High-Concentrate Diets and Polyunsaturated Oils Alter Trans and Conjugated Isomers in Bovine Rumen, Blood, and Milk

Abstract

Three Holstein cows were fed a high-concentrate diet (65:35 concentrate to forage) supplemented with either 5% sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) to examine effects on biohydrogenation and fatty acid profiles in rumen, blood plasma, and milk. Diets were fed in a 3 x 3 Latin square with 4-wk periods with grass hay as the forage. Milk yield, dry matter intake, and percentages of milk fat (2.64) and protein (3.22) did not differ. All diets resulted in incomplete hydrogenation of unsaturated fatty acids as indicated by the profiles of 18:1 isomers, conjugated 18:2 isomers, nonconjugated 18:2 isomers, and 18:0 in ruminal fluid. Percentages of 8:0-14:0 and 16:0 in milk fat were greater with FO. Percentage and yield of trans10,cis12-18:2 were small and greater in cows fed SO (0.14%, 0.57 g/d) than FO (0.03%, 0.15 g/d) or LO (0.04%, 0.12 g/d). Percentage and yield of trans10-18:1, however, increased with FO (6.16%) and SO (6.47%) compared with LO (1.65%). Dietary FO doubled percentage of cis11-18:1 in rumen, plasma, and milk fat. Despite a lack of difference in ruminal percentage of trans11-18:1 (10.5%), cows fed FO had greater plasma trans11-18:1 (116 vs. 61.5 microg/mL) but this response did not result in greater trans11-18:1 percentage in milk fat, which averaged 5.41% across diets. Percentage (2.2%) and yield (14.3 g/d) of cis9,trans11-18:2 in milk fat did not differ due to oils. Unique responses to feeding LO included greater than 2-fold increases in percentages of trans13+14-18:1, trans15-18:1, trans16-18:1, cis15-18:1, cis9,trans12-18:2 and trans11,cis15 -18:2 in umen, plasma, and milk, and cis9,trans13-18:2 in plasma and milk. Ruminal 18:0 percentage had the highest positive correlation with milk fat content (r = 0.82) across all diets. When compared with previous data with cows fed high-concentrate diets without oil supplementation, results suggest that greater production of trans10-18:1, cis11-18:1, and trans11,cis15-18:2 coupled with low production of 18:0 in the rumen may be associated with low milk fat content when feeding high-concentrate diets and fish oil. In contrast, SO or LO could lead to low milk fat content by increasing ruminal trans10-18:1 (SO) or trans11,cis15-18:2 and trans9,trans12-18:2 (LO) along with a reduction in mammary synthesis of 8:0-16:0. Simultaneous increases in ruminal trans11-18:1 with fish oil, at a fraction of sunflower oil supplementation, may represent an effective strategy to maintain cis9,trans11-18:2 synthesis in mammary while reducing milk fat output and sparing energy.

Soybean oil and linseed oil supplementation affect profiles of ruminal microorganisms in dairy cows

“…Supplemental oil in the diet of dairy cows changes the composition of milk fat and enhances the concentration of conjugated linoleic acid (CLA), which has been shown to have potential health benefits, including anticarcinogenic properties (Piperova et al, 2000;Roche et al, 2001;Loor et al, 2005a). Consumption of n-3 fatty acids also has been associated with positive effects on human health.…”

Effect of silage type and concentrate level on conjugated linoleic acids, trans-C18:1 isomers and fat content in milk from dairy cows

“…The effects of including oilseeds and plant oils with different PUFA profiles in high concentrate/low roughage diets on milk fat CLA concentration and milk fat depression have been thoroughly investigated [4,5,12]. Less well studied are the effects of commonly used forages differing in PUFA composition and starch content in combination with different levels of concentrate.…”

Effects of fish oil and starch added to a diet containing sunflower-seed oil on dairy goat performance, milk fatty acid composition andin vivoΔ9-desaturation of [13C]vaccenic acid

“…All the studies examining the contribution of endogenous RA synthesis have been conducted in lactating cows and involved either a chemical inhibition of the D9-desaturase enzyme by sterculic acid (5,34,35) , or a quantification of the duodenal or abomasal flow of VA and RA to estimate the endogenous synthesis of RA (6,7,13,21,36,37) , or a tracer methodology to allow direct measurement of the conversion of VA to RA in vivo (8) . These studies have provided clear evidence that endogenous desaturation of VA is the main source of milk fat RA in cows (with 64 -97 % RA coming from VA), but few of them provided an estimation of VA desaturation in the mammary gland: 25·7 (8) , 28·9 (6) , 19·8 (13) and 21 % (7) .…”