TY - JOUR
T1 - Estimating passage kinetics using fibre-bound 15N as an internal marker
AU - Huhtanen, P.
AU - Hristov, A. N.
N1 - Funding Information:
The authors greatly acknowledge Drs. L. Rode and T. McAllister from Agriculture and Agri-Food Canada for the financial support of the animal trial from which the data for this study were derived.
PY - 2001/11/27
Y1 - 2001/11/27
N2 - Acid detergent insoluble N (ADF-N) is resistant to microbial and mammalian enzymes and natural labeling of ADF-N with 15N could provide an internal marker for digesta passage kinetics studies. Two late-lactation ruminally and duodenally cannulated Holstein cows were used to evaluate fibre-bound 15N as passage kinetics markers. The cows were fed ad libitum on 70% forage:30% concentrate diets based either on lucerne hay (LH) or lucerne silage (LS). A pulse dose of lucerne intrinsically labeled with 15N, applied as (15NH4)2SO4 fertilizer, was given in addition to lucerne in the diet. Duodenal (n = 17) and faecal (n = 14) grab samples were collected for 72 h. The samples were analyzed for 15N-enrichment of neutral detergent fibre-bound N (NDF-15N) and acid detergent fibre-bound N (ADF-15N). Kinetic parameters were estimated using two-compartmental models comprised of either two age-independent compartments (G1 → G1) or one gamma age-dependent and one age-independent compartment (Gn → G1, n = 2-4). The models with an age-dependency in the first compartment improved curve-fitting and explained on average 0.99 of the variation in NDF-15N and ADF-15N-enrichment. Total mean residence time (TMRT) of NDF-15N was shorter (P < 0.05) than that of ADF-15N (40.2 versus 47.0 h). This suggests that part of the available fibre-bound N (NDF-15N minus ADF-15N) was digested and therefore NDF-15N does not satisfy the requirements of an ideal passage kinetics marker. Pre-duodenal sites accounted for 0.91 of compartmental mean residence time (CMRT) estimated from faecal sampling, suggesting that pre-duodenal compartments accounted for the majority of the ascending phase of marker excretion curve. The values of time delay, CMRT and TMRT for ADF-15N of 7.7, 39.3 and 47.0 h were within the range reported for external markers for cows fed at similar level of DM intake. The results from this study suggest that ADF-15N has significant potential as an internal passage kinetics marker. As compared to the commonly used external markers ADF-15N has the advantage that it does not modify the digestibility or flow characteristics of labeled particles.
AB - Acid detergent insoluble N (ADF-N) is resistant to microbial and mammalian enzymes and natural labeling of ADF-N with 15N could provide an internal marker for digesta passage kinetics studies. Two late-lactation ruminally and duodenally cannulated Holstein cows were used to evaluate fibre-bound 15N as passage kinetics markers. The cows were fed ad libitum on 70% forage:30% concentrate diets based either on lucerne hay (LH) or lucerne silage (LS). A pulse dose of lucerne intrinsically labeled with 15N, applied as (15NH4)2SO4 fertilizer, was given in addition to lucerne in the diet. Duodenal (n = 17) and faecal (n = 14) grab samples were collected for 72 h. The samples were analyzed for 15N-enrichment of neutral detergent fibre-bound N (NDF-15N) and acid detergent fibre-bound N (ADF-15N). Kinetic parameters were estimated using two-compartmental models comprised of either two age-independent compartments (G1 → G1) or one gamma age-dependent and one age-independent compartment (Gn → G1, n = 2-4). The models with an age-dependency in the first compartment improved curve-fitting and explained on average 0.99 of the variation in NDF-15N and ADF-15N-enrichment. Total mean residence time (TMRT) of NDF-15N was shorter (P < 0.05) than that of ADF-15N (40.2 versus 47.0 h). This suggests that part of the available fibre-bound N (NDF-15N minus ADF-15N) was digested and therefore NDF-15N does not satisfy the requirements of an ideal passage kinetics marker. Pre-duodenal sites accounted for 0.91 of compartmental mean residence time (CMRT) estimated from faecal sampling, suggesting that pre-duodenal compartments accounted for the majority of the ascending phase of marker excretion curve. The values of time delay, CMRT and TMRT for ADF-15N of 7.7, 39.3 and 47.0 h were within the range reported for external markers for cows fed at similar level of DM intake. The results from this study suggest that ADF-15N has significant potential as an internal passage kinetics marker. As compared to the commonly used external markers ADF-15N has the advantage that it does not modify the digestibility or flow characteristics of labeled particles.
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U2 - 10.1016/S0377-8401(01)00297-8
DO - 10.1016/S0377-8401(01)00297-8
M3 - Article
AN - SCOPUS:0035960592
SN - 0377-8401
VL - 94
SP - 29
EP - 41
JO - Animal Feed Science and Technology
JF - Animal Feed Science and Technology
IS - 1-2
ER -