Nitrogen Utilisation in Young Fattening Bulls Kept on Two Different Energy Levels

Abstract

Twenty six young fattening bulls of the breed German Schwarzbunte and 42 of German Fleckvieh were distributed at random in two groups, which were fed at two different levels of energy supply during the total fattening period from week 14 to 78 of life.

The daily energy supply was determined in relation to the body weight:

• of body weight + 600 SE — group H

• of body weight + 300 SE = group M.

The protein supply was kept at the same level for all animals in relation to body weight ranges. It amounted to 15 — 18% of the energy supply.

From the total number of animals 4 Schwarzbunte and 8 Fleckvieh bulls per group were selected randomly for a 2 weeks survey on metabolism, beginning with week 39, 47, 55, 63 and 71 of life.

The following criteria were investigated with regard to breed, age and energy supply:

• 1) digestibility of crude protein

• 2) nitrogen retention

• 3) utilisation of digestible nitrogen.

The results showed, that the digestibility of crude protein was influenced neither by breed, age or body weight nor by the energy supply. For the utilisation of digestible nitrogen and nitrogen retention with regard to age, weighty and energy supply no difference could be observed in bulls of the German Schwartzbunte breed.

In contrast, bulls of the German Fleckvieh breed showed a decrease in nitrogen retention and nitrogen utilisation with reduced energy supply.