Breeding Ewe Lambs
or
Getting the Most out of Ewe Lambs
David L. Thomas
Department of Animal Sciences
University of Wisconsin-Madison
Should sheep producers in Wisconsin and other farm-flock states mate ewe lambs to lamb at
approximately one year of age? The answer to the question is "yes", with the qualifier "in most
situations". However, some sheep producers still do not mate ewe lambs. This paper will
attempt to describe the advantages and disadvantages of mating ewe lambs and make
recommendations for management of ewe lambs that are mated.
Whether or not to breed ewe lambs is not a new topic of discussion. The first scientific work
in the U. S. on a comparison of ewes bred their first fall with the then more traditional practice of
breeding ewes their second fall was reported over 65 years ago in a North Dakota Agricultural
College bulletin in January, 1936 by Dr. Hilton M. Briggs (Briggs, 1936). The study was
conducted at Fargo, North Dakota with 244 Hampshire-Rambouillet ewes purchased as lambs in
the fall of 1927. The ewes were divided into two groups with one group mated as lambs in the
fall of 1927 and the other group mated first as yearlings in the fall of 1928. The performance of
the ewes was evaluated through the fall of 1934. Of the ewes mated as lambs, 85% produced
lambs at approximately 14 months of age. Over six seasons, the lamb-bred group weaned .69
more lambs and 30.96 more pounds of lamb per ewe exposed than the yearling-bred group.
There was no difference between the two groups in wool production. The ewes mated as
yearlings reached their mature weight at about 21 months of age. The ewes mated as lambs
reached the same mature weight but at 31 months of age; about 10 months later than the
yearling-bred ewes. Through 1932 (the fifth season) approximately 75% of the original ewes
were in both groups. However, starting after the sixth season, ewes bred as lambs started to
leave the flock at a faster rate than ewes bred as yearlings, due to the loss of teeth. At the close
of trial in the fall of 1934 when the ewes were 7 1/2 years old, 56.9% of the remaining yearlingbred ewes had sound mouths while only 45.9% in the lamb-bred group could be so classified.
There were twice as many broken mouths in the lamb-bred group (26.2%) compared to the
yearling bred group (13.5%). This study, reported 66 years ago, showed that well grown ewe
lambs mated at 9 months of age could produce a respectable lamb crop their first year and more
total pounds of lamb over their lifetime than ewes mated first as yearlings. The only detrimental
effect of breeding ewe lambs was increased tooth loss at advanced ages, which in most cases
were older ages than commercial sheep are generally retained.
The very first issue of the Journal of Animal Science published by The American Society of
Animal Science (Vol. 1, No. 1, February 1942) contained the results of a similar study conducted
with purebred Hampshire ewes by South Dakota State University at the Bell Fourche Field
Station at Newell (Spencer et al., 1942). This study, conducted under farm-flock conditions, also
showed an advantage in lifetime lamb production from the mating of ewes first as lambs versus
yearlings. However, the practice of breeding ewe lambs was not adopted by all segments of the
This article is an update of one on the same topic written by the author in 1986.
industry. Dr. W. G. Kammlade of the University of Illinois wrote in his 1947 textbook entitled
Sheep Science, "There is some inquiry about the purchase of ewe lambs for breeding. Much
difference of opinion exists regarding the advisability of breeding ewe lambs so that they will
yean [give birth to] their first lambs when they are approximately one year old. Practically all
men who raise purebred sheep oppose the practice. Range sheepmen, also, do not follow the
practice; perhaps this is not because all are opposed to it but because the conditions under which
they operate make it very inadvisable. ....However, some farm-sheep raisers have followed the
practice for years and think it profitable."
Hohenboken et al. (1977) suggest that the experience gained by a ewe lamb in raising a lamb
at one year of age may make it a better mother at the two-year old lambing than a ewe lambing
for the first time at two years of age. The data for Columbia and Targhee ewes used in this study
is in Table 1. At two years of age both groups gave birth to the same number of lambs per ewe
exposed but the ewes that had been bred as ewe lambs weaned 12 more lambs and 840 more
pounds of lamb per 100 ewes exposed than the ewes exposed first as yearlings. This difference
may be due to the previous maternal experience of the ewes bred as ewe lambs versus the lack of
previous maternal experience of the ewes bred first as yearlings.
Table 1. Performance at two years of age of ewes bred first as lambs or yearlings
Lamb production per ewe exposed
Bred first as:
No. born
No. weaned
Lb. weaned
Wool, lb.
Ewe wt., lb.
Lambs
Yearlings
1.31
1.31
1.14
1.02
83.2
74.8
11.2
11.4
160
159
It also appears that ewes that have the ability to conceive at 7 to 9 months of age and to lamb
at 12 to 14 months of age are more productive throughout their lifetime than ewes that don't have
this ability; even when the lamb crop produced at one year of age is not considered. Hulet et al.
(1969) studied the relationship between occurrence of estrus in 5670 Rambouillet, Columbia, and
Targhee ewe lambs their first winter and subsequent lamb production. The ewes were bred to
lamb first at two years of age. Table 2 presents the cumulative performance of ewes lambing
five times. In all three breeds, cumulative lamb production was greatest among ewes that
exhibited estrus their first winter with an average advantage of .4 lambs and 36.8 pounds of lamb
per ewe over ewes that did not exhibit estrus their first winter. Cumulative wool production was
only slightly lower (-.4 lb.) for ewes exhibiting estrus their first year. These data suggest that
selection of ewe lambs with the ability to lamb at 12 to 14 months of age (i.e., they exhibit estrus
at 7 to 9 months of age) will result in greater lifetime lamb production with little effect on wool
production.
How many sheep producers mate ewe lambs? I’m not aware of any recent surveys on this
topic. However, 18 years ago, of 139 sheep producers surveyed in Indiana (Hudgens, 1984) only
56% bred ewe lambs. Why were only slightly over half of Indiana sheep producers breeding ewe
lambs when positive results from such a practice were reported 50 years earlier? Perhaps the
answer to the question of whether or not to breed ewe lambs is not as straight forward as these
early studies would imply. My impression is that the vast majority of sheep producers in the
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Midwest do now breed ewe lambs, but there are still some that do not. The following points may
reveal why some producers have not had success in breeding ewe lambs.
Cumulative performance over five lambings (2, 3, 4, 5, and 6 years of age) of ewes exhibiting or
not exhibiting estrus their first winter
Cumulative performance
Breed
Estrus first winter
No. lambs born Lb. lamb weaned
Lb. wool
Rambouillet
No
Yes
5.9
6.6
372.5
417.3
58.1
57.6
Targhee
No
Yes
6.6
6.9
456.9
480.9
63.4
62.5
Columbia
No
Yes
6.0
6.3
412.7
454.3
68.2
68.4
Average
No
Yes
6.2
6.6
414.0
450.8
63.2
62.8
Factors Affecting Successful Mating of Ewe Lambs
Some of the following information was taken from an excellent discussion concerning the
breeding of ewe lambs written 24 years ago by Hohenboken et al. (1978) of Oregon State
University and updated with more recent information.
Season. Sheep are seasonal breeders. Their mating activity begins as day length decreases.
Breeds vary in the time of summer or autumn when ewes first become sexually active and in the
length of their breeding season. Fine-wool breeds tend to cycle early and for an extended period
of time; coarse wool breeds and those developed in northern latitudes tend to cycle later and for a
shorter length of time. Ewe lambs begin cycling somewhat later than mature ewes of the same
breed; and their mating season is shorter in duration. Therefore, the opportunity to get ewe
lambs bred is somewhat lower than with mature ewes.
Age. The age at first behavioral estrus generally varies between five to 17 months. Age at
puberty varies between breeds and is affected by the time of birth and by the level of feeding.
The date of birth has an important effect on age at first estrus. Lambs born early in the season
will cycle earlier in the year than later born lambs. This is due to the fact that they are heavier in
body weight and older in average age at the beginning of the breeding season.
Higher levels of feeding both pre- and post-weaning, through their effect on body weight,
lower the age at first estrus. Also, single lambs cycle at a younger age than twins or triplets,
because they tend to be heavier at any given age, at least through eight months.
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Weight. Several workers have reported that ewes of a breed or breed cross at a given time
during the breeding season must pass a specific threshold of body weight before they are
physiologically capable of exhibiting estrus. For Suffolk crossbred ewes a threshold of 88
pounds early in the breeding season decreased gradually to 73 pounds by late December. Other
workers have argued that sheep begin cycling once they reach a fixed percentage of their adult
weight. Since, however, this percentage has varied in different breeds and experiments from
33% to 80%, most research workers have agreed that no such biological constant exists. Most
ewe lambs of the popular breeds in the U. S. reach puberty between 80 and 100 pounds live
weight.
Weight Change During Mating. Nutritional flushing, i.e., having ewes on a rising level of
feed intake and gaining weight going into the mating season, is known to increase fertility and
twinning rate of mature ewes. The effect of flushing on ewe lambs has not been studied
extensively. Limited work suggests that higher levels of feeding will aid conception rate
(measured as the number of ewes lambing per 100 ewes bred) and survival of single embryos.
Flushing has not, however, aided the survival rate of twin embryos or had much effect on
twinning rate in ewe lambs. Apparently, most ewe lambs of many breeds are capable of carrying
only a single lamb to parturition, regardless of whether they have a high frequency of twin
ovulations.
Breed. Differences among breeds and breed crosses in age and weight at puberty have been
documented in several studies. Rambouillets and breeds such as the Targhee and Corriedale that
have a high percentage of fine-wool breeding are not the best candidates for production systems
lambing ewes first at one year of age. Too small a proportion of these ewes conceive and lamb.
The same is true of many of the long-wool breeds (e.g. Romney) and later maturing mediumwool breeds (e.g. North Country Cheviot). Finnsheep and Romanov breeds and their crosses are
very high in both ewe lamb fertility percent and twinning rate. The advantage is carried through
to a larger number of lambs weaned per ewe lambing and per ewe exposed to mating and to
greater gross income per ewe bred.
Mating System. Crossbred ewe lambs cycle at a younger age and exceed straight-bred ewes
for fertility and prolificacy and for total pounds of lamb weaned. Under western Oregon
conditions, crossbred ewe lambs exceeded straight-bred contemporaries by 25% for fertility,
10% for prolificacy, 8% for average lamb weaning weight, and 30% for pounds of lamb weaned
per ewe exposed to the ram.
Selection on "Modern Type". Selection in most purebred breeds of sheep in the U. S is
largely on conformation, with sheep of larger skeletal size at the yearling stage preferred. A
study conducted by Stephenson et al. (1980) in New Zealand suggested that such selection may
be detrimental to ewe lamb productivity. The study was conducted with 783 ewe lambs
representing Romney, Drysdale, Coopworth, Perendale, and Cheviot pure breeds and Merino x
Romney and Dorset x Romney crossbreds. The ewe lambs were born in the spring. Starting
when the ewes were approximately seven months of age, vasectomized rams were run with them
for a period of five months, and the number of estrous cycles recorded for each ewe. Body
weight, height at the withers and length of right and left fore cannon bones (distance between the
knee and pastern) were taken at approximately 11 and 15 months of age. All relationships
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between estrous activity and the other traits were calculated within a breed or crossbred group
so the results apply to animals within a breed and not to differences among breeds.
Ewe lambs that had the greatest number of estrous cycles during the five-month period when
they went from seven to 12 months of age were heavier at 11 and 15 months of age, had shorter
cannon bone lengths at 11 months of age and had lower increases in both body weight and wither
height from 11 to 15 months of age than ewe lambs with fewer estrous cycles.
These data suggest that sexual maturity may be earlier in ewes that have rapid growth up to
approximately one year of age and slower growth thereafter. These ewes will also be short in
their cannon bones and have relatively little increase in wither height from 11 to 15 months of
age. This is a description of an animal that reaches physiological maturity early in life. If these
same relationships exist for U. S. breeds of sheep, one might expect a drop in ewe lamb fertility
over time since current selection programs in most purebred flocks favor the taller, later
maturing individuals.
Management Recommendations
1. Plan the mating season for when you are certain that your breed type of ewe lamb will have
begun seasonal estrous cycling. For many conditions, mating ewe lambs before October 1 is
not recommended, and November mating for March lambing will generally give better
results.
2. Management and nutrition should be such that ewe lambs gain 0.5 pounds a day or more
from weaning through the breeding season. However, ewe lambs probably should not be fed
at levels resulting in maximum possible gains. Many studies on nutrition and growth of dairy
and beef heifers and a few on ewe lambs (reviewed by Tolman and McKusick, 2001) indicate
that heavy feeding and fast growth of prepubertal animals results in less mammary gland
development and less milk production in adult animals. These authors recommend that ewe
lambs be restricted to 65 to 75% as much energy intake as they would eat under free-choice
feeding from approximately 1.5 through 5 months of age in order to maximize mammary
gland development. Following 5 months of age, ewe lambs can be fed at a heavier level if
needed in order to bring them to a heavy enough weight for mating.
3. Unless they are very well grown out, ewe lambs should not be mated until they have reached
an average age of seven to eight months. For medium to large sized breeds and crosses,
lambs below 80 pounds at the start of the mating season should not be saved for replacement
ewes.
4. Replacement ewe lambs should not be selected solely on body weight. Saving only the
heaviest lambs for replacements will favor early born lambs over late born lambs, which is
good, but it will also favor singles over twins and triplets, which is not desirable.
Replacements should be selected preferentially from heavy twins and triplets, than from
heavy singles. This will put selection emphasis on twinning rate and growth rate and should
provide ewes heavy enough to cycle their first fall.
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5. Pregnant and lactating ewe lambs require about 25% more feed than a mature ewe of similar
weight because they have nutritional needs for not only production, but also for their own
continued body growth.
6. Choose a mating system that is compatible with land, feed and equipment resources,
management skills and goals for raising sheep. Systematic crossbreeding should increase
lamb production when breeding ewe lambs. For producers whose goal is the efficient and
economical conversion of forage and harvested feed into lamb for the slaughter market (as
opposed to seed stock production), crossbreeding often will be the mating system of choice.
7. Likewise, breeds or breed crosses should not be chosen primarily for their productivity as
ewe lambs. Rather, breeds should be chosen first for their adaptability to physical and
management conditions, then for their ability to produce lamb and wool efficiently in the
total management program (as ewe lambs and as mature ewes). Once the breed choice has
been made, determine whether the type chosen can perform economically when bred as ewe
lambs. If the choice is a fine-wooled breed, or a late maturing one such as the Cheviot,
Lincoln, or Romney, ewe lamb breeding may well be an uneconomical venture.
8. Many experiments have indicated that ewe lambs have a shorter length of standing heat and
that they are less likely to seek out and court a ram than are mature ewes. The chances of
them being detected in estrus and mated successfully will be increased by:
a. mating them separately from the mature ewes.
b. using a larger number of rams per 100 ewes than would be necessary with mature ewes.
c. using experienced rams but not rams so large there would be danger of injuring the ewes
during mating.
d. mating in confinement or a small enough pasture to prevent ewes being missed by the
rams.
9. Even if the above recommendations are followed, there will be a larger percentage of open
ewes from ewe lambs than from mature ewes. Mating from 30 to 40% more replacements
than actually needed could prevent the expense of carrying open ewe lambs through the
winter. The ewe lambs are then ultrasound pregnancy tested after the end of the breeding
season. Those that are open can be marketed as slaughter or feeder lambs, and they will still
be young enough to fetch lamb, not mutton, prices. Also, the late fall lamb markets are often
stronger than those earlier in the fall.
10. Mating ewe lambs to rams of breeds with smaller mature size (Cheviot, Finnsheep, etc.)
should reduce the incidence of difficult births, especially if the ewe lambs are not as well
grown out as would have been desired.
11. In many flocks, ewe lambs normally begin lambing about the time the mature ewes are
finishing. This is done to allow more management time for lambing difficulties and more
time for ewe/lamb pairs to "mother-up" in lambing jugs.
12. Post-lambing, yearling ewes with lambs should be managed separately from mature ewes
with lambs. In this way, adequate nutrition can be provided and observation of both ewes
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and lambs is easier. Yearling ewes will not produce as much milk as mature ewes so it is
advantageous to have a creep available to the lambs as soon as possible to improve lamb
performance.
13. Lambs born to the ewe lambs should be weaned at six to eight weeks of age. This will allow
the ewe sufficient time for recovery from the strain of lactation and for growth prior to the
next mating season.
References
Briggs, H. M. 1936. Some effects of breeding ewe lambs. North Dakota Agric. Exp. Sta. Bull.
285.
Hohenboken, W. D. M. Vavra, J. M. Levine, R. L. Phillips and R. M. Cedillo. 1978. Reports on
breeding ewe lambs. Oregon Agric. Exp. Sta. Spec. Rpt. 502.
Hudgens, R. E. 1985. Indiana sheep producers - a research study. 1985 Indiana Sheep Day Proc.,
Purdue Univ. p. 41-51.
Hulet, C. V., E. L. Wiggins and S. K. Ercanbrack. 1969. Estrus in range lambs and its
relationship to lifetime reproductive performance. J. Anim. Sci. 28:246-252.
Kammlade, W. G. 1947. Sheep Science. J. B. Lippincott Co., Chicago.
Levine, J. M., M. Vavra, R. Phillips, W. Hohenboken. 1978. Ewe lamb conception as an
indicator of future production in farm flock Columbia and Targhee ewes. J. Anim. Sci.
46:19-25.
Spencer, D. A., R. G. Schott, R. W. Phillips and B. Aune. 1942. Performance of ewes bred first
as lambs compared with ewes bred first as yearlings. J. Anim. Sci. 1:27-33.
Stephenson, S. K., D. C. Dalton and A. H. Kirton. 1980. The relationships of growth, body shape
and body composition to the initiation of oestrus activity in different sheep breeds. Proc.
New Zealand Soc. Anim. Prod. 40:258-267.
Tolman, B. and B. C. McKusick. 2001. The effect of growth rate on mammary gland
development in ewe lambs: A review. In Proc. 7th Great Dairy Sheep Symposium, Eau
Claire, Wisconsin. Department of Animal Sciences, University of Wisconsin-Madison. pp.
143-155.
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