Trends in Herd Age Structure and the Relationships with Management Characteristics in Wisconsin Holstein Herds

Open Access
Publisher Website
Google Scholar
Abstract
Relationships between characteristics of dairy herds and age structure of cows were examined between 1969 and 1984 in member herds of Wisconsin Dairy Herd Improvement Cooperative. Herd totals were summarized yearly from individual lactation records of cows in 376 herds with DHI and DHIR records and 747 owner-sampler herds. Variables studied were average age, percent culled in first lactation, and turnover rate. Herd and year were associated with most of the variation in herd age structure, although, including trend in herd size, herd size, calving intervals, age at first calving, percent nonregistered cattle, average production, production trend, and production of those culled relative to herdmates explained significant variation in some variables after herd and year effects were removed. Average expected herdlife was estimated from turnover rate adjusted for changes in herd size and was 2.8 and 3.4 yr in official and owner-sampler herds. Herd age structures indicated a higher percentage of young cows that has been suggested as economically optimal. Trends for average herdlife for average age and percent culled in first lactation.