BOOROOLA
 
Tamarack Prolific ewe with 5 lambs born unassisted on pasture.
How The Booroola ‘FecB’ Gene Works
Increasing prolificacy in the past...

Increasing prolificacy (number of lambs born) in the commercial flock in the past was primarily limited to the use of Finnsheep or Romanov in the breeding program. Selection can also play a part, but is considerably slower. Research shows it will take 10 years or more to make, at best, only a 20% improvement in lambing percent. This is often at the "cost" of other desirable commercial traits.

Finnsheep and Romanov sheep were typically used in a crossbreeding program where purebred or half bred rams are bred to a chosen breed to produce half or quarter bred ewes that tend to be 25 to 50% more prolific than the native stock.

Because the prolificacy of the Finnsheep and Romanov are due to a multitude of genes, a half Finnsheep is less prolific than a purebred, and a 1/4 Finnsheep is less prolific than the half bred. That is to say, as a breeder dilutes Finn or Romanov traits not wanted in the flock, the genes responsible for prolificacy will also be diluted. This can be used to advantage if a very high level of prolificacy is not desired. However, dilution can be a detriment when high prolificacy, lamb growth rate, carcass, and heavy, quality fleeces are all desired in one package.

Today we have the Booroola "B" gene...

Today the Booroola FecB gene offers a new option that can allow the commercial producer to create a high level of prolificacy and still retain the important other traits desired in the flock. The term "Booroola" was taken from the name of the ranch in Australia where sheep carrying the single gene for prolificacy were first discovered. Booroola now refers to a gene called the B gene (also called FecB for fecundity) which acts independent of the breed or type of sheep that it is contained in. The B gene can be transferred into any breed of sheep. Up until now the most numerous breed of sheep containing the B gene has been the Booroola Merino, the breed it was originally discovered in.

Unlike the multiple genes responsible for high prolificacy in the Finnsheep, Romanov and other prolific breeds, the Booroola B gene is a single gene ( chromosome 6q23-31) and will not be diluted when other, non prolific breeds, are added to the breeding program. This can be an advantage or a disadvantage, depending on how you manage it in your particular flock. If a large lambing percentage is desired, the breeder will find the Booroola B gene a tremendous asset. It is this feature that permits the transfer of the B gene into apparently any sheep breed or type desired, without retaining the original traits of the breed from where the gene came. Where lambing percentages exceeding 200% are not wanted, breeders will find the Booroola B gene undesirable since its effect can not be reduced by crossbreeding.

The expression of the Booroola B gene does appear to be influenced by nutrition. It is not necessary, and actually may be undesirable to flush ewes prior to breeding. Flushing Booroola ewes may result in an increased number of potentially unwanted quadruplets and quintuplets. Feeding maintenance quality hay or pasture is sufficient to produce lambing rates of 240-300% in heterozygous Booroola ewes.

Managing the Booroola FecB gene in your flock

Sheep with two copies of the FecB gene (genotype designated BB) are said to be homozygous for the B gene. Having two copies of the B gene in a breed (flock) of sheep will result in an increase of 1.7 lambs born, per ewe, more than is typical for that breed (flock).

Sheep with one copy of the FecB gene (genotype designated B+) are said to be heterozygous for the B gene. Having one copy will result in an increase of slightly more than one lamb born, per ewe, than is typical for the (non Booroola) breed (flock).

Sheep without the FecB gene are designated as genotype (+ +) .

For example: a breeder introduces the FecB gene into a flock of Targhee sheep (++) that normally produce a 150% lamb crop. The resulting heterozygous (B+) ewes would be expected to produce a 250% lamb crop, while the homozygous (BB) ewes would be expected to produce up to a 320% lamb crop.

Presently, Booroola homozygous (BB) ewes are considered of interest only to breeders wishing to produce homozygous (BB) rams, and are too prolific to be used by the commercial sheep industry.

How is the Booroola FecB gene inherited?

The mode of inheritance of the Booroola B gene is simple Mendelian inheritance . When a homozygous Booroola ram (BB) is bred to non Booroola ewes (++), all of the offspring produced will carry one copy of the B gene (B+). These first generation (F1) offspring are called heterozygous (B+).  The Punnett square below is a graphical method of showing all possible genotype results of simple Mendelian inheritance.

Retained heterozygous (B+) ewe lambs from this first mating (bred to any good ram of your choice) will produce (on average) one more lamb per lambing than what the original non Booroola dam (++) was capable of.

Using a retained heterozygous (B+) Booroola ram lamb from this first mating, to breed to non Booroola (++) ewes, (See below) will produce offspring in which only 50% carry the B gene (B+), while the other 50% will be non carriers (++). This is due to the fact that a heterozygous (B+) animal will only pass on the B gene half of the time, where as a homozygous (BB) animal will pass on the gene every time.

A third scenario that could occur is the mating of a heterozygous (B+) ram to heterozygous (B+) ewes . See below. This mating presents three possible genetic results in the offspring. On average, 25% of the resulting offspring will be homozygous (BB), 50% of the resulting offspring will be heterozygous (B+ and +B ), and 25% of the offspring will be non carriers (++). This scenario is not recommended unless the breeders goal is to produce homozygous (BB) rams.

A fourth scenario, used by breeders intent on producing homozygous (BB) rams, would be the mating of a homozygous (BB) ram to heterozygous (B+) ewes. In this case 50% of the offspring will be homozygous (BB) and 50% will be heterozygous (B+). See below.

Mating a homozygous (BB) ram to homozygous (BB) ewes will simply produce all homozygous (BB) animals.

Below: Tamarack Prolific ewe with triplets born and raised on pasture.

It is also possible to introduce the Booroola gene into the flock, and never need to purchase another Booroola (BB) ram again, by simply retaining offspring from Booroola sired daughters. This is most suitable where there is no intention to maintain an F1 cross (B+) as outlined above; such as in a grade or purebred flock. After initially introducing the gene with a purchased Booroola ram (BB or B+), tracking the gene is simply a matter of using animal identification (ear tags) and good record keeping, particularly for the first two lambings.

For example: In Booroola crosses, when using breeds of moderate prolificacy such as the Dorset, all ewe lambs that produce twins at 12 months of age should be considered as probable (B+) gene carriers. Likewise, all those ewes with singles at 12 months old, are considered non-carrier ewes.

When selecting for the Booroola gene by using twin or single lambing records of 12 month old ewes, there appears to be an error of approximately 10%. That is, of those young ewes producing twins, approx 10% will not be Booroola gene carriers, and of the ewes producing singles, approximately 10% will be Booroola gene carriers. What is important is that your are selecting highly productive ewes for your flock.

The same process of lambing and identification of gene carriers can be used when a heterozygous (B+) ram is used on non carrier ewes. Simply lamb them at 12 months of age, and identify the ewes that produced the twins.

The Booroola B gene can be transferred into another breed by breeding each generation of Booroola B gene carriers to purebred rams of the chosen breed. The same process of identification described above would be utilized to identify each new generation of Booroola gene carrier ewes.

The Tamarack flock required 10 years to transfer the Booroola (B) gene from the Booroola Merino into the the Dorset breed. Of course transferring the gene only required one generation, but the process of ‘grading up’ to remove the Merino traits and recapture the more desirable Dorset traits required much more time. 

For shepherds interested in producing Booroola B+ or BB rams, it is now possible to test a ram's DNA for the presence of the Booroola gene. Of course the process is also possible for ewes, however many producers are content just to use lambing records as a guide for selecting the commercial ewe flock. To test DNA for the presence of the Booroola gene, a blood sample is required. Presently the process is quite simple.   A spot of blood is collected on a blot card and mailed to Genomnz, a division of AgresearchNZ in New Zealand where the Booroola B gene is identified through DNA analysis.

Which sheep are suitable for the Booroola FecB gene?

Research with Finnsheep X Booroola crosses suggest that the two effects are additive, resulting in a sheep that is way too prolific for practical purposes. Litter sizes of 5 and higher have a much poorer chance of survival on pasture systems. Finn X Booroola have conceived litters of up to 9. A significant portion of Finn X Booroola ewes wound up open, because the entire litter was reabsorbed in the uterus. Putting the Booroola gene into highly prolific breeds also creates another dilemma for those wishing to select ewe lambs with the gene. It will be much more difficult to identify the Booroola gene carriers if the flock is already very prolific.

The Booroola gene seems to perform best in low to moderately prolific breeds of moderate body size. “Uterine capacity” (the ability to bear healthy triplets) and milking ability are two important criteria essential for a commercially viable Booroola breed. The Dorset, Texel, and Ile de France breeds meet both of these criteria very well.
There are a number of other moderate sized breeds that may work well with the Booroola gene. Efforts to introduce the Booroola gene into extremely large breeds of sheep have all been abandoned.

There is no special management requirement for sheep with the Booroola gene other than to state the obvious; highly prolific ewes will suffer more from mismanagement. The Tamarack flock is managed outdoors, on pasture, in Minnesota, year round. Tamarack ewes lamb outdoors on spring pasture, and are not jugged. This system depends upon proper (but not excessive) nutrition, and minimizing feed competition that could result in poor nutrition of heavily pregnant ewes. Scanning for fetal numbers can be an immensely useful management tool; not only to properly allocate feed prior to lambing, but by lambing ewes grouped according to fetal number, management can be streamlined and simplified.

Ewes rearing triplets and quads will benefit by additional energy. The feeding of 1 to 1.5 pounds of corn daily while on high quality pasture can increase the weaning weights of lambs by 5 pounds each, and will help ewes maintain body condition.

Other than proper nutrition, a good health program, and avoiding over crowding, there is no special management required.

Conclusion
The Booroola gene has posed the unique and exciting opportunity to add a high level of prolificacy to sheep that fit the environment well, without having to add undesirable traits of another breed. In the Tamarack Prolific, the gene has proved to be trackable and persistent. The Tamarack Prolific has also proven to have sufficient uterine capacity, mothering instinct and milking ability to be able to utilize the Booroola gene well. It is very possible the Booroola gene can be utilized in other breeds with an equal degree of success.

The most exciting feature of the Booroola gene, is that a flock owner can achieve a high level of prolificacy while maintaining other traits important to the adaptability and marketability of that flock.

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"Life is no brief candle to me. 
It is a sort of splendid torch 
which I have got a hold of for the moment, 
and I want to make it burn as brightly as possible 
before handing it on to future generations." 
George Bernard Shaw (1856-1950) 
 
For those who are interested in the history of the Booroola fecB gene, more fascinating info below.

The Ancestry & History of the Australian Booroola Merino Sheep 
The history of how the Booroola gene came to be known in Australia encompasses a colorful sequence of 
people and events covering over 200 years.
 
The ancestor and original source of the Booroola Merino sheep FecB gene is the Garole Sheep from the 
Sunderban ( Bengal ) area of India . The Garole is a small ewe of 12-15 kg, with a mean litter size of 2.3 lambs, 
adapted to hot, humid, swampy conditions of rice paddies. 10 ewes and 2 rams were originally imported 
to Australia in 1792, from Calcutta, India . In 1793, 100 more Garole sheep were imported to AU.
The FecB gene mutation is found in the Garole sheep. Genetic evidence supports the historical records that the 
prolific Garole sheep, when introduced to Australia , bred with the much larger 35-40 kg Merino sheep. Garole sheep 
are virtually all homozygous for the FecB gene ( BB ) 
About this same time, Samuel Marsden was recommended by William Wilberforce (famous for his fight to end slavery) 
as an Anglican English missionary and assistant chaplain to the convict colony in New South Wales , Australia in 1793. 
Marsden and his new wife of 3 months, left on an 8 month journey to Australia on the ship William.
 
The ship William, on this trip, did not carry the ordinary cargo of convicts with their complement of guards, 
but instead was packed with salt beef, barreled pork, and agricultural implements.
Marsden arrived in Port Jackson on the William March 10 th , 1794. 
Just in time to save the shiftless inhabitants of the Botany Bay settlement from the horrors of starvation 
caused by a severe drought. Samuel Marsden eventually became infamous as the “flogging preacher”, for his hatred 
and severe mistreatment of Irish Roman Catholic convicts. 
  
Marsden quickly became a successful farmer, although he was quite inexperienced. 
In 1797 Marsden bought a ram and ewe from a dozen Spanish Merinos imported to Cape Town by John Macarthur.
He also obtained some tiny but prolific Garole sheep. (which were the key source of the Booroola FecB gene) 
By 1802, Marsden had acquired 440 acres and 480 sheep. By 1805, Marsden built his flock to over 1000 sheep, 
and had acquired 1730 acres of land. When Marsden died in 1838, he owned over 10,000 acres. 
Much of this was accomplished with cheap convict labor. 
  
From 1798 on, Marsden made several valuable reports on sheep breeding and wool growing, 
to the colony's Governor Philip G. King. King was impressed by Marsden's efforts and considered him the 
“best practical farmer in the colony”. When Marsden returned to England on leave in February 1807, 
he was highly recommended by Governor William Bligh ( former Captain of the HMS Bounty). 
Marsden's goal was to produce a strong heavy framed sheep which would be more valuable for meat in the colony, 
than the fine fleeced Spanish Merinos. 
  
In 1808, Marsden had a suit made from his own wool, which so impressed King George III, that King George
presented Marsden with a gift of 5 Spanish Merino ewes with young, from his Windsor flock. 
Marsden was the first to export wool from Australia to England. 
The Napoleonic Wars (1792-1815) created a large demand for wool. 
Marsden is also credited with bringing sheep to New Zealand, and the 
Gospel to the Maori people, who highly respected him. 
  
Marsden's son-in-law Jon Betts ran his flocks after Marsden's death in 1838, near the Molong area. 
In 1843, John Smith acquired many of Marsden's sheep, which became the nucleus of Smith's Gamboola Stud (flock). 
By 1855, Smith had over 35,000 sheep. Smith also produced a large frame, plain body sheep with medium strong wool. 
Smith continued with Marsden's breeding methods. 
  
In 1879, the Kater Brothers (Henry Edward & Edward Harvey) acquired Mumblebone Station on the 
Macquarie River near Warren. The Kater Bros. first bought sheep from Smith, and continued to do so for many years. 
Under Edward, Mumblebone became one of the foremost studs in New South Wales; he developed strong wooled, 
large framed and plain bodied sheep. 
  
In 1896 Henry purchased Egelabra, near Warren. In 1906, Henry's partnership with Edward was dissolved, 
and Henry took his half of the Mumblebone Stud. About 1910, Henry Kater formed a partnership with his son 
Norman William Kater, and with the help of expert wool classer E.H.Wass, they formed the still well-known Egelabra Stud. 
The descendants of Edward Kater continued to develop the Mumblebone Stud.


The Discovery of the FecB gene 

It was not until the late 1940's that Australian sheep producers in New South Wales near the town of Cooma, 
took special note of a flock of sheep owned by the Seears Brothers, of Booroola Station (ranch). 
Jack and Dick Seears' Egelabra based flock of 200-300 Merino sheep were consistently producing 
170 –180 % lamb crops, while most Merinos produced less than 100 % lamb crops. 

Keep in mind, throughout the 1950s, many Australian Merino sheep breeders were prejudiced against twins. 
The general opinion among scientists of the time was (because of low heritability estimates) genetic selection for twins 
is not a worthwhile pursuit. However, selection for twins was undertaken as a research project by 
CSIRO of AU. ( Commonwealth Scientific and Industrial Research Organization ) 
Contrary to the general expectation, there was a positive response, which was subsequently publicized in the 
rural agricultural community. 
In 1958, after this positive publicity, the Seears Bros. gave CSIRO a quintuplet ram. 
CSIRO quickly acquired 14 more sheep of multiple births from the Seears. 
  
When the Seears brother's Booroola flock was dispersed in 1965, CSIRO purchased 91 mixed aged 
multiple born ewes and then moved the Booroola flock from Deliniquin to Armidale. 
These Booroola sheep were studied by CSIRO and it was eventually shown that the prolificacy of the 
Booroola strain was due to a single gene of large effect which acts to increase both ovulation rate and litter size.

 
It is interesting to note that the FecB gene survived in the Merinos for about 50 generations without specific selection 
for prolificacy, going largely unnoticed until the Seears Brothers in the late 1940's.
 

The FecB gene was finally “discovered”.
 Later, New Zealand researchers mapped the Booroola FecB gene to chromosome 6q23-31. 
The effect of the FecB gene was found to be additive for ovulation rate and dominant for litter size. 
 
Recently in the USA … 
In the early 1980's Booroola Merino's were obtained from CIRSO by the US MARC (Meat Animal Research Center) 
in Clay Center, Nebraska. By the late 1980's booroola genetics became first available to private individuals outside of 
research stations.
   
At Tamarack Lamb & Wool, Janet McNally introduced the Booroola gene via Artificial Insemination in 1987.
Tamarack and other private breeders imported Booroola semen from 1987 through 1990 from Haldon Station. 
The company that handled the Booroola semen and was doing the AI, dissolved in 1991 when Haldon Station was sold. 
 By the early 90's Booroolas were found at Clay Center NE, University of Wisconsin (Arlington), Hettinger ND, 
and Texas A&M (Maurice Shelton). Possibly more, but these are the ones Janet was in contact with.  
Meanwhile, private importers of Booroola Merinos obtained their genetics through Haldon Station in New Zealand .  
This NZ source had crossed the Booroola Merino with the Corriedale; 
because at the time, importation of any purebred Merino was not permitted. This crossing turned out to have a huge 
positive benefit, as the Corriedale added improved growth and milking ability to the Booroola making the NZ source a 
much more viable and useful Booroola sheep than the AU source.  This difference had a tremendous effect on the outcome of 
research done on the Booroola fecB gene in the USA.
Booroolas from the NZ source could also be found in a private flock in Canada, and on the Rafter 7 ranch
 run by Tom Filben at the time.

Right gene...Wrong package!


Unfortunately the research community in North America, New Zealand, and Australia failed to see beyond 
the Merino when they studied the Booroola. Virtually all research focused on purebred Merino and purebred Rambouillet 
sheep as carriers of the Booroola gene. In Janet's opinion, no poorer host for the Booroola gene could be found. 
These purebred fine wooled breeds have been proven to provide fewer cotyledon attachments in the uterus than the Dorset, 
meaning the dams are less able to support multiple fetuses in the uterus resulting in lower birth weights,  
lower lamb vigor, and therefore, reduced lamb survival at birth. 
Secondly, the fine wooled breeds are born with a very short, tight birth coat which provides less protection 
from cold wet weather.
 
Third, the purebred Merino and the purebred Rambouillet are among the poorest milking breeds.
 
Bottom line is that purebred Merino and Rambouillet ewes were not the optimal choice for rearing twins and triplets. 
These three major disadvantages of the Merino and Rambouillet result in significant newborn lamb mortality 
and poor lamb growth to weaning.   As a result, the research community concluded that the
Booroola gene did not offer any particular advantage.  Unfortunately  US, AU, and NZ research on the potential of the 
Booroola gene never tapped into the true potential.

So why is the Tamarack Prolific  any different?

Janet McNally saw the Booroola gene quite differently; Janet saw a tremendous gene 
for larger litter size that was very simply in the wrong package! The simple inheritance of the 
Booroola gene means it can be easily transferred into any breed of sheep. 
So why not put the Booroola gene into a sheep more suitable for supporting a large litter size? 
Janet proceeded to place the Booroola gene first into the polled Dorset, a sheep very well adapted to the 
Midwest farm flock environment. The Dorset also provided ample cotyledon attachments for multiple feti. 
Those 1980's era production Dorsets were well known for heavy milk production, twins, excellent mothering 
out of season breeding, and lambs quite tolerant of cold, wet weather. 
  
More recently, Janet has introduced the Ile de France, along with selection for number of lambs weaned EBVs. 
This has further enhanced lamb survival to the point that the Tamarack Prolific Sheep Flock now has 
pre-weaning mortality rates as low as 3% ! 
 
This means that Tamarack Prolific Sheep, (with the Booroola gene)  actually has a significantly 
lower  mortality to weaning rate than the US national average!
Remember...these are lambs, born on pasture, with minimal shepherd input!

The Tamarack Prolific  Sheep
 A prolific gene in the right package.
It began in 1792. 
Today, over 200 years later and half way around the world, 
the Booroola FecB gene has found a productive home. 
Why has the Booroola FecB gene worked so well at Tamarack?
 
It's the “package” we put it in!
Tamarack Prolific Sheep
Coming soon to a pasture near you!