Most people are not familiar with a sheep dairy. In 2021, it was estimated that there were only about two hundred sheep dairy farms in the United States. People may be unsure of the details of how sheep produce milk. Some may ask if sheep can produce milk without being pregnant.
Sheep must be pregnant and give birth to produce milk. Pregnancy hormones are responsible for the development of alveoli cells in the udder. The production of milk is controlled by hormonal changes that occur at the birth of the lamb. Occasionally pathological hormonal levels can cause lactation.
It is critical to understand the biological mechanisms of milk production in sheep if you wish to run a sheep dairy.
How Do Sheep Produce Milk?
Sheep produce milk from mammary tissue, or udders, situated between their back legs. Before pregnancy, the udder is flat and small.
During pregnancy, hormones stimulate the development of milk-producing cells known as alveoli. The number of alveoli increases with each of the first five pregnancies. This causes the udder to become more prominent, especially in late pregnancy.
Between day ninety-five and one hundred of the pregnancy, the ewe's udder produces small amounts of milk. However, it is vital to note that the ewe cannot be milked at this stage as it may cause premature birth of the lambs.
Pregnancy Hormones And Milk Production In Sheep
During pregnancy, estrogen and progesterone maintain the pregnancy, but they also inhibit milk production. This is because the pregnant ewe's body is designed to use the nutrients for the growing lambs and not for milk production.
When birth occurs and the placenta is expelled from the body, the amount of estrogen and progesterone drops significantly. The drop in these hormones allows two other hormones, growth hormone, and prolactin, to take effect.
Prolactin and growth hormone initiate the milk-secreting phase in the ewe's body. Oxytocin is secreted in response to the lamb's cries and attempts to nurse.
Oxytocin causes contraction of the muscles which surround the alveoli, causing the milk to be emptied into the gland cistern. Sheep store seventy percent of their milk in the gland cistern and thirty percent in the alveoli lumen. This is the opposite of cows.
When the lamb sucks, the milk moves from the gland cistern into the teat cistern and out of the teat.
The first milk to be produced is colostrum. Lambs are born with no immunity as antibodies do not cross the placenta in sheep. Lambs gain immunity by absorbing antibodies in the colostrum during the first twenty-four hours of life.
Milking during late pregnancy compromises the colostrum and negatively affects the lamb's health. Therefore, ewes must have a drying-off period between pregnancies.
How Long Do Sheep Produce Milk?
Sheep do not produce the same amount of milk throughout the lactation period. Seventy-five percent of the milk yield is produced during the first eight weeks after lambing.
Dairy sheep produce milk for 120-240 days after the birth of their lambs if they are milked. The quantity and quality of the milk decline with the length of time since lambing.
After four to eight months of milking, the sheep must be dried off in preparation for the next lambing season. Even if the ewe is not pregnant again, the milk will stop being produced, or the quality will be too poor for commercial use.
Dairy sheep produce milk for longer periods than meat sheep, which only produce milk for 80-100 days after lambing. Various dairy breeds produce different quantities of milk for different lengths of time.
Why Do Sheep Stop Producing Milk?
As described above, sheep only produce milk for a limited period. Milk production is a high-energy function in the body. It uses fat stores and high levels of nutrients to produce milk that can sustain a lamb.
Sheep naturally breed, so lambs are born in spring when the new grass grows. Spring grass has high levels of nutrients and glucose for energy, allowing the ewe to get maximum energy.
Ewes naturally wean their lambs between three to four months. This allows the ewe to replenish her nutrients before the next pregnancy.
Lactating ewes lose weight and condition due to the high energy and nutritional requirements of producing milk. At a certain point, the body naturally 'turns off' lactation to protect the ewe and ensure her survival.
Correct Feeding Maximizes Lactation In Sheep
Dairy sheep farmers understand the importance of feeding their ewes correctly to fully use the lactation period. A well-fed sheep will produce milk for longer than one which is underweight and in poor condition.
The farmer must feed the ewe correctly throughout her pregnancy so that her body score is good when she gives birth. A thin ewe that gives birth will not produce good quality milk and will rapidly lose weight after the birth.
Can Artificial Hormones Induce Milk Production In Sheep?
Some people query if it is possible to induce lactation in sheep by providing them with artificial hormones. Scientists have considered these possibilities, especially with a view to fostering orphaned lambs.
One study showed that it is possible to induce lactation in sheep with artificially supplied hormones. However, it required a minimum of four weeks of daily induction hormones, followed by a one-to-two-week trigger phase to activate lactation.
The ewes produced sufficient milk to feed lambs, but it was noted that the milk had less dry matter, fat, and immunoglobulin levels than naturally produced milk.
It may be tempting to think that artificial hormones are the answer to lactating sheep without the complications of breeding and lambing. Realistically though, these practices would be frowned upon by the public, who have become conscious of artificial hormones and substances in food-producing animals.
The awareness of animal welfare would also cause most consumers to shun sheep milk products produced in this way.
Producing milk artificially could be detrimental to the health of the ewe. Milk produced artificially would still require the same nutrients and energy from the sheep. Artificial hormones may also cause cancers and shorten the life expectancy of the ewe, resulting in financial losses for the farmer.
Sheep must be pregnant and give birth to produce milk. The lactation period varies, but milk production will eventually wane. At this point, the ewe must have another pregnancy and birth to begin the lactation process once again.