Feeding Acacia saligna to Sheep and Goats with or without the Addition of Urea or Polyethylene Glycol

The objective of the research was to investigate the effect of polyethylene glycol (PEG) or urea supplementation in sheep and goats fed a basal diet of Acacia saligna and wheat straw. The 3 dietary treatments were: (1) Control: ad libitum A. saligna+ 400 g/d wheat straw (95% DM) (basal diet); (2) Basal diet+50 g/d PEG 4000; and (3) Basal diet+1% (on a DM basis) urea sprayed onto the straw and A. saligna 30 min prior to feeding. All animals maintained live weight, regardless of the dietary treatment. All sheep readily consumed the A. saligna in preference to straw. In sheep both DMD and OMD were higher (p<0.05) where PEG was included in the diet compared to the other two treatments. Contrary to findings by other researchers there was no significant difference in DMI, DMD or OMD between sheep and goats in corresponding treatment groups. All animals were in positive N balance. For both sheep and goats, rumen ammonia concentrations were increased with the use of either urea or PEG. In these groups the maximum ammonia concentrations exceeded 50 mg/L, considered the minimum required to maximise microbial growth. This threshold, however, was exceeded only for a period of 8-11 h. Of those measured, rumen ammonia levels were generally the highest at 4 h post feeding. None of the measurements of rumen ammonia for the control group approached 50 mg/L. It is unclear how and why feed intake and live weight were maintained when rumen ammonia levels were often sub-optimal.