ENERGY-UTILIZATION OF FODDER BEETS IN LACTATING DAIRY-COWS

A respiration experiment was conducted in 18 lactating diary cows to investigate the effect of adding 0, 22 and 44 kg fodder beets to a hay-grass silage ration on energy, N balance and milk production parameters. Faeces and urine were analysed in a balance test using quantitative collection technique, and energy retention and utilization measured by means of the CN and RQ method. In addition, effects on the milk-fat pattern and several blood-plasma parameters were studied. The milk yield fell by up to 21 % with rising intakes of fodder beets. However, the milk-fat content increased such that the daily milk-fat output was unaffected by the beets. On the other hand, the lactose produced fell sharply, and the excretion of milk protein also showed a downward trend. The fat pattern shifted in favour of palmitic acid at the expense of the C18 fatty acids (stearic, oleic and linoleic acid). The blood plasma values 2 hours after the beet feed showed a more marked decline of glucose and higher levels of beta-hydroxybutyrate compared to the control. The inclusion of beets increased the digestibility of DM and energy in the total ration, while the digestibility of crude fibre remained unchanged. The metabolizability of energy was raised by up to 4 percentage points. Energy retention, on the other hand, decreased markedly with beet feeding. Compared to the control cows, the efficiency of utilization of ME in the total ration for milk and energy deposition was lower by 6.4 percentage points on 22 kg beets and by 8.4 percentage points on 44 kg beets. The partial utilization of the beets, with reference to their sugar content, was 13 percentage points lower than the utilization of the remaining ME in the ration. However, no differences were observed between the treatments with regard to the relative values of N retention.