The potential of sunflower as a crop for ensilage

The chemical composition and nutritive value of sunflower, cv. Armavirec, was examined at 12 stages of growth. Maximum yield of dry matter (18.2 t ha⁻¹) occurred at the dough seed stage. Ether extract showed a five‐fold increase with the development of the seed. This increase was reflected in the gross energy value which was maximal at 19.1 MJ kg⁻¹ dry matter at the dough seed stage. In‐vitro organic matter digestibility was highest at the onset of flowering when the estimated metabolisable energy value was 10.5 MJ kg⁻¹ dry matter. Throughout the sampling period the calcium to phosphorus ratios varied from 3.9‐5.9:1, an imbalance which would have to be redressed on diets based largely on sunflowers. Fresh and wilted sunflowers were successfully ensiled at the flowering stage, without the use of additives. pH values of the resulting silages were 3.86 and 4.01. The silages were each fed to six cross‐bred wethers and voluntary dry matter intakes were 23.9 and 26.5 g kgW⁻¹ for the fresh and wilted silages respectively. For the fresh silage, intakes of digestible organic matter and digestible nitrogen were 612 and 13.6 g day⁻¹ compared with 684 and 16.7 g day⁻¹ for the wilted silage. Nitrogen retention increased with increase in silage dry matter. The optimum time of cutting for yield of nutrients is at the milky ripe stage. The composition of the crop at this stage should facilitate a satisfactory preservation by ensiling. The crop provides a high yield of dry matter over about 10 weeks in late summer and could provide a valuable standby forage crop for grass in dry areas.