Accurately assessing the economic impacts of diseases and other factors that affect milk production requires that the demand for milk be taken into account. Because demand for milk in the USA is relatively inelastic (i.e., consumers generally purchase a somewhat fixed amount over a given time frame, regardless of fluctuations in price), consumers tend to reap much of the benefit of enhanced production. An examination of the economic impacts of Johne's disease indicated that reduced milk production, associated with the determination of dairy operations as Johne's-positive, reduced consumer surplus by $770 million ± $690 million, and resulted in a total loss of $200 million ± $160 million to the US economy in 1996. Most of the economic surplus lost by consumers was transferred to producers, whose economic surplus increased by $570 million ± $550 million as a result of the reduced milk production associated with Johne's disease. Uncertainty analysis showed that the estimated reduction in milk production on Johne's-positive dairy operations accounted for most of the uncertainty in the economic-impact estimates. If Johne's disease had not been present on US dairy operations, then an additional 580 million ± 460 million kg of milk would have been produced, but the price would have fallen by 1 . 1±1 . 0 cents/kg, and the total value of the milk would have decreased by $580 million ± $560 million.

In a national survey of US dairy operations, 1685 dairy operations reported 47057 new dairy heifers (either births or acquisitions) and 4427 deaths (9·4%) of preweaned dairy heifer calves over a 3 month period. Stepwise logistic regression was used to identify management practices associated with high mortality among preweaned heifers in dairy operations where at least three dairy heifer calves were born alive or moved on to the operation. Analysis was done twice: once by separating all operations by size into high or low mortality; again using only operations with <2 and >10% mortality to eliminate dairy operations with intermediate levels of mortality from the comparisons. Results were similar. Dairy operations in the West were more likely to fall in the high mortality category than dairy operations in the rest of the country. In addition, the following dairy operation characteristics were associated with high death levels in both models: rolling herd average milk production <7710 kg, preweaned heifers placed in groups of seven or more, a male having primary responsibility for the care and feeding of preweaned heifers, calves not receiving hay or other roughages until >20 d old, calves fed on mastitic or antibiotic milk after colostrum and calves not given whole milk after colostrum.

This study focused on aspects of the National Dairy Heifer Evaluation Project that involved neonatal feeding practices and types of milk replacers utilized on dairy farms. Types of milk replacers and the management practices associated with their feeding were studied. Nearly 60% of US dairy farms use milk replacers for some or all of the feeding program for neonatal calves. Regional differences existed in the types of liquid feeds and milk replacers fed to calves. Western producers fed less milk replacer, and western and northeast producers fed replacers with less total CP. Many characteristics of management utilized along with these products reflect accepted management and nutrition practices. During the study period from 1991 to 1992, 11.2% of replacers contained casein. A greater proportion of these were found in the West during the first 6 mo of the study, reflecting changes in the milk replacer formulations during that time.

The goal of this study was to measure the economic impacts of reduced milk production associated with papillomatous digital dermatitis (PDD) in dairy cows in the USA, and of specific risk factors for PDD, in 1996. The method applied was an economic-welfare analysis of producer and consumer surplus, with the GUM Workbench used to analyse uncertainties in the measurements. Reduced milk production associated with PDD was found to reduce consumer surplus by Dollars 750 million +/- Dollars 580 million, and to increase the economic surplus of producers by Dollars 560 million +/- Dollars 470 million, with a net economic loss of Dollars 190 million +/- Dollars 130 million. An examination of the economic effects of specific epidemiologic risk factors for PDD showed that having dairy cows that were not born on the operation had important economic consequences associated with the disease, as did the type of land to which dairy cows had access during the winter months and the type of flooring on which cows walked. Washing hoof-trimming equipment between cows was an important biosecurity measure that was associated with reduced PDD. The epidemiologic model used also implicated hoof trimmers who trimmed cattle hooves on other operations as having an important economic impact associated with this disease, although this finding may have been erroneous.