Effect of dietary fiber sources on feed intake, nutrient digestibility and growth rate of growing rabbits fed water spinach or sweet potato vines with or without supplement of Wedelia trilobata and Hymenache acutigluma

Nguyen Thi Kim Dong and Nguyen Van Thu 
 

Cantho University, Vietnam

ntkdong@ctu.edu.vn

Abstract

Two experiments were carried out in the experimental farm of Cantho University to evaluate the effect of dietary fiber sources from vegetables and fiber supplements. Both experments were 2*3 factorial designs, with 3 replications and. The first factor was vegetable kind [water spinach (WS), and sweet potato vines (SPV)]; the second one was fiber supplement with Wedelia trilobata (WT), Hymenache acutigluma (HA), or none. The feeding trial (Expt. 1) was done on 4 male growing crossbred rabbits at 8 weeks of age in one experimental unit to evaluate on feed intake, growth performance and economic returns. In the digestibility trial (Expt. 2) nutrient digestibility, nitrogen retention and caecum fermentation were determined in 2 twelve-week old rabbits in one experimental unit.

In Expt. 1, the dry matter (DM) and organic intakes were similar (P>0.05) between vegetables and among fiber source supplements. The final weight and weight gain were significantly higher (P<0.05) in the diets fed WS only compared to SPV, and for the none fiber supplement. The lower feed cost resulting in higher benefits was found in the diets fed only SPV and the diet supplemented WT. In Expt. 2 the apparent digestibility (%) of DM, OM were significantly higher in the diet fed only WS (P<0.05), and the diets without fiber supplemented or supplemented WT (P<0.001). NDF and ADF digestibility values were significatly lower (P<0.01) in the diet with HA supplement. The total volatile fatty acids (VFAs) were similar between WS and SPV diets, but significantly higher (P<0.05) in the diets with WT supplement and none compared to the supplemented HA.

It is concluded that water spinach is superior to sweet potato vine as the basal diet for rabbits and that there are no nutritional benefits from offering higher fiber supplements such as Wedelia trilobata or Hymenache acutigluma.

Key words: Digestibility, growing rabbit, Hymenache acutigluma, sweet potato vine, water spinach, Wedelia trilobatas

Introduction

In recent years rabbit production and rabbit meat have been popular in the Mekong delta of Vietnam due to the human demands during the bird flu outbreak. Crossbred rabbits (Local and improved pure breeds) are popularly raised in the Mekong delta, because of good natural conditions such as suitable ambient temperature, rich soil and available fresh water throughout the year. The local green feed resources are abundant in this region for both planted and natural plants such as sweet potato (Ipomea batatas), water spinach (Ipomoea aquatica), Mom grass (Hymenache acutigluma) and Cuc (Wedelia trilobata).  However, there has been a limitation of studies of these feeds in the rabbit diets for further research and farmers’ production.  Therefore, the objectives of the study were to evaluate for rabbit production forages of sweet potato vine and water spinach supplemented with fiber sources from Hymenache acutigluma or Wedelia trilobata.
 

Materials and methods

Experiment 1.  Feeding trial

Animals and experimental design

The experiment was conducted in the experimental farm and laboratories of Cantho University. Seventy two male-crossbred rabbits (local x improved breeds) at 60 days of age were allocated in a 2*3 factorial design, with 3 replications and four male rabbits in one experimental unit. The first factor was kind of vegetable: water spinach (WS) and sweet potato vines (SPV) as main feeds. The second factor was fiber source supplement; Hymenache acutigluma (HA), Wedelia trilobata (WT) or none.  The rabbits had free access to water spinach or sweet potato vine, each with or without access to Wedelia trilobata or Hymenache acutigluma or nothing. The rate of the two feeds in the diets was 1:1 based on DM. Paddy rice was supplemented to all the dietary treatments at the same level of 15g per day per rabbit to provide energy.  The experimental period was 8 weeks.

Feeds, feeding and management

Wedelia trilobata (WT) and Hymenache acutigluma (HA) were collected daily  in the areas belonging to Cantho University. Water spinach and Sweet potato vine were bought from one farm in the city. The animals were fed three times a day at 8:00h, 15:00h and 19:00h.. Fresh water was available for all rabbits almost all day and night time. The refusals and spillage were collected and weighed daily in the morning to calculate the precise feed intake. The animals were vaccinated to prevent rabbit hemorrhagic and parasite diseases.

Measurements

The feeds and refusals were taken for analyses of DM,  CP, EE, NDF, ADF, and Ash following procedure of AOAC (1990) and Van Soest et al (1991). During the experiment the rabbits were weighed individually every week. Daily feed intakes, growth rate, and feed conversion ratios were measured and calculated. After finishing the experiment the rabbits were slaughtered for evaluating carcass and meat quality. The economic analysis was also done. 

Experiment 2. Digestibility trial

Animals and experimental design

The second experimental design was similar to that of the feeding trial, however, thirty six growing male crossbred rabbits at 12-week of age were used. Diets were divided into 3 parts and fed at 7.00, 13.00 and 17.00. The adaptation period for the diets was 2 weeks and feed offered, refusals, faeces and urine were collected for 7 days of the third week to measure feed and nutrient digestibility and nitrogen retention.  At the end of the third week the rabbits in each experimental unit were slaughtered at 9.00 am (3 hours post feeding) to get the caecum content which was treated immediately for measuring VFA concentration following the methods described by Barnett and Reid (1957).

Statistical analysis

The data from both experiments were analyzed by analysis of variance using the ANOVA of General Linear Model of Minitab Reference Manual Release 13.21 (Minitab, 2000). The Tukey test was used to compare the means of the criteria (Minitab, 2000). Economic analyses were done using current prices in Vietnamese Dong (VND) to compare differences of income and the feed cost in different treatments

Results and discussion

Feed characteristics

The chemical composition of the feed ingredients fed to rabbits in the trial is shown in Table 1.

Mom grass (Hymenache acutigluma) had the highest DM content (15.7%) compared to those of Cuc (Wedelia trilobata), water spinach and sweet potato vine (12.1, 9.63 and 8.56%, respectively). These figures were similar to reports of Nguyen Hai Phu (2004), Danh Mo (2003) and Dao Hung (2006). Crude protein content was higher for sweet potato vine and water spinach. These values were slightly lower than those of Nguyen Thi Xuan Linh (2005) and Danh Mo (2004) due to the affects of rainy season for the experiment. The NDF content was high in Mom grass (66.3%). The ADF content of Mom grass and Cuc was higher than those of sweet potato vine and water spinach. Paddy rice supplemented had DM and CP content of 87.4 and 6.68%, respectively.

The DM intake was not significantly different between main feeds (WS and SPV) and among different supplements (Table 2).

These results are consistent with reports of Nguyen Van Thu and Nguyen Thi Kim Dong (2005) being from 51.4 to 61.5 g DM/rabbit/day in a study with SP replacing para grass in growing rabbit diets.

Daily weight gain, feed conversion ratio and economic analysis

Daily weight gain, feed conversion ratio and economic analysis are shown in Table 3.

Final weight and daily weight gain were significantly higher in the WS diet and  in the diet including WS or SPV without supplement of HA or WT (P<0.05).  The results of daily weight gain of crossbred rabbits fed local green foliages in the present experiment ranged from 14.8 to 16.0g. They are consistent with those (from 11.0 to 19.0g) of other reports in Vietnam by Nguyen Thi Xuan Linh (2005) Dao Hung (2006), Nguyen Van Thu and Nguyen Thi Kim Dong (2005) and Nguyen Thi Kim Dong et al. (2006). The values were also within the range reported by Samkol et al (2006). They were slightly lower than those found by Phimmasan et al. (2004) and Khuc Thi Hue and Preston (2006). Feed conversion ratio of the rabbits was from 3.63 to 4.42, and the WS diet had better FCR than the SPV diet (P<0.05). Significantly lower values were found in the diets without HA or WT supplementation (P<0.01).  The economic analysis showed that benefits got from the SPV diet and diet supplemented with WT were higher than the rest of the diets due to lower cost of feeds, despite growth rate and feed conversion ratio of the WS diet and the vegetable diet without supplement being better. Thus the local green feed sources available can be used as staple feeds in the rabbit diets to get better benefits by farmers.  

Mean values for slaughter weights, carcass traits and meat quality of growing rabbits

The criteria of carcass, thigh meat, lean meat and meat quality were not significantly affected by the two kinds of vegetables, and three kinds of fiber supplement (none, HA or WT) (Table 4). Nguyen Van Thu and Nguyen Thi Kim Dong (2005) in a study of sweet potato vine replacing para grass in the diets reported that the carcass and lean meat percentage of growing crossbred rabbits were from 41.6 to 47.1% and from 67.8 to 79.2%, respectively. Crude protein content of rabbit meat in the present experiment was from 18.9 to 19.2%, while this was 22.5% in the study of Nguyen Chu Chuong (2003).  In the current experiment paddy rice was the energy supplement, while in other experiments on pure improved breeds concentrates were mostly used for supplements.

Experiment 2: Digestibility trial

Chemical composition of feedstuffs used (Table 5) was similar to those in experiment 1, except for a slightly lower CP content of the SPV. Feed intakes ranged from 57.8 to 61.0g DM/day, and the values were closed between main feed and among fiber supplements.

The apparent DM digestibility was higher for the diets with water spinach  than for those with sweet potato vines but there were no differences in crude protein digestibility (Table 6). Supplementing the vegetable component with the WT and HA tended to reduce digestibility coefficients although the differences were only significant for the HA supplement.

Perez et al (1996) stated that a high level of fibre in the diet leads to decreased retention time of ingesta and an increase of caecotrope production because of increasing bacterial fibrolytic activity, which in turn results in a reduction of diet digestibility (De Blas et al 1998). In a recent study of water spinach leaves fed to growing rabbits, Nguyen Thi Kim Dong et al (2006) reported that the DM digestibility and CP digestibility were from 62.7 to 73.0 and 82.0 to 84.5, respectively. Samkol et al (2006) reported DM, CP and NDF digestibilities similar to those in the present study.  Nitrogen retention of the rabbits did not differ among treatments (Table 6).

 
Conclusions

The conclusions of the study are that:

·         Water spinach was better than sweet potato vine as the basal diet for rabbits.

·          There were no nutritional benefits from offering high fibre supplements such as Wedelia trilobata and Hymenache acutigluma.

Acknowledgements

Financial support of this work from SIDA-SAREC received through the MEKARN project is gratefully acknowledged. The authors would like to thank the Department of Animal Science, Faculty of Agriculture and Applied Biology of Cantho University for infrastructure support, and also thank to the valuable help of Dr. Brian Ogle.

References

Akinfala E O, Matanmi O and Aderibigbe A O 2003: Preliminary studies on the response of weaner rabbits to whole cassava plant meal basal diets in the humid tropics. Livestock Research for Rural Development (15) 4. http://www.cipav.org.co/lrrd/lrrd15/4/akin154.htm

AOAC 1990: Official methods of analysis (15^th edition). Washington, DC. Volume 1: 69-90.

Barnett A J G and Reid R  L 1957 Studies on the production of volatile fatty acids from grass by rumen liquor in an artificial rumen. The volatile fatty acid production from grass. J. Agric. Sci. Cam. 48. pp, 315-321.

Danh Mo 2003: A study of improving in vitro forage digestibility measurement by using rumen fluid as nutrient source replacing chemicals for microbes in swamp buffaloes (Vietnamese). MSc thesis. Faculty of Agriculture and Applied Biosciences. Cantho University. Vietnam.

Dao Hung, 2006: Breed characteristics and productivity; and effect of crude protein levels on growth rate, feed intake, nutrient digestibility and nitrogen retention of crossbred rabbits (Vietnamese). MSc thesis. Faculty of Agriculture and Applied Biosciences. Cantho University. Vietnam

De Blas E and Gidenne T 1998: Digestion of starch and sugars. In: The Nutrition of the Rabbit (Editors: C De Blas and J. Wiseman). CABI Publising. Wallingford. Pp: 17-38.

Hongthong Phimmmasan, Siton Kongvongxay, Chhay Ty and Preston T R 2004: Water spinach (Ipomoea aquatica) and Stylo 184 (Stylosanthes guianensis CIAT 184) as basal diets for growing rabbits. Livestock Research for Rural Development. Vol. 16, Art. No. 34. http://www.cipav.org.co/lrrd/lrrd16/5/hong16034.htm

Khuc Thi Hue and Preston T R 2006: Effect of different sources of supplementary fibre on growth of rabbits fed a basal diet of fresh water spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 18, Article No. 58. http://www.cipav.org.co/lrrd/lrrd18/4/hue18058.htm

Minitab  2000: Minitab reference manual release 13.20. Minitab Inc.

Nguyen Chu Chương 2003: Questions and Answers on rabbit husbandry, Agriculture Publishing house. Pp. 43 – 45.

Nguyen Hai Phu 2004: Growth characteristics and nutritional values of Mom (Hymenache acutigluma)  and para grass (Brachiaria mutica) grown at SOHA farm. BSc thesis. Faculty of Agriculture and Applied Biosciences. Pp. 3.

Nguyen Thi Kim Dong, Nguyen Van Thu, Ogle R B and Preston T R 2006: Effect of supplementation level of water spinach (Ipomoea aquatica) leaves in diets based on para grass (Brachiaria mutica) on intake, nutrient utilization, growth rate and economic returns of crossbred rabbits in the Mekong Delta of Vietnam. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article # 20. Retrieved, from http://www.mekarn.org/proprf/kimd2.htm

Nguyen Thi Xuan Linh 2005: Effect of sweet potato vines replacing para grass (Brachiaria mutica) on feed and nutrient digestibility and nitrogen retention of growing crossbred rabbits. BSc thesis. Faculty of Agriculture and Applied Biosciences. Pp. 4-12, 17.

Nguyen Van Thu and Nguyen Thi Kim Dong 2005: Effect of replacement of diffferent levels of para grass by sweet potato vines on feed utilization, growth rate and carcass quatily of crossbred rabbits in the Mekong delta of Vietnam. In proceedings of Integrating Livestock-crop systems to meet the challlenges of globalisation. Ed. Rowlinson, P., Wachirapakorn, C., Pakdee, P., and Wanapat, M.  Vol 2: T51.

Perez J M, Gidenne T, Bouvarel I, Arveux P, Bourdillon A, Briens C, Le Naour J, Messager B and Mirabito L 1996: Apports De Cellulose Dans L’alimentation Du Lapin En Croissance. Ii. Consequences Sur Les Performances Et La Mortalite. Annales Zootechnologie, 45, 299-309.

Pok Samkol, Preston T R and Ly J 2006: Digestibility indices and N balance in growing rabbits fed a basal diet of water spinach (Ipomoea aquatica) supplemented with broken rice. Livestock Research for Rural Development. Volume 18, Article No. 22. http://www.cipav.org.co/lrrd/lrrd18/2/samk18022.htm

Van Soest P J, Robertson J B and Lewis B A 1991. Symposium: Carbohydrate methodology, metabolism and nutritional implications in dairy cattle: methods for dietary fiber, and non-starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74: 3585-3597.

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