This is a draft schedule. Presentation dates, times and locations may be subject to change.
109
Effect of Delayed Wrapping and Wrapping Source on Nitrogen Balance and Blood Urea Nitrogen in Gestating Sheep Offered Alfalfa Silage
Exposing ensiled forage to oxygen can result in dry matter deterioration and reduce silage intake by animals. This study was conducted to investigate the effects of two different wrapping sources and time intervals between baling and wrapping on N balance and blood urea N in gestating sheep offered alfalfa silage. Alfalfa forage was baled in large round bales then wrapped in stretch plastic film with (KURA) or without (SUN) an oxygen-limiting barrier embedded in the plastic wrap. Bales were wrapped on the day of baling, or after a 1-, 2-, or 3d delay. Beginning in January 2016, silages were chopped and packed into plastic-lined trash containers, then offered randomly for ad libitum intake to 16 gestating ewes (63.5 ± 1.71 kg BW) to provide 2 observations per treatment for 3 experimental periods. Each period consisted of a 10-d dietary adaptation period followed by 7 d of total fecal and urine collection. Blood samples were harvested the last day of each period immediately prior to feeding and 4 and 8 h after feeding. Data were analyzed using PROC MIXED of SAS for a 2 × 4 factorial arrangement of treatments, while blood data were treated as repeated measures. No interactions were detected (P ≥ 0.05) between wrap type and time delay after baling for N balance and BUN. Retained N (% of N intake and % of absorbed N) was greater (P < 0.05) from silage wrapped with KURA. Nitrogen absorption (%) and N apparently absorbed (g/d) decreased linearly (P < 0.05) as wrapping was delayed after baling. Total N intake (g/d, g/kg BW), urinary N (g/d) and N retained (g/d, g/kg BW) were not affected (P ≥ 0.05) by wrap type and time delay between baling and wrapping. Concentrations of BUN (mg/dL) were affected quadratically (P < 0.05) by delay between baling and wrapping and were greater (P < 0.05) 4 h after feeding than immediately prior to feeding. In general, wrap type and time delay after baling affected N utilization, but N intake and N excreted in urine were not affected by wrap type and time delay after baling. Therefore, delaying wrapping alfalfa silage bales after baling may have negative effects on forage protein utilization by animals.
The study was supported in part by USDA-ARS specific cooperative agreement 58-3655-4-052.