Sheep are seasonal breeders, though some are able to breed all year round. The declining sunlight during Autumn stimulates them to cycle. As with other mammals, sheep reproduction occurs sexually.


Reproduction

Female sheep and rams reach puberty around 6 months old, though rams have been known to be fertile much earlier. Pregnancy in the ewe lasts around 5 months.

Reproductive failure is a common consequence of spontaneous abortion or infections.

Abortion

Between 3-5 percent of sheep farms in New Zealand will experience and abortion outbreak in any one year. Most abortion outbreaks start off slowly so the occasional aborting ewe is often ignored. The cost of losing even a few pregnancies can become quite high.

Campylobacteriosis

Is the most commonly diagnosed cause of infectious abortion in ewes in New Zealand, most commonly during the last six weeks of pregnancy. Infection is spread via contact with aborted fetuses, afterbirth or contaminated feed and water. Vaccination is an effective tool to prevent abortion losses due to campylobacteriosis. Sheep that have never been vaccinated will need two vaccinations 4-6 weeks apart. Annual boosters are recommended thereafter.

Toxoplamosis

Can result in foetal death in any stage of pregnancy. Lambs can be born dead or alive at normal term. This can make recognition of a problem related to toxoplasma infection difficult to identify. Toxovax is a highly effective made-to-order live vaccine only required once in a ewes lifetime. Contact Franklin Vets to place your order in advance and get advice on transportation.

Inbreeding depression

This tends to occur in smaller flocks and where only a few rams are used. The inbreeding can depress growth rates, litter size and the adult size of sheep.