Lipolysis and Biohydrogenation of Soybean Oil in the Rumen In Vitro: Inhibition by Antimicrobials

Abstract

This experiment attempted to lower rumen lipolytic activity, biohydrogenating activity, or both using antimicrobial compounds. In vitro incubations were carried out with rumen fluid, 80 mg of soybean oil, and .5 g of commercial concentrates as substrate. Unless stated otherwise, the final concentrations of the additives in the incubation was 20 ppm. Lipolysis and biohydrogenation were determined by separation of triacylglycerols and FFA by TLC; the fatty acid composition of each was determined by GLC before and after incubation and with or without additive. With some of the antibiotics, lipolysis was inhibited 10 to 20%, and the most potent inhibitors were ionophores and amoxicillin. Biohydrogenation (including C18:1) decreased only for lasalocid, but no additive could prevent hydrogenation of linolenic acid liberated from triacylglycerols. Some additives decreased hydrogenation of linoleic acid, but only slightly. Lipolytic activity decreased VFA production more than the other potent additives (amoxicillin, avoparcin, lasalocid sodium, monensin, and salinomycin sodium). This result could indicate a more specific toxic effect on lipolytic microbes. Finally, different antimicrobials influenced fermentation patterns differently (VFA proportions and CH4 production), but shifts were always in accordance with stoichiometric principles.

Targets and procedures for altering ruminant meat and milk lipids

“…No intermediate production of partial acylglycerols has been demonstrated, and free FA form the major lipid fraction in rumen and duodenal lipids, even when high amounts of fat are fed. Lipolytic activity has been shown to be inhibited by pH values below 6 (Van Nevel & Demeyer, 1996c) and by antibiotics such as ionophores (Van Nevel & Demeyer, 1996a). From results of incubation of rumen contents with free soyabean oil (Van Nevel & Demeyer, 1996a, c), it can be calculated that on average 67 and 80 % of the linoleic and linolenic acids respectively were released from triacylglycerols, whereas 92 % of the released FA were recovered after incubation, suggesting some specificity of lipolysis.…”

“…Lipolytic activity has been shown to be inhibited by pH values below 6 (Van Nevel & Demeyer, 1996c) and by antibiotics such as ionophores (Van Nevel & Demeyer, 1996a). From results of incubation of rumen contents with free soyabean oil (Van Nevel & Demeyer, 1996a, c), it can be calculated that on average 67 and 80 % of the linoleic and linolenic acids respectively were released from triacylglycerols, whereas 92 % of the released FA were recovered after incubation, suggesting some specificity of lipolysis. At increasing rates of oil infusion into the rumen, the free FA : triacylglycerol and mono-: diunsaturated octadecenoic acid values in rumen total lipids and free FA respectively suggest that lipolytic activity is not limiting the rate of FA biohydrogenation in the rumen (Immig et al 1993).…”

Effect of storage on fatty acid profile of butter from cows fed whole or ground flaxseed with or without monensin

“…Monensin is known to decrease in vitro ruminal biohydrogenation of PUFA (Van Nevel & Demeyer, 1995) and to increase total CLA concentration in vitro (Fellner et al, 1997) and in milk of dairy cows (da Silva et al, 2007). Moreover, feeding ground compared with whole flaxseed increased concentrations of conjugated linoleic acid and cis3-18:3 in milk fat (da Silva et al, 2007).…”

Fontes de lipídio e monensina sódica na fermentação, cinética e degradabilidade ruminal de bovinos

“…A monensina parece atuar negativamente na proliferação de microrganismos lipolíticos (Van Nevel & Demeyer, 1995), o que pode causar diminuição da biohidrogenação ruminal. Por conseguinte, há aumento na quantidade de ácidos graxos insaturados no rúmen, o que pode prejudicar a degradação ruminal, principalmente em dietas com alto teor de grãos, assim como ocorreu neste estudo, em que a degradabilidade potencial da matéria seca foi menor para dietas com caroço de algodão e monensina.…”

“…Mesmo atuando nas bactérias gram-positivas, algumas bactérias gram-negativas podem mudar suas propriedades metabólicas em presença de ionóforos (Van Nevel & Demeyer, 1995). A lipólise ruminal é realizada por bactérias gram-negativas, sendo que a utilização de monensina, em dietas com adição de gordura, poderia reduzir a bio-hidrogenação.…”