This document provides tips for improving lambing and kidding percentages through management, genetics, and selection. It discusses establishing benchmarks for lambing/kidding percentages on your farm and compares typical percentages to benchmarks. The key factors that affect lambing/kidding percentages are fertility, litter size, and survival from birth through weaning and beyond. Management practices, genetics, nutrition, and selection can all be used to improve percentages.

1. TIPS FOR IMPROVING LAMBING
AND KIDDING PERCENTAGES
Management, Genetics, and Selection
SUSAN SCHOENIAN (Shāy nē ŭn)
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu – www.sheepandgoat.com

2. Lambing/kidding percentage
is one of the most important
factors affecting profitability of
sheep and goat enterprises.
$$1 2 3

3. However, the percentage needs
to be matched to the production
environment, available resources,
and goals of the enterprise.
Range lambing, South Dakota Pasture kidding, Missouri Shed lambing, Maryland

4. What is lambing/kidding percentage?
100 ewes put with rams (34 days)
96 ewes lambed
178 lambs born
171 lambs born live
160 lambs weaned (marked)
157 lambs sold or retained
Definition, calculation %
Number of lambs/kids born per ewe/doe lambing/kidding [178 ÷ 96] 185%
Number of live lambs born per ewe/doe lambing/kidding. [171 ÷ 96] 178%
Number of lambs/kids born per ewe/doe exposed for breeding. [171 ÷ 100] 171%
Number of lambs/kids weaned (marked) per ewe/doe exposed. [160 ÷ 100] 160%
Number of lambs/kids sold or retained as a percentage of the total number of
females exposed for breeding during a given period. [157 ÷ 100]
157%

5. How do you compare?
Sheep
State
Lambs born or docked
per 100 ewes
Iowa 167
Minnesota 158
West Virginia 141
Michigan 140
OHIO 136
Kentucky 129
USA 111
Pennsylvania 97
Texas 77
Source: USDA NASS, JAN 2015
Meat goats
Per doe kidding Average
Number born n=3057
(per doe kidding)
1.84
Number weaned n=2906 1.56
Source: Kentucky State University GHIP FEB 2015

6. 90
100
110
120
130
140
150
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
2007
2009
2011
2013
# lambs per 100 ewes (1+ yr)
USA Ohio
Is the industry making any progress?
Source: USDA NASS
40-year trend
Ohio +31 lambs (0.31 lambs/ewe)
USA +16 lambs (0.16 lambs/ewe)

7. Establish benchmarks for your farm
Trait
Your
farm
Sheep
Prolific
Sheep Goat
Conception, 1st cycle, % ? > 80 > 80 > 80
Prolificacy, % ? > 200 > 150 > 200
Still births, % ? < 5 < 10 <5
Pre-weaning losses, % ? < 15 < 10 < 10
Post-weaning losses, % ? < 5 < 5 < 5
Lambing/kidding % ? <200 <150 <200

8. Benchmarks for my farm

9. Lambing & Kidding Percentage
is a composite trait.
1. Fertility
(conception/pregnancy rate)
2. Litter size
(number born, prolificacy)
a) Ovulation rate (OR)
b) Embryo survival
3. Survival
a) Perinatal
b) Pre-weaning
c) Post-weaning

10. Many factors affect lambing/kidding
percentage.
Animal factors
 Breed
 Age
 Sex
 Genetics
 Body weight and condition
 Health
 Male-to-female ratio
 Lambing/kidding interval
 Length of exposure
Environmental factors
 Season (photo period)
 Climate – weather - temperature
 Stress
 Nutrition
 Pasture composition
 Lambing/kidding system
 Management - labor

11. How to improve fertility
Management
 Breeding Soundness
Exam (BSE) for males
 Monitor breeding activity
with marking harness or
painted brisket
 Use multiple sires
 Male: female ratio
 Good nutrition during
early pregnancy
 Breed in fall
 Don’t breed on certain
kinds of pasture
 Use ram/buck effect to
induce estrus
 Hormones or CIDRs to
induce estrus
Genetics
 Raise a more fertile breed
 Raise a more heat tolerent
breed.
 Introduce a more fertile
breed
 Crossbreeding
 Use a crossbred ram for
breeding
 Select a less seasonal
breed or breed cross
Selection
 Select breeding stock
from females that
lamb/kid early in
season.
 Select replacements
from females that
lamb/kid out-of-
season.
 Cull open females
 Cull females that
don’t breed in first
heat cycle.
 Do not use males with
small testicles for
breeding.

12. Breeding Soundness Exam (BSE)
Up to 10-15% of rams/bucks are of unsatisfactory reproductive breeding quality.*
1. Physical exam
a) Body condition
b) Structural soundness
c) Health
2. Assessment of reproductive
organs, including measuring
scrotal circumference
3. Semen evaluation
4. Libido (serving capacity)
*https://www.extension.purdue.edu/extmedia/AS/AS-599-W.pdf
At least 30 days before breeding

13. Scrotal circumference (SC)
 Scrotal size is strongly related to semen
production capacity.
 There is evidence to suggest that female
progeny from males with larger scrotal
circumference reach puberty earlier than
progeny from males with smaller testicles.
 Scrotal circumference can vary by season and
with body condition.
 Mature rams should have a minimum scrotal
circumference of 33 cm; 30 cm is acceptable
for ram lambs (6-8 m of age).
 It is recommended that mature bucks have a
minimum scrotal circumference of 25 cm; a
minimum has not been established for buck
kids < 14 m.

14. Libido or serving capacity
10% of rams will not mate with ewes.
 Serving capacity is a moderately heritable
trait that can be evaluated in a pen test
using females (in estrus).
Indirect selection for serving capacity
 Rams born to prolific ewes, and preferably
born as twins or triplets themselves, are more
likely to have a high serving capacity than
rams born to low fecundity ewes. (Australia)
 Rams born as co-twin to another ram are more
likely to have a high serving capacity than
rams born as co-twin to a ewe lamb.
(Australia)
 No difference in serving capacity of rams born
from high or low line ewes (Montana State
University).
 Monitor breeding activity
 Marking harness
 Painted brisket
 Use multiple sires
 Use clean-up rams/bucks

15. Male-to-female ratios
Breeding scenario Male: female Length of breeding season
Mature male 35-50 2 heat cycles
Young male 15-25 2 heat cycles
Synchronized matings 5-10 1 heat cycle

16. Summer breeding considerations
Increased body temperature due to high temperatures (>90°F) and
humidity. Also from grazing endophyte-infected fescue.
Males
 Scrotum cannot cool testicles below body
temperature.
 Temporary infertility that can last for up
to 60 days.
 Shearing
 Separate for feeding
 Keep in cool place during day
 Turn rams out at night only..
 Cull rams susceptible to heat stress.
Females
 Delayed heat cycles
 Lower ovulation rates
 Increased embryonic mortality
 Shade, natural breezes
 Do not work sheep in middle of day
 Shearing

17. Breeding pastures
Phytoestrogens
 Phytoestrogens are a diverse group
of naturally occurring non steroidal
plant compounds that, because of
their structural similarity with
estradiol have the ability to cause
estrogenic or/and anti-estrogenic
effects.
 The major plants producing phyto-
estrogens that are of importance to
animal agriculture are legumes,
clovers (subterranean
and red) and alfalfa.
 Can cause infertility and
other reproductive
problems.
 Sheep most sensitive.
Ergot alkaloids
 Kentucky 31 tall fescue is infected
with a microscopic fungus commonly
known as the endophyte.
 There is evidence that the toxin
produced by the endophyte can
affect growth, reproductive, and
lactation rates in small ruminants.
 Inhibits prolactin production which
could affect mothering response and
inhibit lactation.

18. Crossbreeding to improve fertility
Average heterosis effects in the crossbred lamb (individual) 2.6%
Average heterosis effects in the crossbred ewe (maternal) 8.7%
Average heterosis effects in the crossbred male ?
Source: Nitter, 1978

19. Litter size (number born, prolificacy)
Ovulation rate (OR)
 Number of eggs ovulated by
female.
 Sets the upper limit for litter size.
 Affected by breed, age, season,
genetics, and nutrition.
Embryo survival
 Factors affecting embryo survival: breed type,
genetics, nutrition, and ovulation rate.
Embryo age % mortality
< 25 days 28
> 25 days 15
Each 20 days beyond 25 3-4
Total 43
Pregnancy Wastage, West Virginia University

20. How to increase litter size (number born)
Ovulation rate + embryo survival
Management
 Breed females when
they are in optimal
body condition.
 If necessary, flush
females at beginning
and during early
part of breeding
season.
 Good nutrition
during early part of
gestation.
 Breed in fall.
Genetics
 Raise a more
productive breed,
e.g. Polypay or
Katahdin
 Introduce a prolific
breed, e.g. Romanov
or Finnsheep.
 Introduce FecB gene
(Booroola Merino)
into flock.
 Heterosis via
crossbreeding
Selection
 Select breeding stock
from most productive
families.
 If no other data is
available, select breeding
stock from large litters.
 Select breeding stock
with high EBVs for
number born (NLB).

21. 90 percent of the differences in litter
size are due to non-genetic factors
 Season
 Age
 Nutrition
 Static
 Dynamic

22. Season
Season of breeding can have a large effect on lambing/kidding rates.
 Sheep and goats are short-day breeders;
fall is their most natural time to breed.
 Females bred in the fall will usually have
higher conception rates, ovulation rates,
and lambing/kidding percentages.
 Females bred outside the “normal”
breeding season will usually have lower
conception rates, ovulation rates, and
lambing/kidding percentages.
 A VA Tech Study showed that spring
lambing was consistently more profitable
than winter and fall lambing.

23. Age
Age (of female) has a large effect on litter size.
Virginia Tech study, using NSIP data from
Targhee, Polypay and Suffolk breeds (n=29,567)
Ewe age # of lambs
As compared to 4-7 (8) year old ewe
1 year old ewes - 0.6 – 0.7 lambs
2 year old ewes - 0.3 lambs
3 year old ewes - 0.1 lambs
> 7, 8 years - 0.21 lambs
As compared to 12 month old ewe
15 month old ewe lambs + 0.21 lambs

24. Body condition (BCS, 1-5)
 Females in better body condition have
higher ovulation rates and higher
lambing/kidding percentages.
 Conversely, over-conditioned females
(BCS >4.0) have reduced reproductive
performance.
 Aim for a body condition score of 2.5
to 3.5 (depending upon production
system).
 Access body condition of ewes/does
several months prior to breeding and
manage accordingly.

25. Flushing
Increasing nutrient intake and body condition prior to ( ovulation rates)
and during early part ( embryo survival) of breeding season.
 Accomplished by providing ewes/does
with fresh pasture, supplemental
harvested forage, or up to 1 lb. of grain
per head daily.
 Response to flushing varies by age,
breed, body condition, and stage of
breeding season.
 Mature > Yearlings
 Less prolific > more prolific
 Early > late
 Thin > above average BC
2-2.5 BCS > 3-3.5 BCS

26. Prolific breeds
 With the exception of Suffolk,
Rambouillet, Targhee and Finnsheep,
few studies have been done to
compare the prolificacy of different US
sheep breeds.
 Romanov and Finnsheep ewes have the
highest prolificacy of any breeds,
giving birth to 2.0 to 1.5 x as many
lambs as Suffolk ewes (avg. 1.71).
 Other breeds superior to Suffolk are
Booroola Merino (with at least one
copy of FecB+ gene), hair breeds, and
Polypay.
 With the exception of Angora goats,
prolificacy of goats does not vary
significantly among breeds and tends
to be higher than most sheep.

27. Selecting for increased litter size
H2 ~10%
Requires a long-term commitment: expect 1-2% improvement per year.
 Select females that are more likely
to produce multiple births and/or
males that are more likely to sire
prolific daughters.
 Select for birth type or a
composite trait, such as pounds of
lamb/kid weaned.
 Select replacements that are born
as multiples from young mothers.
 Select replacements from females
who have demonstrated a lifetime
of multiple births.
 Select replacements from same
sex litters.

28. Enhancing selection with EBVs
[via National Sheep Improvement Program (NSIP) -- for goats, too!]
 An EBV is an estimated breeding value.
 It is an estimate of an animal’s genetic worth.
 It predicts differences in performance of offspring.
 EBVs are calculated from the animal’s own
performance, performance from genetically-related
traits, and performance of relatives for those traits.
 EBVs are calculated by Sheep Genetics (of Australia) via
LambPlan. There is also a KidPlan.
 Purebred or seedstock producers should consider
enrolling their flocks and herds in NSIP. AS part of re-
launch program, first year enrollment fee is being
waived (up to 3 years for young producers, < 22 years).
 Commercial producers should purchase males with
desired EBVs.
nsip.org

29. Estimated breeding values are a proven
technology in other countries and animal
industries.
Targhee Katahdin

30. Lamb/kid survival
There are many causes of lamb/kid mortality and many contributing factors.
Perinatal
 Abortion
 Diseases
 Birth trauma/injury
 Starvation
 Exposure
 Hypothermia
 Pneumonia
 Scours (diarrhea)
 Predators
Pre-weaning Post-weaning
 Diseases
 GI problems
 Coccidiosis
 Nematodes (worms)
 Predators

31. To improve survival, you need to
document the loss pattern.
 Lamb and kid mortality usually
varies from 5 to 25 percent.
 It varies by production system
and geographic location.
 Losses are usually highest
during the first 48 hours after
birth.
Age %
First 24 hours 37.8
> 24 hrs, < 1 week 31.8
> 1 week, before weaning 30.4
Cause of death %
Scours 46
Starvation 20
Pneumonia 8
US Sheep Experiment Station
USDA APHIS NAHMS

32. Birth weight
 Birth weight is a major factor affecting lamb/kid mortality.
 In sheep, birth weights vary from 3.5 to 20 lbs.
 Although these differences are associated with
breed, dam age, and litter size, they are highly
dependent on nutrition and in particular
energy intake during the last month of pregnancy.
 Inadequate energy intake during this period will
result in lowered birth weights which in turn is
a major factor affecting lamb/kid mortality.
 There may be as high as a 12 percent increase in
lamb mortality for every 2 pound decrease in lamb
birth weight.
 On the other hand, excessive levels of feeding may result in lambs/kids
with increased birth weights leading to lambing/kidding difficulties.

33. Neonatal care: Clip, dip, strip, and sip
 Clip: shorten navel cord with
scissors if necessary.
 Dip: Spray or dip navel cord in
disinfectant, e.g. iodine or
chlorhexidine.
 Strip: strip teats to remove wax
plugs and evaluate milk supply
 Sip: make sure lambs/kids nurse
as soon as possible.

34. Crossbreeding to improve survival
Average heterosis effects in the crossbred lamb (individual) 9.8%
Average heterosis effects in the crossbred ewe (maternal) 2.7%
Average heterosis effects in the crossbred ram ?
Source: Nitter, 1978

35. Tips for improving perinatal lamb/kid
survival
 Attended ewes/does at lambing/kidding
 Shed lambing/kidding
 Good hygiene: lamb/kid in a clean, stress-free environment.
 Adequate shelter: well-ventilated, but draft-free
 Control/eliminate diseases.
 Vaccinations, as needed.
 Have ewes/does in optimal body condition for lambing/kidding.
 Do not underfeed or overfeed energy during late gestation.
 Assist with difficult births, as needed.
 Make sure lambs/kids consume adequate colostrum; assist, if
necessary.
 Use jugs to encourage bonding, especially for first-time moms.

36. Tips for improving pre-weaning
lamb/kid survival
 Adequate colostrum intake.
 Good nutrition to maintain milk supply.
 Vaccinate pregnant females for clostridial diseases: CDT or
7,8-way
 Other vaccinations as necessary.
 Include a coccidiostat in feed or mineral.
 Control predation: fencing, guardians, night penning,
shooting, trapping, denning etc.
 Cull poor mothers.
 Select for number weaned or pounds of lamb/kid weaned.

37. Tips for improving post-weaning
lamb/kid survival
 Vaccinate lambs/kids for clostridial diseases once colostridial
immunity starts to wane.
 Deworm pregnant females to control periparturient egg rise:
primary source of infection for lambs and kids grazing summer
pastures.
 Integrated parasite management: pasture rest/rotation,
alternative forages, multi-species grazing, and targeted
selective treatment.
 Test for anthelmintic resistance.
 Good nutrition to ensure good growth rates and disease
resistance.
 Feed balanced rations, e.g. Ca: P of >2:1
 Avoid digestive disturbances, e.g. acidosis, bloat.
 Control predation: fencing, guardians, night penning,
shooting, trapping, denning etc.

38. Importance of sire selection
 Most genetic improvement is made
through the male.
 The male contributes half the
genetics to the flock or herd.
 There are considerable differences
among breeds and sires for maternal
traits.
 It is more difficult to make genetic
improvement in maternal traits, as
they are less heritable and are not
expressed in the male.
 NSIP provides the means to evaluate
maternal traits in sheep and meat
goats, especially males.

39. Thank you for your attention. Questions, comments?
SUSAN SCHOENIAN
SHEEP & GOAT SPECIALIST
UNIVERSITY OF MARYLAND EXTENSION
SSCHOEN@UMD.EDU – WWW.SHEEPANDGOAT.COM