The effect of steam-flaked and extruded full-fat soybeans on the concentration of conjugated linoleic acid in the milk fat of dairy cows

Abstract

Conjugated linoleic acid (CLA) is naturally produced in ruminants and exerts many beneficial health effects to humans. Feeding dairy cows with extruded soybeans has been reported to boost the CLA concentration in milk. However, the impact of steam-flaking soybeans on milk CLA content remains unknown. To study the potential of feeding steam-flaked soybeans on enhancing the CLA concentration in milk, a total of 27 Holstein lactating cows were fed with either conventional corn-soybean meal-based (control, CON) diet, steam-flaked full-fat soybean-based (SFS) diet or extruded full-fat soybean-based (ES) diet (nine cows per treatment) in an eight-week trial. Milk yield and other milk components were largely unaffected by dietary treatment. As compared with the CON diet, feeding SFS and ES diets resulted in an increase (p < 0.05) in the concentration of cis-9, trans-11 CLA from 0.76–1.00 and 0.98 g/100 g fatty acids in milk fat, respectively. Similarly, the concentration of trans-11 C_18:1 in milk fat also increased (p < 0.01) with feeding the SFS and ES diets. No statistical difference in either cis-9, trans-11 CLA or trans-11 C_18:1 concentration was observed between the SFS and ES diets. Collectively, our results suggest that, similar to extrusion, steam-flaking of full fat soybeans can increase milk CLA.

Keywords:

• dairy cows
• soyabeans
• extrusion
• flaking
• milk yield
• milk composition
• conjugated linoleic acid

Acknowledgements

This study was financially supported by the China Ministry of Agriculture 948 Project no. 2003-Z77. The authors acknowledge the staff of the Beef Cattle Research Center of China Agricultural University for their assistance in the feeding of dairy cows, sampling, and laboratory analyses.