Details

Autor(en) / Beteiligte

• Gustafsson, Anders H

Titel

Acetone and urea concentration in milk as indicators of the nutritional status and the composition of the diet of dairy cows

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

1993

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The studies reported in this thesis were designed to examine the factors affecting the concentrations of acetone and urea in milk, and to evaluate the relationships between these concentrations and the diet, management, milk yield and fertility of dairy cows. The data were derived from a study which used data obtained from a total of 23,334 dairy cows in 474 herds over three years, an experiment with four cows of which three had rumen fistulae, and a study with 29 herds containing an average of 38 cows/herd which were fed wilted silage. Increases in the frequency of feeding and increases in the intake of energy were correlated with a lower risk of hyperketonaemia ($>$0.4 mM milk acetone), with higher milk yields, and with improved reproductive efficiency. A concentration of acetone in milk above 2.0 mM was correlated with a 6.5 to 8.5% lower long-term milk yield, with a 5 day longer calving to first service interval and with an increased risk of cystic ovaries in first parity cows in comparison with a milk acetone concentration $<$0.4 mM. Milk yield and reproductive efficiency tended to be highest in cows with milk acetone concentrations between 0.4 and 1.0 mM. The critical borderline concentrations for milk acetone were 0.7 and 1.4 mM. The peak serum urea concentration was observed 1.5 to 2.0 hours after the peak concentration of ammonia in the rumen. The concentration of urea in milk equalled the concentration in serum 1 to 2 hours earlier, when the rate of change of the concentration in serum was 0.5 to 1.0 mM/hour. At this rate of change the average difference between serum and milk urea concentrations was 0.8 mM. If milk urea concentration is to be used as an indicator of the dietary composition or nutritional status of dairy cows, diurnal variations associated with the time of feeding in relation to the time of milk sampling need to be considered. Higher concentrations of ammonia nitrogen in the silage were correlated with reduced reproductive efficiency. (Abstract shortened by UMI.)