Not getting pregnant is a risk to the genital health

Young rhino with his mother in the wild

Space limitations or genetic overrepresentation are reasons 
for preventing wild animals in captivity from getting offspring. 
Yet, contraception may have another purpose, specifically in animals beyond their breeding age.

The Impact of Delayed Breeding on Female
Fertility in Captive Wildlife

Zoos and other wildlife institutions are crucial for species conservation through education, research, and as sources for reintroduction. However, in some captive populations face space limitations. Breeding is often not infrequent or not desired at all. This delay can negatively impact the fertility of females in several species, such as felids, canids, bears, tapirs, primates, elephants, rhinoceros. Research showed that prolonged non-breeding periods cause reproductive disorders in these species. Breeding females early and regularly can mitigate fertility issues. Yet, this approach has demographic, genetic, logistical, and political implications.

A mixed strategy of breeding and non-breeding intervals may be necessary. For this, regular fertility assessments show the current breeding potential, avoid unnecessary animal transports between institutions or occupation of valuable space by infertile animals.

References:

Hermes R, Göritz F, Saragusty J, Stoops MA, Hildebrandt TB. Reproductive tract tumours: the scourge of woman reproduction ails Indian rhinoceroses. PLoS One 2014; 9(3):e92595.
https://doi.org/10.1371/journal.pone.0092595

Hermes R, Hildebrandt TB, Göritz F. Reproductive problems directly attributable to long-term captivity–asymmetric reproductive aging. Animal Reproduction Science 82–83 (2004) 49–60.
https://doi.org/10.1016/j.anireprosci.2004.05.015

Penfold LM, Powell D, Traylor‐Holzer K, Asa CS. “Use it or lose it”: Characterization, implications, and mitigation of female infertility in captive wildlife. Zoo Biology 33 (2013) 1–9.
https://doi.org/10.1002/zoo.21104