Nutritional and physiological studies of differences between
Friesian cows of high and low genetic merit
A.W.F. Davey, C. Grainger, D.D.S. MacKenzie, D.S. Flux, G.F.
Wilson, I.M. Brookes, C.W. Holmes
Department of Animal Science, Massey University, Palmerston
North
Proceedings of the New Zealand Society of Animal Production.
1983, 43: 67-70
The results of experiments with Friesian cows with breeding
indices of 126 (HBI) or 102 (LBI) are presented. HBI cows produced an
average of 153 kg milkfat/cow in the 1979 to 1981 lactations and LBI
cows produced 125 kg milkfat/cow. HBI cows lost 0.7 of a condition
score during lactation whereas LBI cows maintained their condition
score. In 2 of the 4 staff feeding experiments the dry matter intake of
pasture/kg 0.75 was significantly higher for HBI cows than LBI cows.
There were no differences between the 2 groups of cows in their ability
to metabolise dietary energy, nor in their heat production. JBI cows
partitioned a greater proportion of their dietary energy to milk energy
than LBI cows.
Blood samples taken hourly for 24 h periods from cows fed indoors were
analysed for growth hormone, insulin, glucose, ß-OH butyrate, and non-
esterfied fatty acids. Some of the animals also received glucose
infusions. Differences between BI groups for levels of individual
metabolites and hormones were observed and these differences varied
depending on the level of feeding. Milk flow measurements were made on
5 occasions during the 1981/82 season. HBI cows despite higher milk
yields, milked out more rapidly than LBI cows because of a higher
maximum milk flow rate.
Keywords: NZSAPAB;
Friesian cows; breeding index; milk fat production; condition
scores; energy balances; blood metabolites and hormones; milking rates
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Last Updated 03-05-1997
