Influence of hay particle size at different concentrate and feeding levelson digestive processes and feed intake in ruminants. 2. Passage, digestibility and feed intake

In order to study the main effects of particle size, three ruminally fistul ated cows (550 to 580 kg BW) were fed a constant low concentrate level (3.5 6 kg DM/d, 20% of total DMI) and a fibre-rich hay (approximately 60% NDF in DM) in long (28.7 mm), chopped (9.2 mm) and fine ground (2.9 mm) form in a 3 x 3 Latin square design. In another three factorial experiment with 8 we thers (4 animals were ruminally fistulated, mean BW = 68 kg) the main effec ts and interactions of the above mentioned hay particle sizes at two concen trate levels (10.4 to 13.3% and 29.5 to 40.1% of DMI, resp.) and two intake levels (restricted and ad libitum) were investigated. In comparison to lon g hay (28.7 mm), feeding of chopped hay (9.2 mm) at low concentrate levels, increased not only the hay intake (7% in dairy cows and 13% in sheep) but also the intake of digestible organic matter (12% in dairy cows and 32% in sheep), due to an increase in the apparent digestibility of OM by 3.8% in d airy cows and 8.2% in sheep. Ad libitum feeding of fine ground hay in combi nation with low concentrate amount in the ration increased the passage rate in the hindgut and consequently the hay intake, but not the intake of DOM, due to a significant depression of digestibility, especially of fibre frac tions (4 to 7% in dairy cows and 4.5 to 14% in sheep), in comparison to 28. 7 and 9.2 mm hay particle sizes. The digestibility decreased significantly with restricted feeding of fine ground hay in sheep only in comparison to 9 .2 mm particle size. A threefold increase of concentrate amount levelled ou t all effects of the particle size reduction. The effect of particle size w as more pronounced in sheep than in dairy cows.