Effects of soybean oil supplement to diets of lactating dairy cows, on productive performance, and milk fat acids profile: a meta-analysis

摘要

The aim of this paper was to investigate the effects of soybean oil, an oilseed rich in the polyunsaturated fatty acid C18:2, on dry matter intake (DMI), milk yield (MY) and milk composition(including fatty acid profile) of dairy cows by using a meta-analysis approach. In the meta-analysis, effect size for all outcomes was reported as standardised means difference with 95% confidence intervals. Q test and I2 were calculated to detect the heterogeneity, with a metaregression also used to investigate sources of heterogeneity. Results of the meta-analysis indicated that adding soybean oil to the diet of dairy cows decreased DMI, milk fat percentage(MFP), milk fat yield (MFY) and milk protein percentage (MPP), whilst significantly increasing MY.Unsaturated fatty acids C18:2, C18:1 trans-11 and C18:2 cis-9 trans-11 conjugated linoleic acid(CLA) all significantly increased with soybean oil inclusion in the diet, whereas C18:3 was numerically higher but not significantly different. Milk composition, including MFP, MFY, MPP, shortchain and medium-chain fatty acids (C4–C20) and unsaturated fatty acids showed a significantpercentage of heterogeneity. Results of the meta-regression indicated that dose of soybean oil,total fatty acids in the diet, and the concentration of C18:2 between groups receiving soybeanoil and control are the most important factors affecting this heterogeneity. By performing metaanalysis and meta-regression it can be concluded that dietary supplementation of soybean oilto lactating dairy cows decreased DMI, and increased MY and the amount of unsaturated fattyacids in milk.