Lambing

As with other mammals, domestic sheep reproduction occurs sexually. Their reproductive strategy is very similar to other domestic herd animals. A flock of sheep is generally mated by a single ram, which has either been chosen by a farmer or has established dominance through physical contest with other rams (in feral populations). Most sheep have a breeding season (tupping) in the autumn, though some are able to breed year-round.

Largely as a result of the influence of humans in sheep breeding, ewes often produce multiple lambs. This increase in the lamb births, both in number and birth weight, may cause problems in delivery and lamb survival, requiring the intervention of shepherds.

Ewes generally reach sexual maturity at six to eight months of age, and rams generally at four to six (ram lambs have occasionally been known to impregnate their mothers at two months). Ewes enter into oestrus cycles about every 17 days, which last for approximately 30 hours. In addition to emitting a scent, they indicate readiness through physical displays towards rams. The phenomenon of the freemartin, a female bovine that is behaviorally masculine and lacks functioning ovaries, is commonly associated with cattle, but does occur to some extent in sheep. The instance of freemartins in sheep may be increasing in concert with the rise in twinning (freemartins are the result of male-female twin combinations).

Without human intervention, rams may fight during the rut to determine which individuals may mate with ewes. Rams, especially unfamiliar ones, will also fight outside the breeding period to establish dominance; rams can kill one another if allowed to mix freely. During the rut, even normally friendly rams may become aggressive towards humans due to increases in their hormone levels.

Historically, especially aggressive rams were sometimes blindfolded or hobbled. Today, those who keep rams typically prefer softer preventative measures, such as moving within a clear line to an exit, never turning their back on a ram, and possibly dousing with water or a diluted solution of bleach or vinegar to dissuade charges.

Without ultrasound or other special tools, determining if a sheep is pregnant is difficult. Ewes only begin to visibly show a pregnancy about six weeks before giving birth, so shepherds often rely on the assumption that a ram will impregnate all the ewes in a flock. However, by fitting a ram with a chest harness called a marking harness that holds a special crayon (or raddle, sometimes spelled reddle), ewes that have been mounted are marked with a color. Dye may also be directly applied to the ram's brisket. This measure is not used in flocks where wool is important, since the color of a raddle contaminates it.

...
Wikipedia