Reddy et al.

in the complete ration was also reported (Nagalakshmi

proportion could be due to active degradation of protein

et al. , 2005). The high positive correlation between gas

and hydrolysis of NPN substances. Ammonia liberated

production and OM digestibility has been reported (Datt

during incubation was incorporated into microbial

and Singh, 1995). The findings of the present study were

protein synthesis. If the availability of N and energy are

also supported by the reports that, the roughages deficient

not synchronized, results in lowered microbial protein

in fermentable carbohydrates reflected relatively low OM

synthesis (Mc Donald et al., 1988). In this study, though

digestibility (Jayasuriya, 2002). Ahmed and El-hag (2004)

the ammonial nitrogen (mg/100 ml) was increased linearly

stated that, excess amount of hemicellulose and cellulose

from 100R:0C to 30R:70C, highest (P<0.01) (45.19

acts as antinutritional factors and lower the digestibility

mg) microbial biomass production (MBP) noticed at

and gas production. This might be another reason for

60R:40C and 50R:50C (43.59 mg) (Table 2). This might

lowest gas production and IVOMD with incubation of

be due to matching supply of ammonia and fermentable

sorghum stover solely. Carvalho et al. (2005) also stated

carbohydrates to the bacteria.

that, high cellulose and hemicellulose contents could

Partitioning factor (PF) is defined as the ratio of substrate

lower the organic matter digestibility.

truly degraded in vitro (mg) to the volume of gas (ml)

Among all the rations, ration contained 70% concentrate

produced by it. PF is an index of the distribution of

has shown highest (P<0.01) ME and TDOM compared to

truly degraded substrate between microbial biomass

other rations and the trend observed in ME, TDOM values

and fermentation waste products (Thirumalesh and

reflected that, as the concentrates proportion increased,

Krishnamoorthy, 2009). When less gas is produced per

these values were also proportionately increased. The

unit weight of substrate truly degraded, proportionately

increased ME value was in accordance with the increased

more substrate is converted into microbial biomass, which

IVOMD values of rations containing higher proportion

means that, a higher PF would reflect higher conversion

of concentrates, which shown that, poor digestibility of a

of truly degraded substrate into microbial biomass and

nutrientsresultedinloweredMEavailability.Theincreased

vice versa and higher PF rations increased microbial yield

TDOM was a reflection of increased IVOMD values of

(Darshan et al. , 2007). Hence, calculation of PF in in vitro

the rations. The higher fermentable carbohydrates and

study provides meaningful information for predicting the

available nitrogen reflecting a better nutrient availability

microbial biomass production in the rumen from the dry

for rumen microorganisms was reported when crop

matter taken. In an in vivo study with sheep, microbial

residues were supplemented with concentrates (Blummel

biomass flow to the duodenum was positively correlated

et al. , 2009 and Khanum et al. , 2007). The predictive ME

with the PF of the mixed ration (Blummel et al. , 2003). In

values (8.13 to 9.90 MJ/kg DM) were found within the

the present investigation, highest (P<0.01) PF was noticed

range of reported values for a large number of feedstuffs

at 60R:40C and 50R:50C. The higher EMBP observed at

(Krishnamoorthy et al. , 1995).

60R:40C was positively correlated with higher PF of the

Total volatile fatty acids (TVFA, meq/l) production was

ration. Based on the truly digestible organic matter and

increased with increase in the concentrate proportion of

efficiency of microbial biomass production sorghum stover

the inoculum. TVFA production was comparable among

can be incorporated up to 60 percent in the complete diets

the rations contained R:C at 50:50, 40:60 and 30:70. This

of ruminants for efficient nutrient utilization and animal

result was in consistent with the findings of Getachew

performance.

et al. (1998) who concluded that TVFA production was

positively correlated (P<0.01) with in vitro gas production.

REFERENCES

The concentration of rumen ammonia nitrogen was

Ahmed, M.M.M. and El-Hag, F.M. 2004. Degradation

significantly (P<0.01) differed linearly among the

characteristics of some Sudanese forages and tree pods using

experimental rations (Table 2). The results of the present

in sacco and gas production techniques. Small Rumin. Res.,

54: 147–156.

study were also in agreement with the earlier reports

(Madan Mohan et al. , 1997). The increased ammonia

AOAC Association of Official Analytical Chemists, Official

Methods of Analysis, 1997. 16 th edition, Maryland.

nitrogen in the rations with increasing the concentrates

50

Journal of Animal Research: v.5 n.1. April 2015