PROBLEM STATEMENT
Pigs are vital for smallholders in the uplands of Lao PDR, providing cash for essential needs such as food, school fees, and medical expenses, while also playing a role in traditional ceremonies Approximately 75% of households in these areas raise pigs, with native breeds constituting 85.1% of the livestock under smallholder systems These hardy pigs thrive on low-input, extensive systems that utilize naturally occurring feed, primarily agricultural by-products like rice bran and natural grasses Despite the abundance of rice bran in most households, its poor nutritive value limits optimal pig performance Since feed accounts for 50-60% of production costs, the quality of feed is crucial for successful pig farming, as low-quality feed can lead to poor appetite, slow growth, and high feed conversion ratios A significant challenge for farmers is the lack of affordable protein sources, such as soybean and fish meals, in rural areas.
Cassava plantations primarily focus on root production, with yields varying based on soil fertility, management practices, and irrigation systems On eroded soils, cassava root yields can range from 10 to 15 tonnes per hectare without additional inputs (Howeler, 1991) In Laos, the cultivation of cassava is significant for agricultural productivity.
Manihot esculenta, commonly known as cassava or 'Man Ton', ranks as the third most significant crop in Laos, following rice and maize, particularly for smallholder farmers in remote upland regions This crop has gained prominence as a cash crop for both domestic consumption and export, owing to its versatility in food, feed, and industrial applications, especially in starch production The rise of cassava in Lao PDR is largely attributed to the export of starch derived from its roots, supported by five cassava starch factories operating across a total planted area of 60,475 hectares, yielding an average of fresh roots.
Cassava farms yield approximately 27 tonnes per hectare, contributing to an annual production of around 1.6 million tonnes (Ministry of Agriculture and Forestry, 2013) They serve as a vital income source for rural households and a key energy component in pig diets due to their high soluble carbohydrate content (75-85%) and low crude protein levels (2-3%) The highly digestible starch in cassava roots, combined with solid state fermentation technology, can enhance protein content, potentially creating a nearly complete feed for pigs (Boonnop et al., 2009) Research indicates that fermentation can significantly increase true protein levels in cassava pulp and roots, with reported increases from 2% to 12% and 2% to 7% respectively (Sengxayalth and Preston, 2017a; Vanhnasin et al., 2016a) Solid state fermentation using Trichoderma pseudokonigii has also shown promise in enriching cassava flour and starch factory wastes (Balagopalan et al., 1988) Furthermore, the inclusion of yeast and bacteria in fermentation processes can improve the nutritional value of agro-industrial by-products (Okpako et al., 2008; Aderemi et al., 2007) Studies have shown that replacing maize with fermented cassava pulp containing 13% crude protein maintains digestibility and nitrogen retention similar to control diets (Huu and Khammeng, 2014) Protein-enriched cassava root (PECR) can contribute 25-28% of dietary protein in pig diets, effectively replacing ingredients like ensiled taro foliage or soybean meal (Vanhnsin and Preston, 2016b; Sengxayalth and Preston, 2017b), with positive growth responses noted in pigs fed cassava pulp enriched with true protein (Phuong et al., 2013).
Smallholder pig systems often rely on local feeds such as rice by-products, planted feeds, and various green materials, which unfortunately possess low nutritional value Women play a crucial role in this process, dedicating 2 to 3 hours daily to collect and prepare feed Farmers typically lack knowledge on optimizing these resources, resulting in a modest growth rate of only 100 to 120 grams per day when relying solely on local feeds While commercial feeds with high-quality protein sources like fish meal and soybean meal are available, their high costs make them inaccessible for smallholder farmers Therefore, enhancing the nutritional value of locally abundant feeds, particularly through microorganism fermentation, presents a viable solution to improve pig diets in Laos, ultimately reducing feed costs and providing economic benefits to rural farmers.
OBJECTIVES
This thesis aimed to enhance the nutritional value of cassava roots through the fermentation process using Saccharomyces cerevisiae, along with the addition of urea and di-ammonium phosphate The study focused on utilizing the improved cassava as a protein source in the diets of Moo Lath pigs.
To study nutritive value of casssava root by fermentation yeast (Saccharomyces cerevisiae), Urea and Di-ammonium phosphate additive
To study the limiting factor to the synthesis of true protein from crude protein in the fermentation of cassava root
To evaluate the use of protein-enriched cassava root as partial replacement of taro silage in a ensiled banana stem - based diet fed to Moo Lath pigs
HYPOTHESES
• Nutritive value of cassava root will be increased by fermentation with increase level of di-ammonium phosphate with yeast, Urea and additive
• The pH decreased with fermentation time could be limiting factor to the synthesis of true protein from crude protein in the fermentation of cassava root
• The protein-enriched cassava root as a partial replacement for taro silage in a diet will be improve growth performance of Moo Lath pigs.
SIGNIFICANCE/INNOVATION OF THE DISSERTATION
The innovations of the thesis study are:
This thesis presents findings from four experiments aimed at enhancing the nutritive value of carbohydrate-rich cassava root feeds through solid-state fermentation using yeast (Saccharomyces cerevisiae), urea, and di-ammonium phosphate (DAP) It includes the creation of a database detailing the chemical composition and nutritive profiles of protein-enriched cassava root (Manihot esculenta Crantz) The research also examines growth performance, feed intake, digestibility, and nitrogen balance in local Moo Lath pigs The results are designed to aid rural farmers in maximizing the use of locally available feed resources to improve pig performance, despite the widespread availability of cassava root in Laos.
The yeast Saccharomyces cerevisiae has significant potential to improve the nutritional and economic values of livestock feed, thereby boosting farming profitability and creating job opportunities However, its biotechnological applications in producing protein-enriched agro-industrial products in Laos remain largely unexplored This study aims to evaluate the utilization of Saccharomyces cerevisiae in this context.
Solid-state fermentation using Saccharomyces cerevisiae enhances the protein content of cassava roots, making them a valuable feed source for pig production This process transforms cassava into protein-enriched cassava root (PECR), which, when used to replace taro silage, improves the nutritional value of banana stem-based diets The highly digestible starch in cassava roots, combined with the protein-rich foliage of taro, offers a promising feeding strategy for small-scale pig farming in Laos Research indicates that incorporating PECR, up to 25% of the diet alongside ensiled cassava roots, taro foliage, and banana stems, significantly boosts feed intake, digestibility, and nitrogen retention in native Moo Lath pigs However, increasing PECR proportions to 50% and 75% results in a linear decline in these benefits.
LITERATURE REVIEW
PIG PRODUCTION IN LAOS
In Lao PDR, pig farming is prevalent, with 77% of households participating in production, highlighting its significance in rural livelihoods and food security (FAO, 2016) Small-holder pig farming systems not only serve as a vital income source for families but also support cultural practices, debt repayment, and savings They provide employment opportunities and facilitate access to essential resources such as food, medication, and education for children (CelAgrid, 2006) Additionally, pigs thrive in foraging systems, making them well-suited for local farming practices (Phengsavanh et al.).
Pigs are advantageous livestock due to their ease of raising and selling, requiring minimal space while efficiently converting various crop and kitchen wastes into higher income compared to other animals like ducks or chickens Their manure serves as a valuable fertilizer for crops and a protein source for growing pigs In Vietnam, farmers profit by selling pig manure to improve soil quality, while in Laos, a study revealed that 60 pigs can generate enough manure to support a hectare of fish pond, yielding up to 4,000 kg of fish annually Additionally, pig farming provides significant employment opportunities, contributing over 50% of total family income in remote areas of Northern Lao PDR.
In Southeast Asia, pig production serves three key functions: diversifying resources and mitigating socioeconomic risks, fostering connections among various resource components such as land, water, crops, and animals, and creating value-added products through processes like recycling fibrous crop residues for meat and utilizing manure In Laos, there has been a notable increase in protein consumption from animal sources, with meat consumption requirements rising to 57 kg per capita, of which pork accounts for 14.6 kg Projections by DFL (2017) indicate that between 2018 and 2020, meat consumption needs will reach 60-70 kg per capita, with pork consumption expected to rise to 15.6-16.8 kg per capita Notably, approximately 58% of the population shows a preference for pork, highlighting its higher demand compared to other meats.
Table 1 Number of meat consumption in 2017 of Lao PDR
The number of pig production being increased surrounding year In 2010-2016, pig production was approximately increased from 2.8 million to 3.7 million heads (table 2; figure
In Laos, the demand for meat consumption is on the rise, leading to increased pig production predominantly through smallholder farms These farms account for approximately 3.15 million local breed pigs, representing 85.1% of the total While there are around 645 commercial intensive pig farms, including 41 dedicated boar and sow farms with a total of 23,200 sows, they only produce about 400,000 piglets annually This falls short of the required 700,000 piglets needed to meet market demand (DLF, 2017).
Table 2 Statistic of livestock population in Laos (2010-
Nu m be r o f p ig s, h ea ds
Figure 1 Number of pigs in Laos from 2010-2016
According to animal statistics from the Ministry of Agriculture, Forestry and Fishery (MAF) from 2015, the Northern region experienced a significant pig population from 2005 to 2010, while the Southern region saw an increase in pig numbers between 2011 and 2015 (MAF, 2017).
Table 3 Pig population in Laos (2005-2015)
Years Northern region Central region Southern region
1600000 Northern region Central region Sourthern
Figure 2 Characteristic of pig in northern, central and southern in 2005-2015
1.3 PIG PRODUCTION SYSTEM IN LAOS
Pig production in Laos can be classified into three main categories:
In the past decade, Laos has seen a significant increase in commercial pig farms, with a rise of 645 farms, particularly in the Mekong corridor near population centers, driven by high pork demand (MAF, 2017) These farms primarily utilize imported breeds like Large White, Landrace, and Duroc, with feeding practices centered around concentrated and bagged commercial feed, supplemented by rice bran for finishing pigs Some commercial operations also create and formulate their own feed.
Pork production is primarily concentrated near urban areas, utilizing cross-breeds with imported varieties like Landrace, Large White, and Xingjin from China These pigs are kept in housing systems and are fed a combination of locally sourced feed ingredients, including rice bran, broken rice, cassava root, and maize, along with concentrates This feeding regimen lasts for 3 to 4 months, enabling the pigs to achieve a marketable weight of 90 to 100 kg (Wilson, 2007).
Considerable numbers of pigs are raised by smallholders using three different production systems: a) free-scavenging, b) semi-scavenging and c) year-round confinement (Phengsavanh et al., 2011). a Free-scavenging system:
In remote areas with limited accessibility, pig farming plays a significant role in local culture and economy, particularly during traditional festivals, weddings, and community events Pigs are allowed to scavenge freely year-round, providing minimal input costs for farmers who typically raise 1-3 native pigs per household, accounting for 96% of Lao pig production While this system offers a source of emergency cash for necessities like seeds, fertilizers, and school fees, it also presents challenges, such as slow growth rates—taking up to 15 months to reach 40-50 kg—and limited disease control, particularly concerning classical swine fever (CSF) Overall, the reliance on poor-quality feed and infrequent vaccinations underscores the need for improved livestock management practices in these communities.
Photo 1 Local pigs are allowed to scavenge freely all year round b Semi-scavenging system:
In remote areas where cash crop cultivation is prevalent, smallholder farmers often allow pigs to scavenge freely only after the main crops have been harvested During this scavenging period, farmers supplement the pigs' diet with a small daily feed while the pigs forage for the majority of their food In contrast, during the crop planting season, pigs are kept in pens or enclosures close to villages or crop production areas, where owners provide feed such as rice bran, maize, cassava, and forest greens This management system supports both piglet production and fattening, with farmers typically raising 3-4 native pigs combined with improved breeds per household This approach accounts for 3% of all pig production in Laos, emphasizing the importance of proper feeding and care in smallholder pig farming (Phengsavanh et al., 2011; Vongthilath and Blacksell, 1999).
Photo 2 Local pigs in pen c Year-round confinement system:
In areas near the district center, pig confinement is prevalent, utilizing two main systems: pens and enclosures The penning system is designed for fattening pigs for sale, while enclosures serve to protect crops and enhance village sanitation Farmers typically employ exotic and crossbred pigs, providing concentrated feed for piglets and growers, along with regular vaccinations and de-worming Additionally, pigs in enclosures are often fed traditional diets that include rice bran, maize, cassava, and green plant materials.
Photo 3 Feed stuffs available in farm condition
1.3.4 Main problems in smallholder pig production systems
Smallholder pig production in Laos faces significant challenges, including low growth rates, disease outbreaks, and high piglet mortality These issues are prevalent in both free-scavenging and semi-scavenging systems, where traditional management practices lead to inadequate feeding and a lack of vaccination against serious pig diseases Feeding practices vary seasonally; during the rainy season, pigs are often fed only once a day, while in the dry season, they receive two meals primarily consisting of agricultural by-products Although confinement in pens can enhance risk management, improved road access may inadvertently increase the risk of disease transmission due to animal movement and uncontrolled interactions with traders.
1.3.5 Important points to improve smallholder pig production system
Smallholder pig production faces challenges such as disease outbreaks, high piglet mortality, poor growth rates, and significant labor demands The Department of Livestock and Fisheries (DLF) formulates policies and strategies to address these issues, while the National Agricultural and Forestry Research Institute (NAFRI) explores methods to enhance livestock production Urgent solutions are required for nutrition and breed improvement, as over 85% of small-scale producers rely on local breeds, resulting in low productivity and limited investment appeal Many producers utilize traditional scavenging systems or semi-confinement, offering low-nutrient diets primarily from agricultural by-products, particularly low-quality rice bran To enhance pig production, prioritizing nutrition through locally available resources is essential Incorporating high-protein forages like taro, water spinach, mulberry leaves, sweet potato vine, and duckweed can supplement or replace costly protein sources such as fish and soybean meal Local feed sources, including maize, cassava, sweet potato, rice bran, broken rice, and banana pseudostems, serve as energy sources, but care must be taken to limit energy intake to prevent excessive body fat accumulation, which can increase production costs.
2011) One way to improve the protein content of carbohydrate-rich (cassava root) feeds is by solid-state fermentation with fungi and yeasts (Araujo et al., 2008; Hong and Ca, 2013).
1.4 LOCAL PIG BREEDS RAISED BY SMALLHOLDERS
The native breeds have been preliminarily classified into four types (Moo Lath, Moo Chid, Moo Hmong and Moo Deng) by (Keonouchanh et al., 2011; Vongthilath and Blacksell,
In a field survey conducted in 1999, phenotypical differences among pig breeds in Lao PDR were assessed, focusing on general characteristics, production performance, and carcass composition This classification aligns with earlier classifications of pig breeds in the region (FAO, 2007; Wilson, 2007) Native pigs offer several advantages, including hardiness, disease resistance, early sexual maturity, and adaptability to challenging rural environments with minimal resources (Phengsavanh and Stur, 2006).
The first type of this breed is predominantly found in upland regions such as Luang Prabang, Oudomxay, and Xaysomboun Province, as well as in some lowland areas like Saravane and Savannakhet Provinces This breed is larger than the previous type, with a body length ranging from 85 to 100 cm, a girth and height of 84 to 102 cm and 51 to 70 cm, respectively Notable features include short, forward-facing ears and a straight face, with white legs and a white front of the face.
The first oestrus in pigs occurs between 189 and 586 days at an average weight of 39 kg, influenced by extensive management systems Mature sows typically weigh between 47 and 61 kg, with the earliest farrowing occurring around 360 days Depending on management practices, sows produce 1.5 to 1.8 litters annually, yielding 7 to 8 piglets per litter The normal weaning period lasts 60 to 90 days, with piglets averaging a weaning weight of 9.5 kg Mature males, or boars, have a lower average weight of 25 kg, with maximum weights ranging from 30 to 50 kg (Keonouchanh et al., 2011).
1.4.2 Moo Chid, Moo Markadon or Moo Boua
REQUIREMENT OF PROTEIN AND AMINO ACID FOR GROWING PIGS
The protein supply in pig diets is primarily based on crude protein (CP), calculated as nitrogen content multiplied by 6.25 Quality protein should provide the 10 essential amino acids necessary for the normal bodily functions of pigs, as these amino acids are vital for maintenance, growth, gestation, and lactation The amino acid requirements vary depending on the pig's weight and physiological stage, with lysine typically being the first limiting amino acid For growing pigs, the lysine requirement decreases from 1.2% of dry matter (DM) for those under 20 kg body weight to approximately 0.7% of DM for pigs weighing 100 kg or more.
Table 5 Dietary amino acid requirements of growing-finishing pigs (NRC
Body weight of pig (kg)
ME content of diets (MJ/kg DM 13.6 13.6 13.6 13.6
The dietary balance of protein and amino acids (AA) is the most crucial factor influencing pig growth performance, as inadequate protein and AA intake can harm both growth and health (NRC, 2012) Conversely, excess AA can negatively impact performance by increasing protein turnover and heat production (Buttery and D'Mello, 1994; Xue et al., 1997) Research indicates that reducing dietary crude protein (CP) from 19% to 15% without AA supplementation decreases daily gain and feed efficiency in growing exotic pigs (Kerr et al., 1995) However, a well-balanced AA diet with lower CP can outperform a high CP diet with an imbalanced AA profile (Kerr et al., 2003) For instance, the Native Moo Lath pig requires only 18% CP, which is below the NRC's recommendation of 21% for growing pigs weighing 11-25 kg Local pigs, such as the Mong Cai breed, thrive on diets with 13-14% CP (Ly et al., 2003; Pham et al., 2010), while Sivilai and Preston (2017) found optimal growth and feed conversion at 12% CP, primarily from ensiled taro leaves Anugwa and Okwori (2008) demonstrated that local pigs outperformed crossbred pigs on a 12% CP diet, while crossbreds excelled on a 16% CP diet, highlighting the varying protein requirements between local and exotic pig breeds.
A study conducted in 1970 examined the optimal protein levels for growing and finishing pigs in a tropical environment, revealing significant differences in daily live weight gain and feed conversion efficiency between pigs fed diets with 16% and 18% crude protein (CP) However, no notable differences were observed in pigs consuming diets with 12% and 13% CP The findings indicate that higher dietary levels of CP enhance feed conversion efficiency.
FEED STUFFS FOR PIG IN LAOS
In smallholder pig production systems in Laos, feedstuffs primarily include rice by-products like rice bran and broken rice, along with planted feeds such as maize and cassava, and various green plant materials Rice by-products are significant, with Laos producing 4.1 million tons of rice in 2016, yielding approximately 4,000 tons of rice bran, which can constitute 60% to 100% of pig diets These ingredients provide essential energy, while green plant materials like sweet potato and cassava leaves supply protein Although commercial feeds often rely on imported protein sources like fish meal and soybean meal, their high costs limit accessibility for smallholder farmers Additionally, rice distiller’s waste, a by-product from rice wine production, offers a sporadic energy and protein source for fattening pigs, complementing traditional feeds that include boiled vegetables and kitchen waste.
3.1 LOCAL FEED AVAILABLE FOR PIG
Taro (Colocasia esculenta) and cassava root serve as important sources of food for both humans and animals, but their use as animal feed presents challenges Taro contains oxalic acid, which can irritate the mouths and throats of animals that consume it; local farmers often mitigate this issue by boiling the plant to reduce oxalate levels In contrast, cassava root is successfully utilized as an energy source in animal feed Additionally, fresh banana stems are commonly mixed with rice bran to provide energy-rich feed for pigs in Laos.
Taro (Colocasia esculenta) is a member of the Araceae family, originating from India and Southeast Asia, and is widely cultivated in tropical and subtropical regions for its edible corm and leaves It thrives in the Mekong Delta, particularly near water bodies, and is known for its rapid growth in wet conditions and resilience against pests and diseases In Laos, taro is grown on approximately 189,201 hectares, yielding an average of 14.78 tons per hectare The leaf biomass yield can reach up to 250 tons per hectare annually, with optimal harvesting at 30-day intervals Taro can be harvested in 10-12 months under wet conditions and 12-15 months in dryland, with corm yields ranging from 5 to 6 tons per hectare, and up to 12 tons per hectare in fertile soils In Africa, the average taro yield is about 5.1 tons per hectare, significantly higher than maize's 1.6 tons per hectare.
Taro leaves are highly nutritious, offering a wealth of vitamins and minerals, including thiamin, riboflavin, iron, phosphorus, zinc, and particularly high levels of vitamin B6, vitamin C, niacin, potassium, copper, and manganese As a locally available feed resource, taro holds significant potential for livestock, especially pigs, due to its excellent nutritional profile The chemical composition of taro varies based on factors such as variety, growing conditions, and processing methods On a dry matter basis, ensiled taro foliage contains crude protein levels ranging from 15% to 17%, with additional nutrients including 18.1% ash, 14.6% to 26% dry matter, 10.7% ether extract, and 39.8% nitrogen-free extract Fresh taro leaves also demonstrate substantial nutritional value, with a composition of 16% dry matter and 25% crude protein Comparatively, fresh leaves of Xanthosoma sagittifolium, a related species, exhibit a similar nutrient profile, highlighting the potential of taro and its relatives as viable protein sources for animal feed.
Table 6 Chemical composition of taro (Colocasia esculenta) in DM basis
CF,% ADF NDF pH Ca Oxalic acid
*Malavanh et al., (2008); ** Sivilai and Preton, (2017);*** Rodriguez et al., (2006)
3.1.1.3 Constraints of using taro (Colocasia esculenta)
Taro (Colocasia esculenta), commonly referred to as "Old Cocoyam," is a wetland crop primarily grown in tropical and subtropical regions for its edible corms To make the corm safe for consumption, it is essential to cook it, which helps dissolve the harmful needle-like calcium oxalate crystals found throughout the plant These crystals can cause significant irritation to the throat and mouth, as noted by Miller (1929) The presence of oxalates in plants serves several purposes, including deterring insects and herbivores through toxicity, aiding in osmo-regulation, and managing calcium levels within plant tissues (Libert and Franceschi, 1987).
Taro contains high levels of oxalates which are important anti-nutritive compounds(Oscarsson and Savage, 2006) because oxalates can form non-absorbable insoluble salts with
High levels of soluble oxalates in the diet can lead to increased kidney stone formation and decreased calcium absorption, as noted by Holmes and Assimos (2004) Research indicates that most oxalic acid found in plants exists as soluble oxalates, which can bind with minerals such as Ca²⁺, Fe²⁺, and Mg²⁺, rendering them unavailable for absorption (Gad et al., 1982; Savage et al., 2000; Quinteros et al., 2003; Oscarsson and Savage, 2006; Savage et al., 2009).
Oxalate concentration in forage varies significantly across different plant species and even among parts of the same plant Key factors influencing oxalate content include soil nutrient status, the specific plant part (such as petiole, leaves, or tubers), and climatic conditions Notably, the highest levels of oxalates are found in species such as Amaranthus (amaranth), Colocasia (taro or old cocoyam), Xanthosoma (new cocoyam), and Spinacia (spinach) (Noonan and Savage, 1999).
Total oxalate levels in taro (Colocasia esculenta) and sweet potato (Ipomoea halalas) range from 278 to 574 mg/100 g fresh weight, with sweet potato specifically at 470 mg/100 g fresh weight, according to Holloway et al (1989) and Mosha et al (1995) In tropical yam (Dioscorea alata), total oxalate levels vary from 486 to 781 mg/100 g dry matter, but the nutritional impact may be minimal, as 50-75% of these oxalates are water-soluble and can leach out during cooking (Wanasundera and Ravindran, 1992).
(2006) showed that young taro leaves grown in a greenhouse in New Zealand contained 589 mg total oxalates/100 g fresh weight (FW) while older leaves contained 443 mg total oxalates
Oxalic acid is primarily found in the corm and leaves of certain plants, and various methods exist to lower its content for livestock forage Traditional practices among local farmers include boiling to reduce oxalate levels Ensiling, a cost-effective fermentation technique conducted in sealed containers, is widely used to preserve high moisture crops globally Research indicates that ensiling with molasses can decrease calcium oxalate from 2.2% to 0.3%, while cooking and ensiling have been shown to reduce oxalate concentrations by up to 50% Additionally, when leaves are ensiled with rice bran or molasses, calcium oxalate levels drop to minimal amounts, allowing for safe inclusion in the diets of growing pigs at 10% without impacting growth rates Further studies have demonstrated that ensiling taro with sugarcane syrup can reduce oxalic acid from 3.08% to 0.11%, and similar results were observed with taro leaves and petioles, achieving a 37% reduction in oxalate Washing or wilting leaves also contributes to lowering soluble oxalate content by 9.2% and 14.2%, respectively.
Cassava plantation is mainly for root production The yields of root are variable depending on soil fertility, management and irrigation system Cassava root yields can be from
Cassava cultivation on eroded soils can yield between 10 to 15 tonnes per hectare without inputs, but soil fertility declines over time (Howeler, 1991) Harvesting leaves during the maturity period can reduce root yields However, when managed for foliage, cassava can produce annual yields of 80 to 120 tonnes per hectare in Vietnam and Cambodia, achieved through bi-monthly harvesting and substantial fertilization with goat manure or biodigester effluent (Preston, 2001).
In Laos, cassava, locally known as ‘Man Ton,’ is a crucial food crop for smallholder farmers in remote upland areas, ranking as the second most important crop after rice Its significance has grown as a cash crop for both domestic consumption and export, utilized for food, feed, and industrial processing into starch, sweeteners, and ethanol Cassava farms are vital not only for food security but also as a primary income source for rural households The rise of cassava in Lao PDR is largely attributed to the export of starch extracted from its roots, with 12 private domestic companies established between 2005 and 2012 to support this industry.
Eleven foreign companies have registered to operate cassava plantations in the country, with a total capital investment of USD 64.76 million, covering a concession area of 11,428 hectares, according to the Ministry of Agriculture and Forestry (2013) The Food and Agriculture Organization (FAO) reported in 2017 that cassava (Manihot esculenta Crantz) production has risen, driven by the demand for starch exports However, despite the increase in planted area, yields and overall production saw a decline in 2017 compared to the years 2015-2016.
Table 7 Planted area, yield and production of cassava root
3.1.2.2 Nutritive value of cassava root
The nutritional value of cassava varies based on factors such as plant type (root or leaves), geographic location, variety, age, and environmental conditions (FAO, 2011) Primarily composed of carbohydrates, the cassava root serves as a significant energy source, with starch content ranging from 32% to 35% in fresh roots and 80% to 90% in dried roots (Montagnac et al., 2009) The carbohydrate composition includes 83% amylopectin and 17% amylose (Rawel and Kroll, 2003), while sugars like sucrose, glucose, fructose, and maltose are generally present in low amounts (Tewe, 2004) However, sweet cassava varieties can contain over 17% sucrose in their root content (Okigbo, 1980; Charles et al.).
The fiber content in cassava varies based on the variety and developmental stage of the root, with fresh roots containing less than 1.7% fiber, while cassava flour has a fiber composition of approximately 4%.
The lipid content of cassava root ranges from 0.1% to 0.3% of its fresh mass, primarily consisting of nonpolar lipids (45%) and glycolipids (52%) (Hudson and Ogunsua, 1974) Its protein content is minimal, accounting for only 1% to 3% of dry matter, or approximately 1.5 mg per 100 g of fresh mass (Buitrago, 1990; Bradbury and Holloway, 1988) While essential amino acids are present in low quantities, arginine, glutamic acid, and aspartic acid are notable exceptions (Gil and Buitrago).
2002) The mineral content of the roots varies According to Burns at al., (2012) in a study in Mozambique (Maputo and Nampula Provinces) iron content of cassava roots, varied from 8 to
METHOD TO IMPROVE NUTRITIVE VALUE FOR FEED STUFF WITH LOW
S cerevisiae is a species of yeast It has been instrumental to winemaking, baking, and brewing since ancient times It is believed to have been originally isolated from the skin of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-colored fruits such as plums; it exists among the waxes of the cuticle) It is one of the most intensively studiedeukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium It is the microorganism behind the most common type of fermentation S cerevisiae cells are round to ovoid, 5-10 μm in diameter It reproduces by a division process known as budding (Feldmann and Horst, 2010).
S cerevisiae is one of important microbiology which used in microbial fermentation because it high ability of growth and we can control on it easily therefore it used widely in production and industrial projects, in addition to the high contain of protein and health safety (Kadhum et al., 2014) Multiple uses of S cerevisiae in many fields such as bread and glycerol manufacturing and it characterized of not produce the toxins, it also play an important role in enzymes production such as glucose 6 phosphate dehydrogenase (Soufi, 2005; Mohamedawi, 2009) S cerevisiae used for decreasing of aflatoxins poisons (Daraji et al., 2005; Naji, 2007; Yousif and Jugifi, 2015)
Saccharomyces cerevisiae yeast is rich in biologically valuable proteins, B-complex vitamins, and essential trace minerals, offering numerous health benefits Research indicates that it enhances phosphorus availability and utilization in animals, reduces disease infections, and improves feed efficiency Additionally, the manna oligosaccharides and fructooligosaccharides found in yeast cell walls help maintain gastrointestinal balance, promoting eubiosis in the digestive tract Studies have also shown that these oligosaccharides contribute to increased mineral retention and improved bone mineralization in broilers.
Photo 8 Life cycle of Saccharomyces Cerevisiae
The life cycle of the budding yeast Saccharomyces cerevisiae is characterized by its ability to adapt to various growth conditions based on ploidy Haploid and diploid cells can interconvert through mating and sporulation, respectively Both cell types exhibit filamentous growth, biofilm formation, or enter a quiescent stationary phase when faced with nutrient limitations, such as glucose or nitrogen scarcity Additionally, diploid cells can sporulate under carbon and nitrogen source limitations, while secreted alcohols serve as autoinducers to promote filamentous growth.
Nutritional requirements and the factor effect on the growth of saccharomyces cerevisiae
All strains can utilize ammonia and urea as their only nitrogen sources, but they are unable to use nitrate due to their inability to reduce it to ammonium ions Additionally, they can metabolize most amino acids, small peptides, and nitrogen bases; however, histidine, glycine, cystine, and lysine are not easily utilized Notably, S cerevisiae does not secrete proteases, which prevents the metabolism of extracellular proteins.
Yeasts require essential nutrients for optimal growth, including phosphorus, which they assimilate as dihydrogen phosphate ions, and sulfur, available as sulfate ions or organic compounds like methionine and cysteine Additionally, key metals such as magnesium, iron, calcium, and zinc are vital for their development.
Research by Serra et al (2005) indicates that S bayanus var uvarum P3 and S cerevisiae VL3c exhibit optimal wine fermentation at 30 °C with a stable pH of 4.0, while S cerevisiae VL3c thrives at 35 °C when the pH is 5.0 At these optimal temperatures, phospholipids within the cells become free, enhancing particle transport rates, protein synthesis, and substrate transport, which boosts S cerevisiae reproduction (Tai et al., 2007) Additionally, sugar concentration in the growth medium significantly influences S cerevisiae growth; studies by Charoenchai et al (1998) and D'Amato et al (2006) found that sugar levels between 200 g/L and 300 g/L can hinder growth rates High osmotic stress from elevated sugar concentrations can negatively impact fermentation performance, as noted by Ishmayana et al (2011), who observed that three S cerevisiae strains experienced stuck fermentations with 16% glucose or sucrose, leaving substantial residual sugar However, using a yeast nitrogen base, with or without 1% ammonium sulfate, proved nutritionally adequate for complete utilization of 2% glucose.
SSF is defined as the process occurring in the absence or near-absence of free water.
4.2.1 Application of solid-state fermentation
- Agro-food industry (Traditional food fermentation, food additive)
- Less effluent release, reduces pollution
- Resembles the natural habitat of some fungi and BT
4.2.3 Factors influencing solid-state fermentation
Selecting the right micro-organisms is crucial for enhancing product yield; specifically, bacteria, yeast, and filamentous fungi can be utilized Among these, filamentous fungi have demonstrated superior growth in solid-state fermentation (SSF), making them a preferred choice for optimizing production processes.
- Substrate al so important role in determining the growth of micro-organisms, there by increasing product yield
+ Substrate is of two types: One is specific substrate, which requires suitable value- addition and disposal
+ The second is for producing a specific producing from a suitable substrate
- Process optimization: Includes the optimization of physic-chemical and biochemical parameters
+ Size, initial moisture, temperature of incubation, agitation and aeration, age and size of the inoculum
+ Nutrient supplementation such as nitrogen and phosphorus (Phosphorus is required for the growth of all biological entities, including yeast) and trace elements, subplementation of additional carbon source and inducers
+ Extraction of product and its purification
4.2.4 Problem of solid-state fermentation
- Heat transfer: One of the main difficulty is to control the temperature during the fermentation process
- Heat is general during the metabolic activities of micro-organisms, since the substrate used has low thermal conductivity heat removal will be slow
Excessive heat generation can lead to product denaturation, negatively impacting microbial growth and ultimately resulting in reduced yield and quality of the product.
Yeasts thrive in oxygen-rich environments, which can be controlled to regulate their growth They primarily require sugars as a substrate and can ferment these sugars into alcohol and carbon dioxide without air, although oxygen is essential for their growth The optimal temperature for yeast activity ranges from 20° to 30° C, and they can survive in a broad temperature spectrum of 0 to 50° C Most yeasts prefer a near-neutral pH of around 7.0, but they can tolerate acidic conditions, growing in a pH range of 4 to 4.5 In comparison to bacteria and moulds, yeasts have moderate water requirements, needing a minimum water activity of 0.85 or relative humidity of 88% for optimal growth.
Cassava root is widely used by farmers as an energy source, but its consumption is limited by the presence of cyanogenic glucosides, which can convert to toxic hydrocyanic acid (HCN) in animals, and its low protein content However, solid-state fermentation using fungi and yeast can effectively reduce HCN precursors and enhance the protein content in carbohydrate-rich industrial byproducts Research has shown that fermentation with yeast and bacteria can decrease non-nutritional components and increase the nutritional value of agro-industrial by-products Utilizing cassava root as a fermenting feed can boost yeast biomass, which is a rich source of proteins, nucleic acids, and vitamins Yeast biomass is not only produced and consumed in baked goods and other foods but also offers significant advantages over other microbial protein sources.
Cassava peels and roots, byproducts of starch and gari processing, can be transformed into protein-rich animal feed for poultry and fish industries (Bayitse, 2015) This conversion utilizes solid-state fermentation, allowing microorganisms to grow on these substrates and enhance protein content through the breakdown of complex polymers like lignin and pectin (Akinrele, 1967; Tengerdy, 1985) The fermentation process can significantly increase protein levels, making cassava a valuable ingredient for animal feed For instance, fermentation with S cerevisiae raised protein content from 4.4% to 10.9% and reduced cyanide levels (Oboh and Kindahunsi, 2005) Additionally, fermenting cassava peels can boost protein from 2.4% to 14.1% (Antai and Mbongo, 1994) Protein-enriched cassava pulp can be mixed with other feeds, such as rice bran, providing a substantial protein source for fattening pigs (Oosterwijk and Vongthilath, 2003; Hong et al., 2017) Recent studies in Lao PDR demonstrated that true protein content in cassava pulp increased from 2% to 7-12%, contributing significantly to dietary protein needs (Vanhnasin et al., 2016a; Sengxayalth and Preston, 2017a,b).
A study demonstrated that incorporating 16% dried cassava pulp (DM) with 8.1% true protein into an intensive broiler diet did not hinder growth performance or feed conversion Research by Hong et al (2017) indicated a 60% conversion rate of crude protein from urea and DAP to true protein when urea levels ranged from 0.5% to 2% of the substrate DM Utilizing solid-state fermentation with yeast, the protein content of cassava pulp was enhanced, with fermentation conditions including 4% urea, 1% DAP, and 2% yeast Over nine days, true protein increased from 2% to 12% DM, while crude protein rose from 9.5% to 18.4% It was found that approximately 60% of the non-protein nitrogen (NPN) was converted to yeast protein, although the composition of residual NPN remains unclear, likely consisting of ammonium salts The increase in crude protein during fermentation was attributed to a 40% loss of DM, leading to a concentration of the crude protein fraction, and prior steaming of the pulp did not offer any benefits (Vanhnasin et al., 2016a).
UTILIZATION OF FORAGE-BASED DIET FOR PIGS
5.1 EFFECT OF TARO FOLIAGE AS PROTEIN SOURCE ON FEED INTAKE AND DIGESTIBILITY OF PIGS
Taro (Colocasia esculenta) is widely cultivated in Lao PDR, and its leaves are a rich source of protein, vitamins, and minerals, making them a valuable ingredient in pig feeds A preliminary study by Rodríguez et al (2009) highlighted that the protein in new cocoyam leaves has a high biological value, and ensiled new cocoyam leaves (ENCL) improved crude protein digestibility and nitrogen retention, comparable to soybean meals However, research by Chitthavong et al (2008b) found that replacing soybean meal entirely with taro foliage led to a decline in the apparent digestibility of dry matter and crude protein, aligning with Rodríguez et al.'s findings.
(2009) for pigs fed sugar cane juice and fresh leaves of new cocoyam replacing soybean meal
Feeding pigs exclusively with taro silage (TS) results in higher digestibility rates for dry matter (DM) and organic matter (OM), at 87.7% and 93.4%, respectively However, this diet negatively impacts crude protein (CP) digestibility and nitrogen (N) balance, likely due to an imbalance of amino acids and CP fermentation occurring in the caecum (Pheng Buntha et al.).
A study comparing the use of ensiled taro foliage (TF), mulberry leaf silage (ML), and a mixture of both (TF-ML) in a rice bran-based diet for growing pigs found that TF-ML resulted in the highest crude protein (CP) digestibility at 71.1% Additionally, it led to increased nitrogen (N) intake and retention Another research indicated that substituting rice distillers' by-products for ensiled taro foliage in a rice bran diet also enhanced nitrogen retention in growing pigs.
5.2 EFFECT OF TARO FOLIAGE AS PROTEIN SOURCE ON GROWING
Research indicates that diets incorporating 50% taro silage and 50% rice bran enhance feed intake rates (49.9 g DM/kg LW/day) compared to diets with varying taro silage levels (Manivanh and Preston, 2011) Taro leaf silage, when paired with water spinach, can completely substitute soybean meal in the diets of Mong Cai gilts during pregnancy and lactation without impacting reproduction, with consistent daily CP intakes observed (Chittavong et al., 2008) Furthermore, a study by Pheng Bunta et al (2008) demonstrated that taro leaf silage could replace 70-75% of fish meal protein, resulting in higher DM and CP intakes and improved nitrogen retention in growing pigs Additionally, increasing taro foliage in the diet to 30% positively influenced feed intake during pregnancy and lactation, leading to less weight loss and a higher number of piglets at a 60% taro foliage silage level (Chhay Ty et al., 2014) Lastly, protein from ensiled taro leaves did not adversely affect the growth performance or carcass traits of crossbred and native breeds, allowing for a 50% replacement of soybean protein in the diet (Kaensombath and Erik Lindberg, 2012).
5.3 EFFECT OF TARO FOLIAGE REPLACING BANANA PSEUDO STEM ON GROWTH AND DIGESTIBILITY OF PIGS
Farmers in Laos have traditionally utilized banana pseudo-stems as animal feed Although banana pseudo-stems have a low crude protein content, they are rich in sugars in the aqueous fraction, providing a valuable energy source Additionally, these stems can be ensiled effectively without requiring additives like molasses.
Traditional feeding practices for pigs often result in low growth rates due to high water and fiber content and low protein levels To enhance the diet of native pigs in Laos, research suggests combining taro silage with ensiled banana pseudo-stems and taro foliage (Sivilai et al., 2016) Studies indicate that replacing banana pseudo-stems with taro foliage in silage improves the coefficients of apparent digestibility for dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and nitrogen (N) retention (Hang et al., 2014) Furthermore, the use of taro foliage over banana pseudo-stems has been shown to increase DM and crude protein digestibility and N retention for native pigs (Sivilai et al., 2016) Additionally, ensiled banana pseudo-stem combined with taro foliage is more palatable than rice bran, leading to improved DM intake, digestibility, and N retention (Chhay Ty et al., 2014) However, replacing rice bran with taro-banana silage has been associated with decreased birth weights and litter sizes, as well as prolonged periods from weaning to mating, resulting in a reduced number of litters per year (Duyet and Preston, 2013).
Research indicates that high levels of banana pseudo-stem in pig diets negatively impact intake, digestibility, and growth Hang et al (2014) found that a 40% inclusion of banana pseudo-stem resulted in a 26% decrease in growth rate and a 9% decline in feed conversion efficiency Similarly, Sivilai et al (2016; 2017) reported that growth and feed conversion in Moo Lath pigs worsened curvilinearly with increased banana pseudo-stem and reduced taro foliage Nonetheless, the studies suggest that ensiled banana pseudo-stem can be effectively combined with other dietary sources at limited levels Sivilai and Preston (2016) demonstrated that pigs achieved optimal dry matter intake (744 g/d), growth (204 g/d), and feed conversion (3.75) when fed a diet comprising 8% ensiled banana pseudo-stem, 20% broken rice, and 70% ensiled taro leaves and petioles, with a crude protein content of 12%.
5.4 EFFECT OF ENSILED TARO FOLIAGE REPLACED BY PROTEIN- ENRICHED CASSAVA ROOT ON GROWTH PERFORMANCE AND DIGESTIBILITY
Replacing ensiled Taro foliage with protein-enriched cassava root can enhance pig performance due to its higher energy value, with cassava root containing 3.7% crude fiber compared to 11% in Taro foliage (Hang et al., 2015) This improvement in live weight gain is consistent with findings from Phuong et al (2003), who noted similar growth responses in pigs fed cassava pulp enriched with true protein Huu and Khammeng (2014) also reported comparable digestibility and nitrogen retention when maize was replaced with fermented cassava pulp containing 13% crude protein The growth rate enhancement may stem from the superior biological value of the protein in cassava root and the additional B-complex vitamins provided by yeast during fermentation However, higher proportions of protein-enriched cassava in the diet can hinder growth, with almost no growth observed at 100% replacement of Taro/soybean protein It was found that only 50-60% of non-protein nitrogen (NPN) added was converted to true protein, leaving residual NPN, which may be toxic at high levels Sengxayalth and Preston (2017b) proposed that the growth rate improvement with 30% protein-enriched cassava root is due to amino acid synthesis by intestinal bacteria using residual dietary ammonia, while excessive substitution leads to decreased feed intake and growth due to toxicity from residual NPN compounds.
The study found no ill-health symptoms in pigs related to oxalic acid in ensiled taro; however, their feed intake, growth rate, nutrient digestibility, and nitrogen retention were negatively impacted Optimal inclusion of protein-enriched cassava root in diets can enhance growth performance, feed conversion ratio, apparent digestibility, and nitrogen retention Conversely, inappropriate levels of cassava root substitution can lead to significant declines in feed intake and growth due to toxicity from residual non-protein nitrogen compounds in the fermented pulp/root.
Aggelopoulos,T., Katsieris, K., Bekatorou, A., Pandey, A., Banat, I.M and Koutinas, A.A.,
2014 Solid state fermentation of food waste mixtures for single cell protein, aroma volatiles and fat production Food Chemistry, (145), 710 - 6.
Agosin, D., Jarpa, S., Rojas, E and Espejo, E., 1989 Solid state fermentation of pine sawdust by brown-rot fungi Enzyme and Microbial Technology, (11), 511 - 517.
Akinrele, I.A., 1967 Further studies on the fermentation of cassava Research Report No.20 of the Federal Institute of Industrial Research, Oshodi, Nigeria.
Antai, S.P and Mbongo, P.N., 1994 Utilization of cassava peels as substrate for crude protein formation Plant Foods for Human Nutrition, Volume 46, pp 3.
Anugwa and Okwori., 2008 Performance of growing pigs of different genetic groups fed varying dietary protein levels African Journal of Biotechnology Volume 7 (15), 2665 -
Araujo, L.F., Silva, F.L.H., Brito, E.A., Olivera Junior, S and Santos, E.S., 2008 Enriquecimento protộico dapalma forrageira com Saccharomyces cerevisiae para alimentaỗóo de ruminantes. Arquivo Brasileiro de MedicinaVeterinária e Zootecnia, Volume 60, pp 401 - 407.
Aro, S.O., 2008 Improvement in the nutritive quality of cassava and its by-products through microbial fermentation African Journal of Biotechnology Volume 25: 4789 - 4797.
Balagopalan, C., Padmaja, G and George, M., 1995 Improving the nutritional value of cassava products using microbial techniques In: Roots, tubers, plantains and bananas in animal feeding (Editor: D Machin) FAO, Rome AHPP
95 http://www.fao.org/ag/aga/agap/frg/ahpp95/95-127.pdf
Balagopalan, C., 1996 Improving the nutritional value of cassava by solid state fermentation: CTCRI experiences Journal of Scientific and Industrial Research 5, 479 - 482.
Bayitse, R., Hou, X., Laryea, G and Bjerre, A.B., 2015 Protein enrichment of cassava residue using Trichoderma pseudokoningii (ATCC 26801) AMB Express 5, 80 - 85.
Boonnop, K., Wanapat, M., Nontaso, N and Wanapat, S., 2009 Enriching nutritive value of cassava root by yeast fermentation Scientia Agricola Volume 66 no 5
Piracicaba http://dx.doi.org/10.1590/S0103-90162009000500007
Bradbury, J.H., Ho; Oway, W.D 1988 Chemistry of tropical root crop: significance for the nutrition and agriculture in the Pacific Australian Center of International Agriculture Research (ACIAR), (6), 1 - 20
Brook, E.J., W.R and Wallbridge, A., 1969 Fermentation method for protein enrichment of cassava Biotechnology and Bioengineering Volume 11: 1271.
Buitrago, A., 1990 La yuga en la alimentacion animal Centro internacional de Agriculture Tropical (CIAT) Cali, Colombia pp.10 – 18.
I don't know!
Brake, J., 1991 Lack of effect of all live yeast culture on broiler, breeders and progeny performance Poultry Science, (70), 1037 - 1039
Bradley, G.L and Savage, T.F., 1993 The effect of autoclaving a yeast culture of
Saccharomyces cerevisiae on turkey pullet’s performance and the retention of gross energy and selected minerals Animal Feed Science Technology, (55), 1-7
CelAgrid., 2006 Assessment of impacts of action research on pig production systems, management,
Charles, A.L., Chang, Y.H., Ko, W.C., Sriroth, K and Huang, T.C., 2004 Some physical and chemical properties of starch isolates of cassava genotypes Starch-Starke 56 (56), 413
- 418 http://dx.doi.org/10.1002/star.200300226
Charles, A.L., Sriroth, K and Huang, T.C., 2005 Proximate composition, mineral contents, hydrogen cyanide and phytic acid of five cssava genotypes Food Chemistry, (92), 615
- 620 http://dx.doi.org/10.1016/j.foodchem.2004.08.024
Charoenchai, C., Fleet, G., Henschke, P.A., 1998 Effects of temperature, pH and sugar concentration on the growth rates and cell biomass of wine yeasts American Journal of Enology and Viticulture, (49), 283 - 288.
A study by Chhay Ty, Borin, and Preston (2010) examined the impact of silage made from taro leaves and stems, as well as mulberry leaves, on the digestibility and nitrogen retention in growing pigs The pigs were fed a basal diet consisting of rice bran The findings contribute to understanding how different silage types can enhance the nutritional efficiency in livestock feeding practices This research is published in Livestock Research for Rural Development, Volume 22.
#109 Retrieved August 29, 2011, from http://www.lrrd.org/lrrd22/6/chha22109.htm
In a study by Chittavong Malavanh, Preston, T.R., and Ogle (2008), the impact of substituting soybean meal with a combination of taro leaf silage and water spinach on the reproductive performance and piglet outcomes in Mong Cai gilts was examined The findings were published in the Livestock Research for Rural Development, Volume 20, supplement, highlighting the potential benefits of alternative feed sources in swine production.
From http://www.lrrd.org/lrrd20/supplement/mala2.htm
The nutritional status of local pigs in central Lao PDR was examined in a doctoral thesis by Chittavong (2012), highlighting the importance of understanding animal health and nutrition in the region Additionally, Conlan et al (2008) provided insights into pig production and health in Bolikhamxay province, emphasizing the challenges and practices within the local pig farming industry Together, these studies underscore the significance of research in improving livestock management and enhancing the overall well-being of pig populations in Laos.
In: Management of classical swine fever and foot and mouth disease in Lao PDR. Proceedings of international workshop held in Vientiane, Lao PDR, 28-33.
D'Amato, D., Corbo, M.R., Del Nobile, M.A., Sinigaglia, M., 2006 Effects of temperature, ammonium and glucose concentrations on yeast growth in a model wine system. International Journal of Food Science and Technology, (41), 1152 – 1157.
Dao Thi My Tien, Ngo Thuy Bao Tran, Bui Phan Thu Hang, and T.R Preston (2010) presented research on the ensiling of banana pseudo-stems combined with Taro (Colocasia esculenta) leaves and petioles This study was shared at the International Conference on Livestock, Climate Change, and Resource Depletion held at Champasack University in Pakse, LAO PDR, from November 9 to 11, 2010 For more details, visit the conference's abstract page at [MeKarn](http://www.mekarn.org/workshops/pakse/abstracts/tien_agu2.htm).
Department of Livestock and Fishery (DLF)., 2017 Planing implementation of Department of Livestock and Fishery in the year 2017-2018, Ministry of Agriculture and Forestry (MAF), Vietiane Capital, Lao PDR, 1- 6
Devendra, C and Clyde Parris, E.C., 1970 Optimum crude protein levels for growing finishing pigs in a tropical environment Tropical Animal Health Production, (2), 162 - 165.
The study by Du Thanh Hang and Preston (2010) investigates the effects of processing Taro leaves on oxalate concentrations and their potential as a protein source in pig diets in Central Vietnam It was found that oxalate levels were higher in petioles compared to leaves, with significant reductions achieved through cooking and ensiling The research indicates that ensiled Taro leaves can replace up to 30% of fish meal in pig diets without negatively impacting growth performance, while also increasing fiber intake This suggests that Taro leaves, when properly processed, can serve as an effective and sustainable protein alternative in livestock feed.