Rumen-protected methionine and its relationship with milk fatty acid profile in high-producing dairy cows under different planes of dietary energy

Document Type


Publication Date



American Dairy Science Association


Journal of Dairy Science




Suppl. 1






methionine, fatty acids, milk fat


The aim of this trial was to determine the effect of methionine supple- mentation at 2 levels of dietary metabolizable energy (ME) on milk fatty acid (FA) profile of mid-lactation cows. A total of 112 multiparous Holstein cows (49.4 ± 5.3 kg/d of milk; 146.6 ± 68.2 DIM) from a com- mercial herd were blocked by lactation number, milk yield, and DIM. Cows were divided into 4 isoprotein (16.6% CP) diets: control (CON; 1.62 NEL Mcal/kg DM); high energy [HE; CON +1.2% of DM of hydro- genated fat (Prius F 100 Nat Dry, Auster)]; methionine (MET; CON + 24g of Smartamine M, Adisseo SA); and HE+MET. The experimental period was 38 d, and the first 3 d were used as a covariate with all cows fed the CON diet. TMR was provided once a day, with or without the addition of HE treatment, while MET treatments were top-dressed twice a day. Milk samples for FA profile were individually collected on d 36 of the trial and stored −20°C until further analysis. Milk samples were analyzed by gas chromatography to determine 52 FA profile (Finnigan Focus CG, Thermo Fisher ScientificTM). Data were analyzed using the MIXED procedure of SAS. The greater supply of MET improved milk fat concentration (4.13 vs. 3.87%; P < 0.01). Both HE (P = 0.015) and MET (P < 0.01) increased daily fat yield over CON (1.99 and 2.00 kg/d, respectively). There was no difference between treatments in proportion of De novoor mixed FA, but there was a trend (P = 0.10) for MET treatment to increase preformed FA (34.56 vs. 33.58 g/100g fat) and monounsaturated FA (25.13 vs. 24.25g/100g fat; P = 0.05) while decreasing PUFA (3.05 vs 3.44g/100d fat; P < 0.01). C10:0, C16:0, and C18:2cis9cis12 were reduced (P < 0.01) with MET, while C17:0iso, C18:1cis11, and C18:1cis13 were increased (P < 0.05). Higher intake of MET showed a trend (P = 0.07) to increase the C14:1/C14:0 ratio. No interactions were observed between HE and MET on FA profile. Changes observed in mono and polyunsaturated FA, as well as in the C14:1/C14:0 ratio, give us indications that MET may have some effect during the synthesis and modification of FA in the mammary gland.

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