Trans Fatty Acids and Bioactive Lipids in Ruminant Milk

Based on potential benefits to human health, there is increasing interest in altering the composition of ruminant-derived foods. Including rapeseeds in the dairy cow diet is an effective strategy for replacing medium-chain saturated fatty acids (SFA) with cismonounsaturated fatty acids (MUFA) in bovine milk, but there is limited information on the optimum level of supplementation. Decreases in SFA due to plant oils are also accompanied by increases in milk trans fatty acid (FA) content and it is possible that high oleic acid rapeseeds may result in a higher enrichment of cis-9 18:1 and lower increases in trans FAs in milk compared with conventional varieties. Seven multiparous lactating Holstein-Friesian cows were allocated to one of seven treatments in an incomplete Latin square design with five 28-day experimental periods, to evaluate the effect of replacing calcium salts of palm oil distillate (CPO; 41 g/kg diet dry matter, DM) with 128, 168 or 207 g/kg diet DM of conventional (COR) or a high oleic acid (HOR) rapeseed fed as a supplement milled with wheat. Rapeseed variety and inclusion level had no effect ( P . 0.05) on DM intake, milk yield and composition. Both rapeseed varieties decreased linearly ( P , 0.001) milk fat SFA content, which was partially compensated for by a linear increase ( P , 0.001) in cis-9 18:1 concentration. Reductions in milk SFA were also associated with increases ( P , 0.05) in trans 18:1 and total trans FA content, with no difference ( P . 0.05) between rapeseed varieties. Replacing CPO in the diet with milled rapeseeds had no effect ( P . 0.05) on total milk conjugated linoleic acid (CLA) concentration. Relative to a COR, inclusion of a high oleic acid variant in the diet increased ( P 5 0.01) the ratio of trans-MUFA : trans-polyunsaturated fatty acids in milk that may have implications with respect to cardiovascular disease risk in humans. In conclusion, data indicated that replacing CPO with milled rapeseeds at levels up to 1150 g oil/day could be used as a nutritional strategy to lower milk SFA content without inducing adverse effects on DM intake and milk production. HOR reduced milk fat SFA content to a greater extent than a conventional variety, but did not minimise associated increases in trans FA concentrations. However, the high oleic acid variant did alter the relative abundance of specific trans 18:1, CLA and trans 18:2 isomers compared with conventional rapeseeds.

Section: Kliem Shingfield Humphries and Givensmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Effect of replacing calcium salts of palm oil distillate with incremental amounts of conventional or high oleic acid milled rapeseed on milk fatty acid composition in cows fed maize silage-based diets

Kliem

Shingfield

Humphries

et al. 2011

“…Activity of SCD also contributes to approximately 90% of cis-9 14:1 and 50% to 56% of cis-9 16:1 in bovine milk fat (Mosley and McGuire, 2007). A number of other saturated acyl CoA also serve as substrates for SCD including 10:0, 12:0, 14:0, 15:0 and 17:0 (Bauman and Davis, 1974;Shingfield et al, 2008c). Endogenous synthesis via the action of SCD on trans-11 18:1 is responsible for 64% to 97% of cis-9, trans-11 CLA (Palmquist et al, 2005;Glasser et al, 2008b) and virtually all the trans-7, cis-9 CLA secreted in bovine milk (Palmquist et al, 2005).…”

Section: Mammary Lipogenesismentioning

confidence: 99%

Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

Shingfield

Bernard

Leroux

et al. 2010

Self Cite

327

427

Fat is an important constituent contributing to the organoleptic, processing and physical properties of ruminant milk. Understanding the regulation of milk fat synthesis is central to the development of nutritional strategies to enhance the nutritional value of milk, decrease milk energy secretion and improve the energy balance of lactating ruminants. Nutrition is the major environmental factor regulating the concentration and composition of fat in ruminant milk. Feeding low-fibre/high-starch diets and/or lipid supplements rich in polyunsaturated fatty acids induce milk fat depression (MFD) in the bovine, typically increase milk fat secretion in the caprine, whereas limited data in sheep suggest that the responses are more similar to the goat than the cow. Following the observation that reductions in milk fat synthesis during diet-induced MFD are associated with increases in the concentration of specific trans fatty acids in milk, the biohydrogenation theory of MFD was proposed, which attributes the causal mechanism to altered ruminal lipid metabolism leading to increased formation of specific biohydrogenation intermediates that exert anti-lipogenic effects. Trans-10, cis-12 conjugated linoleic acid (CLA) is the only biohydrogenation intermediate to have been infused at the abomasum over a range of experimental doses (1.25 to 14.0 g/day) and shown unequivocally to inhibit milk fat synthesis in ruminants. However, increases in ruminal trans-10, cis-12 CLA formation do not explain entirely diet-induced MFD, suggesting that other biohydrogenation intermediates and/or other mechanisms may also be involved. Experiments involving abomasal infusions (g/day) in lactating cows have provided evidence that cis-10, trans-12 CLA (1.2), trans-9, cis-11 CLA (5.0) and trans-10 18:1 (92.1) may also exert anti-lipogenic effects. Use of molecular-based approaches have demonstrated that mammary abundance of transcripts encoding for key lipogenic genes are reduced during MFD in the bovine, changes that are accompanied by decrease in sterol response element binding protein 1 (SREBP1) and alterations in the expression of genes related to the SREBP1 pathway. Recent studies indicate that transcription of one or more adipogenic genes is increased in subcutaneous adipose tissue in cows during acute or chronic MFD. Feeding diets of similar composition do not induce MFD or substantially alter mammary lipogenic gene expression in the goat. The available data suggests that variation in mammary fatty acid secretion and lipogenic responses to changes in diet composition between ruminants reflect inherent interspecies differences in ruminal lipid metabolism and mammary specific regulation of cellular processes and key lipogenic enzymes involved in the synthesis of milk fat triacylglycerides.Keywords: milk fat, trans fatty acids, gene expression, lipogenesis, ruminants ImplicationsUnderstanding the regulation of milk fat synthesis is central to the development of nutritional strategies to enhance the nutritional value of milk, decrease milk-energ...

“…Therefore, milk fat trans-10, cis-12 CLA concentration can be used to predict the expected extent of MFD contributable to the trans-10, cis-12 CLA isomer during dietinduced MFD (Peterson et al, 2003). Although there is a relationship between milk fat concentration of trans-10, cis-12 CLA and milk fat yield during diet-induced MFD, it is clear this CLA isomer only accounts for a modest portion of the MFD observed during most diet-induced MFD conditions (Peterson et al, 2003;Griinari and Bauman, 2006;Shingfield et al, 2008a). Furthermore, there is often little or no change in trans-10, cis-12 CLA in the milk fat when MFD is induced by feeding fish oils (reviewed by Shingfield and Griinari, 2007).…”

Section: Biohydrogenation Intermediatesmentioning

confidence: 99%

Recent advances in the regulation of milk fat synthesis

Harvatine

Boisclair

Bauman

2009

251

272

In addition to its economic value, milk fat is responsible for many of milk's characteristics and can be markedly affected by diet. Diet-induced milk fat depression (MFD) was first described over a century ago and remains a common problem observed under both intensive and extensive management. The biohydrogenation theory established that MFD is caused by an inhibition of mammary synthesis of milk fat by specific fatty acids (FA) produced as intermediates in ruminal biohydrogenation. During MFD, lipogenic capacity and transcription of key lipid synthesis genes in the mammary gland are down-regulated in a coordinated manner. Our investigations have established that expressions of sterol response element-binding protein 1 (SREBP1) and SREBP-activation proteins are down-regulated during MFD. Importantly, key lipogenic enzymes are transcriptionally regulated via SREBP1. Collectively, these results provide strong evidence for SREBP1 as a central signaling pathway in the regulation of mammary FA synthesis. Spot 14 is also down-regulated during MFD, consistent with a lipogenic role for this novel nuclear protein. In addition, SREBP1c and Spot 14 knock-out mice exhibit reduced milk fat similar to the magnitude and pattern of MFD in the cow. Application of molecular biology approaches has provided the latest chapter in the regulation of milk fat synthesis and is reviewed along with a brief background in nutritional regulation of milk fat synthesis in ruminants.