Milk yield, milk composition, and hepatic lipid metabolism in transition dairy cows fed flaxseed or linola

Citation

do Prado, R.M., Palin, M.F., do Prado, I.N., dos Santos, G.T., Benchaar, C., Petit, H.V. (2016). Milk yield, milk composition, and hepatic lipid metabolism in transition dairy cows fed flaxseed or linola. Journal of Dairy Science (JDS), [online] 99(11), 8831-8846. http://dx.doi.org/10.3168/jds.2016-11003

Plain language summary

Addition of lipids contributes to increase dietary energy density during the periparturient period of dairy cows, but evidence exists that it increases plasma nonesterified fatty acid concentrations that, in turn, could increase hepatic triacylglycerol. The response of transition dairy cows to dietary supplementation with fat sources of various fatty acid profiles could affect hepatic fat metabolism differently. Flaxseed and linola, a new cultivar of flax, are rich sources of n-3 and n-6 fatty acids, respectively. The objective of this study was to compare the effects of feeding whole flaxseed and whole linola versus calcium salts of palm oil (i.e., Megalac) to transition dairy cows on milk production and hepatic metabolism. Milk yield was higher for cows supplemented with Megalac compared to cows fed whole flaxseed and whole linola. There was no treatment effect on blood parameters and hepatic glycogen. Hepatic lipids and triacylglycerol were lower for cows fed flaxseed and linola compared to those fed Megalac. It is concluded that feeding flaxseed (i.e., source of n-3 fatty acid) and linola (i.e., source of n-6 fatty acid) may improve the energy status, and lower hepatic lipids and triacylglycerol contents, which may contribute to enhance the health status of transition dairy cows.

Abstract

The response of transition dairy cows to dietary supplementation with fat sources of various fatty acid profiles could affect hepatic fat metabolism differently. Twenty-eight Holstein cows were blocked for similar calving date 4 wk before expected parturition to compare the effects of feeding sources of n-3 and n-6 fatty acids on milk production and composition, plasma metabolites, and liver parameters. Cows within each block were assigned to 1 of 3 isonitrogenous and isoenergetic diets: control with a source of calcium salts of palm oil (MEG; 1.1 and 2.6% of the dry matter in prepartum and postpartum diets, respectively); n-3 fatty acids supplied as whole flaxseed (WFL; 4.8 and 7.7% of the dry matter in prepartum and postpartum diets, respectively); and n-6 fatty acids supplied as whole linola (WLO; 4.8 and 7.7% of the dry matter in prepartum and postpartum diets, respectively). Diets were fed until wk 14 of lactation. Contrasts of WFL versus WLO and polyunsaturated fatty acids versus MEG were compared. Cows fed polyunsaturated fatty acids increased dry matter intake over time at a greater extent than those fed MEG, which resulted in enhanced energy balance. Cows fed MEG produced more milk compared with those fed polyunsaturated fatty acids, and there was no difference between those fed WFL and WLO. We found no effect on body condition score and body weight. Plasma concentrations of glucose, fatty acids, and BHB were similar among diets. There was no effect of diet on concentration of glycogen and activities of superoxide dismutase and glutathione peroxidase in the liver. We observed higher concentrations of hepatic lipids and triacylglycerol in cows fed MEG compared with those fed polyunsaturated fatty acids, and no difference between WFL and WLO. Hepatic catalase activity tended to be higher on wk 4 after calving for cows supplemented with WFL compared with those fed WLO. Feeding linoleic and linolenic acids as unprotected oilseeds increased dry matter intake over time at a greater extent for cows fed MEG, improved the energy status, and lowered hepatic lipids and triacylglycerol contents, which may contribute to enhance the health status of transition dairy cows.