Structural composition and nutritional quality of wheat pasture subjected to two thermal sums as an interval between grazings

Abstract

To optimize productivity and prevent pasture degradation, management strategies such as the use of thermal sum (TS) to adjust grazing intervals can improve forage efficiency. The aim was to evaluate the effect of different TS as grazing intervals on the bromatological and structural composition of wheat cv. XFront®. The experiment followed a block design with repeated measures over time, with six plots and two treatments: T1) 330 TS and T2) 550 TS, in two years of evaluation. TS were defined by leaf emission speed, based on the phyllochron (110 days). The botanical (wheat) and structural composition was determined by manual separation of components. In general, management by TS did not influence (P > 0.05) the contents of dry matter (DM; 13.9%), organic matter (OM; 10.9%), in vitro dry matter digestibility (IVDMD; 65.7%), percentage of leaves (PL; 54.0%), or percentage of other species (POE; 9.7%). However, there was an effect of TS (P < 0.05) on the percentage of dead material (PDM; 7.7% vs. 10.4%), height (26.7 cm vs. 32.8 cm), dry matter yield (DMY; 9,369 vs. 7,305 kg/ha), and yield per cycle (DMC; 1,787 vs. 2,043 kg/ha) for TS 330 and TS 550, respectively. The variables crude protein (CP; 28.8% vs. 33.0%), hemicellulose (HEM; 23.4% vs. 23.7%), and percentage of stem plus sheath (PS; 24.5% vs. 29.9%) differed between years of evaluation. In conclusion, management with lower TS, i.e., shorter rest intervals, resulted in better nutritional quality of forage biomass, due to greater tissue renewal and reduced senescence.