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Journal of Dairy Science Vol. 67 No. 10 2236-2246
© 1984 by American Dairy Science Association ®
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Blood Constituents in Lactating Holstein Cows Influenced by Hematocrit, Sampling Site, and Diet Protein and Calcium1

J. E. Wohlt2, J. L. Evans2 and J. R. Trout3

Cook College, Rutgers-The State University, New Brunswick, NJ 08903

ABSTRACT

Constituents were measured in jugular vein (days 0, 4, 14, 28, 43, 72, and 151 of lactation) and internal iliac artery and mammary vein (days 28, 72, and 151 of lactation) blood of 24 Holsteins. Six diets of grain:corn silage-urea contained percents of protein and calcium: 12, .6; 12, .9; 15, .6; 15, .9; 15, .6; 15, .9. Grain contained urea (diets 3, 4) or soybean meal (diets 5, 6). All cows were fed diet 3 the first 4 wk of lactation; then four cows were assigned to each of six diets. In jugular blood, calcium and phosphorus were lower on day 0. Hydroxyproline and ketone bodies peaked and magnesium was minimal on day 4. Hematocrit, urea nitrogen, and free fatty acids decreased with lactation. Jugular blood from younger cows had less ketone bodies, free fatty acids, and magnesium and more hematocrit, hydroxyproline, and phosphorus. Sampling site had arterial-venous differences for each constituent, with venous differences for hematocrit, free fatty acids, calcium, phosphorus, and magnesium. Hematocrit decreased with diets 1, 2, 3, 4, or .6% calcium. With a common hematocrit (36%) and change from baseline (day 28), urea nitrogen was less with 12% protein or .6% calcium. Phosphorus and magnesium decreased with 15% protein. More constituents were required from diet and tissues to maintain concentrations in blood as hematocrit decreased, indicating the importance of dietary calcium and protien concentration and quality.

FOOTNOTES

1 New Jersey Agricultural Experiment Station, Publication Number D-06901-2-83, supported by State and USDA Animal Health funds.

2 Department of Animal Sciences.

3 Department of Statistics.






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Copyright © 1984 by the American Dairy Science Association ®.