Effect of level of dietary protein on growth and feed conversion of Moo Lath pigs fed a mixture of ensiled taro foliage (Colocasia esculenta) and of ensiled banana pseudo-stem (Musa spp)

Bounlerth Sivilai and T R Preston¹

Department of Livestock and Fisheries, Faculty of Agriculture, National University of Laos, Vientiane Capital, Lao PDR
lerth_si@yahoo.com
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

Abstract

Twenty female pigs (Moo Lath breed), with average initial live weight of 11.4 kg were housed in individual pens and randomly allocated to 5 dietary crude protein levels ( 8, 9. 10, 11 and 12% in DM), derived from ensiled taro foliage (range of 30-70%), ensiled banana pseudo stem (48-5%) and broken rice (20%) (on DM basis).

Growth and feed conversion were optimized with 12% crude protein in the diet DM, 80% of which was derived from ensiled taro leaves and petioles.   

Key words: broken rice, feed intake, forages, indigenous breeds

Introduction

Pig production is a major economic activity for smallholder farmers in mountainous regions of Lao PDR as well as being a source of meat for consumers.  According to Phengsavanh et al (2010), indigenous breeds such as Moo Lath are preferred as they readily adapt to the traditional system of free grazing and scavenging. However, growth rates are low (100-140 g/day) and up to 2 years may be needed to reach a marketable weight of 60 to 70 kg (Phengsavanh and Stür 2006).

The feeds accessed in scavenging systems are mostly natural grasses which are especially lacking in protein and minerals (Chitthavong et al 2012). Thus there were immediate benefits in the scavenging system from introducing the forage legume "Stylosanthes guianensis" (Phengsavanh and Stür 2006). However, scavenging is not sustainable in the long term as it generates conflicts, especially in areas where crop production is increasing.

Where bananas are grown for human consumption the pseudo stem is often used traditionally as part of the pig diet. The pseudo-stem of the banana plant is potentially of high nutritional value, as in contrast to most trees, the stem (or trunk) is supported by water rather than by lignified fibrous structures. The nutritional constraints are the low content of protein and minerals and the low nutritional density due to the high content of moisture.

In a previous experiment we showed that even when the protein imbalance in banana pseudo stem was corrected by addition of soybean meal, the response of Moo Lath pigs, measured in terms of N retention, was poor, and that a much greater degree of improvement was secured by replacing both the banana pseudo-stem and the soybean meal with ensiled leaves and petioles of the Taro plant (Colocacia esculenta) (Sivilai et al 2016).

The proteins in the leaves of most plants have a good balance of essential amino acids, as the leaves are the growing points of the plant and are rich in enzymes.  Recognition of these characteristics offers the opportunity to economize on the supply of protein to the animal receiving such diets as the balance of essential amino acids will resemble more closely that in an ‘ideal’ protein and overall protein levels can be lower (Wang and Fuller 1989; Preston 2006).

The aims of the present study were therefore to determine the levels of protein needed to optimize growth rates in Moo Lath pigs when the protein source was mainly supplied in the form of ensiled leaves and petioles of Taro (Colocasia ensiformis).

Materials and methods

Experimental site and climate condition

The experiment was carried out from January 2016 until May 2016 in the livestock farm of the Faculty of Agriculture, National University of Laos, Vientiane Capital, Lao PDR. The farm is located 32 km to the south of Vientiane city. The average daily temperature was 28 ˚C (range from 23 to 35 ˚C) at the time of the experiment.

Treatments and experimental design 

Twenty female pigs (Moo Lath breed), with average initial live weight of 11.4 kg were housed in individual pens and randomly allocated to 5 dietary crude protein levels: 8, 9. 10, 11 and 12% in DM, derived from ensiled taro foliage (TF) and ensiled banana pseudo stem (BS) (Table 1).

Animals and housing

The pigs were purchased from smallholder farms in Songhong village, Xaythany district, Vientiane capital, Lao PDR. The individual pens (1.3 m x 0.8 m), built from local materials; thatched roof, and wooden planks for the floor and the walls (Photo 1). The pigs were kept in quarantine pens for 2 weeks after arrival. They were vaccinated against swine fever and dewormed by injection with Ivermectin.

Feed resources

The banana pseudo-stem was brought from the gardens of smallholder farmers near the university; taro foliage was harvested from the banks of ponds in the local village where waste water stored. (Photo 2)The broken rice was purchased from a rice mill in Vientiane capital.

Ensiling the banana pseudo stem and the taro foliage

The outer part of the banana stem was discarded. The central part was chopped by hand into small pieces of 1-2 cm of length and wilted under shade for a day to reduce the moisture content to 80%. Taro foliage (leaves and petioles) was chopped by machine and then wilted under shade fir the same time as the banana stem. The forages were ensiled separately in polyethylene bags (capacity 20-30 liters) which were sealed to ensure an anaerobic condition. The silages were preserved for 7-14 days before being mixed, together with broken rice, in the proportions indicated in Table 1.

Photo 1. Traditional pig housing and Moo Lath pig used in the experiment
Photo 2. Taro and banana plantations
Photo 3. Taro foliage and banana stem chopped and ensiled in plastic bags

Measurements

The pigs were weighed at the beginning of the experiment, and every 14 days. Live weight gain was determined by the linear regression of live weight on time in the experiment. Feeds offered and refusals were recorded daily. Random samples of feeds and refusals were taken at intervals for determination of DM, N, crude fiber and ash according to AOAC (1990) procedures.

Statistical analysist

Data for feed intake, live weight change and feed conversion were analysed by the general linear model option in the ANOVA program of the Minitab software (Minitab 2014). Sources of variation in the model were treatments, replicates and error. Trends in DM intake, live weight gain and DM feed conversion (Y) were determined by fitting linear or quadratic equations to the data.

Results and discussion

Proximate composition of experimental diets

Levels of crude fiber were similar in the ensiled banana pseudo-stem and the ensiled taro foliage, but the latter had more protein and ash and the pH was lower (Table 2).

The achieved levels of crude protein in the final mixed diets were close to the planned levels (Table 3).

Feed intake, growth rates and feed conversion

The data for feed intake, growth rate and feed conversion followed curvilinear trends, indicating that for all criteria, responses were optimized as the crude protein concentration reached 12% in the diet DM (Table 4; Figures 1-4). 

The conclusion from these results is that 12% crude protein in diet DM supports optimum growth and feed conversion in Moo Lath pigs fed diets containing 80% of forages in the form of ensiled leaves and petioles of taro and ensiled pseudo-stem of banana, and with close to 90% of the protein being derived from the taro foliage.

The optimum protein level of 12% in diet DM reflects: (i) the high apparent digestibility (90%) and high biological value (74%) of the protein in diets with similar levels (75%) of ensiled taro foliage fed to Moo Lath pigs (Sivilai et al 2016).

Figure 1. Effect of dietary protein concentration on DM intake	Figure 2. Effect of dietary protein concentration on live weight gain

Figure 3. Effect of dietary protein concentration on DM feed conversion

Conclusion

• Growth and feed conversion in Moo Lath pigs over the live weight range 11-30 kg, fed forage-based diets (70% ensiled Taro leaves and petioles, 8% ensiled banana pseudo stem and 20% broken rice), were optimized with 12% crude protein in the diet DM.

Acknowledgement

This research was done by the senior author as part of the requirements for the PhD degree in Animal Production "Improving Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change Mitigation" of Nong Lam University. The authors acknowledge support for this research from the MEKARN II project financed by Sida/MEKARN II. Special thanks are given to Animal Science Students (Mr. Kou yang, Mr. Seng Thao and Mrs. Tong Song) for their practical help, field work and laboratory assistance during experiment. The Faculty of Agriculture, National University of Laos is acknowledged for providing the facilities to carry out this research.

References

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Sivilai B, Preston T R and Kaensombath L 2016 Feed intake, nutrient digestibility and nitrogen retention by Moo Lath pigs fed ensiled banana pseudo-stem (Musa spp) and ensiled taro foliage (Colocasia esculenta). Livestock Research for Rural Development. Volume 28, Article #6. http://www.lrrd.org/lrrd28/1/boun28006.html

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Wang T C and Fuller M F 1989 The optimum dietary amino acid pattern for growing pigs. British Journal of Nutrition. 62, 17-89

Received 17 July 2016; Accepted 3 January 2017; Published 1 February 2017

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