ABSTRACT
An evaluation of the effects of monensin and calcium propionate on the in vitro kinetics of gas production, digestibility, carbon dioxide, and minor gas production on different days was performed using the ruminal fluid from eight Suffolk lamb donors, after receiving additives for 1, 10, and 20 days. Treatments consisted of a control ration of 40% grain; 30 mg/kg of monensin in a diet with 40% grain; 10 g/kg calcium propionate in a diet with 30% grain; and the combination of both additives in a diet with 30% grain. The gas production was measured up to 72 h of incubation and all incubation procedures were repeated three times on days 1, 10, and 20. On incubation day 20, the volume and production of methane and minor gases were measured. There was an interaction between calcium propionate and monensin for maximum gas production, in vitro dry matter digestibility (IVDMD), carbon dioxide, and minor gases. Monensin reduced gas production on days 1 and 20, whereas calcium propionate increased gas production (Vm) on day 1. The rate of gas production (s) was reduced by calcium propionate on day 1 and by the combination of additives on day 10. Lag time was reduced by monensin on day 10; however, it declined linearly with the feeding time of the additives. Monensin had no effect on IVDMD (62.29 vs. 62.24%), while calcium propionate increased the IVDMD (60.00 vs. 64.53%). The inclusion of monensin increased CO2; however, the combination of monensin and calcium propionate had no effect on CO2 production. Monensin reduced methane (25.37 vs. 20.29%) and increased CO2. None of the additives showed consistent effects on the kinetic parameters of in vitro gas production over time. The treatments with monensin and calcium propionate showed a significant reduction in methane production, with a higher fermentation efficiency since the IVDMD was increased. Both additives are a strategy to consider to reduce methane emissions without affecting the ruminal fermentation.
Key Words:
additive feeding; carbon dioxide; ionophore; methane; rumen fermentation
