Effects of dietary forage-to-concentrate ratio and forage type on milk phospholipids and fatty acid composition of polar lipids.

The effects of grass silage and red clover silage on milk fatty acid (FA) composition are extensively studied, but little is known of their effects on minor lipid constituents of milk fat globule membrane. We investigated the effects of forage:concentrate (FC) ratio in grass silage-based diets and forage type (grass silage vs. red clover silage) on selected molecular species of milk phospholipids (PL) and the FA composition of PL.

Effects of Starch Level and a Mixture of Sunflower and Fish Oils on Nutrient Intake and Digestibility, Rumen Fermentation, and Ruminal Methane Emissions in Dairy Cows.

Four multiparous dairy cows were used in a 4 × 4 Latin square to examine how starch level and oil mixture impact dry matter (DM) intake and digestibility, milk yield and composition, rumen fermentation, ruminal methane (CH) emissions, and microbial diversity. Experimental treatments comprised high (HS) or low (LS) levels of starch containing 0 or 30 g of a mixture of sunflower and fish oils (2:1 /) per kg diet DM (LSO and HSO, respectively). Intake of DM did not differ between cows fed LS and HS diets while oil supplementation reduced DM intake.

The effect of dietary forage to concentrate ratio and forage type on milk fatty acid composition and milk fat globule size of lactating cows.

We examined the effects of 2 grass silage-based diets differing in forage:concentrate (FC) ratio and those of a red clover silage-based diet on intake, milk production, ruminal fatty acid (FA) biohydrogenation, milk FA composition, and milk fat globule (MFG) size distribution. Ten multiparous Nordic Red cows received the following treatments: grass silage-based diets containing high (70:30, HG) or low (30:70, LG) FC ratio or a red clover silage-based diet with an FC ratio of 50:50 (RC) on a dry matter basis. Determinations of MFG were performed from fresh milk samples without addition of EDTA so the results of fat globules >1 µm in diameter are emphasized instead of the entire globule population.

Dietary supplement of conjugated linoleic acids or polyunsaturated fatty acids suppressed the mobilization of body fat reserves in dairy cows at early lactation through different pathways.

To investigate the metabolic changes in the adipose tissue (AT) of dairy cows under milk fat depression (MFD), 30 cows were randomly allocated to a control diet, a conjugated linoleic acid (CLA)-supplemented diet, or a high-starch diet supplemented with a mixture of sunflower and fish oil (2:1; as HSO diet) from 1 to 112 d in milk. Performance of animals, milk yield, milk composition, energy balance, and blood metabolites were measured during lactation. Quantitative PCR analyses were conducted on the AT samples collected at wk 3 and 15 of lactation.

Diet-induced milk fat depression is associated with alterations in ruminal biohydrogenation pathways and formation of novel fatty acid intermediates in lactating cows.

The biohydrogenation theory of milk fat depression (MFD) attributes decreases in milk fat in cows to the formation of specific fatty acids (FA) in the rumen. Trans-10, cis-12-CLA is the only biohydrogenation intermediate known to inhibit milk fat synthesis, but it is uncertain if increased ruminal synthesis is the sole explanation of MFD. Four lactating cows were used in a 4×4 Latin square with a 2×2 factorial arrangement of treatments and 35-d experimental periods to evaluate the effect of diets formulated to cause differences in ruminal lipid metabolism and milk fat synthesis on the flow of FA and dimethyl acetal at the omasum.

Ruminal Infusions of Cobalt EDTA Modify Milk Fatty Acid Composition via Decreases in Fatty Acid Desaturation and Altered Gene Expression in the Mammary Gland of Lactating Cows.

Background: Intravenous or ruminal infusion of lithium salt of cobalt EDTA (Co-EDTA) or cobalt-acetate alters milk fat composition in cattle, but the mechanisms involved are not known.

Objective: The present study evaluated the effect of ruminal Co-EDTA infusion on milk FA composition, mammary lipid metabolism, and mammary lipogenic gene expression.

Methods: For the experiment, 4 cows in midlactation and fitted with rumen cannulae were used in a 4 × 4 Latin square with 28-d periods.

Dietary fish oil supplements modify ruminal biohydrogenation, alter the flow of fatty acids at the omasum, and induce changes in the ruminal Butyrivibrio population in lactating cows.

Four lactating cows fitted with ruminal cannulae and fed a grass silage-based diet were used in a 4 × 4 Latin square with 28-d periods to investigate the effects of incremental dietary fish oil (FO) supplementation (0, 75, 150, or 300 g/d) on the flow of fatty acids at the omasum and populations of rumen bacteria capable of biohydrogenation. FO decreased silage intake and ruminal volatile fatty acid concentrations and promoted an increase in molar butyrate and propionate proportions at the expense of acetate. Extensive ruminal biohydrogenation of 20:5(n-3) and 22:6(n-3) resulted in corresponding increases in numerous 20- and 22-carbon unsaturated fatty acids at the omasum.

Identification and ruminal outflow of long-chain fatty acid biohydrogenation intermediates in cows fed diets containing fish oil.

The abundance of 20- to 24-carbon fatty acids in omasal digesta of cows fed grass silage-based diets supplemented with 0 (Control) and 250 g/day of fish oil (FO) was examined to investigate the fate of long-chain unsaturated fatty acids in the rumen. Complimentary argentation thin-layer chromatography and gas-chromatography mass-spectrometry analysis of fatty acid methyl esters and corresponding 4,4-dimethyloxazoline derivatives prepared from fish oil and omasal digesta enabled the structure of novel 20- to 22-carbon fatty acids to be elucidated. Compared with the Control, the FO treatment resulted in the formation and accumulation of 27 novel 20- and 22-carbon biohydrogenation intermediates containing at least one trans double bond and the appearance of cis-14 20:1, 20:2n-3, 21:4n-3 and 22:3n-6 not contained in fish oil.