Passage of nutrients into the duodenum and their postruminal digestion in cows fed crushed and ground maize

In an in vivo experiment the 2 × 2 Latin square method and Cr as a marker were used to determine ruminal degradation and postruminal digestion of nutrients from a feed ration containing 3 kg of crushed or ground maize (CM vs. GM). The experiment included 4 cows with rumen fistulae and duodenal T-cannulae. Amino acid passage to the duodenum was also determined. The mean concentration of ammonia nitrogen in the rumen fluid was 11.6 ± 6.22 and 11.5 ± 6.41 mg/100 ml in the CM and GM ration, respectively. Crushing considerably decreased starch degradation in the rumen where starch passage reached 33.5% with CM and only 21.5% with GM. Both post-ruminal (82.2% vs. 85.5%) and total digestibility of starch (94.0% vs. 96.8%) was high. The passage of other nutrients was not influenced by crushing. With both feed rations higher amounts of crude protein and amino acids passed to the duodenum than were ingested (127.8% vs. 130.4% and 118.1% vs. 124.5%, respectively). In comparison with intake the highest increase was observed in essential lysine (156.5% and 165.0%, respectively) and glycine (261.1% and 280.2%, respectively). Apparent crude protein digestibility was at the level of 68.5% (CM) and 67.2% (GM).