| Summary: | 碩士 === 國立宜蘭大學 === 生物技術與動物科學系動物科學碩士班 === 101 === Methane energy produced from fermentation of substrate by rumen microbes can not be recycled for use, representing a waste of energy. Alteration of rumen fermentation pathway toward propionate production can consume hydrogen in the rumen and achieve the objective of methane reduction. Decreased methane production equates increased utilization of energy, and may decrease ruminal ammonia concentration. This is due to adequate energy for microbial utilization of ammonia.
Experiment 1 evaluated accuracy of an in vitro rumen fermentation technique to estimate methane production. Simulated diets with similar nutrient composition of domestic or foreign references were prepared. Ruminal gas production trend was monitored and continued by incubation for 24 hours. Results showed that gas production trend from simulated diets agreed with reference diets. Methane production was very similar on the diets with concentrate to forage ratio of 30/70 and 50/50. It appeared that estimated methane production by in vitro rumen fermentation technique had a high reliability. Great accuracy could be achieved in diets, which concentrate to forage ratio is 30/70 and 50/50.
Experiment 2 seperated, according to similarity in nutrient composition, feeds into groups to evaluate rumen fermentation characteristics on the commercial concentrates along with the addition of sodium fumarate in vitro (24 h). Commercial concentrates were groups of dry cow (TC and CLP), milking cow (FS, LC and SS) and high-producting dairy cow (IC, PF and TS), and additional sodium fumarate was 10 mM. Results showed that PF concentrate had lower methane and higher propionate production compared to TS concentrate. Concentrate PF might reduce methane production by increasing ruminal propionate concentration. Addition of sodium fumarate did not influence methane and ammonia production. Sodium fumarate might have been consumed completely before the end of incubation time (24 h). Nevertheless, addition of sodium fumarate enhanced rumen fermentation with elevated volatile fatty acids concentration.
Experiment 3 prepared total mixed ration (TMR) using PF or TS concentrate and evaluated in vitro rumen fermentation characteristics. Results showed that TMR by using PF concentrate still had lower methane and higher propionate production. Results showed similar trend same as in experiment 2. Even adding sodium fumarate (10 mM) to diets produced similar response (Experiment 4).
Experiment 5 used two concentrate (PF or TS, concentrate/forage= 50/50) diets combination with sodium fumarate (6 g/d) on an in vivo study to evaluate nutrient utilization by wether goats. In vitro methane production and animal dry mater intake were used to compute daily methane production (L/d). Goat fed PF concentrate diet had lower methane production. Similar trends were observed for methane production index. Such treatment differences are due to PF and TS diets similar animal intakes, but different methane production. Concentrate TS diet had higher total tract protein digestion, digestible protein intake, intake N and excreted N than PF concentrate diet. Besides, PF concentrate diet had lower blood urea N concentration, reflecting lower ammonia concentration in vitro. Addition of sodium fumarate increased protein digestion, digestible protein intake and excreted N by goats, with a trend towards increased nitrous oxide emissions.
The overall results of this study showed that in vitro rumen fermentation technique was relatively convenient, fast and accurancy approaches to estimation methane production in vitro. In terms of commercial cow concentrates, PF concentrate-made TMR decreased (2–4%) ruminal methane production by increasing propionate production, with decreased (10–15%) ammonia concentration. Such a diet could be appropriate for methane reduction. Adding sodium fumarate enhanced rumen fermentation (total volatile fatty acid increased by about 4%), but did not to reflect on animal performance and increase the cost of diet (2.7%) at same time. Therefore, how sodium fumarate affects methane production and nitrous oxide emissions by animals requires further investigation.
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