Performance of dairy heifers fed whole-plant corn silage treated with benzohydrazide

The objective of this study was to evaluate the performance of dairy heifers fed whole-plant corn silage treated with benzohydrazide. At 26 and 43 d of plant emergence, corn crop was either kept as untreated (control; CON) or sprayed with a solution of benzohydrazide (BZD). Whole-plant corn from CON and BZD plots was mechanically harvested at 2/3 milk line stage and stored separately in bunker silos. After 2 mo of storage, the silages were fed to 24 Holstein heifers (333 ± 88 kg of shrunk body weight) for 60 d. Heifers were blocked by initial weight (12 blocks with 2 heifers each block) and housed in individual pens. Experimental TMR contained (DM basis) 85% whole-plant corn silage (CON or BZD) and 15% concentrate supplement. Intake of DM was measured daily, whereas shrunk body weight, hip height, and withers height were measured at the beginning and end of the experiment. Feeding behavior was recorded on d 15, 16, 36 and 37, total-tract digestibility was measured from d 18 to 22 and 39 to 43, and blood metabolites were determined on d 23 and 48. Intake, feeding behavior, blood metabolites, and digestibility outcomes were averaged by animal for the whole feeding period. Data were analyzed as a randomized complete block design. Initial DMI and shrunk body weight were used as covariates for analyses of intake and body measures, respectively. The DMI was lower for BZD (10.2 kg/d) compared with CON (11.0 kg/d), whereas ME intake and ADG were similar between treatments. Therefore, BZD increased feed efficiency by 11% (0.128 vs. 0.142). Compared with CON, BZD enhanced the total-tract digestibility of NDF (34.0 vs. 37.5%), CP (52.7 vs. 55.8%), and NFC (86.9 vs. 88.8%), and thereby DM digestibility (58.4 vs. 61.9%, respectively). Plasma urea concentration was lower in heifers fed BZD. In conclusion, animals consuming BZD-treated silage had greater in vivo digestibility of NDF, CP, NFC, and DM, which reflected in higher feeding value of corn silage for growing heifers.