• Asian-Australasian Journal of Animal Sciences
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• v.20 no.10
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• pp.1551-1556
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• 2007

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.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.9
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• pp.1367-1373
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• 2007

The aim of this study was to determine the feeding value to sheep of Acacia saligna grown under temperate conditions. Pen trials were undertaken to determine the effects of feeding A. saligna, which had been grown in a Mediterranean environment, on feed intake, nitrogen balance and rumen metabolism in sheep. Sheep were given ad libitum access to A. saligna with or without supplementation with PEG 4,000 or PEG 6,000. PEG 4000 appears to be the major detannification agent used in trials involving high tannin feed despite the fact that PEG 6000 has been shown to be more effective, in vitro. For this reason it was of interest to compare the two, in vivo. Dry matter intake was greater (p<0.05) in sheep supplemented with either PEG 4,000 or PEG 6,000 compared to the control. There was no difference, however, in intake between those supplemented with either PEG 4,000 or 6,000. Although animals were not weighed throughout the trial, a loss in body condition was obvious, in particular in the control group. Intake of N was greater (p<0.05) in sheep supplemented with either PEG 4,000 or PEG 6,000 than in the control. There was no difference in N intake between those supplemented with either PEG 4,000 or PEG 6,000. There were no significant differences in either the faecal or urinary N output between any of the treatment groups and all treatment groups were in negative N balance. Neither the average nor maximum pH of ruminal fluid of the control group was different to those supplemented with PEG. The minimum pH for the control group, however, was significantly higher (p<0.05) than for either of the PEG treatments. The average and the maximum ammonia levels were lower (p<0.05) in the control group compared with those in either of the PEG treatment groups. For all dietary treatments ruminal ammonia levels were well below the threshold for maximal microbial growth. Feeding A. saligna, without PEG, had a definite defaunating effect on the rumen. For all dietary treatments ruminal ammonia levels were well below the threshold for maximal microbial growth. It was concluded that A. saligna was inadequate as the sole source of nutrients for sheep, even with the addition of PEG 4,000 or PEG 6,000. The anti-nutritional effects on the animals were largely attributed to the excessive biological activity of the phenolics in the A. saligna leaves. There is a need to determine other supplements that may be complimentary with PEG to enhance the nutritive value of A. saligna to maintain a minimum of animal maintenance.