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Title: EFFECT OF PARTICLE SIZE ON PASSAGE RATES FROM THE RUMEN TO THE DUODENUM OF LACTATING DAIRY COWS.

Author
item PETERSON, A - UNIVESITY OF MARYLAND
item Baldwin, Ransom - Randy
item KOHN, R - UNIVERSITY OF MARYLAND

Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2006
Publication Date: 7/15/2006
Citation: Peterson, A.B., Baldwin, R.L., Kohn, R. 2006. Effect of particle size on passage rates from the rumen to the duodenum of lactating dairy cows [abstract]. American Dairy Science and Society of Animal Science. 89:242.

Interpretive Summary:

Technical Abstract: The objectives were to determine the effect of particle size and sampling sites (reticulum and duodenum) on passage rates from the rumen. Samples were collected from 8 ruminally and duodenally cannulated lactating Holstein cows every 4 h for 48 h over 4 periods (n=32). Samples were poured through sieves measuring 2.0, 1.0, 0.5, and 0.25 mm. Fractions were composited over 48 h for each cow. The average DM of duodenal samples was 4.89% (SEM=0.067) as compared to 3.21% (SEM=0.046) for the reticulorumen sample (P < 0.01) indicating water and VFA removal between the two sampling sites. For duodenal samples, 48% of DM was in the liquid fraction while 5, 11, 14, and 26% of DM was on the 0.25, 0.5, 1.0 and 2.0 mm sieves respectively. For reticulum samples, the particles contained a lower fraction of DM while the liquid fraction contained 76% of DM. On a DM basis it appears that large particles were under-sampled in the reticulum and/or over-sampled in the duodenum. The NDF% of the duodenal sample was less than that of the reticulum (P < 0.01; 60 vs. 75%) suggesting that at least one of the sampling sites was not representative of total flow. When NDF for each sieve was expressed as a fraction of total sample NDF no difference was found between reticulum and duodenal samples for each sieve. These results suggest that although samples were not representative of flow on a DM basis, reticulum and duodenal samples were similar after removal of cell contents. Based on duodenal samples, 48% of DM flow was in the liquid phase and 26% was retained on the 2 mm sieve. There is a potential to estimate flow using reticulum samples in place of duodenal samples.