Sheep 101 - Lambing

Why are most lambs born in the spring? Ewes are seasonal, short-day breeders. In temperate climates, nature meant for sheep to mate in the fall, so that lambs would be born in the spring when the weather is mild and the grass is plentiful, thus enhancing the lambs' chances for survival. A ewe's reproductive activity is controlled by photoperiod (the number of hours of daylight). In temperate climates, when day length becomes shorter and temperatures become cooler, this change triggers the ewe's brain to release hormones to being the reproductive process. The further away from the equator that a sheep breed originated, the more likely they are to exhibit seasonal breeding patterns. Conversely, sheep developed in the tropics or sub-tropics are likely to exhibit estrus behavior throughout the year. Through selection and management, the sheep's natural breeding patterns have been altered.

Mating During their fertile period, ewes will come into estrus (heat) every 17 days until they are bred or their fertile period is over. Only during estrus will a ewe allow a ram to mate with her. The duration of estrus is 24 to 36 hours. A ewe in heat will seek out a ram. During the peak of estrus, the ewe may sniff, lick, or nuzzle the ram. She may fan her tail. The classic behavioral response of the ram when it detects a ewe in heat is to lift his nose into air and curl his upper lip. This is called the Flehmen response. A fit mature ram can easily mate 100 ewes, though a ratio of 1 ram per 30 ewes is more common. Rams can be racist, showing a preference to mate ewes of their own breed.
Pregnant Katahdin Ewe	Crossbred Ewes
Pregnancy Though it depends on breed and management, ewes can become mothers before they reach their first birthday. For some producers, it is common to breed ewes for the first time when they are 7 to 9 months old, whereas other producers delay breeding until the ewes are approximately 1 1/2 years old. A ewe is pregnant for 142 to 152 days (about five months). Pregnancy is also called gestation.Since ewes are only preganant for five months, it is possible for ewes to give birth to lambs at an interval of every six to eight months. Annual lambing (every 12 months) is most common. Special Care During Late Pregnancy During her last month of pregnancy, the ewe needs extra nutrition because her lambs are growing rapidly inside of her (70 percent during the last six weeks), and she needs to start producing milk for them. If she eats too much extra feed, she may have trouble delivering her lambs, because they may get too big and she may get too fat. If she doesn't eat enough, she may get sick because the growing lambs are taking all of her food intake. It is common to vaccinate ewes (for various clostridial diseases) during the last month of pregnancy. This is a method of passing immunity onto newborn lambs. It is also common to deworm ewes prior to lambing. This is because a ewe's immunity to internal parasites is compromised when she lambs.
Katahdin Ewe and Lambs	Southdown Ewe and Lambs
Singles, Twins, and Triplets Ewes usually give birth to 1 to 3 lambs at each birth. Twin births (two babies) is most common in well-managed flocks, though first time mothers are more likely to have single lambs. Ewes produce their largest litters of lambs when they are between 3 and 6 years of age. There are some breeds of sheep that can produce "litters" of lambs -- four, five or six lambs at one time! The most "prolific" sheep breeds are the Barbados Blackbelly, Finn Sheep, and Romanov. Ewes need a lot more food to take of three or four lambs. Sometimes, the "extra" lambs need to be raised artificially. Because sheep are often raised in harsh environments, sometimes it is more desirable for a ewe to have just one lamb. This is because there may not be enough food for the ewe to carry two lambs or produce milk for two lambs. Or if the flock has to travel far for food and water, it is better to have one big strong lamb, than two or three smaller lambs that may struggle to keep up and eventually die.
Barbdos Blackbelly Ewe with Lambs	Merino Ewe with Lamb
Birth Weights The weight of newborn lambs varies by breed, sex (ram or ewe), birth type (single, twin, or triplet), and ewe nutrition. Lambs from medium to small breeds are similar in size to human babies, usually between 6 and 10 pounds. When birth weights get too heavy (relative to the size of the breed), difficult births can be encountered.
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. . New Words . .

Estrus - period that immediately precedes ovulation and during which the female is most receptive to mating. Heat.

Photoperiod - duration of light in a light/dark cycle.

Hormone - chemical substance formed in the body that is carried in the bloodstream to affect another part of the body.

Gestation - the act of carrying young in the womb; pregnancy.

Clostridial - bacteria that cause disease in animals (and humans), found in soil throughout the world. Most commonly affecting sheep are clostridial perfringins and tetani.

Litter - the offspring of one birth of a multiparous animal.

Prolific - bearing in abundance, especially offspring.

Immunity - the body’s ability to fight a particular disease by having antibodies already present against that disease.

Antibody - special protein that is part of the body's immune system.

How many babies do sheep usually have?

Mary Had a Little Lamb