Effects of harvest date and growth stage on triticale forages in the southwest United States: agronomic characteristics, nutritive value, energy density, and in vitro disappearance of dry matter and fiber

Recently, there has been increased interest in including triticale (X Triticosecale Wittmack) or other winter cereals within forage programs throughout the southwest United States. Our objectives were to screen 14 diverse triticale cultivars for agronomic and nutritive characteristics with specific emphasis on identifying normal, as well as deviant, responses to the calendar date and plant maturity for forages seeded in December and harvested from late February throughout May at Maricopa, AZ. Fourteen cultivars were established in a randomized complete block design with each cultivar represented within each of three field blocks. Plots were clean tilled and established on December 18, 2018, and then harvested at 2-wk intervals beginning on February 27 and ending May 23, 2019. Across all harvest dates, forage (N = 315) energy density (NEL) exhibited strong negative correlations with growth stage (r =  −0.879), plant height (r =  −0.913), head weight (r =  −0.814), and estimated dry matter (DM) yield (r =  −0.886) but was positively associated with percentages of leaf (r = 0.949), and weakly associated with percentages of the stem (r = 0.138). Through April 10, similar correlations were observed within individual harvest dates (N = 45) for growth stage, leaf percentage, and plant height but not for stem or head-weight percentages. Within later harvest dates, only sporadic correlations with NEL were observed. Primarily cubic regression relationships for neutral detergent fiber, acid detergent lignin, 30- and 48-h in vitro disappearance of DM and fiber, and NEL were fit for the mean or typical cultivar using both days from February 1 and growth stage as independent variables. Coefficients of determination (R2 ≥ 0.860) in all cases indicated a good fit for the polynomial models. For NEL, deviation from the typical cultivar when days from February 1 was used as the independent regression variable was largely affected by cultivar maturation rate. When the growth stage was substituted as the independent variable, plant height, stem percentage beginning at anthesis, and low grain-head percentage were associated with the maximum negative deviant cultivar (Merlin Max). The 0.23 Mcal/kg difference between maximum positive and negative deviant cultivars at a common late-boot/early-heading stage of growth suggests that some attention should be placed on cultivar selection as well as forage inventory needs and overall cropping goals.