MEKARN Conference 2010
The hypotheses that were tested in this experiment were:
· Calcium nitrate will support the same growth rate as urea when used as the source of rumen-fermentable N in diets based on sugar cane for growing goats.
Methane concentrations in the rumen gases of goats will be reduced when calcium nitrate is the N source compared with urea
The experiment was with 32 growing goats of 10 kg initial live weight and continued for 84 days at the end of which the ratio of methane to carbon dioxide. in expired air was determined using a “GASMET” analyser. Feeding was chopped sugar cane ad libitum and fresh cassava foliage at the rate of 1.5% of LW (DM basis). The treatments were:
Calcium nitrate or urea as the source of NPN
Sodium sulphate was added to both diets to give 0.4% of S in the diet. The urea/calcium nitrate was dissolved in water and sprinkled over the sugar cane. The sodium sulphate was given in the same solution. The levels of the NPN sources were fixed at 1.2% N in the diet DM equivalent to 5.0% calcium nitrate and 2.6% urea.
|Figure 1. Growth curves of goats fed calcium nitrate or urea as NPN sources in a basal diet of chopped sugar cane and fresh cassava foliage|
|Figure 2: Ratios of methane to carbon dioxide in rumen gas from goats fed sugar cane and fresh cassava foliage, with calcium nitrate or urea as source of NPN; results for goats fed the "normal" diet of grass and concentrates are shown for comparison|