Effect of replacing fish meal by a mixture of ensiled taro (Colocasia esculenta) foliage and ensiled sweet potato vines (Ipomoea batatas L.) on reproduction and piglet performance in VanPa sows in central Vietnam

Tran Thanh Hai, Nguyen Thi Hoa Ly and T R Preston*

Hue University of Agriculture and Forestry, Vietnam
Thanhhai1406@gmail.com
* Finca Ecológica, AA48 Socorro, Santander, Colombia

Abstract

Eighteen VanPa sows (3rd -5th parity and live weight 50 - 60 kg  were were kept individually in concrete floor pens and mated with the semen of the same purebred VanPa boar. The trial was designed as a complete randomized block with 3 treatments and 6 replicates in which the protein source was supplied from a mixture of  50 % ensiled taro foliage  (ETS) and 50 % ensiled sweet potato vines (ESPV) and fish meal. Treatment FM (control diet) contained rice bran, cassava root meal and fish meal. T50 had 50 % of protein from fish meal replaced by protein from a mixture of ensiled  taro foliage and sweet potato vines; T100 had 100 % of protein from fish meal replaced by protein from a mixture of ensiled taro foliage and sweet potato vines. The feed allowance was fixed at 2.5 % of body weight in pregnancy and ad libitum in lactation. Protein levels were 12 % in DM in the diets for pregnancy and 13 % for lactation.

There were no differences in DM and CP intake among treatments for the pregnancy and lactation period. Total CF intake  increased with increased amount of a mixture of  ensiled taro foliage and sweet potato vines replacing fish meal. There were no effects of treatment on any of the parameters of piglet performance at birth, 21 days and weaning, except for mean piglet weight at weaning which was 13% higher for FM than T100. There was a tendency for mortality to weaning to be greater when the forage silage completely replaced fish meal (P=0.12)

It is concluded that a mixture of ensiled taro foliage and ensiled sweet potato vines can replace all the fish meal in diets of VanPa sows in pregnancy and lactation without affecting reproductive criteria, measured as numbers of live piglets born and weaned, and the interval from weaning to estrus. Using protein from a mixture of ensiled  taro foliage and sweet potato vines to completely replace fish meal reduced feed cost/kg piglet by 8.4 %.

Key words: indigenous, local feed resources, mountainous, rural development, small-holder

Introduction

VanPa is an indigenous pig breed that is well adapted to the environmental conditions of smallholder farmers in the uplands in Quang Tri province in Central Vietnam. This pig breed has been kept mainly under foraging system, and they are raised by the ethnic minorities Van Kieu and PaKo people in Quang Tri province due to their advantages, for example high environmental adaptability, good disease resistance, and the ability to utilise poor nutritional quality food.  VanPa sows have  low reproduction and growth performance (Hoa Ly et al 2010a), and piglet body weight at birth is only  0.29 kg/piglet with average litter size of only 4.53, body weight at 120 days old of only 10.4 kg/pig (Tran Thanh Hai and Le Dinh Phung 2009). The smallholder rearing conditions include feeding fibre-rich diets with low energy and protein. So it is very important to help farmers in this area improve the performance of this breed of pig. Conventional feeds are the main protein supplements in the region, including concentrate feed, groundnut cake and fish meal, but they are relatively expensive and are not available in the mountain villages.

Sweet potato is known as a valuable food crop with a high adaptability to different climatic and soil conditions. It has a high yield of both tubers and vines (Woolfe 1992; An et al 2003; Hoa Ly et al 2010b). In many areas, sweet potato leaves are consumed and varieties are grown which are suitable for harvesting of both tubers and leaves, or for harvesting leaves only. Sweet potato is not only used for human consumption but also for animal feed, because of its nutritional properties. In sweet potato vines the crude protein (CP) content in DM can range from 16 to 29% (Farrell et et al 2000; Hartemink et al 2000; Dung 2001, An et et al 2003). Content of minerals and vitamins such as A, B2, C and E are rather high in leaves of sweet potato in comparison with other vegetables. For this reason, both leaves and vines are used as protein and vitamin sources for pigs (Hoa Ly et et al 2010b;  Hoa Ly et et al 2012).

Taro (Colocasia esculenta (L.) Schott) can be a potential protein source for animals, especially pigs due to the good nutritional quality of the leaves. Many studies have been done on using taro for pigs (Chittavong et  al 2006, 2008; Tiep et et al 2006; Pheng Buntha et al 2008; Rodriguez et al 2009; Duyet 2010). Chittavong et al (2008) reported that a mixture of taro silage and water spinach can  replace 100% of soybean meal in pregnancy and lactation diets for Mong cai gilts without affecting sow reproduction. Sivilai et al (2010) concluded that a mixture of taro leaf silage and water spinach can be used in the diet of Mong Cai gilts in pregnancy and lactation without affecting reproduction criteria, measured as numbers of live piglets born and weaned, and the interval from weaning to estrus. The sows can obtain these nutrients by feeding them a high forage diet. Le Thi Men et al (2000) and Hoang Nghia Duyet et al (2003, 2004) showed that a suitable proportion of forage leaves in the diet of Mong Cai sows is 30 - 40 % (in DM) in the pregnancy period and 20 - 30% in the lactation period.

There are difficulties in using taro as animal feed because of its content of oxalic acid and other anti-nutritional factors that cause the mouth and throat of animals consuming it to itch. However, ensiling can be the most appropriate method to preserve taro leaves and reduce anti-nutritional factors for feeding pigs (Tiep et al 2006; Du Thanh Hang and Preston 2010).

In the uplands of Central Vietnam pig production systems using cassava and vegetables (such as taro and sweet potato vines) are common and play an important role in the economics of small farms. However, up to now no data can be found on on reproduction and piglet performance in VanPa sows fed diets based on forages as the protein source. Further research is needed to help farmers in this area on how to use the local protein sources from taro and sweet potato vines as the major protein supplement for VanPa sows with the aim to improve their reproduction and piglet performance. 

This study therefore aims to determine the effect of replacing fish meal by a mixture of ensiled taro foliage and sweet potato vines on reproduction and piglet performance in VanPa sows in Quang Tri province.

Materials and methods

Ensiling

Sweet potato vines were harvested at 60 days after planting, with subsequent harvests at 20-day intervals. At time of harvest, 50 % of the total branches were cut at 10 cm distance from the main stems. The vines were chopped into small pieces of 2- 3 cm and spread out on the floor overnight for wilting to reduce the moisture content. The wilted sweet potato vines were mixed with NaCl at 0.5% of the wilted weight of the vines.  

Taro foliage (leaves and stems) were collected 4 - 6 months after planting with subsequent harvests at 15- 20 day intervals. The foliage was spread out on the floor 15 hours for wilting, then chopped into small pieces (2 - 3 cm), mixed with NaCl at 0.5 % of wilted taro foliage. The silages of sweet potato vines or taro foliage was kept in sealed airtight plastic bags with a capacity of 30 kg and were stored for 14 days prior to feeding.

Samples of silage were taken after 14 days ensiling and were evaluated by approximate analysis for DM, CP, CF and OM (AOAC 1990).  The analysis was done in the Hue University laboratories from January 2011 to March 2011. 

Treatments, animals and experimental design

The experiment was carried out  on station  at the research farm of Quang tri province from January to September  2011. Eighteen VanPa sows (3rd -5th parity and live weight about 50 -60 kg) were  selected and allocated randomly into three groups, with each group consisting 6 pigs. In each group sows were allocated randomly into three treatments with 3 different levels of a mixture of ensiled taro foliage and sweet potato vines. The pigs were kept individually in concrete floor pens.

All VanPa sows in each group were mated with the semen of the same purebred VanPa boar. Three weeks after mating, the sows were fed the experimental diets. The trial was designed as complete randomized block with 3 treatments and 6 replicates in which the protein source was supplied from different mixtures of silage [50 % ensiled taro foliage (ETS) and 50 % ensiled sweet potato vines (ESPV)] and  fish meal (Table 1).  

The treatments were:

• FM (control diet): Basal diet contained rice bran, cassava root meal, fish meal
• T50: Basal diet with 50 % of protein from fish meal replaced by  protein from a mixture of ensiled  taro foliage and sweet potato vines.
• T100: Basal diet with 100 % of protein from fish meal replaced by protein from a mixture of ensiled  taro foliage and sweet potato vines.

Diets and feeding

The diets contained rice bran, cassava root meal, and fish meal and a mixture of  ensiled taro foliage and sweet potato vines.  The feed allowance was fixed at 2.5 % of body weight in pregnancy and ad libitum in lactation. Protein levels were 12 % in DM in the diets for pregnancy and 13 % for lactation (Table 1). The pigs was given three equal meals per day (07:00, 11:00 and 17:00 h); the refused feed was collected and recorded daily.  Water was available ad-libitum.  Feed chemical composition was determined at the laboratory of Hue University before the start of the experiments (Table 2).

Measurements

- Feed intake (recording feed intake in pregnancy and lactation stage)

- Stillbirths and mortality of the piglets after birth and during lactation stage (%)

- Litter size at birth and at weaning (piglets/ litter).

- Live weight of the piglets at birth and at weaning (kg/ piglet).

- Litter weight of piglets at 21 days of age

- FCR and price for producing 1 kg of weaned piglet (kg feed/ kg weaned piglet and price).

- Benefit between treatments

Chemical analysis

The chemical composition of feed was determined according to standard methods (AOAC 1990). Dry matter (DM) was measured by drying fresh samples at 100^oC for 24 hours. Total nitrogen (N) was determined by the Kjeldahl method and crude protein (CP) was calculated from total nitrogen (N*6.25). Ether extract (EE) was determined by Soxhlet extraction without prior acid hydrolysis. Ash was the residue after ashing the samples at 550 to 600⁰C.  

Statistical analysis

Data from the experiment were analyzed by ANOVA using the General Linear Model (GLM) procedure (Minitab Version 14, 2004). The Tukey pair-wise comparisons with a confidence level of 95 was used to determine the effects of dietary treatments. Results are presented as Least Squares Means with their pooled standard errors.

Results and discussion

Feed  intake

There were no differences in DM and CP intake among treatments for the two periods of pregnancy and lactation (Table 4). As expected, CF intake increased as the  mixture of  ensiled taro foliage and sweet potato vines replaced fish meal in the diets.

Piglet performance in lactation

There were no effects of treatment on any of the parameters of piglet performance at birth, 21 days and weaning (Table 5), except for mean piglet weight which was 13% higher for FM than T100. There was a tendency for mortality to weaning to be greater when the forage silage completely replaced fish meal (P=0.12)

Reproductive traits

Reproductive traits were not affected by the treatments (Table 6).  The interval of 14-15 days from weaning to estrus would result in around 2.1 litters/year.

Feed cost

The feed cost/kg piglet weaned was reduced by 8.4% when the taro/sweet potato silages replaced fish meal completely(Table 7).

Discussion

The lack of difference in production parameters, and the saving in feed cost, as taro/sweet potato silages replaced fish meal, confirmed the capacity of VanPa sows to utilize efficiently high forage diets. . This finding is in agreement with the report of Duyet et al. (2004) that the litter size of Mong Cai sows was not affected when soybean meal was replaced by a mixture of fresh leaves (from cassava, water spinach and sweet potato) in the diet. Future research should be directed at evaluating these diets in more productive crosses of Mong Cai with VanPa.

Conclusions

• A mixture of ensiled taro foliage (leaf aand stem) and sweet potato vines can replace 100 % of fish meal in pregnancy and lactation diets for Van Pa sows without affecting sow reproduction, measured as numbers of live piglets born and weaned, and the interval from weaning to estrus.
  
  
• However, weights of piglets at weaning decreased with a linear trend as the fish meal was replaced by the mixture of ensiled taro foliage and sweet potato vines.
  
  
• Replacing all the protein from fish meal with that from a mixture of ensiled taro foliage and sweet potato vines reduced feed cost/kg piglet by 8.4 %.

Acknowledgements

We are very grateful to the Swedish International Development Agency (Sida) through the regional MEKARN Project, for the financial support of this study.

References

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Received 14 January 2013; Accepted 29 January 2013; Published 1 March 2013

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