Abstract
Objectives were to evaluate the rate of primiparous cows leaving herds in the first 60 DIM relative to facilities, management practices, and individual animal factors. A survey was conducted on 55 commercial dairy farms in 2014 to assess and define herd factors for the prior and subsequent year. Dairy records from the on farm herd management software were collected approximately 1 yr later to analyze data for cows entering first lactation in 2013 and 2014. Cull rates (P[mortality, dairy sales, or slaughter]) were established for a 60 d eligible risk period (EXIT60). Risk ratios of EXIT60 were analyzed using Poisson regression with PROC GENMOD of SAS. The cow was the experimental unit within farm, utilizing an exchangeable correlation matrix. Cow level variables of interest for EXIT60 were calving season, age at first calving (AFC), maximum energy corrected milk produced in the first 60 DIM (MECM60), and maximum somatic cell linear score in the first 60 DIM (LSFresh). Peripartum facility and management variables analyzed were bunk space access, relative stocking density (animals per stall), bedding depth, bedding type, commingling with multiparous cows, herd growth mode, culling style of the herd manager (forgiving, moderate, aggressive), years of experience of the herd manager, lactating cow herd size, and whether heifers were all raised on-farm or some purchased. Final EXIT60 included 54 farms with adequate records for analysis and 30,145 cows. Mortality and dairy sales were reported to be 20% and 16% of all EXIT60, respectively, which totaled 6.6% of all cows at-risk. Table 1 summarizes differences and parameter estimates. Calving season, AFC, MECM60, LSFresh, and purchasing cows were associated with EXIT60. Conversely, no facilities or management factors were associated (P > 0.10) with EXIT60 across these herds and their diversity of facilities and management. We conclude that in years 2013 and 2014 calving season, age at first calving, milk production, and linear score were associated with the probability of a primiparous exiting the herd in the first 60 DIM across these 54 dairies in New York.
