Effect of drenching with soybean oil on growth, nutrient utilization and rumen parameters of growing goats fed Vetiver and Trichanthera foliage

Nguyen Van Hon, Nguyen Thi Hong Nhan,Vo Van Son, Ho Thanh Tham, Le Viet Dung, T R Preston*and R A Leng**

Cantho University, Cantho, Vietnam
nthnhan@ctu.edu.vn
* trpreston@mekarn.org
** rleng@ozemail.com.au

Abstract

Rumen parameters, nutrient utilization, growth performance, diet digestibility and growth performance were measured in defaunated and faunated growing goats fed a 50:50 dry basis diet of foliage of  Trichanthera gigantea and Vetiver (Vetiveria zizanioides) during a 100-day experiment. Fifteen Bachthao x local breed weaner goats of  body weight of 9 to11 kg were randomly divided into three equal groups (defaunated goats , refaunated goats and faunated goats) of 5 goats each. All the goats of the defaunated and refaunated group were treated with oil (5 ml soybean oil / kg body weight) after fasting them for 24 h. Oil administration was directly into the rumen through a stomach tube. After 10 days, all the goats of refaunated group was refaunated by inoculating 100 ml goat rumen contents drawn from an untreated and therefore normally faunated goat . The goats in the defaunated group were maintained in isolation throughout the study. The status of defaunation in the goats was checked at 10 day intervals for first month of the experiment by collecting rumen fluid by stomach tube.

Daily  intake of dry matter, crude protein and digestibility of crude protein were similar in the three groups while digestibility of dry matter was higher in the defauanted goats. The growth rate and feed conversion rate of defaunated animals appeared to be improved compared with faunated ones. The rumen pH was similar in defaunated and faunated goats, but ammonia- N concentration was lower for defaunated goat. Numbers of protozoa were decreased while numbers of bacteria were increased by defaunation.

It is concluded that nutrient utilization, diet digestibility and growth performance were better in defaunated than in refaunated and faunated goats.

Key words: Goats, defaunated, refaunated, faunated , feed intake, digestibility, rumen parameters

Introduction

Rumen protozoa play an important role in utilization of lignocellulosic material by fermentative digestion in ruminants (Bird and Leng 1984; Chaudhary et al 1995). It is now well established by a number of in vivo experiments that elimination of ciliate protozoa from the rumen (defaunation) increases the intestinal protein flow to the intestines (Ushida et al 1984; Kayouli et al 1986; Veira 1986) thus improving body weight gain in young ruminants under certain feeding conditions (Bird 1988; Ivan et al 1992). During the last decade many attempts were made in developed countries to generate information regarding the role of protozoa in the rumen metabolism and performance of ruminants (Jouany et al 1988; Demeyer 1988). However, such studies were almost lacking in developing countries. Recently, studies by Nguyen Thi Hong Nhan et al (2001, 2003), Nguyen Xuan Trach (2004) and Mom Seng et al (2001) have shown that drenching with vegetable oil (or direct insertion of oil into the rumen via a stomach tube) eliminated the protozoa from the rumen and, as a result, the cattle grew faster. If similar results can be obtained in goats, this will make an important contribution to improving production in this species.

The reported experiment, therefore, was conducted to study the effect of presence or absence of rumen protozoa on nutrient intake, digestibility and  growth of goats maintained on complete diets containing varying proportions of roughage .The results of the experiment should be especially useful for poor farmers in the Mekong delta who use a variety of low quality forages to feed their goats.
 

Materials and Methods

Animals and defaunation protocol

Fifteen Bachthao x local breed weaner goats of body weight 9 to 11 kg were randomly divided into three equal groups (defaunated goats , refaunated goats and faunated goats) of 5 goats each. All the goats of defaunated and refaunated groups were treated with 5 ml soybean oil / kg body weight after fasting them for 24 h. Oil administration was directly into the rumen through a stomach tube. After 10 days, all the goats of the refaunated group were refaunated by inoculating 100 ml of goat rumen content drawn from an untreated and therefore normally faunated goat . The goats in the defaunated group were maintained in isolation throughout the study. All animals were checked at 10 day intervals by collecting rumen fluid by a stomach tube during the first month and at the end of trial.

Experimental feeding and metabolism trial.

All the animals in the three groups were individually fed for 100 days on a composite feed containing approximately 50:50  (DM basis) of foliage of  Trichanthera gigantea and Vetiver (Vetiveria zizanioides).

Measurements were made of feeds offered and refused daily. Live weight  was determined at 10 days intervals during the entire course of the study. After 100 days of experimental feeding a metabolism trial was conducted with all goats housed  in metabolic cages with provision for quantitative collection of faeces and urine. Composite samples of feed offered , residues, and faeces from the metabolism trial were preserved for subsequent chemical analysis.

Chemical analysis

The feed offered , residues and faeces were analysed for dry matter (DM) by drying at 105 ^oC for 24 h and crude protein (CP) by the  Kjeldahl technique (AOAC 1990). Samples of rumen fluid (100 ml) were taken by aspiration using a plastic tube and syringe every week at 07.00 am before eatting. Protozoa classification, and numbers were counted under a microscope, using 0.1 and 0.2 mm counting chambers. pH was recorded by a digital pH meter. Ammonia concentration was measured by steam distillation of a sample of 20 ml of rumen fluid, with collection of the ammonia in boric acid solution and titration with H₂SO₄ 0.1N.

Statistical analysis

The data on feed intake, nutrient utilization, feed conversion rate, daily gain and values of pH, protozoa, bacteria numbers and ammonia were averaged over sampling times and analysed by the General Linear Model of the ANOVA programme in the software of Minitab (version 13). Sources of variation were treatments and error.
 

Results and discussion

Chemical composition of the diets

The dry matter content of samples of the Vetiver and Trichanthera foliage used in the experiment was in the range of 24.3 to 23.9 % and 16.4 to14.7 %, respectively. Crude protein content (N x 6.25) in dry matter ranged from 10.3 to 11.3 % and 17.8 to 20.8%, respectively.

Nutrient intake and growth performance

Feed intake fell dramatically after oil administration but returned to normal in one week.  The average daily dry matter and crude protein intake of the goats during the entire period of growth study was similar in the three groups (Table 1).  It is evident that the drenching oil in the process of defaunation did not have an adverse effect on voluntary feed intake over the overall trial period.

Total body weight gain during the study and average daily gain were higher in the defaunated than in the refaunated and faunated goats (Table 2).  The pattern of body weight gain was similar in defaunated and faunated goats until 30 days of experiment. Thereafter, the defaunated goats had consistently better growth responses compared to faunated goats. On an average the defaunated goats showed 16 to 20% growth improvement over faunated and refaunated goats. Similar studies conducted elsewhere on growing lambs (Bird and Leng 1985) and calves (Bird et al1979) have also indicated  an average of 15 to 20% improvement in growth of defaunated animals. Feed conversion rate followed the same pattern as growth rate (Table 1).

Table 2: Mean values for changes in live weight of goats infused  with soybean oil into the rumen (defaunated), not treated (faunated) or infused with  oil and then re-faunated
	Defaun	Refaun	Fauna	SEM	Prob.
Live weight, kg
Initial	9.15	8.85	9.77	0.37	0.27
30 days	10.5	10.2	11.3	0.38	0.16
60 days	12.5	11.8	12.9	0.37	0.17
80 days	13.8	12.8	13.9	0.36	0.12
100 days	15.1	13.8	14.9	0.35	0.06
Daily gain, g
0-30 days	44.7	45.4	52	2.31	0.1
31-60 days	65.8	51.9	50.9	2.24	0.003
61-80 days	67.3	51.6	51.2	2.78	0.005
81-100 days	65.7	50	50.7	2.31	0.002
0-100 days	59.7	49.5	51.2	0.95	0.001

 

 

Figure 1: Mean values for live weight gain in goats during successive periods of the experiment

 

Figure 2: Mean values for feed conversion (feed DM/kg weight gain) in goats
during successive periods of the experiment

 

With similar intake of DM and crude protein during the entire period of study, feed conversion rate was better in defaunated than faunated goats (Figure 2). It is evident from the present study that defaunation did not depress voluntary feed intake of the animals as was also observed in earlier reports (Santra and Karim 2000). Higher growth rate and feed conversion effciency in defaunated compared to faunated and refaunated goats was probably due to reduced methanogenesis (Kreuzer et al 1986; Santra et al 1996).  The observed improved growth rate and feed conversion  in defaunated goats could also be due to improved microbial and dietary protein flow to duodenum in defaunated compared to faunated animals (Bird and Leng 1985; Demeyer et al 1982; Van Nevel et al 1985).

Apparent digestibility of DM was lower in faunated and refaunated goats than in defaunated goats (Table 3; Figure 3). Apparent digestibility of crude protein was similar in the three groups (Table 3).

Table 3: Apparent digestibility coefficients for DM and crude protein
	Defauna	Refauna	Fauna	SEM	Prob.
Dry matter digestibility (%)
0-30 days	63.0	64.0	61.9	0.56	0.07
31-60 days	62.8	57.7	54.6	1.71	0.03
61-80 days	61.8	57.5	53.8	1.16	0.004
81-100 days	64.8	61.3	61.5	0.67	0.012
Average	63.1	60.1	57.9	0.6	0.001
Crude protein digestibility (%)
0-30 days	64.1	65.4	63.4	1.67	0.7
31-60 days	64.2	65.5	63.1	1.28	0.47
61-80 days	65.6	64.0	63.6	1.45	0.59
81-100 days	65.6	65.3	63.9	1.07	0.51
Average	64.9	65.0	63.5	0.79	0.36

 

Figure 3: Mean values for DM digestibility in the goats
during successive periods of the experiment

Rumen parameters

Apparently, there were  no change due to defaunation in pH , which confirms the view of Collombier (1981), who reported that defaunation may not effect the pH. Higher values of ammonia nitrogen concentration observed in the rumen of faunated goats (Figure 4) may be attributed to the higher production of free amino acids from the degradation of feed proteins and peptides by protozoa (Itabashi and Katada 1976).

Figure 4: Mean values for rumen ammonia in the goats
during successive periods of the experiment
 

 The population of protozoa was reduced markedly  in the goats given the oil drench and this effect persisted throughout the experiment. These findings are similar to those reported by Nguyen Thi Hong Nhan et al (2000, 2003) and Seng Mom et al (2001), using diets based on untreated rice straw and a similar drench with vegetable oil.

Figure 5.  Mean values for protozoa numbers (x10^-5)/ml in the goats
during successive periods of the experiment

Numbers of bacteria were increased by defaunation.  The results received from a study by Koenig et al (---) indicated that elimination of protozoa from the rumen led to a 43% increase in total culturable bacteria. There are also several reports (Hungate 1966; Kayouli et al 1983/1984; Newbold and Hillman 1990) that defaunation or reduction in the protozoa population leads to an increase in the bacterial population.

Figure 6: Mean values for bacteria numbers (x10^-8)/ml in the goats
during successive periods of the experiment 

It is now generally accepted that in absence of rumen ciliate protozoa, the efficiency of rumen bacterial growth is enhanced and more microbial and dietary protein flows from the reticulo-rumen to the duodenum (Bird and Leng 1985).  Although half of the microbial protein in the rumen can be of protozoal origin, as a proportion of the microbial protein leaving the rumen, protozoal protein is usually under 10% (Owens and Zinn 1988). The absence of rumen protozoa is known to increase the efficiency of net bacterial growth due to elimination of protozoal predation increasing rumen bacterial turnover (Demeyer and Van Nevel 1979). This could have resulted in more microbial protein flow to the duodenum in the defaunated animals.

Conclusions

• Administration of soybean oil into the rumen of goats (5ml/kg live weight) eliminated the protozoa and brought about changes which were beneficial in terms of nutrient utilization, growth and feed conversion.

• To provide substantial support for this finding there is a need of long duration experiments with a range of diets.

Acknowledgement

These studies received financial support from the Mekarn Regional project funded by SidaSAREC.

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