Skip to main content
ARS Home » Research » Publications at this Location » Publication #47189
Title: ADJUSTMENT FACTORS FOR CALVING MONTH AND CALVING AGE WITHIN PARITY FOR HOLSTEIN COWS MILKED THREE TIMES PER DAY

Author
item JAGANNATHA S - UNIV OF NEBRASKA
item KEOWN JEFFREY F - UNIV OF NEBRASKA
item VAN VLECK L DALE - 5438-01-30

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Milk and fat yield records from New York and Pennsylvania of 3x milked Holsteins calving from 1976 to 1992 were analyzed to determine adjustment factors to standardize yield for calving age within parity and calving season. Only lactations one through six with days in milk between 270 and 305 days were included. The 120,881 records of 74,032 cows were randomly split into two sets of equal size for analysis. Calvings were not grouped into different time periods as 95% of calvings were between 1982 and 1992. The model included fixed effects of herd-year, age and calving month within parity, and random effects of additive genetic and permanent environmental effects of the cow, and residual. Solutions for fixed effects were obtained using MTDFREML programs. The data set was randomly split into six sets to estimate variance components for the model. To obtain solutions to calculate adjustment factors, average estimates of heritability (.235), repeatability (.51) and residual variance (.49) of the six sets were used. Multiplicative adjustment factors were calculated using the solutions. The base chosen as mature equivalent to obtain the factors was for sixth parity cow calving in Decmeber at 82 months of age. Factors were higher for younger cows within the same parity for first and second parities. Differ- ences due to age and month increased in parity 1 after yields were standardized to mature equivalent. The same was true with yields standard- ized by currently used factors to convert 3x to 2x milking and then corrected for age and month of calving. Differences due to age and month in standardized yields using the factors obtained in this analysis and the factors currently used were similar.