B. Demjanec et al., EFFECT OF ROASTING ON SITE AND EXTENT OF DIGESTION OF SOYBEAN-MEAL BYSHEEP .1. DIGESTION OF NITROGEN AND AMINO-ACIDS, Journal of animal science, 73(3), 1995, pp. 824-834
Six mature wethers (BW 72 kg) with ruminal, duodenal, and ileal cannul
as were fed a control (no added soybean meal [SBM]) diet or diets cont
aining unheated SBM or SBM roasted at 165 degrees C for 75, 150, 180,
or 210 min in a 6 x 6 Latin square experiment. Concentrations of indic
ators of heat exposure (ADIN, ADF, NDF) in SBM increased with increasi
ng roasting time. Duodenal flows of total N, non-bacterial N, and SBM
N increased (P <.05) linearly with increased roasting time. Small inte
stinal (SI) digestibility (percentage entering SI) of total N and SBM
N was influenced quadratically (P <.05) by roasting time; SI digestibi
lities were modestly increased by heating SBM to 150 min, then decline
d dramatically when SBM was heated for 180 and 210 min. These response
s resulted in a quadratic (P <.05) increase in quantity of total and S
BM N disappearing in the SI; quantities increased as SBM was heated to
150 min and remained unchanged when SBM was heated for 180 and 210 mi
n. These responses resulted in a quadratic (P <.05) increase in quanti
ty of total and SBM N disappearing in the SI; quantities increased as
SBM was heated to 150 min and remained unchanged when SBM was heated f
or 180 and 210 min. Duodenal flows and SI digestibilities of total and
non-bacterial amino acids (AA) and of most individual AA followed pat
terns similar to those observed for N. Maximum quantities of total and
individual AA disappeared from the SI when wethers were fed SBM roast
ed at 165 degrees C for 150 min. Evaluation of the effects of heat tre
atment on the nutritive value of a protein source for ruminants should
include considerations for both ruminal protein escape and SI availab
ility of escaped protein and for the nature of the AA supply absorbed
from the SI.