Influence of different feeding levels on nitrogen and minerals metabolism and acid-base state of cows
1998
Kadarik, K. (Estonian Agricultural Univ., Tartu (Estonia). Faculty of Veterinary Science)
According to special literature N-metabolism influences urea and electrolyte content in plasma urine and also their excretion. In the first test group there were three nonlactating, nonpregnant (NC) cows and in the second group four lactating (LC) cows. All cows had the fistula of the rumen. Ration 1 of the first (NC) group correspondended to the maintenance requirement, rations 2-4 had 30 per cent energy deficit and the crude protein (CP) content in dry matter (DM) was 8.9-18.9 per cent. CP in LC cows feed DM was 14.5-14.9 per cent. In these rations corresponding to production allowance the prescribed energy was given with 25-70 per cent concentrated feed. The plasma Na+ -content and K+ -content was measured with an ion selective electrode, in other fluids with flame photometer. The Cl-content was determined colorimetrically, urea content enzymatically and net acid-base excretion (ABNE) in urine titrimetrically. Because of a higher feeding level of LC it was observed that K+ consumption increased 4-5 times, the K+ content decreased in rumen fluid and the K+ excretion in urine increased 5 times in comparison with NC. In case of Na and Cl- the consumption, the change of concentration and excretion were smaller than in case of K+. One of the reasons for the increase of electrolyte excretion is the increase of their consumption
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