Effects of Physical Form of Barley Straw and Urea Supplementation on Intake and Digestion of Sheep Kept Under High Ambient Temperature

This research was designed to examine the effect of both physical form of the roughage (chaff or ground/pelleted) and or urea supplementation on intake, and digestion by sheep fed barley straw housed at high ambient temperature (40C). The experimental design was factorial 2 x 2 x 4. Sixteen Merino sheep, weighing 26.3 ± 2.1 (SE) kg were randomized into four groups (n=4). Each group was fed one of the following diets: C = chaffed barley straw; CU= chaffed barley straw + 2% urea; P= ground/pelleted barley straw; PU= ground/pelleted barley straw + 2% urea, all with mineral and vitamin supplement. The interactions between treatments were significant on dry matter intake (DMI) (P<0.01) but were not significant on dry matter digestibility (DMD; P>0.05). Dry matter digestibility was lower on diet P than on C (33 vs. 41%), but was not affected (P<0.05) by urea supplementation. The digestible DMI (DDMI) was significantly affected by the interaction between treatments (P<0.01). It was concluded that while urea supplementation and grinding/pelleting led to increase in DMI, the actual response to urea was small and in the case of ground/pelleted material in the absence of urea, there was a concurrent reduction in DMD.