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Alternative Techniques for Measuring Nutrient Digestion in Ruminants

[ digestibility, three-step method, expeller, blood, meat, DDG ]

Commercial samples of dietary protein supplements were collected and evaluated by the ‘Three-Step In Situ/In Vitro Procedure’. Rumen undegradable protein (RUP) was determined by 16 hour incubation of the sample in a Dacron bag suspended in the rumen. Intestininal digestibility (ID) of the residue was estimated by in vitro incubation in acid followed by pancreatin enzyme. Intestinally absorbable dietary protein (IADP) equals the amount of protein from a specific feed that was available for absorption in the small intestine, or the percentage of RUP that was post-ruminally digested.

Protein source

Number of
samples

RUP,
% of CP

ID, % of
RUP

IADP, %
of CP

Soybean meal, solvent extract

5
25
90
22

Soybean meal, expeller

6
47
93
44

SoyPass*

6
66
88
58

Distillers grains, dried

5
56
81
46

Blood meal, batch dried

12
88
63
55

Meat and bone meal

11
59
55
33

SoyPass (lignosulfonate treated SBM) contributed more IADP than either solvent extract or expeller soybean meal, due to its high level of RUP, without significant reduction in digestibility.

Marshall D. Stern, A. Bach, and S. Calsimaglia, (1997), J Anim Sci 75:2256-2276