PS8-4. Effect of Maturity Stage at Harvesting on Rumen Degradation and Intestinal and Total Track Digestion of Dry Matter of Intercropped Oat and Faba Bean Hay in Ruminant Livestock Systems.

Abstract The objectives of this study were to determine the effect of maturity stage at harvesting on rumen degradation and intestinal and total track digestion of dry matter of intercropped oat and faba bean hay in lactating dairy cattle. The oat and faba bean plants were intercropped and grown in three research fields, and were cut at three growth stages for intercropped hay: Maturity stage I with the oat plants at the inflorescence stage and the faba bean plants at the flat pod stage; Maturity stage II with the oat plants at the milk development stage and the faba bean plants at the milk pod stage; Maturity stage III with oat plants at the soft dough stage and the faba bean plants at the late pod stage. Rumen degradation and intestinal and total track digestion of dry matter of intercropped hay in dairy cattle were determined using in situ and in vitro three-step approach. The experimental design was a RCBD with the maturity stage as a fixed effect and growth fields and animals as random block effects. The results showed that the maturity stage at harvesting did not significantly affect effective rumen degradation (EDDM) and rumen bypass dry matter (BDM) with mean value of 508 g/kg DM and 491 g/kg DM, respectively. However, the maturity stage at harvesting significantly affected the intestinal digestibility of rumen bypass dry matter (%dBDM), the maturity stage I had higher (P = 0.021) %dBDM than the maturity stages II and III (39.7 vs. 32.1 and 31.2 % of BDM, respectively). Therefore the intestinal digestible rumen bypass dry matter content (IDBDM g/kg DM) tended to be different (P = 0.077). With increasing maturity stage, IDBDM was decreased from 184 g/kg DM (maturity stage I) to 168 g/kg DM (maturity stage II) and 154 g/kg DM (maturity stage III). For total tract digestible dry matter (TDDM in g/kg DM), with increasing maturity stage, it also tended to be decreased (P = 0.057) from 719 (maturity stage I) to 652 g/kg DM (maturity stage II) and 660 g/kg DM (maturity stage III).