PhD

A study was conducted to elucidate the influence of tannins on synthesis of nucleic acids and protein in liver of rats. In vitro and in vivo studies in buffaloes were also conducted to ascertain the effect of tannins on rumen metabolism.

In experiment 1, 30 weanling rats were distributed into three groups of 10 each in a randomized block design. The influence of addition of 0% (group A), 2.5% (group B) and 5% (group C) tennins in the feed on feed consumption, growth rate, nitrogen and dry matter digestibility was investigated. Further RNA, DNA and protein in liver were estimated to asses liver function.

The feed consumed daily on DM basis (g); weight gain per three day interval (g); and gram feed per gram weight gain, respectively for groups A, B and C were : 20.05 + 7.6, 7.87 + 0.41, 2.73 +0.05; 16.66 + 6.0, 5.69 + 0.35, 3.14 + 0.07 and 16.11 + 5.4, 4.53 + 0.21, 3.80 + 0.11. The DM and N digestibility (%), respectively for groups A, B and C were: 78.56 + 0.44, 78.28 + 0.56; 78.62 + 0.64, 73.50 + 0.86 and 78.82 + 0.52, 69.97 +0.75. Feed consumption in group A was significantly (P <0.01) higher than in group B and C. The difference in feed consumption between groups B and C was not significant. Significant differences were found amongst all treatment groups in weight gain (P< 0.05) and food : gain ratios (P < 0.01). DH digestibility did not reveal any significant difference between groups whereas the differences in N-digestibility were significant (P<0.01). The addition of tennis in the diet significantly depressed feed consumption, weight gain, and N – digestibility which resulted in widened feed : gain ratios.

The average liver weights (g): total protein (mg) ; RNA (mg) and DNA (mg), respectively for groups A, B and C were : 3.61 + 0.21, 717.3 + 4.76, 21.42 + 1.41, 5.36 + 0.41, 2.85 + 0.23, 569.0 + 4.31, 16.40 + 1.60, 4.29 + 0.45 and 2.44 + 0.01, 507.9 + 2.55, 13.79 + 0.58, 3.34 + 0.16. The liver weight in group A was significatly (P<0.05) higher than in group C. The total protein content in group A was significatly (P<0.01) higher than in group B and C. But the difference between groups B and C was not significant. RNA and DNA contents differed significantly (P<0.01) amongst the three groups. The average protein (mg), RNA (mg) and DNA (mg), respectively for the groups A, B and C were : 198.69 + 3.31, 5.93 + 0.18, 1.48 + 0.05, 199.89 + 5.14, 5.68 + 0.16, 1.49 + 0.06 and 208.16 + 2.32, 5.66 + 0.03, 1.38 + 0.04 per gram of tissue. There were no significant differences in the parameters studied amongst the three groups. The body weight : liver weight ratios, protein : RNA ratios and protein : DNA ratios, respectively for groups A, B and C were : 29.0 + 2.23, 33.2 + 1.01, 134.9 + 5.04, 30.3 + 2.45, 35.4 + 1.22, 136.7 + 5.75 and 31.0 + 2.66, 36.9 + 1.01, 153.7 + 4.17. There were no significant differences amongst the ratios except that protein : DNA ratio in group C was significantly (P<0.05) wider than in group A and B indicating probable hypertrophy of liver cells in that group. It was apparent that tannins exerted their harmful effects by affecting protein digestibility in the gastro-intestinal tract and thereby adversely affected liver size and growth rate.

In experiment 2, in vitro trials were conducted by taking buffalo rumen liquor through a rumen fistula on a control ration without tannic acid. For N solubility and DH digestibility studies, the substrate used was : Maize, 50 parts ; grount nut cake, 21 parts and wheat bran 26 parts, ground into 40 mesh size. To study the influence of tannins on protein synthesis, nucleic acid synthesis and production of VFA, the substrates used were : cellulose 0.75 g. starch 0.25 g and ammonium sulphate 151 mg. McDougall’s artificial saliva was used as buffer (PH 6.8) for 32 P uptake by rumen microbes, the substrate was prepared from glucose 600 mg and ammonium sulphate 85mg. A mineral solution containing cysterine – HCL described by Bucholts and Bergan (1973) was used as a buffer. The levels of tannic acid, respectively in groups 1,2,3,4 and 5 were : 0, 1.25, 2.5, 5.0 and 7.5% in all the experiments.

The E solubility and DM digestibility (%) respectively, for treatments 1,2,3,4 and 5 were : 36.72 + 0.425, 43.80 + 2.63 : 24.48 + 0.311, 37.60 + 2.14, 20.81 + 0.589, 30.27 + 1.85 : 17.55 + 0.312, 21.89 + 1.93 and 15.30 + 0.473, 13.20 + 1.15. Addition of tannins depressed N solubility and DM digestibility. The protein – N (mg) ; RNA – N (mg): DNA-N (mg) and TVFA (meq) (all per 100 ml) respectively for treatments 1,2,3,4 and 5 were : 30.19 + 1.274, 2.156 +0.107, 0.795 + 0.054, 15.46 + 0.315, 23.84 + 1.021, 1.565 + 0.101, 0.561 + 0.025, 12.34 + 0.194, 18.59 + 0.582, 1.185 + 0.046, 0.426 +0.021, 9.38 + 0.425, 16.27 + 1.318, 1.00 + 0.042; 0.337 + 0.013, 7.29 + 0.359 and 14.61 + 0.271, 0.865 + 0.034, 0.290 + 0.006, 5.49 + 0.235. Addition of tannins significantly (p<0.01) depressed all the parameters studied and in treatment 5, the levels were more or less the same as in 0 hour control indicating complete inhibition of microbial multiplication at 7.5% tannic acid level. The RNA –N : protein – N, DNA – N: protein – N and total nucleic acid – N: protein – N ratios respectively for treatments 1,2,3,4 and 5 were : 0.072 + 0.0018, 0.026+ 0.0013, 0.098 + 0.0015, 0.066 + 0.0018, 0.023 + 0.0045, 0.089 + 0.0022; 0.064 + 0.0018, 0.023 +0.00084, 0.087 + 0.0024, 0.062 + 0.0016, 0.021 + 0.00077, 0.082 +0.0020 and 0.058 + 0.0013, 0.020 + 0.00055, 0.078 + 0.0016. The ratios were narrower in control group when compared to tannic acid groups.

With regards to 32P uptake by rumen microbes, a progressive decrease was observed with increase in tannin concentration. 32p uptake (mg) per 100 ml respectively for groups 1,2,3 and 4 were : 2.640, 1.835, 1.202 and 0.52. In group 5 there was no 32P uptake. Tannins depressed microbial multiplication indirectly by making the protein source not available due to its precipitation. Direct harmful effect was also possible on microbes, especially, at higher concentrations of tannins in the media without any protein source.

In experiment 3, four adult fistulated female buffaloes were randomly distributed in a Latin square design. The treatments I, II, III and IV respectively contained 0, 1.25, 2.5 and 5% tannins made available from 0, 14, 28 and 40% salseed meal in the ration. In treatment IV, 1.436% pure tannic acid was also added to get 5% total tannins. The DCP and TDN contents were approximately 14 and 72% in all the rations. The effect of tannins in feeds was determined through the levels of protein –N, RNA – N, DNA –N and TVFA.

The protein –N, RNA – N and DNA-N levels ( all in mg per 100 ml of SRL) and TVFA levels ( meq/100 ml of SRL), respectively for treatments I,II,III and IV were : 43.73 + 1.813, 3.86 + 0.134, 1.63 + 0.053, 9.59 + 0.205; 49.087 + 1.912, 3.75 +0.115, 1.59 + 0.057, 0.43 + 0.215, 54.86 + 1.850, 3.62 + 0.089, 1.50 +0.041, 9.20 +0.188 and 61.89 + 2.050, 3.26 + 0.097, 1.37 + 0.046, 8.48 + 0.283. Protein - N level in treatment L was significantly (P< 0.05) lessthan in ratios II, III and IV and there was a progressive and significant (P< 0.05) increase in order of treatments. RNA – N and TVFA levels in treatment I were significantly higher (P< 0.01) than in treatment IV. DNA levels were significantly lesser (P<0.05) in treatment III than in treatment I and again lower in treatment IV than in treatment III. Nucleic acid - N : protein – N ratios is SRL respectively for treatments I, II, III and IV were : 0.125 + 0.0012, 0.108 + 0.0020, 0.093 + 0.0026 and 0.072 + 0.0011. The ratio in treatment L was significantly higher than in treatments II, III and IV. The differences amongst the four treatments were significant (P<0.01). Addition of tannins in the rations resulted in an increase in protein - N, but progressively depressed the RNA – N and DNA – N levels with less production of TVFA.

Further in experiment 3, the protein - N, RNA – N and DNA – N contents of bacteria separated from SRL were also determined to ascertain the effect of tannins on RNA – N: protein – N; DNA – N : protein – N and total nucleic acid : protein - N ratios. Protein – N (mg), RNA – N (mg); and DNA –N (mg) in bacteria separated from 100 ml SRL respectively for treatments I, II,III and IV were : 23.93 + 0.571, 2.385 + 0.87, 1.204 + 0.036, 23.71 + 0.627, 2.296 +0.062, 1.180 + 0.019, 22.79 +0.590, 2.230 +0.044, 1.111 + 0.059 and 20.91 + 0.544, 205 + 0.046, 1.010 + 0.053. Protein -N, RNA –N and DNA – N levels decreased as levels of tannins in rations increased. But the differences were significant (P<0.01) only between treatment I and IV. RNA – N : protein - N, and total nucleic acid – N : protein – N ratios respectively for treatments I, II, III and IV were : 0.099 + 0.0030, 0.150 +0.0027; 0.097 + 0.0023, 0.147 + 0.0029; 0.098 + 0.0024, 0.147 + 0.0017 and 0.098 + 0.0020, 0.146 +0.0025. The differences in the ratios amongst the different treatments were not statistically significant. The addition of tannins at the levels tried had no significant influence on the nucleic acid – N : protein – N ratios in the bacteria.

From the value obtained for nucleic acid – N and nucleic acid – N : protein – N ratios in separated bacteria, the microbial contribution of protein - N to the tungestic acid precipitate of SRL was calculated. The values obtained were : 83.67, 74.01, 63.58 and 51.14 % for treatments I,II,III and IV respectively. The tannins present is the feed partially protected the proteins from microbial attack and hence the contribution of dietary protein - N in the SRL increased. Simultaneously the quantity of microbial protein synthesis decreased due to the limitations imposed by tannins on microbial multiplication.