The growth performance of native pigs (Sus Scrofa) given diets in which soybean meal was replaced by ensiled taro foliage

Tran Trung Tuan^1,2 and T R Preston³

¹ An Giang University, An Giang, Vietnam
tttuan@agu.edu.vn
² Vietnam National University Ho Chi Minh City, Vietnam
³ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

Abstract

Eighteen native pigs were used in a 56-day growth experiment in which a rice bran-soybean diet was replaced by ensiled leaf and petiole of taro (TS) (Colocasia enculenta). The treatments were: TS0, TS50 and TS100 representing 0, 50 and 100% ensiled taro leaf and petiole replacing rice bran-soybean. There were negative trends in all performance traits with linear decreases in feed intake and live weight gain and increases in feed conversion as the rice bran-soybean diet was replaced by taro silage. However, from the farmers’ point of view the 20% decrease in growth rate and the 10% poorer feed conversion were more than compensated by the economic advantages of using a crop byproduct with no sale value. Replacement of an imported feed ingredient (soybean) by a locally produced byproduct also reflects one way in which feeding systems can be developed with benefits, however small, to counter global warming and lost of biodiversity.

Key words: local feed resources, indigenous breeds, protein-rich forages

Introduction

The New Cocoyam (Taro) belongs to the family of Araceae in which there are one hundred genera and more than fifteen hundred species (Rodriguez et al 2009). Taro biomass was reported to yield ranged from 248 to 373 t/ha/year of fresh biomass depended on season, weather, species, soil and cultivation (Hang and Preston 2010). Taro has two groups in Mekong delta, Viet Nam, one is cultivated to harvest tubers for human consumption and waste foliage in the field. The other variety grows wildly in wetlandand farmers use the leaves and petioles for pigs production by cooking them with rice or rice bran and cassava roots. However, taro foliage contains calcium oxalate crystals that cause itchiness if fresh taro foliage is in contact with the skin. According to Hang and Preston (2010) total oxalate levels in petioles (range from 1326 to 3567 mg/100 g DM), higher than in leaves (770 to 2531 mg/100g DM). Sun-drying, soaking, cooking and ensiling reduced calcium oxalate but cooking and ensiling had the most pronounced effect (50% reduction).

According to Rodriguez et al (2006), fresh leaves of Colocasia esculenta contains crude protein (248 g/kg DM), NDF (255 g/kg DM), ADF (198 g/kg DM) and amino acid composition in the leaves of methonine + cystine and threonine better than in soybean meal. Taro petioles are rich in soluble carbohydrates while crude protein content was lower than in the leaf (Hang and Preston 2009; Rodríguez and Preston 2009; Hang and Kien 2012). According to Hang et al (2019) fresh taro leaves contain high levels of calcium oxalates is a major factor to be considered when designing diet for pigs based on taro in pig production, which can reduce substantially the absorption of calcium and magnesium from the digestive tract. Ensiled taro leaves what considerably less oxalate compared with the fresh taro leaves.

According to Truong et al (2017) native pigs were derived from Vietnamese and imports from Thai Lan and China. Native pig production in Viet Nam helped farmers diversify animal products to improve household finance. According to Luu et al (2010) performance of native pigs in Viet Nam were very active, omnivorous and prolific. The age at first estrous of native pigs were 73.5 to 94.4 days. The first mating occurred at 251.5 to 229.5 days of age. The estrous cycle was 21 days and the estrous lasted for 2.5 days and the pregnancy length was 118 days. The weight at birth of native pig was 0.41 to 0.49kg. The average time from the farrowing to the next sexual cycle of sown were 75 to 83 days.

The aims of this experiment were how to make better use of taro foliage for pig production which was traditionally was wasted in the field after harvesting the tubers for human consumption.

Materials and methods

Animals and management

The native pigs used to conduct in the experiment were from a private farm in An Giang Province. Eighteen native pigs (nine castrated male and nine gilts) with average body weight at 60 days of age of 6.9±1.6kg were used. All pigs were vaccinated against hog cholera and foot and mouth disease and were treated against round worms before starting the experiment.

The pigs were housed in individual pens (0.6 m x 1.2 m) made of bamboo with feeding troughs to allow recording of offered feed and to collect refused feed. The pigs were given feed ad-libitum four times per day at 07:00, 11:00, 14:00 and 17:00h and feed refusals were collected and weighed before the morning and afternoon feeding. All pigs had free access to water with nipple drinkers. The experiment was conducted in a private farm in An Giang province.

Processing taro silage and experimental diets

Taro leaves and petioles were collected from the field after farmers had harvested the tuber and were chopped into small pieces (2 to 3 cm) and wilted under sunlight for 2 days to reduce moisture. Before making the silage, all pieces of taro leaves and petioles mixed with rice bran and salt following the formula 90: 9.5: 0.5 ratio and put in plastic bag tightly to reduce the air and fermented for 5 days. The diets were based on rice bran, soybean meal and ensiled taro leaf and petiole taro and were formulated to contain from 14 to 15% crude protein in DM.

Photo 1. Pigs and Taro

Experimental design

The experiment was designed as a Randomized Complete Block with 3 treatments and 6 replications. The pigs were allocated to blocks based on initial live weight and at random within blocks according to treatment. The experiment was conducted over 56 days, Feeding was ad libitum.

The treatments were:

TS0: rice bran and soybean meal.

TS50: 50% control treatment and 50% ensiled leaf and petiole taro.

TS100: 100% ensiled leaf and petiole taro.

Samples of ingredients (Table1) were analyzed for DM, crude protein, crude fiber and ash according to the standard methods of AOAC (1990), Dry matter was determined by using microwave radiation (Undersander et al 1993).

Statistical analysis

The data for feed intake, growth rate and feed conversion ratio were analyzed as a Randomized Complete Block Design by using the General Linear Model (GLM) of the Analysis of Variance (ANOVA) procedure of the Minitab statistical software release 16. Sources of variation were: animals, treatments, blocks and error. Linear regressions were fitted to the performance data using software in Microsoft Excel.

Results and discussion

Ingredients and chemical composition of the diets

Feed intake, growth rates and feed conversion

There were negative trends in all performance traits as the rice bran-soybean diet was replaced by taro silage. (Table 3; Figures 1-4), The crude protein content was similar across diets and higher than the level of 12% in DM reported as optimum for growing Moo Lath pigs fed diets based on ensiled taro foliage (Sivilai et al 2017), Low feed intake seemed to be the determinant factor (Figures 1 and 4) The level of crude fiber was similar on all diets and would not appear to be reason for decreasing intake as the level of taro silage in the diets was increased, The increase in oxalic acid is more likely to be the reason for the decreasing feed intake as shown by Hang et al (2019), these authors showed that the ensiling condition was important and that addition of molasses as silage additive was an important factor leading to reduced level of oxalate in taro silage (Hang et l 2019).

Figure 1. Effect of dietary taro silage on DM intake	Figure 2. Effect of dietary taro silage on LW gain
Figure 3. Effect of dietary taro silage on feed conversion	Figure 4. Relationship between LW gain and DM intake

However, the results must also be evaluated from the economic and environmental viewpoint. In this respect the 20% decrease in growth rate and the 10% poorer feed conversion were more than compensated by the economic advantages of using a crop byproduct with no sale value and reduction in global warming and improved biodiversity, that are likely to result from replacement of imported soybean by a local byproduct.

Conclusions

• Dry matter intake and growth rate were reduced when fed native pigs with ensiled taro foliage alone compared with homemade concentrate diet.
  
  
• Feed conversion ratio of pigs was increased when increasing taro foliage silage in diets.
  
  
• From the farmers’ point of view the slight decrease in growth rate was more than compensated by the economic advantages of using a crop byproduct with no sale value.
  
  
• Replacement of an imported feed ingredient (soybean) by a locally produced byproduct also reflects one way in which feeding systems can be developed with benefits, however small, to counter global warming and loss of biodiversity.

Acknowledgements

The author wishes to thanks Mrs Nhien, pig farm owner who sponsored all materials to conduct the experiment and Mr. Tung who help to take care of the feeding and management of animals.

References

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