Evolution of chemical composition, nutritive value, and fatty acid content of sunflower (Helianthus annuus L.) during the growth cycle

Sunflower (Helianthus annuus L.) has been studied to determine the chemical composition, gross energy GE), in vitro organic matter digestibility (IVOMD), and fatty acid (FA) content of the plant during the growth cycle. Herbage samples were collected five times at progressive morphological stages from the stem extension to the late flowering stage. The evolution of the whole sunflower plant quality during growth was characterised by a progressive increase in the dry matter, neutral detergent fibre, and acid detergent fibre contents, while the ash, crude protein, and ether extract contents decreased from the stem extension stage to the mid flowering stage and then increased. GE was higher at the mid and late flowering stages than at the other stages. IVOMD decreased with increasing growth stage with a mean decrease of 6 g/kg OM/day. The FA analyses disclosed quantitative differences between the plant stages, which were characterised by a high percentage of polyunsaturated fatty acids (PUFA), that made up from 81% to 75% of the total FA of the plant during the growth cycle. The FA profiles in the plant were characterised by four dominant FAs: palmitic acid (C16:0), linoleic acid (C18:2 n-6), ?-linolenic acid (C18:3 n-3). and stearidonic acid (C18:4 n-3), which ranged from 10.0-12.8%, 16.4-21.8%, 54.9-44.6%, and 6.5-8.8% of the total FA, respectively.