Hydroxy methionine Calcium is a calcium salt containing 84% 2-hydroxy-4-methylthiobutyric acid (HMTBA) and is mainly used as a feed additive. MHA-Ca has been used in the livestock industry since the 1950's and has been proven to be a superior methionine source for the feed industry, livestock and pet producers. MHA is a solid granular product containing 100% monomer, which is very cost-effective and provides a number of additional performance benefits beyond its use as a methionine source. Therefore, MHA-Ca is ideal for use in premixes, concentrates and on-farm ingredients. Calcium hydroxy methionine is used as a substitute for methionine and its effect is equivalent to 65 to 86 per cent of methionine on a weight-for-weight basis. Calcium hydroxy methionine is a product whose amino group is replaced by a hydroxy group in the synthesis of DL-methionine, which has the same action and function as methionine and is easy to use, while it is suitable for ruminants. Generally methionine will be deaminated and become ineffective under the action of rumen microorganisms, but calcium hydroxymethionate only provides the carbon framework and does not deaminate itself; ammonia in the rumen can be used as a source of added amino groups to convert it into methionine. The commercial content of calcium hydroxymethionine is more than 97%, and its potency is equivalent to about 80% of 99% methionine, and the dosage can be calculated according to this ratio when dosing.