Some Factors Affecting Fermentation Capacity and Net ...

1 APPLIED MICROBIOLOGY, Sept. 1969, p. 313-317 Vol. 18, No. 3. Copyright 1969 American Society for Microbiology Printed in some Factors Affecting Fermentation Capacity and Net growth of Rumen Microorganisms MANAL ZAKI EL-DIN AND K. EL-SHAZLY. Faculty of Agriculture, University of Alexandria, Egypt, United Arab Republic Received for publication 23 January 1969. Downloaded from on November 27, 2018 by guest The Fermentation rate of rumen microorganisms obtained from a sheep fed on hay was determined at different hours after feeding. The highest rate of fermenta- tion was obtained immediately after feeding whereas the lowest rate was always be- fore feeding. The effect of adding glucose, sucrose, and starch alone or in combina- tion with urea, sodium citrate, or succinic acid on the maximal Fermentation rate was studied.

2 In no case was the maximal Fermentation rate greater than that ob- tained in the presence of concentrate and straw. An investigation on the effect of C/N ratios, dilution, and substrate concentration on the net growth of rumen microorganisms was undertaken. The highest net growth value was obtained with a C/N ratio of to , which is the ratio found for the ration fed to the animal. It was possible to increase net growth approximately threefold by using the proper dilution and fivefold by using the proper feed concentration. A method for measuring the microbial growth carbonate, and type of carbohydrate (glucose, sucrose, in the rumen was proposed by el-Shazly and and starch, 5 to 10 g alone or together with urea, Hungate (9) based on the changes in Fermentation sodium citrate, and succinic acid) on maximal fermen- Capacity taking place within a short period of tation rate were tested.

3 Effect of carbon-nitrogen ratio on net growth . incubation of rumen contents. The diamino- Rumen samples (about 200 g) obtained through the pimelic acid in the same rumen samples was esti- rumen fistula from a sheep fed concentrate plus straw mated. The growth measurements by the two were collected at different hours after feeding. Urea or methods were in good agreement (10). starch were added to samples (200 g) to alter the C/N. Zaki el-Din and el-Shazly (14) produced evi- ratio, and the net growth rate was compared with that dence of the reliability of the method in measuring in samples without these additions. the bacterial and protozoal growth . The effect of C/N ratio on net growth was also The present paper describes Factors Affecting studied on one large sample divided into several small the net growth rates of rumen microorganisms, samples (50 g); to each sample, urea or starch was added to study the whole range of C/N ratios in one , C/N ratio, dilution, and substrate concen- experiment.

4 Tration. Carbon was determined by the method of Walkley (12) utilizing o-phenanthroline as indicator. Nitrogen MATERIALS AND METHODS was determined by the Kjeldahl method according to the official methods of the Association of Official Animals and sampling. The experiments were carried Agricultural chemists (7). In the above experiments out by using two fistulated sheep fed on berseem hay the range of C/N ratios used was obtained by using (2 kg once in the morning) or concentrate plus wheat samples collected at different times. straw in the ratio 3:1 (1 kg once in the morning). The Effect of dilution on net growth . The effect of diluting concentrate mixture consisted of undecorticated the rumen sample with mineral solutions A and B (1). cottonseed cake and rice bran the ratio in 1:1 plus on the net growth was studied in the following experi- calcium hydroxide and 1 % common salt.

5 The maximal Fermentation rate was measured Collection and preparation of samples were done as ments. in the usual manner on a 50-g rumen sample. Similar described previously (14). The rate of Fermentation samples were incubated for 1 hr with different volumes was measured at different times after feeding on sam- of the mineral solution. After 1 hr of incubation the ples obtained from the sheep fed hay. maximal rate of Fermentation was determined after Measurements of maximal Fermentation rate and net making the final volume 200 ml with mineral solution. growth . Maximal Fermentation rates and net growth Effect of feed concentration on net growth . The effect rates of rumen microorganisms were determined by the method of el-Shazly and Hungate (9) as modified of adding different amounts of ground concentrate by Zaki el-Din and el-Shazly (14).

6 Plus straw from the same ration consumed by the The effects of substrate concentration, sodium bi- animal on the net growth values was tested on rumen 313. 314 ZAKI EL-DIN AND EL-SHAZLY APPL. MICROBIOL. samples obtained before and after feeding. The opti- Factors Affecting maximal rates of fermenta- mum dilution level found from the previous experi- tion. The effect of rumen sample concentration, ments was employed throughout these trials. The feed concentration, dilution, and sodium bicar- initial maximal Fermentation rate was first measured, bonate concentration on the maximal rates of then several subsamples (about 50 g each of rumen Fermentation were studied and found similar to contents) were incubated for 1 hr with the following concentrations of the feed: 0, 5, 10, 15, 20, and 25 g. those found by el-Shazly and Hungate (9).

7 At the end of the incubation period, the feed was in- The effect of adding glucose, sucrose, and starch creased to 20 g, and the mineral solution to 200 ml. alone or in combination with urea, sodium citrate, The final maximal rate of Fermentation was then de- or succinic acid was compared with that of adding termined, and net growth was estimated. the feed. In no case was the maximal rate of RESULTS Fermentation greater than that obtained in the Downloaded from on November 27, 2018 by guest presence of concentrate plus straw (Table 1). Normal rates of Fermentation . The Fermentation Net growth rates of rumen microorganisms. rates vary with time after feeding. The highest rate Figure 2 shows typical curves of maximal fer- was obtained immediately after feeding (15 to 30 mentation rates before and after 1 hr of incuba- min), whereas the lowest rate was found before tion at 39 C.

8 From the difference of the slopes of feeding (Fig. 1). 10r c E 6. c ,a, c 2. 0ca Ltn t 2. 4 6 8 10 12 24. rIME FROM FEEDING (hr) TIME (min ) TIME nmin). FIG. 1. Fermentation rates of rumen samples col- FIG. 2. Normal and maximal rates offermentation at lected from a fistulated sheep fed berseem hay. Dif- two different intervals afterfeeding sheep on concentrate ferent curves represent different days. plus straw, 3: 1. TABLE 1. The effect of adding glucose, sucrose, and starch alone or in combination with urea, sodium citrate, or succinic acid on the maximal Fermentation rate Maximal rate Substrate Concna No. of runs of Fermentation (usliters/g/min). Concentrate + straw 10 13 Concentrate + glucose 10 + 1 1 Concentrate + glucose 10 + 2 1 Glucose 10 3 Glucose 5 3 Glucose + urea 5 + 1 Glucose + urea 5 + 1 Glucose + sodium citrate 5 + 2 1 Glucose + succinic acid 5 + 1 1 Glucose + succinic acid 5 + 2 1 Sucrose 10 2 Sucrose 5 2 Starch 10 2 Starch 5 2 Starch + sodium citrate 5 + 1 1 Starch + sodium citrate 5 + 2 1 * Concentration is expressed in grams per 200 ml of buffer.

9 VOL. 18, 1969 NET growth RATES OF RUMEN MICROORGANISMS 315. the two curves the net growth was calculated. 65. The net growth (per cent per hour) for these curves was 62 when the sample was collected 2 hr after feeding, and 17 when the sample was col- lected hr after feeding. Effect of C/N ratios on the net growth rates of rumen microorganisms. The net growth rates in the first experiment (results not reported) 45. differed widely from one trial to another, but it was obvious that C/N ratios close to those found in the feed consumed by the animal gave highest Downloaded from on November 27, 2018 by guest net growth rates. This was confirmed in three ex- 35. x periments whereby urea or starch or both were added in different concentrations to portions of 0. the same rumen sample, thus altering the C/N.

10 Ratio. The highest net growth values were found 25/. when the C/N ratio was between and (Fig. 3) or close to the values of the C/N ratio in the feed the animal was consuming. 2 15. The mean value of total N of 11 rumen samples obtained from a sheep (60 kg) fed on concentrate plus straw 3:1 was + g per 100 g of dry matter. 5. Effect of dilution on net growth rates. Dilution 0 50 00 150 200. 35. DILUTION (ml.). FIG. 4. Effect of dilution on the net growth rate of 25. rumen microorganisms obtained from a sheep fed con- centrate plus straw. 15. of the rumen sample about 3 times (150 ml of I. \:mineral solution to 50 g of rumen sample) gave 5. J xt the highest net growth value (Fig. 4); a higher *x dilution caused a slight drop in the net growth rate of rumen microorganisms. 0 ~. :k The Effect of feed concentration on net growth rates.