Management on the STAR Sheep Production System
The STAR system of sheep production (Figure 1)
has been developed to maximize production of market lambs on a
continuous year-round basis. This even supply of high quality lambs
should allow for improved market development and enhanced prices
for lambs demanded by discriminating consumers. To be successful,
a maternal ewe flock that will breed any time of the year and produce
mostly twins at each lambing is necessary. Sheep are normally seasonal
breeders and lamb only in the spring so proper selection and continued
development of the ewe flock is very important.
There are always 3 groups of sheep within a flock managed on the
STAR system. These are:
- Breeding and pregnant ewes and the rams.
- Lambing and/or lactating ewes and their lambs.
- Growing lambs - both market lambs and the replacement ewe
These three groups are kept and managed separately. Late pregnant
ewes are moved from the breeding and pregnant flock five times
yearly just before lambing and the lactating ewes weaning lambs
are moved to the breeding and pregnant flock at about the same
time to be bred. This shifting of the sheep and the suggested dates
are depicted in Figure
2. Also at the time of weaning, lambs are moved into the growing
lamb group. These lambs are fed in this group until they are ready
for the appropriate market as depicted in Figure
2, thus allowing for a rather continuous supply of market lambs
and a reasonably steady cash flow pattern.
Even on the rather complex STAR system, we
only have to contend with the three groups of sheep. Each group
will be managed and
fed quite differently in order to meet their requirements and to
allow the production expected of them. The producer allocates available
feed resources to those animals that can best utilize them and
can purchase the additional feeds necessary only for those high
producing animals that cannot meet their requirements on the feeds
available on the farm. Resources other than feeds such as labor
and buildings can also be allocated accordingly.
These three groups of sheep can be considered as separate flocks
because their requirements are so different. They are discussed
The Breeding and Pregnant Ewe Flock
This includes all the ewes from the time they wean their lambs
until they are ready to lamb the next time. It also includes the
rams and the young replacement ewes just entering the flock to
be bred for the first time.
Because breeding occurs in this flock, it is here that the genetics
of the entire flock is established, whether the resulting lambs
will be market lambs or have the proper breeding to be replacement
ewes. Sire selection and proper mating for each is very important.
The ewes must be of the type that are not seasonal breeders. Most
sheep are seasonal as a result of their sensitivity to changing
day length, but some breeds are less seasonal that others and there
are some sheep in all breeds that will tend to breed "out of season".
At Cornell, we have preferred the Dorset because they are reasonably
aseasonal and we have an established flock. The fine wool breeds,
namely the Rambouillet and the Merino, also have longer breeding
seasons than most breeds. We have also identified some Finnsheep
that not only are prolific and have lots of lambs but will also
breed out of season. The Polypay is a newer synthetic breed that
has been developed to provide more than one lamb crop per year
- thus, the name "Polypay". They are actually a 4-way cross between
the Dorset the Rambouillet, the Finnsheep and the Targhee.
Producers of several other breeds have also had reasonable success
with fall or out-of-season lambing.
Recent calculations, made on records of the Cornell Dorset flock,
indicates the heritability of out-of-season breeding is about 0.2.
Considering the magnitude of variability present, this estimate
indicates we should make reasonable progress selecting for sheep
that will perform well on accelerated lambing systems such as the
These Breeding and Pregnant Ewes have relatively low requirements.
They need little housing and can be pastured much of the year.
The Cornell Dorset ewes utilized excess stock-piled pasture and
aftermath growth the past two winters until early March. These
were, of course, fairly open winters without heavy snow cover.
The Lambing and/or Lactating Ewes and Their Lambs
This group requires a relatively high level of both feed and management
throughout the year. At Cornell, we lamb all the ewes in the barn
and at this time keep the ewes and their lambs inside until weaning.
Note in Figure
2 that several of the lambings occur in warm weather and these
ewes could be pastured at least some of the time. Also, note that
the ewes in this group shift in and shift out five times a year
on a fixed schedule. It is also possible to "spin" the STAR and
select the set of 5 dates best suited to each individual producer.
We feed ewes in this group either good quality hay or hay-crop
silage free choice and grain at the rate of 1 lb per day for each
lamb. That is, ewes with one lamb get 1 lb and ewes with twins
2 lb. Ewes with triplets or even quads require more. Artificial
rearing is necessary for excess lambs from the very prolific ewes.
Lambs are also given access to creep feed from about two weeks
of age to weaning. Often the same feed is used in the creep that
will be the lambs main feed after weaning.
It is important that lactating ewes not be allowed to lose much
weight as they must be able to re-breed soon after the lambs are
Growing lambs are fed a properly formulated total mixed ration
from weaning to market. When they are marketed depends on the market
demands and the breeding of the lambs. Some markets prefer the
typical hothouse lamb at 35-40 lb live weight. This is a specialty
market and Dorset lambs about weaning time do nicely. Most markets
are for larger lambs weighing from 90-120 lb. Our medium-sized
breeds such as the Dorset have the proper body composition at about
100 lb, with the ewe lambs about 10 lb lighter than the ram lambs.
Lambs sired by large terminal cross sires such as the Hampshire
and Suffolk should be sold at the heavier weights.
All the lambs in this group can be fed and managed the same even
though they are marketed at different weights. The best market
weight for each lamb is really determined by the ram at the time
of breeding. All the ewes in the Breeding and Pregnant flock should
be of moderate size and able to produce twin lambs any time of
the year. This is where the market lambs start and selection of
the proper ram for breeding is very important. Selected ewes in
this group can be mated to the proper maternal sire to produce
This does not begin to cover all aspects of proper STAR sheep
management but should give the reader an understanding of how the
STAR system works. It should also explain how the STAR system can
increase production as well as make a uniform supply of high quality
lamb available to the consumer and provide an even cash flow to