ENERGY BALANCE UNDER RESTRICTED FEEDING IN RUMINANTS

Abstract

Forty-eight adult local desert non-pregnant and non-lactating females, age 4-5 yrs.; Barki sheep (n= 16 and average body weight 34.53 ±1.56 kg), Balady goats (n= 16 and average body weight 31.11 ± 1.63 kg), and Shami goats (n=16 and average body weight 28.08±0.92 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 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: 1-Comparison between Balady goats (BG) and Sheep (SH): 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/ kg0.75/d, for BG and SH respectively). Nitrogen balance (NB) was greater (P<0.01) for SH (107.64 mg/kg0.75/d ) vs. BG (89.47 mg/kg0.75/d) and was greater (P<0.01) for animals fed on CON intake (251.47 vs. 208.55 mg/kg0.75/d, respectively) than those fed on RES intake (-36.18 vs. -29.62 mg/kg0.75/d, respectively), which gave a negative NB. 2.Comparison between Balady goats (BG)and Shami goats (SG): The ADG was not affected (P< 0.05) by animal species (BG vs. SG) being corresponding values 45.1 and 40.6 g/d respectively. However, ADG was affected (P< 0.001) by feed intake level where the RES animal group showed a negative ADG (-55.6 g/d) compared with the CON group that achieved positive ADG (30.1 g/d). Under CON intake, EB was an insignificant decrease in SG compared to BG. However, under RES intake both BG and SG had a negative energy balance (kJ/kg0.75/day) and it was lower (P<0.01) in SG than that in BG. Animals fed on the CON intake level had a greater (P<0.01) value for EB compared to those fed on RES intake and the latter gave a negative balance. Nitrogen balance (NB, mg/kg0.75/day) was a trend to be greater (P<0.10) for SG vs. BG. Also, animals under the CON intake level captured more nitrogen than their counterparts, which lost a large amount of nitrogen. Also, the retention N was increased (P<0.01) in SG than BG under the CON intake level, however, all breeds were lost N under the RES intake level especially in SG (-76.37) followed by BG (-29.62). It could be concluded that with hot conditions, sheep may have an advantage in a decreased 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. It is clear that Balady goats are better than Shami goats in their ability to reduce the energy expenditure via reducing the rate of metabolism when they were fed on restricted intake.