The objective of this study was to investigate the effects of different corn silage : alfalfa silage ratios and full fat extruded soybeans on milk composition, especially that of conjugated linoleic acids content in milk fat and performance of dairy cows. Sixty Holstein cows were divided into 6 groups for a 12 week study. Treatments were arranged in a 2 × 3 factorial with 0 or 5% full fat extruded soybeans meal (dry matter basis) and three forage treatments (dry matter basis): (1) 13.5% corn silage, (2) 10.1% corn silage and 4.1% alfalfa silage, (3) 6.8% corn silage and 7.8% alfalfa silage. Full fat extruded soybeans addition increased the ether extract in diets and content of conjugated linoleic acids in milk, but it had no effect on fat, protein and lactose content in milk. Milk fat and lactose were not affected by replacing corn silage with alfalfa silage in diets. Increasing alfalfa silage content in the diets increased milk yield and milk content of conjugated linoleic acids and protein. Results from this study suggested that more alfalfa silage can be used in the diet of cow as a good source of forages.
Key words: Conjugated linoleic acid, alfalfa silage, corn silage, full fat extruded soybeans.
ADF, Acid detergent fiber; AS, alfalfa silage; BW, body weight; CLA,conjugated linoleic acid; CP, crude protein; CS, corn silage; DIM, days in milk; DM,dry matter; DMI, dry matter intake; EE, ether extract; ESB, full fat extruded soybeans; FA, fatty acids; FCM, fat collected milk; IVDNDF, in vitro digestible dry matter; NDF, neutral detergent fiber; SARA, subacute ruminal acidosis; SCC,somatic cell counts; SNF, solid not fat; TMR, total mixed ration; TVA, trans11-vaccenic acid.
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