Effect of different sizes of sugarcane stalk residue in the basal diet with Operculina turpethum supplement on feed utilization, nutrient digestibility and growth rate of crossbred rabbits

Nguyen Thi Kim Dong and Nguyen Van Thu

Cantho University, Vietnam
 ntkdong@ctu.edu.vn

Abstract

An experiment was carried out at the experimental farm and laboratory of Can Tho University to evaluate feed utilization, nutrient digestibility and growth rate of Crossbred rabbits. It was a factorial design in which the first factor was length of sugarcane stalk residue (SSR) (3 and 10 cm length) fed ad-libitum, and second factor was different supplement of Operculina turpethum (OT) (0, 100, 200 and 300g/rabbit/day) with three replications and 4 rabbits per experimental unit. The results show that the intakes of sugarcane stalk residue were slightly higher (P>0.05) for rabbits fed 3cm length and gradually decreased with increasing supplement of OT in the diets (P<0.05), while OT intakes were remarkably increased (P<0.05). The total DM, CP, EE and ME intakes were higher for rabbits given sugarcane stalk residue at 3cm length (P<0.05) and when increasing the levels of OT supplement (P<0.05). The digestibility coefficients of DM and CP were higher for animals offered 3cm length sugarcane stalk residue (P<0.05), and NDF values were clearly improved with increasing OT supplement in the diets (P<0.05). The higher nitrogen intake and retention were found for rabbits fed 3cm sugarcane residue (P<0.05) and supplemented 300g OT/rabbit/day. The daily gain and final live weight  were significantly higher for rabbits fed 3cm length sugarcane stalk residue and supplemented 300g OT per animal per day (P<0.05).

It was concluded the rabbits fed 3cm length sugarcane stalk residue and supplemented 300g OT per animal per day in the diet had better growth rate and gave higher economic returns.

Key words: Daily weight gain, nutrient intake, nitrogen retention, economic returns

Introduction

Para grass (Brachiaria mutica) is popuparly fed ruminants and rabbits in the Mekong delta (MD) of Vietnam due to the well growth and good nutrient contents, particularly it supplies the fiber source. While Operculina turpethum  is used for offering protein in the diets. Also sugarcane talks have a high sugar content, which could be used for supplying energy source to mono-gastric animals (Preston and Leng, 1987). Nguyen Quang Suc et al (1995) concluded that sugarcane is an important source of fiber and energy for the rabbit. Peeled sugarcane stalk, supplemented with protein-rich feeds (soyabean seed and Canada bean foliage), could replace concentrates and grass for lactating and fattening rabbits. In an early trial in Mauritius, coarsely chopped sugarcane was successfully used to replace one half the balanced concentrate feed ration with no consequent drop in performance. In a complementary trial, the same authors found that, fed ad lib, rabbits chose to replace up to 40 percent of their balanced concentrate feed with chopped sugarcane (Lebas et al., 1997). In the MD sugarcane production has been developed well with 48,000 ha and 3.2 million tons in production year 2010-2011 (SGGP, 2011). Sugarcane stalks are popularly pressed to make fresh juice for human consumption, besides the main product of sugar. In the process of making the juice the lower parts of the stalks with more bud-eyes become the residues, however the studies on their utilization as animal feed resources has been limited. Therefore, this study aimed to determine nutrient utilization and performance of growing rabbits based on sugarcane stalk residue associated with Operculina turpethum supplementation for improving the production and farmers’ income. 

Materials and Methods

Experimenta1 Feeding trial

Animals and experimental design

The experiment was carried out in Experimental farm in Cantho City. Ninety six young crossbred rabbits (local x improved breeds) at 6 weeks of age with similar live weight around 712 - 750g were arranged in a factorial design with 2 factors. The first factor was length of sugarcane stalk residue (3 and 10 cm length) fed ad-libitum, while second one was supplementation levels of Operculina turpethum (OT) (0, 100, 200 and 300g/rabbit/day) with three replications and 4 rabbits (sexual balance) per experimental unit. Para grass, soya waste and dried sweet potato waste were also given with the same amount to all dietary treatments to provide protein and energy. The experimental period was 10 weeks.

Photo 1: Operculina turpethum	Photo 2:  Sugarcane stalk residue	Photo 3:  Dried sweet potato waste

Feeds, feeding and management

Operculina turpethum (OT) and Para grass were daily collected surrounding the farm and soya waste was daily bought from the soya meal factory. The sugarcane stalk residue (SSR) was a lower part left of sugarcane tree after selection a good part to make sugarcane juice for human. Before feeding, the SSR was cut to small pieces of 3cm and 10 cm length.

Dried sweet potato waste was bought in an occasion used throughout the experiment. The animals were fed three times a day at 8:00h, 14:00h and 18:00h. OT and SSR were offered and recorded daily. Fresh water was available for all rabbits almost all day and night time. The refusals and spillage were daily collected and weighed in the morning to calculate the feed intake. The animals were vaccinated to prevent some diseases, especially rabbit Hemorrhagic, parasite and other common diseases.

Measurements

The feeds and refusals were taken for analyses of DM, OM, CP, EE, Ash and NDF following procedure of AOAC (1990) and Van Soest et al. (1991). At the beginning of the experiment, four rabbits per experimental unit were weighed individually weekly. Daily feed intakes, growth rate, and feed conversion ratios were measured and calculated. The economic analysis was also done among the treatments.

Experiment 2: Digestibility trial

Animals and experimental design

The second experimental design was similar to that of the feeding trial; however, two rabbits at 12 weeks of age were used per experimental unit. The animals had two weeks for adaptation and one week for fecal collection. Feeds and refusals were daily measured. Urine was also collected for nitrogen analysis to calculate the nitrogen retention.  DM, CP, EE and NDF digestibility were employed according Mc Donald et al (2002).

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). 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

Experiment 1: Feeding trial

Feed characteristics

Chemical composition of feed ingredients of rabbit is presented in Table 1.

Operculina turpethum (OT) had higher CP and EE contents, but lower NDF component as compared to those of Para grass (PG) (Table 1), while sugarcane stalk residue (SSR) with the lowest CP value. The DM and CP contents of OT in our experiment are similar to the values (11.2% DM and 15.2% CP) reported by Pham Duc Thang (2008). Dried sweet potato waste had higher ME concentration as compared to other feeds to provide energy for the rabbits.

Feed and nutrient intakes in the feeding experiment

Daily intakes of feeds and nutrients of rabbits in feeding experiment are shown in Table 2.

Daily intake of Operculina turpethum (OT) was similar between two sizes of SSR length (P>0.05). However there was considerably increase of OT intakes corresponding with increasing levels of OT in diets (P<0.05), while SSR intake significantly decreased  (P<0.05). Rabbits fed 3cm length sugarcane stalk residue (SSR) tended to have higher intake, but being not significantly different (P>0.05) (Table 2). The total daily intakes of DM, OM, CP and ME were higher for animals fed 3cm length SSR (P<0.05), as a result of short SSR pieces make the rabbits rodent efficiently. The intakes of DM, OM, CP, EE, NDF and ME increased with increasing levels of OT in the diets, reaching the highest values for the OT300 diet (P<0.05), possibly due to  graded supplements of OT in the diets.  The daily DM intakes in a present study are in agreement with the results (57.5-62.7gDM/rabbit), but being lower in CP intakes (10.4- 11.0gCP/rabbit) reported by Ly Hoa Nguyet (2011).

Figure 1: Daily intakes of OT and SSR (g DM/day)

Growth rate, feed conversion ratio and economic analysis in feeding experiment

The results of daily weight gain, final weight and economic analysis of rabbits are shown in Table 3.

Daily weight gain (DWG) and final live weight (FLW) were significantly higher for the rabbits offered 3cm length SSR than those given 10cm length SSR (P<0.05). The explanation is that the animals had higher intakes of DM and other nutrients such as OM, CP and ME. The findings of  DWG and FLW gradually increased corresponding to increasing OT supplement in the diets, getting the highest values in the OT300 diet (P<0.05), probably, due to higher intakes of DM, CP, EE and ME. The daily weight gains of rabbits in this study were also within the ranges (14.4 to 20.3 g/day) reported by Samkol et al (2006a). The results are also consistent with those found by Nguyen Truong Giang (2010) (DWG from15.2-20.0 g/day) in which crossbred rabbits fed sweet potato and Para grass with supplemented molasses. However, the values of DWG and FLW in a present trial were lower than those reported by Tran Minh Thanh (2011) (DWG from 18.5 - 21.7 g/day and FLW from 2075- 2287 g/rabbit). Feed conversion ratio (FCR) was better for rabbits fed 3cm length SSR (P<0.05), as a result of higher DWG. The obtained values for FCR were better than those of 4.5 to 5.5 and 4.6 to 5.2 indicated by Phiny and Kaensombath (2006) and Nakkitset (2007), respectively.  There was a close linear relationship between CP intake and daily weight gain of rabbits shown in Figure 2.

Figure 2: Relationship between CP intake and DG of growing rabbits

The economic analysis was done and showed that the feed cost and total expense were lower for rabbits fed 3cm length SSR and for the OT0 diet. However, the higher income was found in the short SSR length and the OT200, OT300 diets, resulting in more benefits in these diets. The results indicated that the promising diets giving better economic returns for rabbit production could be supplemented Operculina turpethum at levels of 200-300 g/rabbit/day. There were no significantly different interactions between two factors of length of sugarcane stalk residue and levels of Operculina turpethum in all criteria of the feeding experiment (P>0.05).

Experiment 2: Digestibility trial

Feed characteristics

Chemical composition of feeds used (Table 4) was similar to those in feeding trial.

Daily intakes of feed and nutrients of growing rabbits in digestibility experiment

Daily intakes of feed and nutrients of rabbits in digestibility trial are presented in Table 5

Daily intakes of DM and most of nutrients such as OM, CP, NDF and ME of the rabbits between two factors were slightly higher than those obtained in the feeding trial, may be due to data recorded in one week of the 12 week old rabbits in digestibility experiment.

Apparent digestibility of dietary nutrients, nitrogen retention of growing rabbits 

Apparent digestibility of dietary nutrients, nitrogen retention of growing rabbits are shown in Table 6.

The apparent digestibility coefficients of DM, OM and CP were significantly higher (P<0.05) in the 3cm length SSR.  These values were improved when increasing OT supplements in the diets, but being not significantly different (P>0.05) (Table 6). Our results are also in agreement with the findings that the digestibility indices of DM and CP were improved with increasing water spinach levels offered in the diets (Samkol et al., 2006b).  The obtained DM and CP digestibility values are similar to those (65.4 to 75 %DM and 74.3 to 80.6 %CP) of studies reported by Akinfala et al (2003) and Nguyen Thanh Tung (2012), respectively. However, the results in our experiment are lower than those (80.5-85.4 % CPD) found by Huynh Thu Thao (2011).

The results indicate that there was significant difference in both the nitrogen intake and nitrogen retention between two factors (P<0.05), this probable explanation is different CP intakes in dietary treatments caused by graded OT supplementation. The findings of nitrogen intake and nitrogen retention in this experiment are consisted with data of 0.57- 0.74 g/kg W^0,75 stated by Duong Thi Bich Loan (2010). In the present experiment there were no significantly different interactions between two factors of length of sugarcane stalk residue and levels of Operculina turpethum in all criteria of the digestibility trial (P>0.05).

 Conclusions 

·         The sugarcane stalk residue could be used as a feed for growing rabbits.

·         The rabbits fed the 3cm length sugarcane stalk residue had higher nutrient intakes and gave better growth rate and profit.

·         Supplementing Operculina turpethum at level of 300g per rabbit per day had better growth performance and higher profit.

·         Apparent NDF digestibility and N retention were improved with increasing levels of Operculina turpethum in diets.

Acknowledgements

Fund support of this work from MEKARN Project financed by Sida/Sarec gratefully acknowledged. The authors would like to thank Dr. TR Preston for his valuable advices and the Department of Animal Sciences, Faculty of Agriculture & Applied Biology of Cantho University for infrastructure supports.

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