alpha-Tocopherol and beta-carotene contents of forage species in a four-cut system

alpha-Tocopherol and beta-carotene concentrations were measured in herbage of birdsfoot trefoil (Bft), red clover (Rc), white clover (Wc), timothy (Ti) and perennial ryegrass (Pr) grown in four mixtures (Bft+Ti, Rc+Ti, Rc+Pr and Wc+Pr) in a small-plot field experiment at Foulum, Denmark, over 2 years. Plots were fertilized with cattle slurry and harvested in a four-cut system: 30 May/7 June, 5 July/12 July, 22 August/21 August and 24 October/9 October in 2005/2006. Bft was the legume with the highest alpha-tocopherol concentration in most harvests [86 mg kg(-1) dry matter (DM) averaged over all harvests of 2 years], whereas mean alpha-tocopherol concentrations in Wc and Rc were 37 and 34 mg kg(-1) DM respectively. Bft and Wc had higher beta-carotene concentrations than Rc when averaged over harvests and years (80, 67 and 44 mg kg(-1) DM in Bft, Wc and Rc, respectively; P<0.0001). Vitamin concentrations were similar in harvests 1-3, but in most sward treatments they were considerably higher in harvest 4. No clear differences were found between years. Averaged over years and harvests, mean alpha-tocopherol concentrations in timothy and perennial ryegrass were 46 and 50 mg kg(-1) DM, respectively, and mean beta-carotene concentrations were 54 and 62 mg kg(-1) DM. In conclusion, herbage of birdsfoot trefoil generally had higher vitamin concentrations than white or red clover, but differences between the two grass species were small and inconsistent.