatments.  Medical records from the finishing yard were not available.

Health Management.  During the receiving period, cattle were checked once daily for clinical signs of the BRD.  Prerequisite to antibiotic treatment and classification as morbid, an animal had to exhibit at least two of the following clinical signs: depression; lack of fill; occasional soft cough; physical weakness; ocular and/or nasal discharge.  Once declared morbid, a subjective BRD severity score was awarded: 1 – mild; 2 – moderate; 3 – severe, and 4 – moribound.  Calves had to have a severity score of 1 or 2, and a rectal temperature of 104ºF or greater in order to be treated with an  antimicrobial.  Any calves that did not have a rectal temperature of 104ºF or greater were returned to their original pen without treatment.  Animals with a severity score of 3 were treated regardless of rectal temperature.  Morbid animals received antimicrobial drugs in the sequence listed in Table 2.   Following medical treatment, each heifer was returned to its original pen.

Value Determination.  Carcass values were calculated using a basic grid (Table 3) from the Excel Corporation, based on a yearly average U.S.D.A. Choice to U.S.D.A. Select spread of $7.50/cwt.   Gross values were determined by multiplying carcass value by hot carcass weight.  A final net value was calculated by subtracting the medical cost from the gross value.    

Results and Discussion

Finishing Performance.  Final weights and gains of cattle classified by number of antibiotic treatments for BRD during the receiving period are presented in Table 1.  No significant differences (2.83 vs 2.85 vs 2.90 for 0, 1, and >1 treatments, respectively) in LOTADG were detected.  Similarly, performance was not different among treatment groups in TOTALADG despite lower feedlot entry weight for heifers that had been treated with antibiotics more than once.  These results might suggest that calves that exhibited signs of BRD and received antibiotic treatment did not depress subsequent feedlot performance. 

Carcass Traits.  Cattle that had been treated for BRD exhibited some carcass changes as shown in Table 1.  Final live weight was 3 to 4 lb less for heifers that were treated and hot carcass weights (HCW) also averaged 3 lb less for cattle that received multiple antibiotic treatments.  Heifers treated for BRD tended to have lower (leaner) U.S.D.A. yield grades (2.53 vs 2.42 vs 2.36 for 0, 1, and >1 treatments, respectively).  Heifers that received two or more treatments for BRD during the receiving period had markedly lower (P=.02) marbling scores, with a 25% reduction in the percentage of carcasses grading U.S.D.A. Choice or above for heifers that received multiple treatments (66.19 vs 59.36 vs 41.11 for 0, 1, and >1 treatments, respectively).

Carcass Value.  Economic losses associated with BRD and treatment for BRD are summarized in Table 1.  The decrease in marbling score lowered (P=.05) carcass value by a mean of $2.31/cwt of carcass.  Combined with the reduced carcass weight, gross value was decreased by about $4 for heifers with one treatment for BRD and $19 for heifers receiving more than one treatment for BRD.  Medical costs for these groups averaged $7.48 and $18 (Table 1).  Combined with gross value for the carcass, these medical costs mean that when compared to untreated heifers, heifers treated once or more than once netted $11.48/head and $37.34/head less, respectively.

Implications

BRD can have adverse effects on carcass characteristics 200-d post backgrounding period.  These data show that the impact of BRD extends far beyond the cost of medication, death loss, and reduced animal performance, emphasizing the importance of prevention as early as possible. 

Literature Cited

Edwards, A.  1996.  Bovine Pract. 30:5.

Gardner, B.A. et al.  1999.  J. Anim. Sci.  77:3168.

Perino, L.J.  1992.  Compend. Cont. Educ. Pract. Vet.  14 (Suppl.):3.

Stovall, T.C. et al.  1999.  Okla. Agr. Exp. Sta. Res. Rep. P-973:171.

Acknowledgements

The authors gratefully acknowledge the work performed by the people at the Willard Sparks Beef Research Center and Farmland Industries Corp. for assistance in obtaining carcass data.  Also, the authors extend gratitude to Drs. H. Glen Dolezal and Fred N. Owens for technical assistance with this manuscript.