Effect Of Different Ratios Of Short-Medium Chain Fatty Acids To Long Chain Fatty Acids On Milk Fat Content And Composition In Lactating Dairy Cow

This study evaluated different ratios of SMCFA to LCFA, which have equivalent fatty acids (FA)proportions to those in milk, on milk fat synthesis. Thirty-six Holstein cows (183±46DIM) wereblocked by average daily milk yield, DIM, and parity, and randomly assigned to1of3treatments, witheach treatment having12cows. Cows in treatments were supplemented with80g/d SMCFA mixtureand320g/d LCFA mixture (20SM80L, ratio of SMCFA to LCFA was20:80);400g/d of butterfat(40SM60L, ratio of SMCFA to LCFA provided was40:60);240g/d SMCFA mixture and160g/d LCFAmixture (60SM40L, ratio of SMCFA to LCFA was60:40). The FA composition of the SMCFA mixture(a blend of6%caproic acid,4%caprylic acid,9%capric acid,10%lauric acid,32%myristic acid and39%palmitic acid, by weight percentage) and of the LCFA mixture (a blend of59%cocoa butter,16%olive oil, and25%palm oil, by weight percentage), were similar to the de novo synthesized fatty acids(except C4:0) and preformed fatty acids (except trans fatty acids) found in the butterfat, respectively.Fatty acids supplements and butterfat were consumed by cows daily before the morning feeding duringthe9wk experimental period.1. The effects of different ratios of SMCFA to LCFA on performance and rumen fermentation resultsshow that, dry matter intake, milk yield,3.5%FCM, ECM, ECM/DMI were not different among thetreatments. Milk fat percentage tended to be increased in a linear fashion, and milk total solidsproportion was increased linearly by the increasing ratios of SMCFA to LCFA in the supplements, whilemilk fat yield, milk protein concentration and yield, milk lactose concentration and yield, and solid-notfat concentration were not changed. The pH value, NH3-N, butyrate, isobutyrate, isovalerate andvalerate content were not different in the treatments. Acetate, propionate, and total VFA concentrationwere increased as the increasing ratio of SMCFA to LCFA in the supplements, however, the differenceswere not significant, and acetate: propionate was not influent.2. The effects of different ratios of SMCFA to LCFA on milk fat fatty acids composition and yieldresults show that, total SMCFA concentration in milk fat tended to be increased in a linear fashion bythe increasing ratios of SMCFA to LCFA in the supplements, while the yield was not changed. As theratios of SMCFA to LCFA increased, LCFA and C16:0concentrations and yields were not changed,C14:0concentration was increased linearly. Content and yield of PUFA and total≥C20:0were increasedquadratically (the highest was40SM60L), however, the difference of PUFA yield was not significant.3. The effects of different ratios of SMCFA to LCFA on dairy cow lipids metabolism in blood showthat, as the ratios of SMCFA to LCFA increased, LCFA, PUFA and SFA in blood were changedquadratically, LCFA and PUFA were highest in40SM60L, and SFA was the lowest. C16:0and SMCFAwere not different in the treatments. High-density lipoprotein cholesterol, very low density lipoproteincholesterol and insulin were increased quadratically (the highest were40SM60L) by the increasing ratios of SMCFA to LCFA, growth hormone was increased in a linear fashion, but not significant.Glucose, triglycerides, low density lipoprotein, phospholipids, and NEFA were not different in thetreatments.To conclude, different ratios of SMCFA to LCFA have no effect on DMI, milk fat yield and rumenfermentation. As the ratios of SMCFA to LCFA increased, milk fat concentration and total concentrationof SMCFA in milk fat were increased linearly, and milk fatty acids composition and lipid metabolismwere changed. We suggest that dietary supplementing SMCFA might contribute more than LCFA tomilk fat synthesis.