PSI-27 - Effect of dietary unsaturated fatty acid ratio on milk performance, digestibility and serum index of dairy cows

Abstract: Our objective was to evaluate the effect of dietary unsaturated fatty acid radio on milk production, digestibility and serum index of dairy cows. Ten multiparous Holstein cows with two parity and similar milk in days (210 ± 10 d) were randomly divided into two groups. The two groups were fed two different unsaturated fatty acid (UFA) percentage (low unsaturated fatty acids: LUFA=35.5 ± 0.21%; high unsaturated fatty acids: HUFA=80.60 ± 0.50%) with similar fat content (59.5 ± 0.1 g of fat/ kg dry matter). The intake, digestibility, milk yield, milk composition, milk fatty acid and serum index were analyzed using t test in SAS version 9.4 software (SAS Institute Inc., Cary, NC, USA). The results showed that dry matter intake (DMI) in HUFA group was significantly lower than that in LUFA group (P < 0.05), but the milk yield and nutrient apparent digestibility were not affected between two group (P > 0.05). The milk fat rate, milk protein rate, milk fat yield, 3.5 % fat corrected milk (FCM) and energy corrected milk (ECM) in HUFA group were significantly lower than that in LUFA group (P < 0.05). Furthermore, the concentration of C13:0. C18:0, C18:1n9c, C18:2n6c, C18:3n3, CLA-c9t11 CLA-t10c12, C20:0, C20:1, ΣUFA, ΣCLA, ω-3 polyunsaturated fatty acid (PUFA), and ω-6 PUFA of milk in HUFA group was higher compared with LUFA group (P < 0.05). In contrast, the concentration of C16:0, C16:1, C20:3n6 and the ratio of ω-6 to ω-3 PUFA were lower in the HUFA group than that in LUFA group (P < 0.05). The blood urea nitrogen (BUN) and alkaline phosphatase (ALP) content in HUFA group were significantly decreased compared with LUFA group (P < 0.05). These results indicated that increasing the proportion of UFA in the diet reduced milk fat rate but did not decrease milk production. Meanwhile, the content of UFA was higher and fatty acid profile was more in line with human needs.