Iso butylidene di urea as a source of nonprotein nitrogen for ruminants 1. rumen fermentation digestibility of the nutrients and microbial protein synthesis in dairy cows
Voigt, J.; Piatkowski, B.; Krawielitzki, R.; Bergner, H.; Goersch, R.
Archiv fuer Tierernaehrung 31(1): 45-56
In 3 experiments 2 lactating dairy cows received a mixed ration consisting of 10 kg maize silage, 2.5 kg hay, 2.0 kg barley, 1 kg dried sugar beet pulp, 1.5 kg maize starch, 0.5 kg sugar, 0.2 kg of a mineral-vitamin mixture and 0.08 kg non-protein N (NPN)/animal per day. The ration contained 8.3 kg dry matter, and 1.18 kg crude protein, 0.5 kg of which from NPN, and was given in equal shares twice a day. Urea (I) or isobutylidene diurea (IBDU), to which the animals were not adapted (II) or adapted (III), were the sources of NPN. IBDU was a very slow source of NH3 in the rumen. At 2 h after the intake of NPN 48-75, 5-9 and 5-12 mg NH3/100 ml were detected from I-III, respectively. Up to the 3rd h the concentration of IBDU and urea increased in III due to the slow distribution of the slowly soluble IBDU in the fluid digesta. The urea level was .apprx. 25 and 1 mg/100 ml for III and I, respectively, 12 h after feeding IBDU. In the first 3 h after supplying NPN the pH-value of I was > 1 U higher than II and III. There were no significant differences in the fermentation models between the variants, the concentration of volatile fatty acids was 12.6, 12.3 and 11.1 mmol/100 ml. In the stomachs the digestibility of the organic matter was 52, 51 and 54%, that of the crude cellulose 64, 62 and 66% and that of the starch 91, 93 and 98%. At the duodenum the passage rate of N was 87-93, 107-126 and 96-130% of the N-intake, that of NH3-N 6, 43 and 22 g/day and that of bacteria-N 61-76, 78-100 and 76-96% of the N-intake. In the rumen 2.3-2.8, 2.6-3.2 and 2.1-3.1 g bacteria-N were formed per 100 g day matter fermented. In the intestines 55-61, 57-64 and 48-71% of the feed-N were available as non-NH3-N. In comparison to urea and concerning IDBU, the rumeno-hepatic circulation plays a significantly bigger role for the N-supply of the rumen microbes and may result in better N-utilization.