Journal of Dairy Science, Vol 77, Issue 5 1457-1465, Copyright
© 1994 by American Dairy Science Association
Comparison of United States and Danish strains of Jerseys for yield
J. S. Metzger, L. B. Hansen, H. D. Norman, C. W. Wolfe and J.
Department of Animal Science, University of
Minnesota, St. Paul 55108.
Eleven US and 11 Danish young bulls were AI sampled in the US and
Denmark. The milking daughters of these sires provided an opportunity
for comparison of the US and Danish Jersey populations. Danish age
and month of calving and DIM adjustment factors were developed so
that Danish and US records could be compared on a standardized basis
(305-d lactation, mature equivalent). Least squares and animal model
analyses were used to estimate strain differences and effects of
heterosis. Jerseys from the US had superiority over Danish Jerseys of
approximately 1000 kg for milk and 17 kg for protein. However, Danish
Jersey had an advantage of 20 kg for fat. Estimates of heterosis from
crosses of US and Danish Jerseys were 1.5 to 3% of the mean for milk,
fat, and protein yields. Correlations of EBV from official genetic
evaluations of the US and Denmark were high, > or = .78, for the
project bulls, providing little evidence of an interaction of
genotype and environment.