Abstract
High concentrate diets are fed to early and mid-lactation stages dairy ruminants to meet the energy demands for high milk production in modern milk industry. The present study evaluated the effects of a high concentrate diet on milk fat and milk composition, especially, cis-9, trans-11 CLA content in milk and gene expression of lactating goats. Eight mid-lactating goats with rumen fistula were randomly assigned into a high concentrate diet (HCD) group and low concentrate diet (LCD) group. High concentrate diet feeding significantly increased lipopolysaccharides (LPS) in plasma and decreased milk fat content, vaccenic acid (VA) and cis-9, trans-11 CLA in milk of the lactating goats. The mRNA expression levels of sterol regulatory element binding protein B 1c (SREBP1c), lipoprotein lipase (LPL), fatty acid synthetase (FASN) and acetyl-CoA carboxylase α (ACACA, ACCα) involving in lipid metabolism were analyzed, and ACACA and LPL all decreased in their expression level in the mammary glands of goats fed a high concentrate diet. DNA methylation rate of stearoyl-CoA desaturase (SCD) was elevated and decreased, and SCD mRNA and protein expression was reduced significantly in the mammary glands of goats fed a high concentrate diet. In conclusion, feeding a high concentrate diet to lactating goats decreases milk fat and reduced expression of SCD in the mammary gland, which finally induced cis-9, trans-11 CLA content in milk.
Highlights
Diet plays an important role in the modulation of fatty acid composition in ruminant products
Recent studies showed that induced SARA altered the milk fatty acid profile in dairy cows The milk fat percentage was decreased but milk protein increased in ruminants suffered from SARA, concentration of C18:0 and c9t11CLA decreased, and so on. [20, 21] In a recent study, we indicated that long-term SARA affected milk fatty acid composition [22]
LPS content in ruminal fluid tended to be elevated in the high concentrate diet (HCD) group, but, it was significantly increased in plasma (P
Summary
Diet plays an important role in the modulation of fatty acid composition in ruminant products. The types and proportion of fatty acids in food have different effects on human health maintenance and disease prevention [1]. Polyunsaturated fatty acids (PUFAs) are fatty acids containing two or more double bonds. In particular n-3 fatty acids, which first double bond is 3 carbons from the methyl end of the fatty acid chain, includes linolenic acid (LNA, C18:3n-3), eicosapentaenoic acid (EPA, C20:5n-3), docosapentaenoic acid (DPA, C22:5n-3) an
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