359
Effect of delayed wrapping and wrapping source on intake and digestibility of alfalfa silage in sheep
Delays often occur between baling and wrapping during production of baled silage that increases exposure time of the forage to oxygen. This study was conducted to investigate the effect of two different wrapping sources and time intervals between baling and wrapping on intake and digestibility of alfalfa silage by gestating sheep. Alfalfa silage was baled in large round bales, and then wrapped with plastic either with or without an oxygen-limiting barrier; wrapping occurred either the day of baling, or 1, 2 or 3 days after baling. Beginning in January, silages were chopped and packed into plastic-lined trash containers, and then offered randomly for ad libitum consumption to 16 gestating ewes (n = 16; 63.5 ± 1.71 kg BW ) to provide 2 ewes 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. Ewes were housed in individual 1 x 1.5-m pens with plastic coated expanded metal flooring and were re-randomized to different treatments each period such that ewes were not offered the same treatment in any subsequent period. Data were analyzed using PROC MIXED of SAS for a 2 x 4 factorial treatment arrangement and orthogonal polynomial trend analyses were used to assess effects of time delay for wrapping after baling. Intakes of DM responded with linear, quadratic, and cubic effects (P < 0.05), while OM responded with linear and quadratic effects (P < 0.05) as wrapping was delayed after baling. Digestibility of DM and OM responded cubically (P < 0.05), that of NDF increased linearly (P < 0.05), and digestible DM and OM intake (g/kg BW) responded linearly, quadratically, and cubically (P < 0.05) with time delay between baling and wrapping. In general, intake and digestibility were greatest in silage wrapped the day following baling. Type of wrap tended (P = 0.10) to affect DM digestibility, and digestible OM intake was affected (P < 0.05) by the wrap type x wrapping time after baling interaction, but other intake and digestibility measurements were not affected (P≥ 0.15) by wrap type and the interaction of wrap and wrapping time after baling. Therefore, delaying wrapping alfalfa silage bales beyond 1 day after baling may have detrimental effects on energy status in gestating ewes. The study was supported in part by USDA-ARS specific cooperative agreement 58-3655-4-052.
Keywords: alfalfa silage; sheep; digestibility