why can't mules reproduce?

Answer 1

Because a mule is a hybrid between a horse and a donkey, it is a sterile animal. Check out the source for more info

Answer 2

In its common modern meaning, a mule is the offspring of a male donkey and a female horse. The reverse, the offspring of a male horse and a female donkey, is called a hinny. The term "mule" (Latin mulus) was formerly applied to the offspring of any two creatures of different species – in modern usage, a "hybrid".

The mule, easier to breed and usually larger in size than a hinny, has monopolized the attention of breeders. The chromosome match-up more often occurs when the jack (male donkey) is the sire and the mare (female horse) is the dam. Sometimes people let a stallion (male horse) run with a jenny (female donkey) for as long as six years before getting her pregnant. Mules and hinnies are almost always sterile (see fertile mules below for rare cases) (see External links). The sterility is attributed to the different number of chromosomes the two species have: donkeys have 62 chromosomes, whereas horses have 64. Their offspring thus have 63 chromosomes which cannot evenly divide.

A female mule, called a "molly", that has estrus cycles and can carry a fetus, can occasionally occur naturally as well as through embryo transfer. The difficulty is in getting the molly pregnant in the first place.

Answer 3

While it is commonly accepted that a hybrid (offspring resulting from a mating between species) is sterile, mules will reproduce with enough frequency that it needs to be mentioned.

I once attended a seminar on mules presented by Dr. Melvin Bradley, Professor at Missouri University. He spoke of a mule named Blue Moon - and later on a sibling White Lightning - both live birth foals out of a molly (mare) mule. This man was one of the most respected figures in the mule world and he even said that he had to revise his thinking on mule reproduction. Cool that he had the wherewithal to admit he'd held an incorrect notion.

Anyway, according to Bradley, apparently molly mules cycle so infrequently - and a jack's active semen count is so low that they rarely (emphasis on rarely) reproduce. Keep in mind that because they do tend to display stallion aggression, most jack mules are gelded.

BUT - if you pasture a young, fit, molly with a stallion, there is a slim (albeit mighty slim) chance they will reproduce.

(Learn more about mules from this link: http://www1.usu.edu/utahstatetoday/archives/may2003/05-30-03/newsreleases-05-30-03.cfm

Answer 4

Mules are a cross between a male donkey and a female horse, which are both different species. When two different species are bred together, their offspring will be fertile because of certain proteins in their DNA that will not allow them to fertilize or be fertilized.

Answer 5

all mixed hybrids are not capable of reproducing youngsters