Joining maiden ewes
Joining maiden ewes improves the lifetime productivity of the ewe flock but can decrease wool production and growth rates. Maidens also have a higher risk of not rearing the lamb due to mismotherment (related to inexperience). Body condition is the critical factor for successful joining of maiden ewes. Ewes start to ovulate and will become pregnant when they reach about 75% of their mature bodyweight. For example, a mob of ewes that have expected mature weight of 60kg will begin to cycle when they reach 40-45kg. At 75-80% of mature weight they would be expected to have 80% conception (= number of ewes pregnant at scanning/number of ewes mated).
Maiden ewes have shorter oestrus (‘heat’) periods and do not show their heat behaviour as strongly as mature ewes. It is necessary to use mature rams and use higher numbers of rams to compensate. Maiden ewes may suffer injury from being mounted by large rams. Rams should be screened, so that very large rams are not used over small ewes.
| Reproductive Cycle of Ewes |
| Stage |
Average |
|
Range |
| Puberty age |
5 to 12 Months |
| Oestrus cycle |
17 days |
|
13-19 days |
| Oestrus duration |
30 days |
|
18-48 days |
| Ovulation release |
20-30 hours after start of Oestrus |
| Gestation |
146 days |
|
135-150 days |
Table 1 - Variation in Ewe Reproductive Cycle
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