Thank you major sir for clarifying my understanding.

Respected doc.. I don't know whether you are a doctor or not but you me and all horses and all mammals will be intrauterine before birth...I think that answers your question.during the process of development intrauterine in various phases the testicles desend from the level ok kidneys down below to the scrotum....for any reference refer text book of embryology...

@ Dr Vinay

There is very hilarious gaffe in ur post. You said the testis are intra uterine before birth. As far as i know uterus is found in FEMALES and testis are found in MALES. So intra uterine testis is,.... i dont know what to call it

Do u mean to say Intra abdominal?????

Also u said testis descend after birth which is very INCORRECT. Testis are formed in abdomen and start descending when the fetus is in womb (starts as early as 150 days of gestation or conception ) through a passage called onguinal canal and lands in scrotum 30 days before birth or upto 10 days after birth.

I am not veterenarian and might be wrong about timeline but the process is correct.

I hope the mistakes are inadverent,

Testicles are usually developed close to the kidney intrauterine(before birth)but they descend to the current position post birth..In some horses only one testis might decend or both into the scrotal sac...There might be super numery testis inside the abdomen.....This horse is called a rig..some times when these rigs are gelded the testosterone levels will still be high bcos the intrauterine testis might still produce testosterone giving the false high levels of steroids suspecting doping in the horse.

...

MTG means might get grey 

.@ All

   As a former Keeper of the Indian Stud Book, I would like to state the correct position:-

    'rig' - This is an abbrevation for 'ridgling' or 'ridgeling' which means a male horse with one undescended testicle.

    'mtg' - This is an abbrevation for 'may turn grey'. Mustang is not a colour recognised for Thoroughbreds.

Thanks , one and all for clearing my doubts and thanks to indiarace, horse talks too 

MTG is the abbreviation of Mustang. Mustang is colour like bay or grey.

Mtg stands for mustang. It's denotes a colour which is mixed ie grey and bay.

I hv not come across MTg. I don't know where u hot this. Rig is the one with the testicles imbedded with the body and r almost like gelded . These animals will have more strength.

MTG -Tis the color of the coat,May Turn Grey

Rig is not an abbreviation. An imperfectly gelded horse is a rig, not sure about mtg.