The objective of the study was to investigate the effects of oil sources in the diet on milk yield, milk composition, and fatty acid (FA) profiles in mid-lactating dairy cows. Forty-eight Chinese Holstein dairy cows averaging 150 days in milk (DIM) at the start of the experiment (body weight 0596919 kg; milk yield 029.793.00 kg/d) were used in a completely randomized block design. The animals were assigned into four dietary treatments according to DIM and milk yield, and supplemented with no oil (control), 2% flaxseed oil (FSO), 2% soybean oil (SBO), and 2% oil from extruded soybeans (ESB). The experiment lasted nine weeks including the first week for adaptation. Milk yields, milk compositions (fat, protein, and lactose), and milk FA profiles were measured. Daily milk yield from cows fed with FSO, SBO, and ESB were higher than milk yield of the control cows (27.0, 27.0, and 26.5 vs. 25.4 kg/d). Milk fat percentage of the control cows was greater than those cows fed with oil-supplemented diets. However, increasing dietary fat content resulted with no change in fat-corrected milk yield. The FA profile of milk was changed by fat supplementation. Feeding oil reduced the proportion of both short-chain (C 8:0 to C 12:0 ) and medium-chain (C 14:0 to C 16:1 ) FAs, and increased the proportion of long-chain (]C 18:0 ) FAs in milk fat. Cis-9, trans-11 conjugated linoleic acid (CLA) in milk fat was increased from 0.38% for the control to 0.79, 1.51, and 1.56% of fat for the cows supplemented with FSO, SBO, and ESB, respectively. Feeding oils rich in linoleic acid (SBO and ESB) was more effective in enhancing cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (FSO). There was a linear relationship between transvaccenic acid and cis-9, trans-11 CLA content in milk. Overall, feeding the FSO, SBO, and ESB diets increased monounsaturated and polyunsaturated fatty acids and decreased the saturated fatty acid in milk fat.

The evaluation from prospective cohort studies on the dietary ω-3 long-chain polyunsaturated fatty acid (LCPUFA) supplementation and nutritional value is consistent. However, the effect of different types of ω-3 long-chain PUFA (ω-3 LCPUFA) on microbiota in intestine is inconsistent. In this study, the mice were divided into three groups (N, PL, FO), with AIN-93M (N), AIN-93M + Phospholipids type ω-3 LCPUFA (PL) and AIN-93M + triglyceride type ω-3 LCPUFA (FO), respectively. Denaturing Gradient Gel Electrophoresis (DGGE) was used to detect the structure of intestinal microbiota. The data showed that the composition of gut microbiota was changed by treating with the two types of ω-3 LCPUFA. The results revealed that gut microbiota' enrichment in FO group was decreased while in PL group was increased. The data also showed that the histological morphology of the small intestine in treated mice was improved especially in group PL, which was much more significant and suggested that Phospholipids type ω-3 LCPUFA is beneficial to intestinal health.