MATERIALS AND METHODS

An in vivo trial was then conducted to determine the effect of cassava leaves, phosphorus and sulphur supplements on dry matter intake, digestibility and daily weight gain in cattle fed the roughage rice straw ammoniated. The trial was initiated on Mei 15, 2008 and ended on September 26, 2008. In this study, 16 Pesisir calves aged 9-12 months were divided into 4 equal groups on the basis of their body weights. All the calves were maintained under similar housing and management conditions and had free access to drinking water.

The calves were fed mixture of rice straw ammoniated (50%) and concentrate (50%). The composition of the feeds, including the concentrate is given in Table 1. Each group of the calves was randomly assigned to one of the following 4 treatments:

Table 1:	Ingredient composition and nutrition of experimental diet

Ammonia Treatment of Rice Straw
In this experiment, rice straw was sprayed with 4 kg urea in 100 L of water/100 kg dry matter of rice straw and stored between sheets of plastic for 3 weeks in anaerobic condition. The ammoniated rice straw was aerated prior to feeding.

Feed was offered twice daily at 08:00 h and 13:00 h and intake of roughage was measured each day throughout the trial. Fed was offered at 3% LW. The data on daily feed intake and weight gain were collected during a study period of 60 days and 7. Feed samples were analyzed weekly. Feed intake was recorded on the basis of dry matter intake. Samples of feed and feces, composite by animal across the 7 day collection period were analyzed for DM, OM and N by standard procedures (AOAC, 1984). Fecal sub samples (10%) were dried partially at 50°C for 48 h.

Statistical Analysis
The collected data were statistically analyzed using randomized complete block design (Steel and Torrie, 1984). Least Significant Difference (LSD) was used for comparison of means of treatments.

RESULTS AND DISCUSSION

Dry Matter Intake and Organic Matter Intake
Dry Matter Intake (DMI) in calves increased due to the highest intake DM and OM occurred in Diet D, followed by C, B and A. However, a minimum in DMI and OMI was found in control group. Statistical analysis indicated that DMI was significantly increased due to cassava leaves, phosphorus and sulphur supplementation. This result showed that cassava leaves, phosphorus and sulphur could improve population of rumen microbe than will be increase the rate of passage in rumen. It also has been demonstrated before that cassava leaves could improve the digestibility (Wiktorsson and Khang, 2004).

The improvements in digestibility and intake of poor quality roughages supplemented with protein (Berger et al., 1980; Orskov et al., 1980). Valk and Sebek (1999) who pointed out that phosphorus supplementation, increased DMI in dairy animals. Weiss and Wyatt (2004) reported that when the dietary phosphorus was increased from 0.34 to 0.45% of dry matter in diet of cows, DMI increased from 12.4 to 30.5 kg day^-1. However, non-significant difference was found between B, C and D diets (Table 2). The possible reason for low DMI in the A diet was indicated that rumen microbe cannot grow with ammonia as sole nitrogen source. Supplementation cassava as source protein, phosphorus and sulphur improved number of rumen bacteria and increased the digestibility and intake of ammoniated rice straw.

Table 2:	Feed intake, digestibility and live weight gain of cattle with experimental diet
Value with columns without common letters differ (p<0.01). A: Control (mixture ammoniated rice straw and concentrate), B: A supplemented with 5% cassava leaves, C: B supplemented with 0.4% phosphorus, D: C supplemented with 0.3% sulphur

Digestibility and Weight Gain
The addition of cassava leaves, phosphorus and sulphur affected all digestibility variables (p<0.01). Control diet (A) had the lowest DM, OM, protein, NDF and ADF digestibility (p<0.01) (Table 2).

Supplementation cassava leaves, phosphorus and sulphur was effective in stimulating dry matter, organic matter, protein and fibrous fraction digestibility. The increase in digestibility of DM, OM, protein and fibrous fraction of ammoniater rice straw that have been supplemented with cassava leaves, phosphorus and sulphur vs. control demonstrate that supplementation could develops the rumen bacterial growth, resulting in a greater rate of digestibility. This study has also shown that ammoniated RS were deficient in protein, phosphorus and sulphur and it supplementation is important to improve fibre digestibility of fibrous feedstuffs. The present results were in agreement with the results of Little (1986) Komizarczuk and Durand (1991) and Wanapat et al. (2000). The researchers had indicated that improvement in fibre degradation by cassaca leaves, phosphorus and sulphur supplementation occurred through its specific stimulation on growth of rumen cellulolytic bacteria and anaerobic rumen fungi.

The weight of calves increased due to cassava leaves as protein source, phosphorus and sulphur supplementation. Maximum increase in daily weight was in diet E (610.25 g day^-1), followed by C (530.50 g day^-1), B (423 g day^-1) and A (289.75 g day^-1). Statistical analysis indicated that daily weight gain was significantly affected by nutrient supplementation (Table 2). These results are agreement with the result of Wanapat et al. (2000), Valk and Sebek (1999), Karn (2001) and Zinn et al. (1997) indicated a significant effect of cassava leaves, phosphorus and sulphur supplementation on weight gain.

CONCLUSION

Based on the findings of the present study, it was concluded that cassava leaves, phosphorus and sulphur supplementation had beneficial effects in terms of daily weight gain in cattle when given alone or combination in ammoniated rice straw diet to growing cattle. The best result achieved when they were given on combination.

ACKNOWLEDGMENTS

This work was supported by an Hibah Bersaing by Directorat General Higher Education, Department of National Education Republic of Indonesia in 2008. The study would not have been possible without the cooperation of technical assistance of Laboratory Ruminant Nutrition of Animal Science Faculty of Andalas University.