I need meat because of vitamin deficiency, however, if you are born vegetarian (from vegetarian family) then you wont have that problem.
Do you mean that if you grow up eating meat you have to continue it or else you will get a vitamin deficinacy? I may mis understand your statement if so please feel free to correct me.
Regarding halal and Kosher slaughter practices. The animal is not stunned prior to being killed. A razor sharp knife is then swifty used to slit the animals throat. The swiftness of the cut is believed to cause minimal pain and a quick death. Modern times have permitted the use or restraint boxes, where the head of the animal is held whilst the final cut is made.
In some halal (muslim slaughter) houses, employees use a short knife instead of the recommended one which should be as twice as thick as the animals neck. This short knife causes definite distress and struggling in cattle. If they do not stun the animal it is also recommended that the knife is razor sharp. Some slaughter houses use reversible head-only electrical stunning, which is accepted if the knife is short.
Some religious slaughter houses do not use stunning and restraint boxes. However it is recommended these be used and more slaughter houses are agreeing to them. It is extremely important that the person performing the slaughter makes a clean cut and not remove the animal from the restraint box until it is insensible, otherwise this causes severe pain, there have been cases where an animal was removed. Without the knowledge of a reputable slaughter house which is known for its experience consumers will never know if the cut is made cleanly. You must research this if you ever plan on eating kosher or halal meat.
If you do not you may support a slaughter house where a cut is not made cleanly and second or third cuts must be made in order for the animal to die. Also the slaughter house may remove the animal from the restraint box, before it is dead causing more pain. Some slaughter houses have also been reported to not use stunning equipment when using a short knife. This will cause severe ditress in the animal as a clean cut is not made fully.
Cutting an animals throat may cause less pain then the tradional bolt gun to the head used in factory farming but unless you truely know which slaughter house your meat came from you may never know if the cut is made cleanly.
Any death causes pain, and halal and kosher practices cause pain, same as any other killing. Animals cannot communicate so we may never know how much or how little pain they are in.
For more information on slaughter practices and kosher and halal meat click:
https://www.grandin.com/ritual/kosher.slaugh.html
Regarding vitamin deficiancies. Changing to a vegetarian/vegan diet is not hard if you balance your vitamins and minerals. What is the medical name of the conditon you have that does not allow you to ''absorb'' these minerals? Is there any medication you can take?
B12 is found in: dairy products or free-range eggs. ½ pint of milk (full fat or semi skimmed) contains 1.2 µg of B12. A slice of vegetarian cheddar cheese (40g) contains 0.5 µg. A boiled egg contains 0.7 µg. A range of B12 fortified foods are available. These include yeast extracts, Vecon vegetable stock, veggieburger mixes, textured vegetable protein, soya milks, vegetable and sunflower margarines, and breakfast cereals.
These foods all contain B12 and have no meat in them whatsoever.