Biohydrogenation of dietaryn-3 PUFA and stability of ingested vitamin E in the rumen, and their effects on microbial activity in sheep

Abstract

The present study investigated the susceptibility of dietary n-3 PUFA to ruminal biohydrogenation, the stability of ingested vitamin E in the rumen and the subsequent uptake of PUFA and vitamin E into plasma. Six cannulated sheep were assigned to six diets over five 33 d periods, in an incomplete 6 £ 5 Latin square. The diets, based on dried grass, were formulated to supply 50 g fatty acids/kg DM using three lipid sources: Megalac w (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK), linseed (formaldehyde-treated; Trouw Nutrition, Northwich, Ches., UK) and linseed-fish oil (formaldehyde-treated linseed þ fish oil). The diets were supplemented with 100 or 500 mg a-tocopheryl acetate/kg DM. Fat source or level of vitamin E in the diet did not alter microbial activity in the rumen. Biohydrogenation of linoleic acid (18 : 3n-6; 85 -90 %), linolenic acid (18 : 3n-3; 88 -93 %), docosahexaenoic acid (22 : 6n-3; 91 %) and EPA (20 : 5n-3; 92 %) was extensive. Feeding formaldehyde-treated linseed elevated concentrations of 18 : 3n-3 in plasma, whilst 22 : 6n-3 and 20 : 5n-3 were only increased by feeding the linseed -fish oil blend. Duodenal recovery of ingested vitamin E was high (range 0·79 -0·92 mg/mg fed). High dietary vitamin E was associated with increased plasma a-tocopherol (2·57 v. 1·46 mg/ml for 500 and 100 mg a-tocopheryl acetate/kg DM respectively), although all concentrations were low. Plasma vitamin E levels, however, tended to decrease as the type and quantity of PUFA in the diet increased. The present study illustrates that nutritionally beneficial PUFA in both fish and linseed oils are highly susceptible to biohydrogenation in the rumen. Although a-tocopheryl acetate resisted degradation in the rumen, plasma vitamin E status remained deficient to borderline, suggesting either that uptake may have been impaired or metabolism post-absorption increased.

The effect of fish oil supplementation of pregnant and lactating ewes on milk production and lamb performance

“…Although concentrations of C 18:2 (n-6) were lower in the diets containing fish oil compared with Megalac, proportionally, the reduction in plasma concentrations was higher, suggesting significant ruminal biohydrogenation of C 18:2 (n-6). This concurs with data presented by Chikunya et al (2004) and Sinclair et al (2005) in fish oil-supplemented sheep.…”

“…The increased amounts of C 16:0 observed in plasma of ewes offered Megalac concur with Petit (2002) who reported higher amounts of C 16:0 in plasma of dairy cows fed Megalac compared with linseed or soya beans. Addition of fish oil to the ruminant diet has been shown to increase the plasma concentrations of both C 18:1 trans isomers and CLA produced by incomplete ruminal biohydrogenation of PUFA (Baumgard et al, 2000;Wachira et al, 2000;Chikunya et al, 2004), results that concur with the increase in C 18:1 trans fatty acids conferred by fish oil supplementation within the current study. Although concentrations of C 18:2 (n-6) were lower in the diets containing fish oil compared with Megalac, proportionally, the reduction in plasma concentrations was higher, suggesting significant ruminal biohydrogenation of C 18:2 (n-6).…”

“…The significant increase in plasma C 20:5 (n-3) and C 22:6 (n-3) in ewes offered diets containing fish oil were a direct result of the increased dietary supply of preformed long-chain PUFAs. However, Wachira et al (2002) and Chikunya et al (2004) reported the presence of C 20:5 (n-3) and C 22:6 (n-3) within muscle and plasma fatty acids of sheep fed diets in which these fatty acids were not detected. The endogenous synthesis of C 20:5 (n-3) and C 22:6 (n-3) from C 18:3 (n-3) may therefore provide an explanation for the presence of long-chain n-3 PUFA within plasma of Megalac-supplemented ewes.…”

“…The combination of a low dietary supply of long-chain PUFA and the high level of PUFA biohydrogenation within the rumen (Wachira et al, 2000;Chikunya et al, 2004) may limit the quantities of these fatty acids available for absorption at the ovine small intestine. Nevertheless, Cooper et al (2004) demonstrated that feeding diets high in eicosapentaenoic acid (C 20:5 (n-3)) and C 22:6 (n-3) to growing lambs -E-mail: jlc268@cornell.edu.…”

Fatty acid profile and meat quality of young bulls fed ground soybean or ground cottonseed and vitamin E

“…Furthermore, some studies indicate that pre-intestinal vitamin E losses may be as high as 42% in sheep (Alderson et al, 1971) and up to 52% in cattle (Shin and Owens, 1990). There appears to be little evidence that vitamin E is absorbed across the rumen epithelium (Alderson et al, 1971;Hidiroglou and Jenkins, 1974) and rumen microorganisms are implicated as the main cause of vitamin E loss (Chikunya et al, 2004). There are eight different analogues (α-β-γ and δ-tocopherols and tocotrienols) designated as vitamin E, and α-(most abundant in animal tissues) and γ-(most abundant in plants) tocopherols has been mostly studied (Van Acker et al, 1993;Jiang et al, 2001).…”