51.   A few have even mated and produced offspring.

52.   Chances the pair will mate and produce offspring are slim.

53.   In the case of the threatened dik-diks, a type of antelope, it explained why some produced infertile offspring.

54.   Ling Ling the giant panda is getting a second chance to produce offspring.

55.   Ling Ling the giant panda is returning to Japan after spending five months in Mexico, a visit that zoo officials hope will produce offspring.

56.   Men with fertility problems who father children through artificial insemination are likely to produce fertile offspring, according to a study released Friday.

57.   Normal flies that mated with the sterile flies failed to produce offspring, reducing their numbers.

58.   Sometimes animals become pregnant and produce infertile offspring.

59.   Some are females too old to produce offspring normally.

60.   Some of those smaller fish also are reaching sexual maturity earlier, producing offspring that are both small and programmed to be mothers while still young.