The in vitro rumen fermentation method in which gas production and microbial mass production are concomitantly measured has several major advantages:
i) it has the potential for screening a large number of feed resources, for example in breeding programmes for the development of varieties and cultivars of good nutritional value,
ii) it could also be of great value in the development of supplementation strategies using locally available conventional and unconventional feed constituents to achieving maximum microbial efficiency in the rumen;
iii) it has an important role to play in the study of rumen modulators for increasing efficiency of microbial protein synthesis and decreasing emission of methane, an environmental polluting gas, and
iv) it provides a better insight into nutrient-antinutrient and antinutrient-antinutrient interactions, and into the roles of various nutrients (by changing the composition of the incubation medium) with respect to production of fermentative gases, SCFA and microbial mass.
The method is also being used increasingly to screen plant-derived rumen modulators. These products have a lower toxicity to animals and humans, and are environment friendly. Consequently, they are becoming increasingly popular with consumers. Further studies are required on:
i) the development of simple approaches for identifying the incubation time in the in vitro gas system at which the PF (a measure of the proportion of fermented substrate which leads to microbial mass production) is maximum,
ii) the effect of nitrogen in the incubation medium on the PF, and
iii) the in vivo significance of the PF so obtained.
The results of the limited experiments conducted so far have shown that simple models employing gas kinetic parameters and the PF are capable of predicting the dry matter intake of roughages and level of emission of methane by ruminants. Experiments also need to be done to test whether, for any given feed, the microbial protein synthesis as derived from digestion kinetic parameters (including PF) in vitro is sufficient to explain the observed microbial protein supply to the small intestine in vivo. At present, the simplest way of determining the latter parameter is to calculate it from the level of urinary purine derivatives. This validation excercise should be conducted for a wide range of feed constituents and diets which should enable the above mentioned simple technique of measuring gas and microbial mass to be a routine and powerful tool for feed evaluation thus avoiding the need for time-consuming, laborious and expensive feeding studies. Lately, much emphasis has been given to the development of statistical or mathematical models that best fit the gas production profiles and describe the gas evolution with high accuracy. Experiments must be designed to understand the biological significance of the various statistical and functional parameters being calculated using these models, and also to incorporate a measure of microbial mass into these mathematical descriptions. Research and development efforts are required to establish a feed library for unconventional feedstuffs that includes information on nutritive values in addition to routine composition analysis. In the case of tannin-containing feedstuffs, there is a need to incorporate approach(s) measuring the biological activities of tannins as well as measuring tannin levels by chemical methods.
Keywords: Scarcity; Unconventional feed resources; Ligno-cellulosic stovers; UMMB; Soil erosion; Food security.
Original Article
P. 103-121
