B12 and Antibiotics for Chickens

It's hard to accept and explain the feeding of antibiotics to chickens and other farm animals for growth promotion.  Did Dr. Frankenstein have a second career in farming?  To better understand, we need to review history.

After the 1900's, the supply of meat was in greater and greater demand, and getting more and more expensive.  Food riots broke out about unaffordable food, and meat shortages.  Farmers were using affordable feeds and by-products, including fish meal, cod liver oil, and “tankage” (rendering-plant byproducts).  World War I caused more shortages, including fish meal imported from Japan, and increased the demand for meat.  Forced to used plant-based protein sources, farmers found that the animals grew more slowly, and were subject to more diseases.

The US government, wanting to avoid more food riots, put their best scientists on the case to find an animal feed substitute or supplements.

The story of chickens and antibiotics needs to discuss Vitamin B12 to understand how all this got started.  In 1948, Merck discovered the active ingredient in cod liver oil, Vitamin B12.  B12 can't be created by the human body, we must obtain it from our food.  Without B12, we have anemia, which can be deadly.  Merck produced the B12 using a ton of liver to produce 12 milligrams of B12.  Looking for a better source of B12, they discovered a better source in Merck's own backyard.

During the growing of penicillin, billions of microbes are grown in large fermentation vats from which the penicillin is extracted. Scientists soon discovered that those bacteria not only produced antibiotics, they produced B12 also.  Extraction of B12 was soon efficiently produced as a by-product of antibiotics.

When the pharmaceuticals industry started making fermented B12, they had large volumes of spent liquid that needed to be disposed.  Like other food wastes, farm animals were a possible customer for these biological by-products.

Poultrymen had noticed that when the chickens were on fresh bedding, their weight gain diminished.  When chickens had access to manure (their own or manure from other animals), scratching and pecking in it, they had faster weight gains, laid more eggs, and had lower mortality.  In 1950, American Cyanamid’s Lederle laboratory discovered that animal manure contained significant amounts of Vitamin B12.  They used the waste left over from an antibiotic batch of Aureomycin which caused the animals to grow 50% faster. Non-antibiotic fermentations (eg. brewer's yeast, etc.) for B12 were tried as a competitive alternative, but were not as effective.  The  tiny amount of residue antibiotics in the B12 broth supplement (ie. incomplete antibiotic removal by the primary antibiotic production process), was the secret.

Today, about 80% of antibiotics are consumed by farm animals.  Started simply, finished badly.

This discovery of adding antibiotics, when combined with the better genetics from the "Chicken of Tomorrow" contest, established the chicken meat bird as a separate industry from the chicken egg business.

The edible part of a raw egg (USDA Food # 01123) is 90% water, 12.6% protein, 10.6% fat. 1.12% carbohydrate. The shell is an additional 12%.  To produce an egg, the chicken has to drink water, and provide 36.32% of the balance from the metabolites of its food intake.

A chicken lays an egg every 28 hrs on average.  Assuming a 60 g. egg, that's 51.43 g of egg per 24 hr day.

For whole, raw chicken (meat + skin, USDA Food # 05006), it is 65.99 % water, 18.60% protein, 15.06% fat, and 0.00% carbohydrates.  The bones are an additional 31% of the weight.  Bones are generally composed of 40% Calcium and 18.5% Phosphorous on a dry basis.  I'll assume 30% water for raw bones.  Therefore the overall composition of a raw chicken is 54.83% water, 12.83% protein, 10.39% fat, 8.65% Calcium, 4.02% phosphorous.  To grow a chicken, the chicken has to drink water, and provide 35.89% of the balance from the metabolites of its food intake.

Therefore we see only a 1.2% weight difference between growing an egg and growing the chicken on what is derived from the chicken feed.

Assuming a starting broiler chick weight of 60 grams, a 2 kg live finish weight at 6 weeks (42 days), and constant rate of exponential growth, that is 8.7074% per day weight gain for a broiler.  After 28 days, the broiler is adding weight faster than the egg layers production rate (51.43 g. per day).

Therefore chicken feed for broilers becomes more demanding (on a weight created per day basis) after the 28 day point, than for layers.  Without adequate feed (quantity or nutritional quality), feed will more and more stunt the growth of the broiler chicken.

After the Chicken of Tomorrow identified the best genetics for the meat bird, cross-breeding the best with the second best made even better hybrids.  This was repeated again and again to maximize the effect.

Reference:  Scientific American, CBC News