Conference participants examined dairy culling

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The 8th DISCOVER Conference on Food Animal Agriculture was held in October at the Abe Martin Lodge in Brown County, Indiana. “Reducing Culling Rates in the Dairy Herd: Creating an Environment for Success”, attracted 80 registrants from 23 states and 5 countries.

Five overall themes emerged from the conference. Clarifying the terminology of culling, understanding the meaning of culling rate, evaluation of reasons used to explain culling, examination of underlying causes of culling, and examination of some of the tensions between visions of food animals as economic units and sentient beings.

Over recent decades, several terms have been used to describe the magnitude of culling and the calculation methods have been interchanged. The traditional business term “turnover rate” is the number of cows removed from the herd for all reasons divided by the average number of cows in the herd over the same period of time. Turnover rate was recommended as the standard index to measure culling and terms such as “cull rate” and “replacement rate” should be synonymous and calculated in the same way.

Concerns have been raised that turnover rates in the dairy industry are too high.  Presenters urged that the national herd be distinguished from individual herds. At the national herd level, turnover rate is determined primarily by the availability of replacement heifers. The national herd turnover rate has increased since the 1920’s when USDA began tracking numbers, but has been relatively steady over the past 15 years.

At the individual herd level, however, turnover rate is highly variable. Some people suggest that low herd-level turnover rates represent good herd health management and that high cull rates indicate poor health management. Turnover rates should not be used independently to assess health management, but should be used in conjunction with other health indicators such milk production, somatic cell count, breeding records, and specific disease records.

At the individual cow level, discussions focused on why cows are culled herds. Recording organizations usually ask that dairy owners to indicate why cows leave by using only a single choice such as mastitis. But this compromises recording of actual reasons, since cows are usually removed for a combination of several reasons. Some people advocate the abandonment of culling reasons and the use of net present value calculations only to make the decision. Others support a recording scheme based upon destination (death, salvage, market cow, or dairy sale), with a second-tier that allows multiple entries of causative reasons. For example, the cow was sold to slaughter because of mastitis and infertility. A consensus on culling reasons was not reached.

A wide range of risk factors ranging from reproductive performance to mastitis to cow comfort issues that result in culling were presented. The relationship between high production and infertility was examined, but generated diverse opinions. Effects of heat stress, social turmoil in continuous entry pens, overstocking, and infringement of cow time budgets were discussed. A session on metabolic disease illustrated how metabolic diseases cascade into subsequent disease problems that result in increased odds ratios for culling.

There appears to be considerable opportunity to improve dairy cow health through genetic selection. If dairy cow health is improved, culling can be based increasingly on poor productivity instead of disease. To accomplish this, the US dairy industry needs to report disease events so that geneticists can identify sires that transmit improved health to their daughters. The USDA-AIPL group has proposed a disease recording scheme to be used by DHIA centers. The project has tremendous potential, but will need broad support by producer groups, bovine practitioners, DHI processing centers, dairy health companies, and dairy extension services.

DISCOVER Conferences are designed to encourage in-depth discussion of topics important to the food animal agriculture industry. This 8th Conference brought together broad perspectives on the culling issue, with members of the research community, veterinarians, livestock breeders and producers; leaders of livestock industries and organizations; equipment and facilities manufacturers; animal health industries; DHIA industry, dairy software professionals and governmental and regulatory agencies among those represented.

For more conference information, including interpretive summaries of each speaker’s presentation, go to http://www.adsa.org/discover/

The DISCOVER Conference Series is a program of the American Dairy Science Association.

American Dairy Science Association



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