Effect of ensiling time and hybrid type on fermentation profile, nitrogen fractions, and ruminal in vitro starch and neutral detergent fiber digestibility in whole-plant corn silage

The objective of this study was to evaluate the effect of ensiling time and hybrid type on fermentation profile, N fractions, and ruminal in vitro starch (ivSD; 7 h) and NDF (ivNDFD; 30 h) digestibility in whole-plant corn silage (WPCS). Samples from 8 hybrids [4 leafy (LFY) and 4 brown midrib (BMR)] were collected at harvest, vacuum-sealed in plastic bags, and ensiled for 0, 30, 120 and 240 d. Starch and DM concentration were unaffected (P > 0.10) by ensiling time or hybrid type. Ethanol concentration and pH were greater (P = 0.01) for LFY than BMR, but lactate and acetate did not differ (P > 0.10). Soluble-CP concentrations tended (P = 0.09) to be greater for LFY than BMR, but ammonia-N and ivSD concentrations were unaffected (P > 0.10) by hybrid type. Measurements of lactate, acetate, and total VFA concentrations were greater (P < 0.01) for whole-plant corn silage fermented for 30, 120, and 240 d compared with unfermented samples. Gradual increases were observed (P = 0.001) from 0 to 240 d for soluble CP (33.5, 41.2, 48.9, and 54.5% of CP for 0, 30, 120, and 240 d, respectively) and ammonia-N (2.6, 4.6, 6.0, and 7.9% of N for 0, 30, 120, and 240 d, respectively). Likewise, ivSD measurements increased (P = 0.001) with ensiling time. The ivNDFD measurements were greater (P = 0.001) for BMR than LFY but were not affected (P > 0.10) by ensiling time. Positive relationships between ivSD and ammonia-N or soluble CP were observed (P = 0.001). Fermentation profile, ammonia-N, soluble CP, and ivSD were greatly influenced by ensiling time but minimally by hybrid type. The ivNDFD was affected by hybrid type but not ensiling time. Ammonia-N and soluble CP were good indicators of ivSD in whole-plant corn silage.