Cow Faeces in In vitro Digestibility Assays of Forages

The present study investigated the use of cow faeces as a source of micro-orgattisms instead of sheep rumen liquor in in vitro digestibility assays of forages. Initially 40 forage samples comprising ryegrass, wheat, maize and barley were screened to select a wide range of digestibility (327-794 g/kg) of forages. Finally 8 forage samples were assessed using rumen liquor as well as faecal liquor. The absolute organic matter digestibility (OMD) values using faecal liquor were lower than those with rumen liquor. However, the relationship between OMD using rumen liquor and faecal liquor was highly significant (p < 0.001). The R2 value exceed 0.90. The results suggest that micro-organisms from faecal liquor are capable of digesting forage samples. (


INTRODUCTION
Most of the experiments on in vitro forage digestibility have been made using rumen liquor as a source of inoculum (McLeod and Minson, 1969). There is a need for alternative inocula to rumen liquor. Although limited information on the use of sheep faeces in digestibility assays is available (El Shaer et al., 1987), no literature is available on the use of cow faeces to use as the inoculum. Akhter (1995) investigated the possibility of using cow faeces with only one forage. For a in vitro digestibility technique to be useful, it must be capable of assessing forages covering a wide range of digestibility. Many workers (Tilley et al., 1960;Terry, 1963 andNelson et al., 1976) established the relationship between two methods (e.g. in vtvolin vitro) considering a wide range of digestibility of forages. Therefore, this experiment was conducted to produce forages representing a wide range of in vitro digestibility which were then used in investigating regression relationship between rumen liquor and faecal liquor.

Types and quality of forages produced
Forty forage samples comprising of ryegrass {Lolium perenne), wheat (Triticum aesttvum), barley (Hordeum vulgca-e) and maize (Zea mays) cut at different dates were produced (table 1). The sample was then assessed for in vitro digestibility using the two-stage Tilley and Terry (1963) method. The forages were grown at Centre for Dairy Rese인ch (CEDAR), University of Reading, U.K. All the forages were cut at ten days intervals during May-J미y, 1992. The samples were dried at 60-65 °C to avoid damage to forage quality (Minson and McLeod, 1972). Some of the samples were separated into leaf (with sheath) and stem fractions (table 1) separated into leaf (with sheath) and stem fractions (table 1) to ensure the production of forages with a wide range of digestibility. All the samples were ground through a 1 mm dry mesh screen to perform in vitro digestion.

Source of rumen liquor and faeces
Rumen liquor was collected from 3 fistulated Suffolk wethers maintained on ad libitum hay (N2, ADF, NDF were 23, 414 and 715 g/kg DM respectively) and concentrate (200 g/d). Concentrate mixture had in vitro DMD of 878 g/kg and N of 32 g/kg DM. Faeces was obtained from 3 Jersey cows. Each animal was offered ad libitum ryegrass hay (N》ADF, NDF were 25, 421 and 713 g/kg DM respectively) as their daily feed. Individual housing facilities were provided to all animals.

Inocula preparation
Rumen liquor was collected from the fistulated sheep and preserved in a prewarmed (39°C) vacuum flask until required. Rumen liquor was strained through two layers of muslin and 50 ml of the inoculum was added to the AJAS 1998 Vol. 11 (No. 1) 51-54 substrate.
Freshly voided faeces were collected from the rectum of the cows and preserved in a prewarmed (39 C) vacuum flask until used which was not longer than 1.5 h. Faecal liquor was made using 333 g faeces per litre artificial saliva (McDougall, 1948). The faeces inoculum was prepared by mixing faeces with CO2 saturated artificial saliva, straining through two layers of muslin. 50 ml of inoculum was added to 0.55 g forage for the in vitro fermentation.

In vitro digestibility procedure
Firstly forty forages were assessed in triplicate fbr in vitro digestibility using the two・sta응e technique of Tilley and Terry (1963). Finally 8 forage samples (representing a wide range of digestibilities) were assessed using rumen liquor and faecal liquor as inocula.

Statistical analyses
The data obtained from the experime마 were analyzed in a 2 x 8 factorial form. The relationship between OMD of rumen liquor source and faecal liquor source was also investigated using the programme Statistical Analysis System (SAS, 1985).

RESULTS
The cutting dates and in vitro OMD of different forages are presented in table 1. The range of digestibilities (g/kg) obtained from the experiment was 327-794. It is readily apparent from the results (figure 1) that the digestibilities of the forages declined with time (May-July). The leaf fractions (irrespective of forages) exhibited higher digestibilities compared to other fractions. However, this pattern was not consistent in all samples. The absolute in vitro digestibility using rumen liquor was higher to those with faecal liquor (table 2).
The regression line (figure 2) relating the OMD values from faecal liquor and rumen liquor sources indicate that there was a concordance between rumen liquor and faecal liquor. The linear relationship showed a significant (p < 0.001) correlation between OMD determined in rumen liquor and those obtained in faeces. The R2 value exceeded 0.90.

DISCUSSION
The present study was confined to assessing whether rumen liquor in the Tilley and Terry (1963) technique could be replaced by micro-organisms from cow faeces. The regression relationship suggest that cow faeces can be Table 2. In vitro organic matter digestibility (g/kg) of different forages using faeces (F) and rumen liquor (R) Ta비e 1. In vitro organic matter digestibility (g/kg), determined by the conventional two stage technique (Tilley & Terry, 1963)    used as a source of micro-organisms. The results highlighted the need for more research in this field. 50 ml of faecal inoculum per in vitro digestibility tube was used used in the experiment. It would be interesting to see if high digestibilities would occur if more liquor per tube be used.
One could argue about the necessity of carrying out the initial investigation. Final investigation could be carried out with forages acquired from other sources. The fact is that laboratory facilities vary from place to place. All the processes such as collecting, drying and milling the forages was under taken with special care. Variability due to drying and milling conditions could affect in vitro digestibility (Tilley and Terry, 1963). Emphasis was given on maintaining identical sample preparation and procedures used in in vitro methods.
The fact that the in vitro digestibilities measured by the Tilley and Terry (1963) method give results for forages which are in line with the literature (Kamstra et al., 1958;Melling et al., 1962 andNeathery, 1972) suggests that the relationship we have obtained (figure 2) will be a support to allow use of this technique in the countries where maintenance of fistulated animals is difficult and other techniques e.g. cellulase are too expensive.