Recovered energy and efficiency of digestion in sheep and goats fed Atriplex nummularia compared to alfalfa hay

An experiment was carried out to examine differences between sheep and goats in utilizing forages varying in feeding value. Twenty four non-lactating females (Age=3.5 years; Barki sheep, n=12 and Balady goats, n=12) were individually housed in 1.0×1.5 m pens with sand floor for a 25-d period and then moved to metabolic cages. Animals of each species were offered either alfalfa hay or Atriplex nummularia foliage as sole diet for ad libitum consumption. Dry matter intake and digestibility were greater (P<0.001) for animals fed alfalfa hay than Atriplex nummularia. Intake of organic matter (g/kg metabolic body weight (BW0.75)/d) and gross energy (kJ/kg BW0.75/d) was greater (P<0.05) for goats than sheep. The significant interaction between forage type and animal species indicated that digestibility (%) of organic matter and energy was only greater for goats than sheep fed Atriplex nummularia, while no significant differences were observed between animal species when fed alfalfa hay. However, NDF digestibility was similar between both animal species fed either roughage. Energy expenditure (kJ/kg BW0.75/d) was similar between goats and sheep, and greater (P<0.001) for animals fed alfalfa hay than Atriplex nummularia. The significant interaction between forage type and animal species indicate that recovered energy (RE, kJ/kg BW0.75/d) was similar for both animal species when fed alfalfa hay, while it was greater for goats than sheep when fed Atriplex nummularia. It is concluded that apparent digestibility and RE were practically similar in sheep and goats when they consumed the high quality forage (i.e. Alfalfa), while low quality forage (i.e. Atriplex nummularia) was better utilized by goats than sheep.