I'm new to chickens and have been reading like mad learning everything I can about these wondrous little critters. Lately I've been reading about apple cider vinegar and baking soda (sodium bicarbonate) and how they benefit our backyard chickens. Here's some information I've learned that I thought I would share for those looking for the same info. I'm sure many of you know all of this already, but for those just starting out, perhaps it will be useful. (And please feel free to add corrections and additional information as I'm always open to learning in order to create a happy, healthy life for my chickens. ) Apple Cider Vinegar HOW MUCH TO USE: Apple cider vinegar (ACV) is suggested for use at the rate of 1 Tbs. per gallon of water (double the amount of ACV if you have hard water). Ultimately, you want the pH of drinking water to be around 4 after adding ACV. Adding too much ACV can cause chickens to stop drinking, so be sure to keep your ratios in check. KINDS OF ACV: ACV can be purchased raw or pasteurized. Raw ACV contains a live culture known as a mother of vinegar, which consists primarily of acetic acid-producing bacteria, or acetobacter. Acetobacter requires oxygen to survive. Pasteurized ACG has been heated in an effort to remove potentially harmful bacteria, a process by which the acetic acid-producing bacteria of the mother are also destroyed. The kind of ACV (raw or pasteurized) one chooses to use is inconsequential as a chicken's crop contains lactic acid-producing bacteria which require an oxygen-free (anaerobic) environment to thrive. If one chooses to use raw ACV, the live acetobacter won't survive long in the anaerobic conditions of the crop. Additionally, the other beneficial amounts of nutrients that may be contained within the mother are in such small amounts that they become insignificant in affecting a chicken's overall health. So, the type of ACV used (raw or pasteurized) is really immaterial. BENEFITS OF ACV: Beneficial intestinal bacterial prefer a pH range of 5.5-7 (slightly acidic). Disease-causing bacteria prefer a pH of 7.5-9 (slightly basic or akaline). The pH of a healthy chicken crop is between 5 and 6. Vinegar is a natural antimicrobial with a pH of around 2-3. Used full strength, it makes an excellent sanitizer for cleaning feeders and drinkers. Used at a ratio of 1 Tbsp. per gallon of drinking water, it helps to maintain an acidic environment within a chicken's crop, helping to prevent the proliferation of harmful pathogens particularly during times of stress and illness (which is where its benefits lie - overall, ACV will not effect pH within the GI tract past the crop). A chicken under stress will drink less, which can cause pH imbalance within the crop, increasing the chances of pathogens making their way into the body. Adding a bit of ACV to drinking water encourages a chicken to drink more during times of stress and helps to maintain an acidic environment within the crop. Stress or illness can also cause a chicken to lose its appetite which results in an increased pH in the stomach (an empty stomach will not produce acid). Increased stomach pH discourages the growth of beneficial bacterial and encourages the growth of pathogenic bacteria. A sign of high stomach pH is loose droppings. ACV added to drinking water will encourage chickens to drink more, which encourages them to eat more, which will balance out GI tract pH. Additionally, ACV can be used to help relieve respiratory distress caused by excess mucous in the mouth and throat as a result of illness/disease. Apple peal can also be used with the same effect as the tannin in the peal will help to dry out the mouth. WHEN NOT TO USE ACV (Use baking soda instead!): Do NOT use ACV if a hen is experiencing heat stress during hot/humid weather (range: 80° F/100% humidity - 95° F/5% humidity and above). To cool down, a hen will pant excessively. Rapid breathing will result in an increased loss of carbon dioxide from her body. Carbon dioxide is derived from bicarbonate, which is used as a buffer in the blood to regulate pH and extracted from the blood by the lungs as carbon dioxide. An increased loss of carbon dioxide, therefore, results in an increased loss of bicarbonate, which results in increased blood pH. This condition is called respiratory alkalosis. Adding ACV to drinking water reduces the availability of dietary calcium. A lack of calcium due to respiratory alkalosis and decreased dietary calcium can result in fewer laid eggs, thin egg shells and interrupted nerve impulses causing weak muscles and trouble laying eggs. One would think that if the blood is alkaline, adding ACV will help to reduce the pH of the blood, but this isn't the case—ACV (acetic acid) has no effect on blood pH, it can only effect the pH of the crop. So what does one do to help reduce the loss of calcium during heat stress? Add baking soda (sodium bicarbonate) to drinking water at the rate of 1/4 c. per gallon of drinking water. When the kidney's detect that the blood is alkaline, the kidneys attempt to decrease blood pH by filtering out bicarbonate and excreting it. Adding sodium bicarbonate helps to keep bicarbonate levels up, thusly, helping to maintain the pH of the blood during hot weather. NOTE ON ACV: ACV can erode metal waters and valves, so only use in plastic waterers.