Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/26/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Intestinal digestibility was estimated for the putative RUP from 4 protein sources: solvent soybean meal (SSBM), expeller soybean meal (ESBM), blood meal (BM) and corn gluten meal (CGM). RUP were prepared with in situ and in vitro pre-incubations. Proteins were added to dacron bags; bags were soaked in buffer then inserted into the rumens of two cannulated cows. After 16 h of in situ incubation, bags were removed, washed and dried (24 h, 60 C). Residues were harvested and ground. Rumen contents were collected from the same cannulated cows and filtered through 8-layers cheesecloth; this fluid was mixed with an equal volume of McDougall's buffer and incubated with proteins in vitro at 39 C for 16 h. Residues were collected by filtering on cheesecloth, washed, dried (24 h, 60 C) and ground. Intestinal N digestibility was estimated by pepsin-pancreatin digestion. Samples (8 mg N) of residues or mixed microbes were incubated with 7.5 ml 0.01% (w/v) pepsin in 0.01 N HCl for 3 h at 39 C. Then 3.75 ml 0.2 N NaOH and 3.75 ml of 0.053% (w/v) pancreatin (0.1 M phosphate buffer, pH 8) were added and incubated for 6 h at 39 C. Incubations were stopped with trichloroacetic acid (TCA); TCA supernatants were analyzed for total soluble N. Apparent and "true" intestinal digestibility of RUP was computed from the total N recovered as TCA-soluble N. Apparent and true pepsin-pancreatin digestibility were not different (P = 0.49). Overall RUP digestibility was different (P less than 0.01) for protein, averaging 74.3, 71.9, 81.1 and 49.7% for, respectively, SSBM, ESBM, BM and CGM. RUP digestibility for in vitro residues (mean = 71.6%) was greater (P less than 0.01) than for in situ residues (mean = 67.0%); however, there was a significant pre-incubation by protein interaction (P less than 0.01).