Troegeler-Meynadier A, Nicot M C, Bayourthe C, Moncoulon R, Enjalbert F
Ecole Nationale Vétérinaire, Département Elevage and Produits, Laboratoire d'Alimentation, 31076 Toulouse Cedex, France.
J Dairy Sci. 2003 Dec;86(12):4054-63. doi: 10.3168/jds.S0022-0302(03)74017-X.
Three experiments were conducted by in vitro incubations in ruminal fluid to investigate the effects of pH and amounts of linoleic and linolenic acids on the extent of their biohydrogenation, the proportions of conjugated linoleic acid (CLA) and trans-C18:1 as intermediates, and the ratio trans-10:trans-11 intermediates. The effects of pH and amount of linoleic acid were investigated in kinetic studies, and effects of the amount of linolenic acid were studied with 6-h incubations. With identical initial amounts of linoleic acid, its disappearance declined when the mean pH during incubation was under 6.0 compared with a mean pH over 6.5, and when the amount of linolenic acid increased from 10 to 180 mg/160-ml flask, suggesting an inhibition of the isomerization step of the biohydrogenation. Low pH decreased the ratio of trans-10:trans-11 intermediates. With initial amounts of linoleic acid increasing from 100 to 300 mg, the percentage of linoleic acid disappearance declined, but the amount that disappeared increased, without modification of the trans-10:trans-11 ratio, suggesting a maximal capacity of isomerization rather than an inhibition. Moreover, increasing initial linoleic acid resulted in high amounts of trans-C18:1 and an increase of C18:0 that was a linear function of time, suggesting a maximal capacity for the second reduction step of biohydrogenation. High amounts of initial linolenic acid did not affect the amounts of CLA, trans-C18:1, or the ratio trans-10:trans-11. Based on these experiments, a ruminal pH near neutrality with high amount of dietary linoleic acid should modulate the reactions of biohydrogenation in a way that supports CLA and trans-11C18:1 in the rumen.
通过在瘤胃液中进行体外培养开展了三项实验，以研究pH值、亚油酸和亚麻酸的量对其生物氢化程度、共轭亚油酸（CLA）和反式C18:1作为中间产物的比例以及反式10:反式11中间产物比例的影响。在动力学研究中考察了pH值和亚油酸量的影响，并用6小时培养研究了亚麻酸量的影响。在亚油酸初始量相同的情况下，与平均pH值超过6.5相比，当培养期间的平均pH值低于6.0时，其消失量下降，并且当亚麻酸量从10毫克/160毫升烧瓶增加到180毫克时，表明生物氢化的异构化步骤受到抑制。低pH值降低了反式10:反式11中间产物的比例。随着亚油酸初始量从100毫克增加到300毫克，亚油酸消失的百分比下降，但消失的量增加，而反式10:反式11比例未改变，表明异构化具有最大能力而非受到抑制。此外，增加初始亚油酸会导致大量反式C18:1以及C18:0随时间呈线性增加，表明生物氢化的第二步还原具有最大能力。大量的初始亚麻酸不会影响CLA、反式C18:1的量或反式10:反式11比例。基于这些实验，接近中性的瘤胃pH值与高量的日粮亚油酸应以支持瘤胃中CLA和反式11C18:1的方式调节生物氢化反应。
