Effects of growth stage and growing degree day accumulations on triticale forages: 1) Dry matter yield, nutritive value, and in-vitro dry matter disappearance

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin; Kalscheur, Kenneth; Brink, Geoffrey; CAVADINI, JASON - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2018
Publication Date: 9/18/2018
Citation: Coblentz, W.K., Akins, M.S., Kalscheur, K., Brink, G.E., Cavadini, J.S. 2018. Effects of growth stage and growing degree day accumulations on triticale forages: 1) Dry matter yield, nutritive value, and in-vitro dry matter disappearance. Journal of Dairy Science. 101(10):8965-8985. https://doi.org/10.3168/jds.2018-14868.
DOI: https://doi.org/10.3168/jds.2018-14868

Interpretive Summary: The use of triticale in dairy-cropping systems has expanded greatly in recent years, in part to improve land stewardship by providing winter ground cover. Our objectives were to establish relationships between various indices of nutritive value and the growth stage of triticale forages at harvest. Replicated plots were established following removal of corn silage or soybeans, and then harvested at various growth stages the following spring. Two key summary points are important: i) triticale forages are highly digestible at the stem elongation or boot stages of growth; and ii) the DM digestibility of triticale stabilizes, and may even increase, during grain fill. Although DM yields at boot stage were only about 30% of those at the soft-dough stage, an informed harvest-management decision for lactating cows may still favor a boot-stage harvest because of superior nutritional characteristics, a need to plant double-cropped corn expeditiously, or both. Harvest timing of triticale forages for other livestock classes requiring lower nutrient densities is more flexible, but prioritizing a subsequent double-crop of corn or soybeans may reduce effects on DM yield and/or synchronization of nutritive value with nutrient requirements for specific livestock classes to secondary considerations.

Technical Abstract: The use of triticale (X Triticosecale Wittmack) in dairy-cropping systems has expanded greatly in recent years, partly to improve land stewardship by providing winter ground cover. Our objectives were to establish relationships relating indices of nutritive value with growth stage or accumulated growing degree days (GDD) > 5oC for triticale forages grown in central Wisconsin. Replicated 3.7 × 9.1-m plots were established following removal of corn silage (Fall 2015) and soybeans (Fall 2016), and then harvested at various growth stages the following spring. Plants were assigned a numerical growth stage based on a linear staging system suitable for use as an independent regression variable. Response variables, such as DM yield, indices of nutritive value, as well as parameters from in-vitro DM disappearance kinetics were regressed on growth stage and GDD using linear, quadratic, cubic, or quartic models. For Spring 2016, the mean DM yield at the boot stage (3,804 kg DM/ha) was only 30% of that observed at the soft-dough stage of growth (12,642 kg DM/ha); although yields were reduced during Spring 2017, primarily due to spring flooding, the relationship between respective yields at these growth stages was similar (1453 vs. 5399 kg DM/ha). Regressions of DM yield (kg/ha) on growth stage for 2016 were explained by a cubic model (Y = 0.0663 x3 – 9.44 x2 + 595 x - 9810) compared to a simple linear response for 2017 (Y = 103 x – 3024); in both cases, coefficients of determination were very high (R2 = 0.934). Many nutritional and in-vitro DM disappearance characteristics were affected by the juxtaposition and balance of two generally competing factors: i) increased concentrations of structural plant fiber coupled with concurrent lignification as plants matured; and ii) the accumulation of highly digestible carbohydrate during seed-head development. A comparison of respective energy yields between the boot and soft-dough stages of growth for 2016 (2488 vs. 8141 kg TDN/ha) and 2017 (1033 vs. 3520 kg TDN/ha) suggests that yields of energy are greater at soft-dough, and mostly driven by DM yield. An informed harvest-management decision for lactating cows may still favor a boot-stage harvest because of superior nutritional characteristics, a need to plant double-cropped corn expeditiously, or both. Harvest timing of triticale forages for other livestock classes would appear to be more flexible, but prioritizing a subsequent double-crop may reduce effects on DM yield to a secondary consideration.