Forage production and nutritional value of silage of safflower (Carthamus tinctorius L.) varieties harvested at four phenological stages

Abstract

The aim was to study the forage yield and nutritional value of four safflower varieties harvested in four phenological stages. A completely randomized block design with a 4×4 factorial arrangement was used to evaluate two spineless varieties (FORRCART 2020 and Selkino) and two spiny varieties (Gila and Guayalejo) harvested at the beginning of capitulum formation (E50), capitulum clearly separated from the younger leaves (E55), distinguishable medium and intermediate external bracts (E59), and beginning of flowering (E60). Forage yield and nutritional value of the silage were determined in terms of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), net energy for lactation (NE_L), and in situ NDF and dry matter (DM) digestibility. The variety FORRCART 2020 had a DM yield similar to Gila and Guayalejo, which yielded more than Selkino. Dry matter yield increased as the phenological stage progressed from E50 to E61. The interaction between variety × harvest stages modified the nutritional value and the NDF digestibility of silage. Silage CP content of all varieties was reduced when maturity advanced from E50 to E61, but FORRCART 2020 presented the greatest decrease from E59. Similarly, the silage of the FORRCART 2020 variety had the largest drop of NE_L in E61. Silage NDF and ADF concentrations were higher in all varieties harvested in E61. The NDF digestibility was higher in the Selkino silage harvested at E50, but equal to other varieties harvested in the first three stages. Silage DM digestibility was different by the harvest stage, indicating a reduction of this as the crop's maturity progressed from E50 to E61. The spineless FORRCART 2020 variety had the same forage yield as the spiny varieties and the best silage nutritional value when harvested between E50 and E55.