Effect of potassium nitrate and urea as fermentable nitrogen sources on growth performance and methane emissions in local “Yellow” cattle fed lime (Ca (OH) 2) treated rice straw supplemented with fresh cassava foliage
Sixteen male local “Yellow” cattle with initial weight 63-100kg were fed lime-treated rice straw and fresh cassava foliage in a randomized complete block design (RCBD) with to two treatments: potassium nitrate or urea as NPN source. The NPN sources were dissolved in 100 g molasses diluted with 500 ml of water. The experiment lasted 120 days at the end of which concentrations of methane and carbon dioxide were determined in eructed gas mixed with aif in a closed chamber in which the animals were kept for 5 minutes prior to measurement of the gases so as to ensure equilibration of the eructed gases with the air in the chamber Daily live weight gain and DM feed conversion were improved by supplementation with nitrate rather than urea. There was no difference between treatments in DM intake. Feed intake as g DM/kg live weight and growth rate were linearly and positively related to initial live weight. The ratio of methane to carbon dioxide in the mixed eructed gas and air was decreased by feeding nitrate with an overall 25% reduction in methane emission, for animals fed nitrate compared with those fed urea. This is the first research to reportbetter growth rates and better feed conversion ratios when nitrate replaces urea in a low quality diet. This result mabe related to the pattern of feeding of the straw /molasses nitrate.diet which were given every 6 hours.
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