Effect of sodium bicarbonate supplementation on feed intake, digestibility, digesta kinetics, nitrogen balance and ruminal fermentation in young fattening lambs

Resum

Twenty-two Merino lambs (average weight=15.3 kg) were used to study the effects of inclusion of sodium bicarbonate in the concentrate on feed intake, digestibility, rate of passage, nitrogen balance and ruminal fermentation in vivo and in vitro. Lambs were allocated to two experimental groups receiving concentrate and 20 g kg-1 sodium bicarbonate (group Bic) or concentrate alone (group Control). Both groups received barley straw ad libitum. Faeces and urine were collected for 5 days to estimate digestibility, nitrogen balance and rate of passage. After slaughter (at 25 kg live weight), samples of rumen fluid were collected from each lamb to determine parameters of ruminal fermentation and to be used as inocula for batch cultures of rumen microorganisms. There were no significant differences between treatments (P>0.10) in concentrate intake, dry matter digestibility, nitrogen balance and digesta kinetics. However, straw intake was greater (P<0.05) and neutral- detergent fibre digestibility showed a tendency to be higher in the group Bic (P<0.10). No differences, due to the supplementation with sodium bicarbonate, were observed for in vivo pH, ammonia-N and volatile fatty acids concentrations (P>0.10). Results for rumen fermentation parameters determined in in vitro batch cultures and for fermentation kinetics estimated with the gas production technique followed a similar trend to results observed in vivo. Most parameters showed no significant differences between groups. Nevertheless, the extent of degradation of barley grain in vitro tended to be stimulated (P<0.10) by the use of sodium bicarbonate