Relationship between condensed tannin structures and their ability to precipitate feed proteins in the rumen.
BACKGROUND
Tannins can bind to and precipitate protein by forming insoluble complexes resistant to fermentation and with a positive effect on protein utilisation by ruminants. Three protein types, Rubisco, rapeseed protein and bovine serum albumin (a single high-molecular weight protein), were used to test the effects of increasing concentrations of structurally different condensed tannins on protein solubility/precipitation.


RESULTS
Protein type (PT) influenced solubility after addition of condensed tannins (P < 0.001) in the order: Rubisco < rapeseed < BSA (P < 0.05). The type of condensed tannin (CT) affected protein solubility (P = 0.001) with a CT × PT interaction (P = 0.001). Mean degree of polymerisation, proportions of cis- versus trans-flavanol subunits or prodelphinidins versus procyanidins among CTs could not explain precipitation capacities. Increasing tannin concentration decreased protein solubility (P < 0.001) with a PT × CT concentration interaction. The proportion of low-molecular weight rapeseed proteins remaining in solution increased with CT concentration but not with Rubisco.


CONCLUSIONS
Results of this study suggest that PT and CT type are both of importance for protein precipitation but that the CT structures investigated did not allow identification of parameters that contribute most to precipitation. It is possible that the three-dimensional structures of tannins and proteins may be more important factors in tannin-protein interactions.
Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences SLU, Kungsängen Research Centre, 753 23, Uppsala, Sweden.
Martin M
MM
Lorenz
Loy
L
Alkhafadji
Elisabetta
E
Stringano
Staffan
S
Nilsson
Irene
I
Mueller-Harvey
Peter
P
Udén
D000821:Animal Feed / Q000009:adverse effects*; D000818:Animals; D029741:Brassica rapa / Q000737:chemistry; D011232:Chemical Precipitation; D004044:Dietary Proteins / Q000737:chemistry* / Q000378:metabolism; D007887:Fabaceae / Q000009:adverse effects / Q000737:chemistry; D005285:Fermentation; D005638:Fruit / Q000009:adverse effects / Q000737:chemistry; D008954:Models, Biological; D015394:Molecular Structure; D008970:Molecular Weight; D009994:Osmolar Concentration; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D044945:Proanthocyanidins / Q000009:adverse effects / Q000737:chemistry* / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000378:metabolism; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology; D012418:Ruminants; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D013237:Stereoisomerism
D004044:Dietary Proteins; D010940:Plant Proteins; D044945:Proanthocyanidins; D012710:Serum Albumin, Bovine; D012273:Ribulose-Bisphosphate Carboxylase
Lab on Chip; Rubisco; bovine serum albumin; condensed tannins; flavanol composition; rape seed