Nutritional Yield and Composition of Spiny and Spineless Varieties of Safflower (Carthamus tinctorius L.) Forage Harvested at Four Phenological Stages

Abstract

Background: Delaying harvesting in spineless safflower (Carthamus tinctorius L.) can increase dry matter (DM) yield, maintaining an acceptable nutritional composition. Objective: The objective of this study was to compare the forage potential of spineless safflower cultivars with that of spiny cultivars harvested in four phenological stages. Methods: The research was carried out during the 2017-2018 and 2018-2019 cycles in Matamoros, Coahuila, Mexico. Two spineless (CD868 and Selkino) and two spiny (Gila and Guayalejo) cultivars were evaluated. The phenological stages were: beginning of capitulum formation (E50), capitulum clearly separated from the younger leaves (E55), distinguishable medium and intermediate external bracts (E59), and beginning of flowering (E61). A randomized complete blocks design was used with four replications in a 4 × 4 factorial arrangement of treatments. Results: No interactions were found between phenological stages and cultivars. The spineless cultivars showed better or equal nutritional composition when compared to spiny cultivars but with better forage in E50. Yields of DM and nutrients increased when harvesting was delayed from E50 to E61, maintaining an acceptable nutritional composition. The highest yields of DM (10816 kg ha-1), crude protein (CP) (2071 kg ha-1), net energy for lactation (NEL) (52978 MJ ha-1 DM), and digestible DM (6350 kg ha-1) occurred in E61. Conclusion: Spineless cultivars harvested at stage E61 increased the forage potential with regards to the spiny cultivars harvested in E55, which did not have fully developed spines, due to their higher yields of DM (58%), CP (29%), NEL (39%), and digestible DM (41%).