Ruminal and post-ruminal phytate degradation of diets containing rapeseed meal or soybean meal

• Published in: Archives of animal nutrition Vol. 76; no. 3-6; pp. 233 - 247
• Main Authors: Chi, Yung-Ping, Haese, Eva, Rodehutscord, Markus
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 02-11-2022; Taylor & Francis Ltd
• Subjects: Abomasum; Animal Feed - analysis; Animals; Blood plasma; Brassica napus; Brassica rapa; Cattle; Degradability; Degradation; Diet; Diet - veterinary; Dietary Proteins - metabolism; Digestion; Experiments; Female; Flour; Glycine max; Goats; Inositol; inositol phosphates; Inositols; InsP; Jejunum; Lactation; Male; Mathematical analysis; myo-inositol; Phytic acid; Phytic Acid - metabolism; Rapeseed; rapeseed meal; Rumen; Rumen - metabolism; ruminants; soybean meal; Soybeans; Titanium dioxide; soybean meal; ruminants; rapeseed meal; InsP6 degradation; inositol phosphates; myo-inositol
• ISSN: 1745-039X; 1477-2817
• DOI: 10.1080/1745039X.2022.2164158

This study aimed to investigate ruminal and post-ruminal degradation of phytic acid (InsP
6
) in diets containing either rapeseed meal (RSM) or soybean meal (SBM). In Experiment 1, the effective degradability of crude protein (CPED) and InsP
6
(InsP
6
ED) was evaluated by incubating RSM and SBM in situ in three rumen-fistulated lactating Jersey cows for 2, 4, 6, 8, 16, 24, 48 and 72 h, and calculating effective degradability at rumen passage rates of 2% and 5%/h. In Experiment 2, eight wethers were assigned for 8 weeks to two dietary treatments (Diet RSM and Diet SBM) containing 150 g of either meal and 100 g of maize silage per feeding time and had free access to hay and water. Titanium dioxide (TiO
2
) was added to the diets for the last 5 days of the study. The wethers were then stunned, exsanguinated and digesta from the reticulo-rumen, omasum, abomasum, jejunum, colon, and rectum were sampled. In Experiment 1, the InsP
6
ED of RSM (InsP
6
ED
2
: 83%; InsP
6
ED
5
: 64%) decreased almost identically to that of CPED with increasing passage rate (CPED
2
: 78%; CPED
5
: 63%) and was significantly lower than that of SBM (InsP
6
ED
2
: 93%; InsP
6
ED
5
: 85%). In Experiment 2, ruminal InsP
6
disappearance was significantly higher in wethers fed Diet SBM (89%) than in those fed Diet RSM (76%). Total post-ruminal InsP
6
degradation was 6% for Diet RSM and 4% for Diet SBM (p = 0.186). The total tract InsP
6
disappearance was higher in Diet SBM (93%) than in Diet RSM (82%). Considering higher InsP
6
contents in RSM, Diet RSM resulted in significantly higher amounts of ruminally (Diet RSM: 4.5 g/d; Diet SBM: 3.4 g/d) and total tract (Diet RSM: 4.9 g/d; Diet SBM: 3.5 g/d) degraded InsP
6
. InsP
5
was quantified in most of the digesta samples after feeding Diet RSM but was not detectable in the majority of digesta samples for Diet SBM. Concentrations of myo-inositol (MI) tended to be higher (p = 0.060) in the blood plasma of wethers fed Diet RSM. The consistency between ruminal InsP
6
disappearance in wethers and in situ calculated InsP
6
ED
2
, along with the very low extent of post-ruminal InsP
6
degradation, suggests that at a low rumen passage rate, InsP
6
-P from the feed becoming available to ruminants is almost entirely from InsP
6
degradation in the rumen.