Energy intake, heat production and energy and nitrogen balances of sheep and goats fed wheat straw as a sole diet

Large areas of the Negev desert are used for rain-fed winter cereal production. Consequently, cereal straw is an important dietary component of sheep and goats raised by the Bedouin in the Negev Desert under both grazing and pen-fed conditions. Often, it is the sole feed offered, although it is relatively low in crude protein content and metabolizable energy yield. We determined metabolizable energy intake and heat production in desert adapted fat-tailed Awassi sheep (n = 8; 49.5 +/- 6.6 kg) and mixed breed goats (it = 8; 42.6 +/- 11.7 kg) when offered only wheat straw ad libitum, and calculated their energy and nitrogen balances. We hypothesized that there is a difference between sheep and goats in the ability to use wheat straw and predicted that goats would be better able to use wheat straw as an energy and nitrogen source than would sheep. Dry matter intakes of the wheat straw by sheep and goats were Similar, 43.4 and 42.6 g kg(-0.75) d(-1), respectively, as were apparent dry matter digestibilities, 44.1% and 43.6%, respectively. Metabolizable energy intakes in sheep and goats were also similar, 308.9 and 302.9 kJ kg(-0.75) d(-1), respectively, as were their heat productions, 502.3 and 501.0 kJ kg(-0.75) d(-1), respectively. Sheep and goats were in negative energy balance. and both lost similar amounts of body reserves. 193.6 and 198.1 kJ kg(-0.75) d(-1), respectively. Also, both were in negative nitrogen balances: however, the goats were in a lesser deficit (P<0.05) than the sheep, 0.161 and 0.196 g kg(-0.75)d(-1), respectively. Therefore, our predictions were partially confirmed in that the goats were better able to use the nitrogen but not the energy when consuming low-quality wheat straw. (C) 2009 Elsevier B.V. All rights reserved.