A study of the nutritive value of white clover (Trifolium repens L.) in relation to different stages of phenological maturity in the primary growth phase in spring

This paper reports the effects of onset of phenological maturity on the nutritive value of white clover ( Trifolium repens L.). The study comprised (i) examination of an extensive data set on nutritive value and (ii) investigation of the constituents of nutritive value, in vivo feeding value, protein degradability and metabolizable protein content of white clover harvested at three stages of maturity (early-flowering, full-flowering, ripe seed stages) during the primary growth phase in spring in Australia. The data set on nutritive value showed a consistent pattern of high nutritive value during cool season months, progressive decline through spring and uniformly lower nutritive value over summer. Results from laboratory determinations, in sacco degradability studies and a digestibility trial on white clover harvested at early-flowering, full-flowering and ripe seed stages were consistent with results from the data set on nutritive value. Onset of maturity during the primary growth phase in spring was accompanied by large changes in nutritive value: neutral-detergent fibre (NDF) increased from 184 to 301 g kg^?1 dry matter (DM), nitrogen (N) declined from 36 to 20 g kg^?1 DM, in vitro digestibility declined from 0·74 to 0·65 and metabolizable protein content declined from 144 to 67 g kg^?1 DM from early-flowering to ripe seed stage. These nutritive value changes were accompanied by a decline of in vivo digestibility at the rate of 0·0032 d^?1 and an 0·2 reduction in voluntary intake.