ENERGY AND NITROGEN BALANCES AS AFFECTED BY ANIMAL SPECIES AND INTAKE LEVEL UNDER DESERT CONDITIONS

Abstract

Thirty-two adult dry females, age 4-5 yrs.; Balady goats (n= 16 and average body weight 31.11 ± 1.63 kg) and Barki sheep (n= 16 and average body weight 34.53 ±1.56 kg) were used to study effects of long-term restricted feeding regime on body weight changes and balance of energy and protein. Animals of each species were allocated to two levels of feed intake; control feeding treatment (CON) where animals were fed a diet at a level of feeding to meet approximately the metabolizable energy for maintenance requirement (MEm), while those on the other dietary treatment was fed almost 50% of these quantities on a BW basis, termed as the restricted treatment (restricted; RES). Alfalfa hay and concentrate feed mixture (50:50% as DM basis) were given based on requirement recommendations. The results could be summarized as follows: The ADG was not affected (P<0.05) by animal species (BG vs. SH), however, it was affected (P<0.01) by feed intake level where the RES animal group showed a negative ADG (-65.6 g/d) compared with the CON group that achieved positive ADG (36.4 g/d). Both of SH and BG had similar negative energy balance (EB) values (67.0 vs. 61.4 KJ/ kg 0.75 /d, for BG and SH respectively). Nitrogen balance (NB) was greater (P<0.01) for SH (107.64 mg/kg 0.75 /d ) vs. BG (89.47 mg/kg 0.75 /d) and was greater (P<0.01) for animals fed on CON intake (251.47 vs. 208.55 mg/kg 0.75 /d, respectively) than those fed on RES intake (-36.18 vs. -29.62 mg/kg 0.75 /d, respectively), which gave a negative NB. It could be concluded that with desert conditions, sheep may have an advantage in a decreasing Metabolizable energy for maintenance (MEm) requirement and reduction in heat production of a magnitude adequate to maintain body weight. There is a similar rate of using the energy between sheep and goats with moderate or limited nutrition planes.