[Eds.’ Note: Keith has practiced sustainable farming at the Aloha House Orphanage in Puerto Princesa for 15 years, producing nutritionally dense, farm-derived food that is consumed both at the orphanage and by local customers. ECHO Asia has had the privilege of visiting Keith and his family at Aloha House on different occasions, including during the two ECHO Asia Philippines Sustainable Food Production Workshops, which they co-hosted. The Aloha House property produces impressively in a small area, with very few off-farm inputs. Keith is continually generous and open in sharing his experience and knowledge with visitors and the broader ECHO network. In ECHO Asia Note 20, Keith shared about farm-generated fish feed and in ECHO Asia Note 25, he wrote about farm-generated pig feed. In this issue, Keith will share some basics for farm-generated chicken feed production; the concurrent idea in all of these articles is to reduce off-farm inputs, thus saving money and raising food more sustainably].
Farm-generated fertility contributes to a more sustainable agricultural system. Crop residues and manures are part of the nutrient cycle for plant production and can lower input costs through the use of thermophilic composting, vermiculture, bokashi production, and/or green manures. Farm-generated feeds can also reduce expenses, as farmers manage and utilize resources already available to them. Chickens in particular can be very expensive to feed on a small scale with purchased commercial feeds. In this ECHO Asia Note, we will explore a variety of alternatives for small flock feeds.
Chicken feed ingredients vary from area to area throughout the world. Selection is usually based on availability, quality, and cost. While the use of some materials are based on scientific principles, like crude versus digestible protein, the nutritional benefits of many of these materials are not well researched or proven. Chickens are omnivores and do well on pasture, in confinement, or even ranging freely in forest environments. In this article, I will share ways to maximize farm-generated feeds for chickens that are pasture-raised, utilizing as many natural feed options as are appropriate for your circumstances. Later in this article I will describe how to intensify the feed ration, in case you only have a small exercise yard for your birds or they are confined and caged.
Pasture can be anything from thick lush legume and grass polycultures to weedy scrub brush fields. Get your birds out in the sunshine; this is a great way to boost vitamin D for chickens’ health and improve the nutrient density of the eggs and meat. We don’t want “feed lot livestock” or confined chickens that are deprived of sunshine and living in the dark (Figure 1)!
One challenge of a natural, foraged diet in Southeast Asia is protecting poultry
from predators. Pasture or forest can be rich in insect protein and forage, but it comes with the risk of predation and even theft. The chicken tractor is one way to protect your investment. It is a movable cage built for small flocks: our 1.2 m x 3 m tractor stocks 10 to 15 meat birds, or half as many layers. The chicken tractor has a water supply and feed tray. We move it once or twice a day, depending on stocking density and bird size. It is light enough to be moved by one person (Figure 2). We found wheels to be problematic on our rugged Palawan
terrain, and designed the “Aloha Chicken Sled” as an alternative to wheel-based units (Figure 3).
When moving a chicken tractor, be careful to push the rig from behind, to prevent running the chickens over. Chickens tend to flee away when they are disturbed, so if you pull from the front they will run to the back and may get injured.
On a larger scale, a movable solar electric feather net can be used to keep predators out. “The live foods they [chickens] forage— green growing plants, wild seeds, earthworms, slugs, and insects—are of a quality we cannot hope to match with anything from a bag,” writes Harvey Ussery in “Managing Poultry on Pasture with Electronet” (Ussery 2005). Perhaps you are curious if you can modify an electric fence meant for cattle, to use it for chickens. At the Aloha House, we have a solar charger built into a control unit with battery to electrify our cattle fence, which we use to manage planned grazing for cattle. The fencing is livestock-specific, so make sure yours is specific for poultry; we do not recommend cattle fencing for poultry. Instead, we recommend using the feather net or “Electronet,” designed specifically for poultry.
If you are unable to manage electrical technology in your area, you should at least ensure that your birds have access to a scratch yard: a small, fenced-in, predator-proof area with a good dose of sunshine! A scratch yard can be improved with the addition of cut greens, crop waste from your garden, and/or various grasses. I have friends in Dubai that use grass cuttings as a feed supplement as well as for bedding. Be resourceful and you can find many “waste” streams that may be appropriate for your flock feed!
A larger space for chickens to forage is even better. In the Philippines, we plant mongo bean (Mung bean, —available from the ECHO Asia Seed Bank) on alternate rotating pastures for our layers. We try to time it as a fodder crop and let it get to flowering stage then let the chickens devour it before beans are formed. If you want to grow and harvest the beans you can, but the forage nutrition will be less than in the flowering stages. When one area is depleted, it is closed down and replanted while the chickens are transferred to the next area for foraging. I recommend three pastures or more if you have the room.
You can supplement your poultry’s grazing diet by distributing grains into the bedding, exercise yard, or pasture. Most farmers have a special call to alert their birds to this supplemental feed that is thrown out into the grass or dispersed into a deep litter bed (to enhance aeration as the chickens search for the grains). Supplementing like this stimulates the chickens to forage and encourages them to move out to areas they may not have yet exploited. It also enables the farmer to take inventory and do a head count.
Cracked corn is a preferred supplemental feed in most areas, but is not always
cost effective. In fact, many different beans, seeds, and grains can enhance the growth and performance of your birds. This list is not exhaustive, but wherever chickens are raised around the world, farmers have tried a large variety of supplements: cracked corn, pili nuts, mongo beans, kidney beans, peanuts, etc (Figure 4). When selecting scratch feeds, locate supplements that disperse well by hand, are locally available, and are cost-effective.
Benefits of Grass-Fed Livestock
The cheapest, and certainly the easiest, ways to feed livestock are to provide them with access to pasture or to provide them with greens through a cut-and-carry system. Various protein sources from around the farm like azolla or black soldier fly (BSF) larva can be used to augment pasture and greens.
Grass-fed livestock offers plenty of nutritional benefits that include:
- More fat-soluble vitamins (A, D, E, K) in the fat.
- Higher Conjugated Linoleic Acid (CLA), an anti-cancer and weight loss compound, in the fat.
- More minerals - mostly in the fat.
- With fewer grains and more greens, along with insects, fish, coconut meal, etc., the ratio of omega 3 and omega 6 fatty acids in grass-fed poultry is more in-line with traditional diets and much more healthful for consumers than consumption of modern poultry. Feedlot grain-fed livestock have high levels of omega 6 fatty
acids. Instead of adding omega 3 fatty acids to the chicken diet, reduce the omega 6 fatty acids by reducing grain and use insects and fish meal for balanced nutrition. Dr. Weston Price found a near-equal ratio of omega 3/6 fatty acids in human diets, not totaling more than 5-6% of fat intake by calories, to be optimum (Figure 5) (Fallon et al. 2000). For meat, egg, and fat quality to be balanced for human consumption and poultry health, we want that balance of omega 3 and 6 fatty acids in the feed.
On-Farm Production of Chicken Feed, Including Formulas
With experimentation and careful recordkeeping, chicken farmers can produce their own high-quality feed. In many countries, farmers can purchase readily available ingredients to produce cost-saving feeds. However, farm-generated ingredients make chicken feed even more economical! At our farm, two people can produce 200 kg of moist feed in less than an hour. Many items can potentially be used to produce a balanced ration. The best advice I can give is to be flexible depending on your context and what is cheaply (or freely!) available. Keep your options open and do some research! Below I describe some of the options available in Southeast Asia.
Floating Ferns and Duckweed as an Alternative Feed
Many floating ferns and aquatic plants are high in protein. Aquatic plants can
grow well in ponds that have adequate fertility to support them. They can be utilized for chicken feed and are excellent as a cost-saving supplement when expensive purchased feeds are used. Floating ferns such as Azolla spp. and Salvinia spp. can be utilized if they are cultured and harvested efficiently (Figure 6). Duckweed (various genera and species) can also be used. Swine and poultry (both omnivores) readily eat large quantities of these greens as a feed source. Options for production include net-protected rafts within a fish culture, or separate dedicated ponds, containers or troughs. Remember, any fodder crops grown within a fishpond must be protected or isolated from the fish, otherwise the fish will over-graze and deplete the crop. In Figure 6, fish are kept in a separate tank and azolla is growing from the pumped nutrients and water and returned to the fish cleaned and oxygenated. [Eds.’ Note: For more information on using floating ferns and duckweed for fish food and hog feed, see Asia Notes 20 and 25.]
Experimental trials have been done in India, comparing Lemna minor (common duckweed), Ipomoea reptans (kang kong or morning glory), Trapa natans (water caltrap), and Salvinia cucullata (often mistaken for azolla). Both duckweed and morning glory had good feed conversion ratios and high protein: 28% and 32% respectively (Kalita, 2007). Both of these can be great fodder crops. I wish that azolla (Azolla caroliniana) had been included in the India study; it is another fast-growing floating fern, and has a reported protein range of 19-30%.
Be careful not to overharvest floating ferns and other aquatic plants, or production will not be sustainable. As a general rule of thumb (under ideal conditions), you should harvest no more than half of the floating biomass per week (or 1/7th of the total biomass per day). The trick is to keep the plant in a rapid vegetative stage. To do this, you will have to monitor which method of harvest is the most productive in your system. Azolla tolerates moving water better than duckweed. Salvinia grows the fastest, but can be very invasive. Our one-year study measuring azolla yields in aquaponic conditions showed yields ranging from 310 grams to 490 grams per day, depending on various factors.
Auto-Harvesting Black Soldier Fly (Hermetia illucens) Grub Culture
Kitchen waste or manures can be utilized for black soldier fly (BSF) (Hermetia illucens) grub production, to supplement the natural diet of your chickens. BSF larvae are very nutritious and can be grown economically on waste. Actively feeding grubs will secrete a natural fly repellant called a synomone (a substance used for interspecies chemical communication) that alerts and warns other kinds of flies to stay away from the food, as BSF are already present. Numerous designs for auto-harvesting BSF devices are available online. These act as containers for grub production; when properly managed the mature grubs migrate from the container on a 35º incline and are dropped into a holding container, directly into a fish pond, or into a chicken coop (Figures 7 & 8).
Benefits of Fermentation in On Farm Feed Production
The fermenting activity of certain beneficial microorganisms during the production process can enhance the digestibility and shelf life of chicken feeds. According to one study, the use of microorganisms increased the crude protein in copra meal from 17.24% to 31.22%. An amino acid was also found to be greatly improved in quantity (Cruz, 1997).
Please note that not all flocks like a wet feed. You can mix feed without fermenting in the morning and use it immediately if your chickens do not appreciate fermented feeds, which tend to be wet. In addition to chicken feed, you can also ferment your feed for hogs, ducks, and fish with the help of diverse probiotic groups of microbes. However, we do not recommend fermentation for ruminant feeds (this will be covered in an upcoming ECHO Asia Note).
When fermenting feed, be sure to use proven strains of probiotic groups of bacteria, yeasts, and microbes that are not cross-contaminated with wild pathogens. At the Aloha House, we use EM-1, a commercial product that undergoes laboratory testing and is approved for livestock and aquaculture by the Department of Agriculture and the Bureau of Fisheries and Aquatic Resources in the Philippines. EM-1 was formulated by Dr. Teruo Higa in Ryukyus University, Okinawa, Japan, and it is readily available in over 100 countries. Thailand now consumes more EM-1 than Japan!
EM-1 contains cultures of robust lacto-bacilli, photosynthetic bacteria, beneficial yeast, and more. The microorganisms feed on sugars and other carbohydrates while creating secondary metabolites that increase the nutrient range of the feed. The probiotic value is very high. If you would like to learn more about using EM-1, my book A Natural Farming System for Sustainable Agriculture in the Tropics is a user’s guide to EM technology. It is available online as a free PDF download, can be obtained at the ECHO Asia office, or can be purchased online through the ECHO Florida Online Bookstore.
If EM-1 is not available, try using cheese whey or yogurt whey, sourced from a local creamery. Start small by substituting the whey at the same rate as EM-1 in the formula below, and add more in subsequent batches if it does not have an effect. Good fermentation should create a sweet and sour smell after two weeks. If a foul “rotten egg” odor (from sulfides) or black mold occurs, do not feed it to your chickens. Instead, add your small failed experimental batch to the compost heap and use it as fertilizer.
Another alternative to EM-1 is to use indigenous microorganisms (IMOs). In the Korean Natural Farming (KNF) system, materials are mixed with sugar, salt, and IMO solution. [Eds.’ Note: For more information on the creation and use of IMOs, please see the presentation “An Introduction to Asian Natural Farming” on ECHOcommunity. org. In addition, the Natural Farming Text and Cartoon Books from Mae Jo University discuss IMOs at length and are available at the ECHO Asia office in Thai, English, and Khmer, and will soon be available in Burmese, Bahasa Indonesia, Karen, Tagalog, and Mandarin.]
Fishmeal is a good source of protein. Marine fishmeal and tilapia meal have been used in various settings with good results. The use of fishmeal is typically restricted to 5-10% of poultry diets. We use more than that in our chicken ration. Our natural flock management includes pasture, greens, scratch, feeds, and free choice minerals; with lots of choice available, the birds are able to select and balance their diet themselves, naturally adjusting or compensating to get the right amounts of nutrients. Please note that fishmeal can vary considerably in quality and can potentially be a source of Salmonella contamination when included in poultry diets. Also, high levels of fishmeal in poultry diets can result in fishy-tasting meat and eggs (Ponce et al. 2002).
Documented Problems with Soy and GMO Crops
Aloha House is a soybean-free operation due to the detrimental health effects of soy. The phytoestrogens and enzyme inhibitors of unfermented soy are problematic for both livestock and humans. Documented concerns with soy include the following:
- High levels of phytic acid in soy reduces a body’s assimilation of calcium, magnesium, copper, iron, and zinc [Eds.’ Note: Please see EDN 103 “Phosophorus (and other) Deficiencies in a Diet High in Phosphorus,” to learn more about the problem with phytic acid].
- Phytic acid in soy is not neutralized by traditional preparation methods such as soaking, sprouting, and long, slow cooking.
- Diets high in phytic acid have caused growth problems in children.
- Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals, consumption of soy containing trypsin inhibitors resulted in stunted growth.
- Soy phytoestrogens (i.e. plant estrogens) disrupt endocrine function, and can potentially cause infertility and promote breast cancer in adult women.
- Soy phytoestrogens are potent anti-thyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to auto-immune thyroid disease.
- Vitamin B12 analogs in soy are not absorbed, and actually increase the body’s requirement for B12 (Nienhiser 2003).
[Eds.’ Note: See the “Soy References Cited” section for more information.]
GMOs (genetically modified organisms) are also potentially problematic in animal feed. A recent study linked cancer in hogs to their consumption of GMO soy and maize (Carman et al. 2013). With so many other non-GMO crops to choose from, we have chosen to avoid GMOs at the Aloha House. The effects of feeding processed kidney bean meal (Phaseolus vulgaris) instead of soybean meal was linked to reduced egg quality of white leghorn hens (Hussein et al. 2015). Soy protein is cheap, but may not have the best amino acids for poultry growth compared to fish meal. Fish meal may be best because in evaluation of fishmeal protein supplementation to commercial feeds for egg layers and egg quality in warm tropical regions a study showed an important link to the usable amino acid profile of fishmeal (Omeke et al. 2013).
The Aloha Fermented EM Feed
Our all-around “Aloha Fermented EM Feed” contains 19.00% crude protein and costs 0.36 USD/kg here in Palawan, Philippines (Table 1). We have had good success feeding it to broilers and layers. The fine (<0.5mm) agricultural limestone included in the ration is important for bone development. Layers also need access to additional calcium, which will be discussed further in sections below.
The recipe in Table 1 is a good starting point for creating a farm-derived poultry feed that saves time and recycles inputs. If you can manage a more complicated schedule for the protein demands of your flock as the birds develop, you can adjust your ration’s protein by adjusting the quantity of fish meal.
Health Supplements Starting with Day-Old Chicks
You can increase the feeding capacity of chicks without using hormones by using natural health supplements that can also be created from on-farm inputs (Table 2). These supplements will give them better growth and development and increase their disease resistance. Details for each supplement are given below.
Bamboo Leaves and Brown Rice Supplement
For day-old hatchlings, we finely chop bamboo leaves and mix with an equal amount of brown rice flour. Don’t worry about depriving the birds—for the first day the chicks are “coasting” on the egg food and will not be set back by the high fiber. Rather, this treatment elongates their G.I. tracts and gives them extra feeding capacity. [Eds.’ Note: While feeding rice flour and chopped bamboo to day-old chicks is a common practice, it has not been scientifically studied.] Most feed suppliers admit that “chicks don’t need feed or water the first 48 hours after hatching” (Hamre, 2013).
Chopped Banana and Watermelon Supplement
Feed your chicks an equal amount of chopped banana and watermelon as an addition to other feed like rice bran or corn grits. Have it free choice - available at their own discretion and separate from your other feeds.
Herbal Water Supplement
Finely chop 100 grams of aloe vera and 100 grams of ginger, and mix with 100 grams of molasses and 100 ml of EM1. Ferment in 2 liters of water for 2 weeks. Filter this fermented solution and dilute 1:1 with water. Natural vinegar can be added at 1-3% by volume when you serve it to your chicks.
“Effective Microorganisms Activated Solution” (EMAS ) water helps to aid digestion by guiding the enzyme process. To make EMAS water, we dilute EM with 200 parts of water, to create a ratio of 1:200. We feed EMAS water on demand.
At Aloha House, we always maintain a supply of grass, kang kong (morning glory), or other greens, to support layers’ egg production. We practice a Thai-style feeding regime for our adult birds that we learned in Saraburi called “chicken salad”. We add chopped greens (including azolla) on top of the morning feed ration (Figure 9). Layer chickens are large birds that are prone to exhaust their pasture and are often in need of additional greens. Serving your flock “chicken salad” provides them with a regular supply of nutrition beyond the fermented feed.
Our natural flock management includes the provision of greens, scratch, rationed feeds (fermented or mixed feed), and (starting at 18 weeks as indicated below) a free-choice source of calcium in the form of coarse, crushed limestone (1.5 mm – 3.5 mm). This means that we set out a diversity of options, including a source of calcium. It’s important to note that layer hens typically lay eggs in the morning, and finish forming the egg shells as they sleep; they pull calcium from their digestive tract, mainly the gizzard. They require coarse agricultural lime or other calcium carbonates such as clamshells (1.5 mm – 3.5 mm). While a starting ratio of 70% coarse to 30% finely-powdered livestock lime (<0.5 mm) is recommended in a commercial feed; according to Leiterman, “A general rule of thumb is to have at least a 50:50 ratio of coarse to fine particle size calcium in the diet. Since layers eat very little during darkness, it is critically important for good eggshell development that there be adequate amounts of calcium still in the gizzard during the hours of darkness when the eggshells are being formed” (Leiterman 2013). The birds choose and balance their own diet from the selection of goodies that we provide at Aloha House. With the availability of the extra, coarse limestone, our egg production has almost doubled and we have seen increased eggshell quality and strength.
Ducks and Mixed Flocks
At Aloha House, we run Muscovy ducks on pasture with our chickens (Figure 10).
They seem to forage differently, but do well together. We feed the ducks our basic feed ration but also provide a tub of water for hygiene so that they can clean themselves. Muskovy ducks are not big swimmers but do really well on grass! They also snatch flies out of the air. Local turkeys have also grazed well with our meat chickens, but the local Palawan Muscovy ducks we tried performed poorly in general. We will try again when we get a better breed!
Our meat ducks (Peking) and layer ducks (Malard) do better with a small pond of good quality water. We move the water through a grow area for plants with a small pump, in a closed-loop recirculating “duckponic” system (Figure 11). The plants use the nutrition in the water (from the duck feces), simultaneously cleaning it, while the ducks swim, aerate, and fertilize the plants with their waste that is deposited in the water. All of the plants grown in the system are used to feed hogs; they are not appropriate for human consumption. We include kang kong (morning glory), water cress, azolla, and duckweed in our duckponic system.
Many poultry-raising options and feed sources exist in Southeast Asia. Thankfully, the costs of poultry production can be reduced by using a variety of alternative feed sources, many of which can be created on-farm or locally. Properly-fed, chickens, ducks, and turkeys are an important source of fat-soluble vitamins, protein, fats, and minerals for the human diet. At the Aloha House, we have had very good success with our natural flock management, which includes greens, scratch, rationed feeds, and free-choice calcium for poultry. We also provide access to pasture and plenty of sunshine. Together, these strategies will ensure profitable and high-quality production for your family and customers.
A Convenient Reference Book for All Persons Interested in the Production of Eggs and Poulty for Market and the Breeding of Standard-Bred Pounltry for Exhibition. 1912. I.C.S Poultryman’s Handbook. Available: http://www.lionsgrip.com/ babychix.html
Carman J.A., H.R. Vlieger, L.J. Ver Steeg, V.E. Sneller, G.W. Robinson, C.A. ClinchJones, J.I. Haynes, J.W. Edwards. 2013. A long-term toxicology study on pigs fed a combined genetically modified (GM) soy and GM maize diet. Journal of Organic Systems. Available: http://www.organic-systems.org/journal/81/8106.pdf
Cruz P.S.. 1997. Aquaculture feed and fertilizer resource atlas of the Philippines. FAO Fisheries Technical Paper (366). Available: http://www.fao.org/docrep/003/ W6928E/W6928E00.HTM
Fallon S., M.G. Enig. 2000. Splendor from the grass. Westin A. Price Foundation. Available: http://www.westonaprice.org/ health-topics/splendor-from-the-grass/
Fatty acid composition of certified organic, conventional and omega-3 eggs. 2009. Food Chemistry. Available: http://aquaplant.tamu.edu/plant-identification/alphabetical-index/filamentous-algae/
Hess J.B., J.P. Blake, D.H. Garner, J.A. Chappell. 2009. Effects of catfish meal blend inclusion in broiler feeds on live performance and carcass yield attributes. The Journal of Applied Poultry Research. Available: http://japr.oxfordjournals.org/ content/18/2/232.abstract
Hamre M.L.. 2013. Hatching and brooding small numbers of chicks. University of Minnesota Extension. Available: http:// www.extension.umn.edu/food/small-farms/ livestock/poultry/hatching-and-broodingsmall-numbers/
Hussein T., M. Urge, G. Animu, S. Fikru. 2015. Effects of feeding processed kidney bean meal (Phaseolus vulgaris) instead of soybean meal on qualities of eggs of white leghorn hens. Veterinary Science & Technology. Available: http://www.omicsonline. org/open-access/effects-of-feeding-processed-kidney-bean-mealphaseolus-vulgaris-by-replacing-soybean-meal-on-eggfertility-and-qualities-of-chicks-of-whiteleghorn-hens-2157-7579-1000S12-001.pdf
Kalita, P., P. Mukhopadhyay, and A. Mukherjee. 2007. Evaluation of the nutritional quality of four unexplored aquatic weeds from Northeast India for the formulation of cost-effective fish feeds. Food Chemistry (103) 204-209). Available: http:// www.sciencedirect.com/science/article/pii/ S0308814606006303
Leiterman D.. 2013. Managing dietary calcium in poultry layer diets. Crystal Creek Natural Farm. Available: http:// crystalcreeknatural.com/pdfs/December_2013/04ManagingDietaryCalciumInPoultryLayerDiets.pdf
Omeke B.C.O., P.A. Nnadi, W.S. Ezema. 2003. Evaluation of fishmeal protein supplementation to commercial feeds for egg lay and quality in warm tropical region. Nigerian Veterinary Journal. Available: http://www.ajol.info/index.php/nvj/article/ view/3451
Ponce L.E., A.G. Gernat. 2002. The effect of using different levels of tilapia by-product meal in broiler diets. Poultry Science. Available: http://ps.fass.org/ content/81/7/1045.short
Simopoulus A.P.. 2004. Omega-3 fatty acids and antioxidants in edible wild plants. Biological Research. The Center for Genetics, Nutrition and Health. Available: http://www.scielo.cl/pdf/bres/v37n2/art13. pdf
Simopoulos A.P., N. Jr. Salem. 1989. n-3 fatty acids in eggs from range-fed Greek chickens. The New England Journal of Medicine. Available: http://www.nejm.org/ doi/full/10.1056/NEJM198911163212013
Swistock B.. 2016. Filamentous algae. Penn State Extension. Available: http:// extension.psu.edu/natural-resources/ water/ponds/pond-management/aquatic-plants/filamentous-algae
Ussery H.. 2005. Managing poultry on pasture with electronet. Backyard Poultry Magazine. Available: http://www.themodernhomestead.us/article/electronet-1.html
The Soy Controversy References Cited
Campbell T.C., T.M. Campbell. 2005. The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss and Long-Term Health. BenBella Books.
Chang K.C., Ed. 1977. Food in Chinese Culture: Anthropological and Historical Perspectives. Yale University Press.
Enig M., S. Fallon. 1999. The oiling of America. Nexus Magazine. Available: http://www.westonaprice.org/know-yourfats/the-oiling-of-america/
Harras A., Ed. 1996. Cancer Rates and Risks, 4th Edition. Diane publishing.
IEH assessment on Phytoestrogens in the Human Diet. 1997. Final Report to the Ministry of Agriculture, Fisheries and Food. Leicester, and the Institute for Environment and Health (IEH).
Messina M., V. Persky, K.D. Setchell, S. Barnes. 1994. Soy intake and cancer risk: A review of the in vitro and in vivo data. Nutrition and Cancer. Available: http:// www.ncbi.nlm.nih.gov/pubmed/8058523
Nagata C., N. Takatsuka, Y. Kurisu, H. Shimizu. 1998. Decreased serum total cholesterol concentration is associated with high intake of soy products in Japanese men and women. Journal of Nutrition (128) 209-13. Available: http://www.ncbi. nlm.nih.gov/pubmed/9446845
Nienhiser J.. 2003. Studies showing adverse effects of dietary soy, 1939-2014. Weston A. Price Foundation. Available: http://www.westonaprice.org/health-topics/ studies-showing-adverse-effects-of-dietary-soy-1939-2008/
Nienhiser J.. 2003. Studies showing adverse effects of isoflavenoids, 1939- 2013. Weston A. Price Foundation. Available: http://www.westonaprice.org/ health-topics/studies-showing-adverse-effects-of-isoflavones-1950-2010/
Rackis J.J.. 1974. Biological and physiological factors in soybeans. Journal of the American Oil Chemists’ Society 51 (1) 161-174.
Rackis J.J., M.R. Gumbmann, I.E. Liener. 1985. The USDA trypsin inhibitor study. I. Background, Objectives and Procedural Details. Qualification of Plant Foods in Human Nutrition 35 (1) 213-242.
Searle C.. 1976. Chemical Carcinogens, American Chemical Society. ACS Monograph 173.
Torum B., H. Wilke. 1979. Nutritional Quality of Soybean Protein Isolates: Studies in Children of Preschool Age. Soy Protein and Human Nutrition. Academic Press.