Apparent digestibility, nitrogen balance in crossbred Mong Cai*Moo Laat pigs fed diets varying in proportions of ensiled Taro forage

Taysayavong Lotchana, Vyraphet Phetsamay, Vivasane Souksakone and T R Preston*

Champasack University
Champasack province, Lao PDR
Lotchanasouks@yahoo.com

* UTA (Colombia), AA #48, Socorro, Santander, Colombia 

Abstract

Five crossbred castrated male pigs (Mong Cai*Moo Laat pig), with average weight 13 kg, were allocated at random to 5 diets within a 5*5 Latin square with periods of 14 days (7 days for adaptation and 7 days for collection of data). The treatments were proportions of ensiled Taro foliage and rice bran (RB: TS: 80:20, 60:40, 40:60, 20:80 and 0:100, DM basis). The diets were fed to appetite and adjusted to minimize residues.

DM intake and apparent digestibility coefficients of DM, OM and crude protein were high and tended to increase as the proportion of taro silage in the diet was increased from 20 to 100%. N retention followed the same trend with highest values for the diets with 80 and 100% Taro silage. Urine excretion was increased by increasing the proportion of Taro silage in the diet.

Key words: Taro (Colocasia esculenta), crossbred pigs, digestibility, ensiling, N balance.

Introduction  

Taros are an important food crop in many parts of the tropical world. The corms and cormels are rich in starch and may be eaten in a manner similar to potatoes, boiled, baked, roasted, fried or as a basis for soups for people. The leaves have been fed successfully to pigs (Preston 2006). However, both stems and leaves can be fed when ensiled together (Rodriguez et al 2009). The protein in Taro foliage was more digestible than the protein in mulberry leaves but the biological value of the protein was found to be similar for both foliages (Ty Chhay et al 2010).  

Research to develop alternative sources of protein for pigs has a high priority. It is also important that the alternative feed resources can be grown on the farm as this will: (i) directly benefit the poorer farmers, who do not have cash resources to purchase supplements from outside the farm; and (ii) be an active response to the need to localize the farming system as a defense against the decreasing availability and increasing prices of petroleum-based fuels which will drive up the costs of transport. In addition the use of these vegetative protein sources is facilitated when they are accompanied by energy sources that are low in both fibre and protein. A low content of fibre in the energy source compensates for the fibre present in the leaves of plants, while the protein in leaves is mainly present as enzymes having a balanced array of essential amino acids (Preston  2006). 

Thus feeding forages to pigs can have a number of important advantages, in that they are an inexpensive source of protein, can be grown at small-farm level, and are often by-products or co-products of multipurpose crops and trees. Feeding locally produced green forages to growing pigs and sows will in most cases significantly increase the sustainability, stability and profitability of the farming system

The aim of the present experiment was to evaluate the effect of ensiled Taro foliage (leaves and stems) on intake, apparent digestibility and N balance of crossbred castrated male pigs given a basal diet of rice bran.

Materials and methods

Location

The experiment was carried out at the Integrated Farming Demonstration center of Champasack University, situated about 13 km from Pakse city, Pakse District, Champasack Province; Laos PDR. The temperature in the area averages 23°C (Range 22 to 25). The experiment began from 21^st September to 1^st December 2011.

Experimental design

The experiment was a 5*3 Latin Square design arrangement of five dietary treatments applied to five crossbred castrated male pigs (Mong Cai*Moo Laat pig) (Table 1).The treatments were:

•  RBTS 80:20: Rice bran 80% + Taro silage 20%
• RBTS 60:40: Rice bran 60% + Taro silage 40%
• RBTS 40:60: Rice bran 40% + Taro silage 60%

• RBTS 20:80: Rice bran 20% + Taro silage 80%

•  RBTS 0:100: Rice bran 0% + Taro silage 100%

Animals and management

Five crossbred castrated male pigs (Mong Cai*Moo Laat pig) (Photo 1) were from the same sow with an initial weights ranging from 16 ± 1 kg were used in the experiment. The pigs were housed in metabolism cage during the whole trial (42 days). The metabolism cages (60*80 cm) were built to allow the quantitative collection of faeces and urine. With wood floors and the wall of cage was bamboo and provided with feeders, and automatic water drinkers. The metabolism cages were installed in an open stable. Each experimental period consisted of 14 days; 7 days to adapt to the diets followed by another 7 days for collection of faeces, urine and feed residues. The pigs were vaccinated against salmonella disease and de-wormed with Ivermectin before the start of the experiment.

Feeds and feeding 

The amounts of feed offered daily were fed to appetite and adjusted to minimize residues. The diets were formulated to contain 12.7% to 19.3% crude protein in the diet DM (Table 2). The diets proportions (% DM) were 80:20, 60:40, 40:60, 20:80 and 0:100 for rice bran and Taro silage. 

Taro (Photo 2) was brought from Phatomponh City. All Taros was hand-chopped with a knife into small pieces of about 2 to 3 cm and ensiled after mixing with salt (8 kg Taro with 0.5 % salt). They were stored in plastic bag for 14 days before being fed to the pigs. The purpose of processing the Taro silage (Photo 3) was to reduce the content of calcium oxalate (Ca₂C₂O₄) which causes irritation in the mouth and reduction in intake. Rice bran was purchased from a market in Champasak City. All the diet ingrediente were mixed together before feeding the pigs, which was done in two meals per day at 07.30 and 16.00 hours. For water was supplied through nipple drinkers.  

Measurements

The pigs were weighed at the beginning of the trial and every 7 days. Samples of feeds offered and feed refusals and total amounts of faeces were collected every day and were kept frozen in plastic bags until analysis at the end of each period for DM, N, Organic matter and crude fiber. Urine was collected in a plastic bucket to which sulphuric acid was added to maintain the pH below 4.0 (20 ml of a solution of 10% concentrated sulphuric acid added daily). The volume of urine was measured everyday and 10% of the total volume stored until the end of each period, when it was analysed for N.

Chemical analysis 

Samples of feeds and refusals were analyzed for dry matter (DM) by micro-wave radiation (Undersander et al 1993), and Nitrogen (N), Crude fibre (CF), Organic matter (OM) and Ash following AOAC (1990) procedures.

Statistical analysis 

Data were statistically analysed using the General Linear Model (GLM) option of the ANOVA program in the Minitab software (Minitab release 13.3, 2000). The sources of variation in the model for the statistical analysis were: Diets, periods and error.

Results and discussion

Chemical composition of diets 

The rice bran was high quality compared with that used by Nhan et al (2011). However, the Taro silage was also high in crude protein content (CP 19.3% in DM) (Table 3) when compared with the data reported by Nguyen Tuyet Giang 2011 (18.7% in DM). 

Feed intake  

The DM intake and CP intake of the diet increased linearly with the increase in the level of Taro silage (Leaf + stems) (Table 4; Figure 1). DM intake as a function of live weight was closely related with daily intake of crude protein (Figure 2). Diets with 100% of taro silage without rice bran (DM basis) supported higher rates of feed intake (70.4 g DM/kg LW/day) than the other diets. 

Apparent digestibility

Apparent digestibility coefficients of DM, OM and crude protein were high and tended to increase as the proportion of taro silage in the diet was increased from 20 to 100% (from 61.1 to 92.6 for DM and 54.3 to 91.1% for OM and from 79.3 to 94.3% for crude protein). Compared to Nouphone et al (2011) and Chhay Ty et al (2010), apparent digestibility coefficients in the present study were higher for the diets containing Taro silage. 

Nitrogen balance

N intakes were higher with increasing the level of Taro silage with 20, 40, 60 and 80 with intermediate values with 100% taro silage in the diet (Table 6 and figure 5). These intakes mostly reflected differences in DM intake which was highest on the RBTS0:100 diets. N retention followed the same trend with highest values for the RBTS0:100 diets.  

Diuretic effect of Taro silage  

The volume of urine excreted by the pigs increased (Table 6) with a curvilinear tendency (Figure 7) as the intake of taro silage increased.  

Conclusions

• The DM intakes and the apparent digestibility of DM, OM and Crude protein by crossbred castrated male pigs (Mong Cai*Moo Laat) were increased as the proportion of taro silage in the diet was increased from 20 to 100%.
• N retention was higher with 100% Taro silage in the diet than with 20, 40, 60 and 80% taro silage
• Urine excretion was increased by increasing the proportion of Taro silage in dietary intake from 20 to 100% of the diet.

Acknowledgements 

We would like to acknowledge the support of the Swedish International Development Agency (Sida) in funding this experiment as part of the MSc program in the regional MEKARN project. We also thank the students of the Faculty of Agriculture of Champasack University for their help in the management and feeding of the animals

References

AOAC 1990 Official Methods of Analysis Association of Official Analytical Chemists 15^th Edition (K Helrick editor) Arlington pp 1230
 

Chittavong Malavanh, Preston T R and Ogle Brian 2007 Effect of replacing soybean meal with a mixture of Taro (Colocasia esculenta (L.)Schott) leaf silage and water spinach on apparent digestibility in Mong Cai gilts at two stages of gestation, from: http://www.mekarn.org/msc2005-07/thesis07/mala3.htm

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