Effect of Different Dietary Fatty Acid Profiles on Individual Milk Fatty Acid Yields by Dairy Cattle Fed Diets with Less than 3% Total Fatty Acids
Dietary fatty acid (FA) composition can affect milk fat yield but also relative yields of different FA. This study examined the effects on yield of individual milk FA resulting from different dietary FA profiles at FA levels below 3% of diet dry matter (DM). Trial design and production performance data were discussed in a 2013 ADSA abstract. Briefly, 60 cows were paired (within parity) to form 30 experimental units. Pairs were fed six diets in five 6x6 balanced Latin squares with 21-d periods. There were two control diets: a corn control diet (CC) containing 1.8% FA and a low oil control (LOC) containing 1.2% FA. A portion of the food grade corn starch in LOC was replaced with 1.7% diet DM of a 50/50 blend of corn and high linoleic safflower oils (CO), high oleic sunflower oil (OO), palm oil (PO), or 1.8% diet DM calcium salts of palm FA (ML, Megalac®) to create four treatment diets that were enriched in either linoleic (CO), oleic (OO), or palmitic acid (PO and ML). Milk FA composition was measured on d 20, and milk yield and fat concentration were measured for the last 5 d of each period; these data were combined to determine yield of individual milk FA. There were significant treatment effects on the yield of 31 out 53 milk FA measured including 10 out of 14 C18:1 isomers (P<0.05). Palmitic acid (C16) yield was lower for CO compared to other treatments (P<0.01) and C18:1 and total C18 yield were higher for OO when compared to PO and ML (P<0.01, P<0.01). Trans-10 C18:1 yield was higher for CO when compared to the other treatments (P<0.01) and for OO compared to PO and ML (P=0.01). Trans-10, cis-12 yield was also higher for CO when compared to all other treatments (P<0.01). Linear regression analysis was also conducted to examine the effect on milk FA yield of the increased dietary linoleic, oleic, and palmitic acid concentrations of the treatment diets over LOC. Dietary linoleic decreased short chain (<C16) and C16 FA yield (P=0.02, P<0.01), dietary oleic increased total C18 yield (P<0.01), and dietary palmitic increased C16 yield (P<0.01). These differences in milk FA profile are consistent with the idea that linoleic acid depresses short chain and C16 FA, resulting in milk fat depression even at dietary FA levels below 3%.
Milk Fat Depression
Milk Fatty Acid