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Site of Digestion in Dairy Cows Fed Different Soy-Protein Supplements

[ digestibility, lysine, expeller, roasted soybeans ]

Cannulated dairy cattle were used to evaluate the site and extent of digestion of various soy-protein supplements including solvent extract soybean meal (SSBM), expeller soybean meal (ESBM), nonenzymatically browned soybean meal (SoyPass), and whole roasted soybeans (WRSB).

 
Soya Protein Sources
 

SSBM

ESBM

SoyPass

WRSB

N intake, g/d

579

622

613

567

~ Passage to duodenum ~

NAN, g/d

467
514
564
498

NAN, % of N intake

81.6
85.2
95.8
88.1

NANMN, g/d

222
283
323
289

NANMN, % of N intake

40.0
47.4
56.0
51.0

Microbial N, g/d

245
227
236
209

Microbial N, g/kg OMTD

25.4
22.2
25.2
22.4

Total AA, g/d

2390
2478
2953
2640

Essential AA, g/d

1163
1179
1409
1279
Lysine, g/d
166
164
197
186
Methione, g/d
58
59
64
61

SoyPass delivered the highest percentage dietary protein the duodenum (NANMN) without having any negative impact on microbial synthesis. The net result was a higher level of essential amino acids delivered to the duodenum, particularly lysine, but also methionine.

I. R. Ipharraguerre, J. H. Clark, and D. E. Freeman, (2004), J Anim Sci 82, Suppl. 1, 214.