Effect of Intake of Italian Ryegrass Hay on Chewing Behavior, Rumen Volume and Fecal Particle Size in Heifers
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概要
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This experiment was designed to elucidate the relationships among intake, chewing behavior, digestibility, and the digesta passage through the rumen. Four Holstein heifers (average body weight, 455kg), each with a large ruminal cannula, were given Italian ryegrass hay at one of four intakes (2.44, 4.88, 7.33 and 9.49kg DM/day) in 4×4 Latin square design (12 days per period). Measurements were made for diet digestibility, chewing behavior, rumen volume, outflow rate of rumen fluid and fecal particle size distribution. The apparent digestibilities of the chemical components except crude fat and crude protein decreased with increasing intake. The apparent retention time of dry matter in the rumen was longest (P<0.05) at the intake of 2.44kg/day. However, the values had no significant differences among the higher intakes since rumen volume increased proportionally to the increase of intake. The percentage of fecal particles retained on sieves of 1 and 2mm opening size was significantly (P<0.05) higher in lower intakes (2.44 and 4.88kg/day). While eating time (min/kg DM intake) increased as intake increased, rumination time decreased slightly with the increase in intake. Thus, the total chewing time per unit of intake did not differ significantly among the intakes. The chewing rate during rumination and the total number of chews were higher for higher intake levels. From these results, it was considered that the depression of the digestibility at the higher intakes was influenced not only by the passage rate through the rumen but also partly by lower digestion rate in the post-ruminal digestive tracts. Moreover, under the maintenance level of intakes, the particle size that escapes from the rumen might be longer on account of the lower total chews for unitary intake and the longer particle size of feces.
- 社団法人 日本畜産学会の論文
- 2001-09-25