Influence of chemical treatment of wheat straw on carbon–nitrogen and energy balance in sheep

Abstract

Energy balance studies through C–N balance were conducted on 15 adult male sheep of Muzaffarnagari breed. The animals weighing 42 kg were randomly assigned to three groups of five animals each and were fed ad lib wheat straw treated with urea (4 kg urea per 100 kg DM) with a storage time of 21 days (group I, control) or urea (1.5 kg per 100 kg DM) without storage time (group II) or urea plus calcium hydroxide (3 kg urea plus 3 kg calcium hydroxide per 100 kg DM) with a storage time of 21 days (group III). The cell wall and dry matter digestibility was higher ( P<0.05) in groups I and III than in group II. Results revealed that carbon balance in groups I and III was higher ( P<0.05) than that of group II. The losses of carbon through faeces as percent of carbon intake were significantly ( P<0.01) different among the groups with highest losses in group II and lowest in group III. Carbon losses in the form of carbon dioxide as percent of intake of carbon was higher ( P<0.05) in group II than that of groups I and III. The N balance was 1.67, 0.70 and 2.46 g/day in groups I, II and III, respectively, which differed significantly ( P<0.01) among these groups. The same trend was observed in protein deposition (g per day), energy storage in the form of protein (kJ per day) whereas, fat deposition (g per day) and energy storage in the form of fat (kJ per day) was lower ( P<0.01) in group II than those of groups I and III. The energy balance was +105, −31 and +161 kJ kg −1 W 0.75 per day in groups I, II and III, respectively. It was significantly ( P<0.01) higher in groups I and III than that of group II. It is concluded that treatment of wheat straw with urea and/or a mixture of urea and calcium hydroxide followed by storage can improve the dry matter and cell wall digestibility and utilisation of energy and nitrogen as compared to urea supplementation just prior to feeding.