The costs of common diseases of dairy cattle (Proceedings)

Knowing the cost of common diseases can help dairy farmers and their veterinarians plan treatment and prevention strategies that are likely to improve the profitability of the dairy. If the cost of the problem and the components of that cost are known, it is easier to judge whether allocation of resources can be expected to reduce that cost and return a net profit. Rarely are complete data available from a farm to permit calculation of overall disease costs. This paper evaluates data from published reports, the authors' veterinary practice, and estimates when no data was found for the factors that contribute to the overall cost of common diseases of adult dairy cattle.

Milk fever, dystocia, retained placenta/metritis, ketosis, left displacement of the abomasum, clinical mastitis, and lameness were chosen since they represent the majority of the clinical conditions of dairy cows. The author recognizes that many of these diseases have nutritional, environmental, or management policy components as inherent risk factors. These are the things that are most amenable to change. The author further acknowledge that there are complex interrelationships among the disease entities discussed in this report even though they will be ignored during this analysis.

Sources of information for this report were chosen to reflect as closely as possible the current situation on medium to large commercial dairies. Hence, data from some recent surveys and epidemiological studies were excluded since the herd base from which the data derived was judged too dissimilar from typical commercial dairies. Some estimates from published works were modified with information from our up-to-date herd files (Dairy Comp 305) representing about 11000 milking cows in large herds in the vicinity of Ithaca, New York. The intent of this analysis is to make the information relevant to veterinarians, consultants, and managers particularly those serving large free-stall herds. Prices for dairy cattle, milk, feed, and labor used in the report were current in central New York in spring 2008.

Disease definitions were 1) milk fever (MF): abnormal behavior or weakness requiring treatment with calcium from 2 days before to 5 days after calving. 2) Dystocia (DYS): calving that requires assistance. 3) Retained placenta/metritis (RP): failure to expel the placenta within 24 h of calving or metritis characterized by malodorous uterine discharge, fever, and inappetance. 4) Ketosis (KET): reduced appetite accompanied by ketonuria in the first 5 weeks of lactation. 5) Clinical mastitis (MAST): grossly abnormal milk with or without systemic illness. 6) Left displacement of the abomasum (LDA): abomasum displaced dorsally and to the left of the rumen diagnosed by simultaneous auscultation and percussion. 7) Lameness (LAME): Limping or reluctance to move due to painful conditions of the digit(s).

Diseases cost producers through direct effects in extra labor for treatment, veterinary fees, and drugs. Treatments may require discarding milk due to drug residue. Diseased cows may produce less milk than expected due to reduced feed consumption resulting in indirect costs through lost potential income. Diseases occurring early in lactation may lead to delayed conception. Cows may be culled directly or indirectly as a consequence of disease (via low milk production or delayed conception) and some cows die of the diseases being considered.

Cost calculations

Replacement of dead cows was assigned a cost of $1800. Cows that are culled involuntarily were given a slaughter value of $.45 / lb liveweight and an average weight of 1350 lb for a selling price of $600. Replacement heifers were valued at $1800 so a replacement costs $1250. This replacement cost is based on current cash accounting method and does not offset the cost of the replacement with her future income potential. A better method of calculation might consider the net present value of the sick cow had she not become diseased and her current value as a marketable cull. The result of our method is probably an overestimation of the cost of culling but does capture the upper limit of this cost and was chosen for the convenience of calculation. Veterinary fees were taken from published reports or estimated from a $20 stop charge and $100 /h. The entire veterinary visit was assumed to be for treatment of the single sick cow considered in the analyses. Veterinary costs are reported as time or professional fees and do not include medications. Out of hours fees for emergency care typically carries a surcharge of about $25. These assumptions for veterinary fees will result in overestimation of the likely actual costs for veterinary services but represent a reasonable upper limit. Drug costs for treatment of specific diseases was not available for most diseases under consideration. Typical costs for the medications required were estimated from the retail value of the appropriate drugs from national distributors or from our pharmacy. Labor costs for treatment of sick cows were calculated from estimates of the extra time required to perform the tasks of segregation, restraint, and therapy. Farmer's labor was valued at $15 /h. Milk not available to sell due to drug residues was considered available for calf feeding at half the market value of $.14 /lb or $.07 / lb. Milk not produced due to illness was assumed to occur secondary to reduced feed intake. Feed costs were set at $.09 per lb DM. Feed intake above maintenance yields 2.5 lb milk per lb DM consumed (NRC, dairy). Thus, the opportunity cost of milk not made is $.14 /lb minus the marginal feed cost per lb of milk produced ($.09 / 2.5 = $.036) or $.10 / lb. Delay in conception beyond the herd goal was assigned the value of $3.00 per day with no additional costs assessed for reproductive inefficiency.

Disease data

The following tables summarize the outcomes for the listed diseases compiled from many published sources. Where published data was unavailable data extracted from the records of our client herds was used. If no data were available the authors best guess was employed. The final calculations are made in a spreadsheet but extracted here for the reader. The spreadsheet and specific references are available from the author.