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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #120763
Title: PREDICTING THE EFFICIENCY OF RUMINAL MICROBIAL PRODUCTION OF SILAGE-BASED DIETS

Author
item Blummel, Michael
item SUDEKUM, K - UNIVERSITY OF KIEL
item Grings, Elaine

Submitted to: Proceedings of the Society of Nutrition Physiology
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2001
Publication Date: 4/1/2001
Citation: BLUMMEL, M.R., SUDEKUM, K.H., GRINGS, E.E. PREDICTING THE EFFICIENCY OF RUMINAL MICROBIAL PRODUCTION OF SILAGE-BASED DIETS. PROCEEDINGS OF THE SOCIETY OF NUTRITION PHYSIOLOGY. 2001. v. 10. p. 31.

Interpretive Summary: It has been suggested that the efficiency of microbial production (EMP) for forage diets can be predicted by combined in vitro gas volume and true substrate degradability (TSD) measurements conducted after 24 h of incubation. In forage fermentation 1 ml of gas was associated with the requirement of 2.2 mg of carbon (C), hydrogen (H) and oxygen (O) for the formation of the SCFA-GAS complex (=stoichiometrical factor SF) and substrate degraded above SF requirements was available for microbial biomass production (MBP). In vitro EMP can then be estimated as: EMP = 1 - [(gas volume x SF)/TSD]. For the present work 4 silage-based diets were analysed by this approach and the in vitro results compared with renal allantoin excretion in steers fed the 4 diets. The results obtained from this work show that the suggested in vitro approach can be improved in two ways. First, in silages attention needs to given to the fermentation acids (FS) in that EMP is corrected as follows: EMP = 1 - [(gas volume x SF)/(TSD-FS)]. Second, differences in the in vitro microbial growth kinetics need to be acknowledged and EMP should be examined at substrate-specific times, rather than uniformly after 24 h of incubation. This can be achieved by examining EMP at time t1/2 which was defined as the halftime of asymptotic gas production in the exponential model =B (1-exp (-c(t-lag))). EMP can then be estimated as: EMP = 1 - [(gas volume at t1/2 x SF)/(TSD at t1/2 -FS)].

Technical Abstract: It has been suggested that the efficiency of microbial production (EMP) for forage diets can be predicted by combined in vitro gas volume and true substrate degradability (TSD) measurements conducted after 24 h of incubation. In forage fermentation 1 ml of gas was associated with the requirement of 2.2 mg of carbon (C), hydrogen (H) and oxygen (O) for the formation of the SCFA-GAS complex (=stoichiometrical factor SF) and substrate degraded above SF requirements was available for microbial biomass production (MBP). In vitro EMP can then be estimated as: EMP = 1 - [(gas volume x SF)/TSD]. For the present work 4 silage-based diets were analysed by this approach and the in vitro results compared with renal allantoin excretion in steers fed the 4 diets. The results obtained from this work show that the suggested in vitro approach can be improved in two ways. First, in silages attention needs to given to the fermentation acids (FS) in that EMP is corrected as follows: EMP = 1 - [(gas volume x SF)/(TSD-FS)]. Second, differences in the in vitro microbial growth kinetics need to be acknowledged and EMP should be examined at substrate-specific times, rather than uniformly after 24 h of incubation. This can be achieved by examining EMP at time t1/2 which was defined as the halftime of asymptotic gas production in the exponential model =B (1-exp (-c(t-lag))). EMP can then be estimated as: EMP = 1 - [(gas volume at t1/2 x SF)/(TSD at t1/2 -FS)].