32 pairs of monozygons twins were fed ad lib. with a complete diet feed
during the first 20 weeks post partum. The heritability (in broader sense)
for milk yield, feed intake and energy deficit was 0.39, 0.17 and 0.19
resp. The genetic and phenotypic correlations between daily milk yield
and feed intake were 0.14 und 0.26 resp. Therefore selection for feed
intake should be based on progeny groups of A.J. bulls. To estimate the
feed intake under field conditions the content of ketone-bodies in milk
at the first and second test day p.p. can be combined with the milk yield
and fat- and protein content. The correlation between estimated and actual
energy deficit in 101 cows was r = 0.71. In field data with about 7500 cows
there was a genetic variance of the acetone content in milk in cows with 2 2 two and more lactations with h = 0.17 + 0.09 and h = 0.09 + 0.06 for the 
first and second test day p.p. resp., but not in heifers.

H. O Gravert, K. Pabst

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume IX. Breeding programs for dairy and beef cattle, water buffalo, sheep, and goats., , 106–111, 1986
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