Genetic Theory supporting Booroola F+ gene for commercial lamb production - Part 1
Twenty Years of Experience with the Booroola F+ Gene in Commercial Lamb Production ... Part 2
Managing Prolific Ewes and Large Litters... (Located to the right)
Revisiting the Booroola F+ Gene
Part 3 of 3
Managing Prolific Ewes and Large Litters
By Robert Leder, DVM
When dealing with prolific ewes, some extra care and consideration is required to realize the benefits of increased ovulation rates. Conception failure, embryonic and fetal losses, stillbirths and pre-weaning death losses can all negate the benefits of higher ovulation rates. There is no such thing as a “free lunch” when it comes to biology. Resources needed to support twins and singles are less than those necessary for triplets or quads. With a little effort though, combining the appropriate resources will allow a shepherd to capture the benefit of increased ovulation rates.
The first consideration in managing prolific ewes is their nutrition. Mixed grass and clover pasture is the primary forage utilized by our flock. Management and nutrition for the flock is dictated largely by our growing season. We’ve created a system approach based on our resources. Recognize that our system is specific to our resources and may not apply to your situation if your resources differ significantly. Besides pasture and grass/clover hay, our flock of 90 ewes consumes about four ton of grain per year, slightly less than one hundred pounds per ewe annually. We buy the grain, usually barley, off the field from an area farmer at harvest time. The flock is also supplemented with salt and mineral.
We start lambing about the fifth of April, with the goal of being 90% done by last week of April. By synchronizing lambing with spring “green up”, high quality intensively managed pasture provides all the nutrition for lactation sometime after the first week of May. The only exception for this is our group of ewes raising quads and yearlings with triplets. This group, usually 4-7 ewes, is set stocked in a paddock near the farmstead and fed one pound of barley per ewe daily for the month of May. Besides giving these ewes extra energy from the barley to produce more milk, this paddock provides a calm, stable environment for an extra month. When we’ve had an orphan group, those lambs are mixed with the quad group. The orphans have access to a nipple bucket feeder in early May. All the lambs in this group have access to a creep feeder in a moveable shed. The quad lambs have eaten more grain when we have had orphans because the orphans have learned what grain is prior to being moved out to the quad group paddock. The quads mothers help teach the orphans to eat grass and “be sheep”. Sometime in early June, as the flock rotates across the farm, the quads and orphans are “picked up” in the grazing rotation with the rest of the flock and grain feeding ends.
Our flock is grazed through the remainder of the summer as one mob. By selling our feeder lambs in August or early September, we remove a significant demand on our grass inventory as grass growth is waning. This allows us to stockpile grass for fall grazing; not feeding hay until sometime in December. The 12 to 20 replacement ewe lambs plus ten or so lambs destined to be locker lambs are then moved onto good pasture, and the ewes are dried up by returning to an already grazed paddock. After about five days of scavenging the old paddock with little to nothing in it, the ewes are given low quality hay. We usually try to select a paddock in need of renovation to dry the ewes up in. Overgrazing that area removes grass residue and improves the odds of frost seeding the following spring.
Without a doubt our yearling ewes are the most nutritionally challenged during lactation. After about 2-3 weeks of drying off the ewes, the yearling ewes are rejoined with the replacement ewe lambs and locker lambs to build condition back on them before breeding in November. The remainder of the flock is fed hay or poor pasture until a couple of weeks before breeding, at which time the whole flock is rejoined and flushed on high quality grass/clover pasture. All breeding is done in groups on stock piled pastures in November and into December.
Around the tenth of December, the breeding groups are reshuffled. All the replacement ewe lambs are put into one group and fed second crop orchard grass hay that has been harvested off the farm at a feeding station. Feeding stations consist of stacks of big square bales surrounded with feeding gates in the field. The sheep are allowed to self feed at the station. Because the majority of the lambs do not know what grain is, we add two or three older thinner ewes to the lamb group to teach them to eat grain. The older ewes also serve as the leaders for this group, making the whole group much calmer and easier to manage. Since they are still growing and pregnant, this group of ewes will be worked up to one half pound of grain per head per day. The second crop hay is usually in the 17-19% crude protein range.
Depending on the grass inventory and snow depth, the mature ewes are grazed longer or given access to a first crop hay station. The first crop hay ranges from 8-12% CP. The flock is then managed as two groups for the reminder of the winter.
I place the hay feeding station for the mature ewes in the field where the soil is poor. Sandy, low organic matter knolls make good locations for the feeding stations. The ewes are checked several times a week during the winter depending on the weather. The feeding gates are adjusted and rejected coarse stems are pulled out of the feeding station when checking the flock. Hay wastage of up to 20% is tolerated at the mature ewe flock feeding station when the hay quality is especially poor. Allowing this wastage raises the crude protein of the “consumed hay”. The feeding station for the ewe lamb and large litter group is in a paddock near the buildings, making it easy to carry the grain to that group. There is minimal waste of hay from the second crop feeding station. While some may consider Wisconsin winters harsh and undesirable, snow cover shortly after freeze up is pretty reliable. This is a resource that we appreciate and utilize. Both groups of sheep rely on snow for water during the winter. The only shelter provided for the sheep are the feeding stations, which act as wind breaks for them.
Our flock is ultrasounded for pregnancy and to determine fetal count approximately 75 days after the onset of breeding, usually sometime around the 20-25th of January. The information gathered from the ultrasound results is then used to match the nutritional needs of the ewes to our feed resources. Any ewes that are scanned with quads are immediately added to the replacement ewe lamb group at the time of scanning. The old “leader” ewes are removed from this group if they are not carrying a large litter. Three to four weeks later, in mid to late February, ewes that were scanned with triplets are added to the lamb group. Each time the ewes are brought through the sorting chute in the winter, I put my hand on them to check for body condition. Any ewe that is not maintaining her body condition is put with the lamb group. After the “triplet” sort in February, nearly half the flock is in the lamb group on second crop hay. The grain feeding rate for the ewe lamb/large litter group continues at one half pound per head per day. The goal of grain feeding in the middle of gestation is to get these ewes acclimated to grain, and to prevent any loss of body condition during the remainder of gestation. In early March the grain is slowly increased to one pound per head per day. The mature ewes with twins or singles remain on first crop hay (8-12% CP) throughout the winter. The nutrient analysis of our first crop hay has always met the NRC nutritonal requierments for the first two thirds of gestation. The mature ewes with twins or singles receive no grain until after shearing.
Immediately after shearing in mid to late March, the flock is given access to the barn and barnyard. The entire flock is usually fed second crop hay after shearing. The layout of our buildings allows us to divide the barnyard into thirds, allowing us to sort the flock into three groups during lambing. To create the three groups, the first group sorted off is the mature ewes expecting large litters, which have significantly distended abdomens. This group of 12-15 ewes, nicknamed the “fats”, has access to the south side of the barn and a sixteen by twenty foot area of the main barn for shelter. The rationale for sorting out this group is targeted nutrition and reduced competition.
The “fats” are fed the most grain at this time and are worked up to 1.5 -2 pounds of grain per day. Increasing the dietary caloric density for the last two to four weeks of gestation in this group of ewes is justified by the demands of the fetuses, and the fact that the digestive tract is squeezed smaller and smaller as the uterus grows. More calories have to be squeezed into a smaller space. We have had ewes that weigh approximately 175 pounds at breeding deliver over fifty pounds of lamb. We have not had a single case of pregnancy toxemia since the early nineties when we started feeding our “fats” as a separate group.
The second reason to sort the “fats” out is competition; these ewes are all equally slow. They all move at the same slow rate of speed and competition between them is pretty even. They all arrive at the grain trough at the same time and get to eat what is intended for them. A direct benefit of sorting this group off at this time has been the elimination of prepubic tendon rupture. The prepubic tendon is the attachment of the belly muscles to the pubic bone above the udder. Prior to implementing this sorting, we had an occasional ewe that would rupture her prepubic tendon while running and trying to compete with the rest of the flock. Prepubic tendon rupture is an incurable injury; affected ewes are culled after the production cycle that season.
The second group of ewes that are sorted off after shearing are the last twenty or so ewes due to lamb that are carrying singles or twins. They are fed the least grain of any group, getting a quarter to one half pound of grain per head per day and free choice hay in a feeding station. If second crop hay is in short supply, they will get first crop hay. The grain feeding to this group is just to get the rumen ready for more grain later when they are mixed with the rest of the flock half way through lambing when there is more room in the lambing barn.
The third group, the majority of the flock, has access to a second crop hay feeding station and is fed one half to three quarters of a pound of grain per day. We used to feed the main group of ewes one pound of grain per head per day, but we were getting large lambs and dystocia by the end of lambing. Feeding less grain and sorting off the late lambing ewes for the first half of the lambing season has significantly reduced this problem. Our adjustment of feeding less grain to the main pregnant flock during lambing has saved us a bit of grain, this year we have about one half ton of barley left.
As the ewes lamb, we jug them two to four days, then move them to small mixing pens, and then to a single large group. We do not mix ewes after lambing by litter size except ewes that are raising quads. Quad families are kept in jugs a bit longer and are put together as a separate group.
The lactating ewes are fed second crop orchard grass/clover hay plus two pounds of grain per head per day while lactating in the barnyard. Mature ewes with singles do not need this much grain if any, but it is a short period of time and we don’t have the space to sort them out. Feeding less grain would significantly short change the yearling ewes and ewes with triplets.
By the middle of April, the grass is just starting to grow here in Northeast Wisconsin. The ewes that have lambed and made it through the jugs and small mixing groups are left out to graze the fresh sprouts of grass during the day. The ewes and lambs are moved to and from pasture in a gated off electronet lane that serves as a grain feeding area. Feeding the grain in this setting allows us to carefully observe the new families twice daily. It is amazing how full the ewe’s rumens and udders are when they return to the barnyard at night even though the pasture still looks quite brown. Moving these young families to pasture for the day and back to the barnyard for night teaches the lambs to find a gate in the electric fence. The ewes have free choice access to second crop hay in the barnyard over night.
It is well recognized in the dairy industry that the care and nutrition of the transition cow (from dry to early lactation) has a huge impact on peak milk production six to eight weeks after freshening, and total lactation milk production. This is why we feed grain at the time of lambing. We want the ewes to express their full genetic milking potential when they are put on grass full time.
Another use of the ultrasound results is to aid in the effort to graft “extra” lambs to ewes that can feed more lambs than they are carrying. Slime and stanchion grafts are utilized to move extra lambs to foster mothers. By knowing in advance which ewes will have “extra” lambs, and which will have singles, a concerted effort is made to move lambs to foster mothers rather than making an orphan pen. With the exception of 2007 and 2008, we usually only have 2-3 orphans per year, which are sold as bottle lambs, avoiding the need to establish an orphan pen. This past lambing season 16 “extra” lambs were moved to foster mothers; we did not establish an orphan group and no bottle lambs were sold. Even yearling ewes are candidates to be foster mothers, making twins on those we expect to have enough milk. (See photo of yearling with her lambs) Mature ewes with sufficient East Friesian blood are candidates to have their litter expanded to three.
While there is reluctance by many shepherds to leave triplets on a ewe, we expect our mature ewes to achieve this level of milk production. A common problem with triplets is the development of a “runt” in the litter. We have developed a novel approach to this problem, and have significantly reduced this phenomenon. Rather than defining unequal triplets as not enough milk, we’ve redefined the problem as one or two lambs getting too much milk. The problem is one of milk distribution. We have observed of one or two new born triplets in a jug with their mother gorged with milk while the last born is trying to catch up. The hungry, struggling lamb can quickly develop a defeatist attitude. I reasoned that if dairy calves can be fed every twelve hours, a lamb could survive that feeding schedule a couple of times. About ten years ago, we started to intervene with the survival of the fittest mode in triplet lambs. We stepped in when we observed disparity just beginning to develop within a set of triplets. The well fed lamb or lambs are placed behind a light wire divider in the corner of the jug. This gives the slow, hungry lamb a chance to fill itself without the competition from its siblings.(See photo of jug with divider) The mother stays calm as she can see, smell and communicate with her robust lambs while the slow lamb experiences success feeding itself. If the disparity is caught early, the length of time using the “equalizing gate” is short (one day), if the weak lamb falls significantly behind and develops a defeatist attitude, the gate will have to be used longer. The robust lambs are simply removed periodically from behind the gate, allowed to nurse and romp, and then put back behind the “equalizing gate” after a few minutes. When the lambs are observed competing reasonable well, the gate is removed from the jug. I admit that this strategy does require longer stays in the jug for affected families, but we feel the effort is worth it. The alternative is establishing an orphan pen or a dead lamb. (See photo of ewe with equalized triplets.)
Another challenge presented by large litters is adequate colostrum consumption for the newborn lambs. Because I work primarily with dairy farmers, I am able to secure cow colostrum from select herds. The herds used are those that have tested serologically negative for Johne’s disease. At the time of colostrum donation, the donor cow is again tested for Johne’s as well as Bovine Leukemia virus. Both diseases can be transmitted to sheep. We test the donors to reduce the risk of transmission. When large litters are born (four or more) we will thaw the colostrum in hot water, and try to feed all the lambs what they will take rather than wait and see which lambs don’t fill up on the mother’s colostrum. By doing this we reduce the competition for the ewe’s teat, and are assured that all the lambs have gotten adequate antibodies.
The following chart summarizes 2009 lambing, grafting and growing season. Out of 91 ewes lambing, there were 20 yearlings (22%). We averaged two seventy-one pound, 104 day old lambs per ewe on July 26. The lambs were weaned one week later.
The growing season in Northeast Wisconsin and our pastures and market conditions have defined and shaped our system over the years. Our climate and soil produce high quality mixed grass and clover pasture for 90 day ewe lactations. The genetics we’ve combined in our crossbreeding scheme along with the Booroola F+ gene allow us to make maximum use of those basic resources. The quality of our forages for the most part supports prolific ewes. By adding a little grain at strategic times to select sheep we are able to improve productivity and avoid metabolic problems associated with large litters of lambs. Grain feeding is a worth while investment for us. By dividing the flock into two groups when stored feeds are being fed in the winter, the specific nutritional demands of the sheep can be more appropriately targeted. These slight adjustments to our resources allow us to capture the economic benefits of higher ovulation rates.
I hope this series has sparked new thoughts. I welcome comments or questions about any of the ideas or practices I’ve presented.
Please feel free to email me at: firstname.lastname@example.org