Effect of particle size and exogenous enzymes on degradability of corn grain rehydrated and ensiled for a short time

Abstract Text: At times, farmers may be obligated to open the corn silo sooner then what is recommended, causing a shorter time of storage which can reduce the benefits of the ensiling process. Flint (FT) and floury (FL) corn of varying particle sizes are known to have altered degradability due to time of ensiling. Therefore, our objective was to evaluate two enzymes in a complete randomized design, with 12 treatments from the combination of two corns (FT and FL), two particle sizes (260 and 320cm²/g) and three enzyme combinations [amylase (A), protease (P), or both (AP)]. Each treatment was replicated in 5 bags. Silos were stored for one month in vacuum sealed bags and each bag contained 1kg of corn (75% DM). The enzyme concentration was 650g/t for A, 200g/t for P and their sum for AP. The weight, pH, and temperature were measured at time of bag opening. Samples were analyzed for DM, prolamin, and 18h in vitro degradability. Statistical analysis was performed using the MIXED procedure in SAS. At time point zero FL and FT had 29.86 and 30.48% DM with DM degradability of 32.0 and 33.8%, respectively. Among the three variables analyzed, there was a difference for hybrid on prolamin (4.30 and 5.32 g/100gDM; P < 0.001) and DM loss (- 0.56 and - 5.36% ensiled; P < 0.0001) for FL and FT, respectively. There was an enzyme effect for silo DM (P = 0.004), with the highest DM being 30.16% for AP, 29.93% for A, and 29.69% for P. Treatment AP had the smallest (P < 0.001) DM loss during the ensiling period (- 0.008% ensiled) when compared to A (- 2.575% ensiled) and P (- 6.297% ensiled). In addition, treatment AP had the lowest temperature at silo opening (21.77^oC P < 0.001). Enzyme A increased (P= 0.047) the rate of degradability from 3 to 7 h, represented by the smallest Kd (- 0.3312%/h) when compared to (- 0.2523%/h) P and (- 0.2581%/h) AP. In conclusion, degradability was not directly affected by corn processing or enzyme application. Rate of degradability was affected by enzyme application. Collectively, the results can be used in a strategy to control other variables that impact rehydrated corn grain silage quality.

Keywords: corn hybrid, dry corn silage, protease, amylase