Agriculture Reference
In-Depth Information
reproductive activity is highest. Ewes all go into heat and are capable of
breeding during these seasons, though some individual ewes and par-
ticularly some breeds of ewes can breed year-round, or “out of season.”
But even within breeds that are known for out-of-season lambing, the
ovulation rate is lower during the spring and summer than it is in fall
and winter. Thus, by breeding out of season, you may have fewer lambs.
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Temperature.
Although high temperatures don't have as much effect
on reproductive activity as day length, they do have some. During hot
weather, rams may be infertile, and ewes are likely to miscarry.
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Age.
Ewe lambs generally begin cycling later than mature ewes, don't
tend to have as strong a heat, and don't release as many eggs per ovula-
tion. Reproductive activity may be reduced in aged ewes.
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Nutrition.
Flushing, or increasing the level of nutrition prior to breed-
ing, increases reproductive activity.
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General health.
Good health pays off with more lambs born and greater
lamb survival.
REPRODUCTIVE FUNCTIONS
Here are some rules of thumb for reproductive functions — but
remember, all animals are unique individuals, and some don't fol-
low the rules!
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First estrus: This generally occurs when animals are at least
6 months of age and weigh two-thirds of their adult weight,
though a few breeds are known for coming into estrus as early
as 4 to 5 months of age.
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Length of estrous cycle: The range is 14 to 19 days between
cycles, with 17 days being the average; if all ewes have been
exposed to the ram for 34 days, they theoretically should have
had two estrous cycles in which to breed.
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Length of time standing in heat: The average is 30 hours, but
this can range anywhere from 3 to 73 hours.
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Time of ovulation: 28 hours after the start of the estrous cycle
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Length of time the egg remains capable of being fertilized:
12 to 24 hours
