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Ultrasound  Monitoring  of  Embryonic,  Follicular,  and  

Uterine  Dynamics  of  Early  Pregnancy  in  the  Alpaca  

Sara  Brunsden  

Introduction:  

  The  alpaca,  Vicuna  pacos,  is  a  member  of  the  Camelidae  family,  along  with  llamas,  

guanacos,  vicunas,  and  Bactrian  and  Dromedary  camels.  Traditionally  found  in  the  altiplano  

of  South  America,  the  popularity  of  the  alpaca  has  caused  it  to  spread  all  over  the  world,  

including  here  in  the  United  States.  In  South  America,  they  are  predominantly  used  for  their  

fleece,  while  the  industry  here  revolves  mainly  around  breeding.  However,  relatively  little  

is  known  about  the  reproduction  of  the  alpaca.  It  is  the  overall  goal  of  this  study  to  discover  

more  about  the  gestation  of  the  female,  specifically  the  embryonic  stage  from  conception  to  

forty  days  of  pregnancy.  

  Like  the  rabbit  and  cat,  the  alpaca  is  an  induced  ovulator,  meaning  that  the  act  of  

copulation  triggers  the  female  to  ovulate.  Differing  information  has  been  presented  on  

whether  alpacas  have  waves  of  follicular  development  similar  to  other  mammalian  species.  

According  to  studies  by  Bravo  (1991)  and  Sumar  (2000),  the  follicles  grow,  mature,  and  

regress  in  a  distinct  pattern.  However,  a  study  by  Donovan  (2011)  at  the  University  of  

Massachusetts  Amherst  did  not  find  a  pattern  of  definitive  follicular  waves.  

  Alpacas  are  considered  to  have  a  low  fertility  rate  compared  to  other  domesticated  

mammals,  with  the  highest  rate  of  early  embryonic  death  (EED)  occurring  within  the  first  

month  of  pregnancy,  possibly  due  to  weak  maternal  fetal  tissue  associations  (Olivera  

2003).  The  rate  of  EED  has  been  suggested  to  be  as  high  as  58%  (Fernandez-‐Baca  1970),  

with  44%  occurring  before  Day  27  (Ratto  2011).  Ratto  (2011)  also  suggests  that  lactating  

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females  have  a  decreased  occurrence  of  early  embryonic  death  as  compared  to  females  that  

did  not  have  a  cria  the  year  before.  The  rate  of  early  embryonic  death  is  investigated  in  the  

study  animals  to  compare  to  these  suggested  rates.  

  One  aspect  of  alpaca  reproduction  that  is  widely  agreed  on  is  that  nearly  all  

pregnancies  implant  in  the  left  uterine  horn.  Ratto  (2011)  found  that  the  rate  for  left  

uterine  horn  implantation  is  98%,  while  Brown  (1999)  states  that  “few  embryos  that  are  

produced  and  implant  in  the  right  side  survive  beyond  30  days  gestation  and  none  survive  

after  87  days.”  Olivera  (2003)  believes  that  this  phenomenon  is  due  to  “specific  surface  

molecule  expression  on  the  uterine  epithelium  allowing  embryo  apposition  and  adhesion  

only  in  restricted  areas.”  This  study  also  investigates  which  uterine  horn  the  embryonic  

vesicle  first  appears  in  the  study  animals.  

  Another  feature  of  the  alpaca  gestation  that  has  consistently  been  found  to  be  true  is  

that  the  corpus  luteum  (CL)  is  of  utmost  importance  in  maintaining  the  pregnancy  (Olivera  

2003).  It  was  found  by  both  Fernandez-‐Baca  (1970)  and  Brown  (1999)  that  the  CL  reaches  

its  maximum  size  by  Day  8-‐10  of  pregnancy.  Olivera  (2003)  also  found  that  the  corpus  

luteum  is  more  prevalent  on  the  left  ovary,  suggesting  that  more  ovulations,  and  therefore  

more  large  follicles,  occur  on  the  left  ovary.  The  development  of  the  corpus  luteum  is  

followed  throughout  the  pregnancies  in  this  study.  

  The  gestation  of  the  horse  has  been  well  studied  and  a  great  deal  of  information  is  

known  concerning  early  events  in  pregnancy.  Because  of  the  similar  gestation  length  of  345  

days  and  the  similar  epitheliochorial  placenta  of  the  alpaca  and  the  horse,  it  would  stand  to  

reason  that  many  of  the  events  that  occur  during  pregnancy  would  also  be  similar.  

According  to  Allen  (2001),  the  equine  embryo  should  be  seen  in  the  uterus  between  Day  12  

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and  14  and  remains  spherical  in  shape  until  implantation.  The  uterine  horns  will  be  closely  

monitored  during  this  study  to  see  when  the  alpaca  embryo  appears  and  what  shape  it  

takes.  

Methods:  

  Five  females  were  studied  over  the  course  of  a  year,  from  January  2011to  December  

2011.  The  females  ranged  in  age  from  13  years  to  4  years  and  were  all  proven  breeders  

with  at  least  one  previous  cria  (Figure  1).  

Animal   Age   Dates  Observed   Number  of  Crias   Time  Since  Last  Cria  A   13   September  12-‐December  16   8   2  months  B   5   June  20-‐September  9   1   12  months  C   4   January  28-‐November  16   1   4  months  D   6   August  1-‐September  9   2   11  months  E   8   January  31-‐September  30   2   18  months  

 

 

The  females  were  studied  three  days  per  week  with  at  least  one  day  between  

observations.  At  the  start  of  each  session,  an  intact  male  was  brought  to  the  group  of  

females  to  determine  their  receptivity  in  a  process  known  as  behavior  testing.  If  the  

females  were  receptive,  they  would  drop  to  the  ground  in  sternal  recumbency,  or  “kush”.  If  

they  were  not  receptive,  they  would  exhibit  nonreceptive  behavior,  such  as  kicking,  

spitting,  and/or  running  away.  Different  males  were  used  each  day  in  order  to  keep  females  

from  becoming  used  to  a  certain  male.  Females  will  also  react  differently  to  a  more  

aggressive  male  as  compared  to  a  more  subordinate  male.  Receptivity  was  graded  on  a  

scale  of  1  to  3,  as  described  in  Figure  2  and  shown  in  Figure  3.  

Figure  1:  Study  Females.  

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  After  behavior  testing,  each  female  was  then  haltered  and  brought  into  the  lab  for  

examination.  The  female  was  restrained  in  a  chute  and  any  manure  found  in  the  caudal  

rectum  was  removed.  In  order  to  gain  good  contact  for  the  ultrasound,  60  mL  of  water-‐

soluble  lubricant  was  inserted  into  the  rectum.  The  ultrasound  examination  was  then  

performed  transrectally  using  a  7.5  MHz  ultrasound  probe.  If  the  female  was  receptive  and  

had  a  significantly  sized  follicle,  she  was  bred.  Significant  follicles  were  determined  to  be  

those  ≥5  mm  in  diameter,  as  stated  by  Brown  (2000).  Seven  males  were  used  for  the  

Grade   Behavior  1   Not  receptive:  Spat,  kicked,  ran  way,  did  not  allow  male  to  mount  2   Not  receptive:  Allowed  male  to  mount  but  did  not  drop  into  kush  position  3   Receptive:  Dropped  into  kush  position  after  mounted  by  male  

Male   Age   Proven   Left  Testis  Length  x  Width  (cm)  

Right  Testis  Length  x  Width  (cm)  

A   Unknown   Yes   3.9  x  2.4   3.95  x  2.5  B   2   No   4.1  x  3.3   4.8  x  3.2  C   3   Yes   3.8  x  2.3   3.6  x  2.2  D   8   Yes   4.7  x  2.6   4.6  x  2.6  E   6   Yes   4.0  x  3.1   4.1  x  3.1  F   4   Yes   3.9  x  2.2   3.4  x  2.7  G   Unknown   Yes   4.6  x  3.1   4.6  x  3.0  

Figure  2:  Receptivity  Grading  Scale.  

Figure  4:  Study  Males.  Teste  dimensions  were  measured  with  calipers.  

Figure  3:  Receptivity  Grading  Scale.  A:  Grade  1,  Female  (right)  spitting  at  Male  (left).  B:  Grade  2,  Female  standing  to  be  mounted  by  Male.  C:  Grade  3,  Female  

dropped  in  kush  position.  

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breedings  (Figure  4).  Six  were  proven  and  one  was  not.  

  After  the  female  was  bred,  the  observations  continued  every  other  day  for  forty  

days,  which  is  when  the  embryonic  stage  of  gestation  ends  and  the  fetal  stage  begins  using  

the  convention  associated  with  the  horse.  Pregnancy  was  determined  to  be  established  

when  the  embryonic  vesicle  was  seen.  Photos  and  video  were  taken  of  the  ovaries,  uterine  

horns,  and  embryonic  vesicle  when  present.  The  diameter  of  each  ovary  was  recorded,  as  

well  as  the  diameter  of  any  significant  follicles.  If  any  follicles  under  5  mm  in  diameter  were  

present,  they  were  recorded  as  multiple  small  follicles  (msf).  The  diameter  of  the  corpus  

luteum  was  measured  and  the  ultrasound  appearance  was  noted.  The  contractility,  or  

movement,  of  each  uterine  horn  was  graded  on  a  scale  from  1  to  3,  with  1  being  low  and  3  

being  high.  The  diameter  of  each  uterine  horn  was  also  recorded  and  the  amount  of  

curvature  was  noted.  When  the  embryonic  vesicle  and  embryo  proper  became  apparent,  its  

location  and  size  was  noted,  as  well  as  when  the  heartbeat  was  first  seen.  When  the  forty  

days  was  reached,  the  females  were  used  for  another  study  looking  at  fetal  development,  

after  which  the  pregnancies  were  terminated  with  a  subcutaneous  injection  of  

prostaglandin  F2α.  When  the  females  came  back  into  receptivity,  they  were  rebred  and  

used  again  for  this  study.  

Results:  

  In  total,  ten  pregnancies  were  achieved  during  this  study.  Early  embryonic  death  

occurred  in  four  of  them,  at  a  rate  of  40%.  This  is  lower  than  the  rate  of  58%  suggested  by  

Fernandez-‐Baca  (1970).  When  the  rate  of  EED  in  the  two  lactating  females  (Female  A  and  

C)  was  calculated,  it  was  found  to  occur  in  two  of  the  five  pregnancies  at  a  rate  of  40%  

(Figure  5).  The  rate  of  early  embryonic  death  in  the  three  females  (Females  B,  D,  and  E)  

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that  did  not  have  a  nursing  cria  was  also  40%,  as  two  out  of  five  pregnancies  had  early  

embryonic  death.  This  is  in  contrast  to  findings  by  Ratto  (2011)  who  found  that  lactating  

females  had  a  lower  rate  of  EED  at  30%  and  the  females  without  a  cria  had  a  higher  rate  of  

46%  EED.  However,  it  must  be  noted  that  the  sample  size  in  the  Ratto  study  is  much  larger  

than  in  the  present  study.  

 

Ratto  (2011)  also  found  that  44%  of  early  embryonic  death  occurred  before  Day  27  of  

pregnancy.  Our  data  concludes  otherwise  (Figure  6).  One  of  the  pregnancies  did  stop  by  

Day  12,  but  the  other  three  occurred  at  Days  30,  31,  and  41.  

 

 

When  the  degree  of  uterine  contractility  was  compared  between  the  pregnant  and  

nonpregnant  females,  inconclusive  data  was  found,  as  shown  in  Figure  7.  In  two  of  the  ten  

pregnancies,  the  contractility  was  increased  during  gestation,  but  in  two,  the  contractility  

Animal   Pregnancy   Day  Early  Embryonic  Death  Noted  A   1   30  B   1   41  B   2   12  C   1   31  

Figure  5:  Lactational  Status  of  Female  Versus  Outcome  of  Pregnancy.  

Figure  6:  Day  Early  Embryonic  Death  Noted.  

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decreased.  There  was  no  change  in  three  of  the  pregnancies,  and  in  three  of  them,  the  

contractility  varied  from  observation  to  

observation  and  no  trend  could  be  

established.  Different  pregnancies  in  the  

same  female  could  also  vary  in  the  

amount  of  contractility  as  compared  to  

that  observed  in  the  female  when  she  

was  not  pregnant.  It  does  not  appear  

that  uterine  contractility  correlates  with  

outcome  of  pregnancy.  As  shown  in  

Figure  8,  both  the  six  pregnancies  that  

were  successfully  carried  past  the  forty-‐day  mark  and  the  four  pregnancies  that  resulted  in  

early  embryonic  death  were  associated  with  all  four  of  the  categories  of  contractility.    

 

Figure  7:  Trends  in  Uterine  Contractility  from  Nonpregnancy  to  

Pregnancy.  

Figure  8:  Uterine  Contractility  Versus  Outcome  of  Pregnancy.  

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It  was  also  found  that  the  embryonic  vesicle  tended  to  appear  in  the  left  uterine  

horn  first  before  spreading  into  the  right  horn.  In  seven  out  of  the  nine  pregnancies  that  

data  was  available  for,  the  vesicle  was  found  in  the  left  horn  at  least  three  days  before  it  

was  seen  to  expand  into  the  right  horn  as  well.  According  to  Brown  (2000)  and  Ratto  et  al  

(2011),  the  right  horn  has  a  luteolytic  effect  on  embryos,  which  must  migrate  to  the  left  

horn  in  order  to  implant.  The  data  shown  in  Figure  9  supports  these  findings  in  78%  of  the  

pregnancies  in  this  study.  The  time  period  during  which  the  embryonic  vesicle  appears  in  

the  uterus  does  not  appear  to  follow  that  of  the  horse.  Allen  (2001)  stated  that  the  horse  

embryo  should  appear  between  Day  12  and  14,  while  only  one  of  our  alpaca  pregnancies  

fell  into  that  time  range,  with  one  embryonic  vesicle  being  seen  before  and  the  others  after.  

 

 

 

 

Animal   Day  First  Seen  in  Left  Uterine  Horn  

Day  First  Seen  in  Right  Uterine  Horn  

A   Pregnancy  1   7   18     Pregnancy  2   34   25  B   Pregnancy  1   18   29  

  Pregnancy  2   12   Pregnancy  Lost1  C   Pregnancy  1   19   Pregnancy  Lost2     Pregnancy  2   Data  not  available3   Data  not  available3     Pregnancy  3   16   19  D   Pregnancy  1   20   15  E   Pregnancy  1   18   21     Pregnancy  2   29   36  

Total   10  Pregnancies   Left  Horn  First:  7/9  (78%)   Right  Horn  First:  2/9  (22%)  

Figure  9:  Day  of  Pregnancy  when  the  embryonic  vesicle  first  appears.  1:  Last  observation  Day  19.  2:  Last  observation  Day  28.  3:  Embryonic  vesicle  location  not  recorded.    

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Throughout  the  observations,  follicles  of  significant  size  (≥  5  mm  diameter)  were  

found  on  the  ovaries  of  all  five  of  the  females  during  all  pregnancies.  The  largest  recorded  

was  12  mm  in  diameter,  although  the  average  diameter  was  7  mm.  On  several  occasions,  a  

single  ovary  even  had  more  than  one  significant  follicle  present  (Figure  10A).  Multiple  

small  follicles  (<  5  mm  diameter)  were  also  noted  but  not  measured  (Figure  10B).  Although  

a  greater  number  of  follicles  developed  on  the  ovary  opposite  the  corpus  luteum,  follicles  

were  also  seen  on  the  same  ovary  as  the  corpus  luteum,  as  shown  in  Figure  10C.  In  contrast  

to  nonpregnant  follicular  growth  as  reported  by  Donovan  (2011),  there  are  waves  of  

follicular  development  and  regression  during  pregnancy.  It  is  a  possibility  that  a  large  

amount  of  follicular  development  may  be  indicative  of  early  embryonic  death  (EED).  In  

three  of  the  four  pregnancies  that  resulted  in  EED,  at  least  one  significantly  sized  follicle  

was  found  during  almost  every  observation.  In  contrast,  in  five  of  the  six  pregnancies  that  

were  successfully  carried  past  the  forty-‐day  mark,  large  follicles  were  found  only  a  few  

times.  The  initial  hypothesis  was  that  the  follicles  seen  at  the  beginning  of  pregnancy  were  

remnants  of  follicular  development  from  before  the  female  was  bred.  However,  follicles  

were  also  found  throughout  the  forty  days  being  observed,  not  just  at  the  beginning,  

making  the  hypothesis  unlikely.      

   

   

 

 

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The  

appearance  of  the  

corpus  luteum  

(CL)  was  tracked  in  consistently  in  Female  A  in  this  study.  In  the  second  pregnancy,  the  CL  

showed  a  bright  white  center  and  a  dense  white  outline  on  the  periphery  for  the  first  two  

weeks  after  ovulation.  By  the  third  week,  the  CL  interior  became  darker  with  a  white  line  

through  the  middle,  which  continued  throughout  pregnancy  (Figure  11A).  In  the  first  

pregnancy  that  had  early  embryonic  death,  the  CL  became  uniformly  white  in  appearance  

(Figure  11B)  instead  of  developing  the  echodense  line  in  the  center,  which  could  perhaps  

be  used  as  a  sign  of  early  embryonic  death.  The  appearance  of  the  corpus  luteum  was  not  

regularly  followed  in  the  other  pregnancies,  though  the  CL  seems  to  follow  the  same  trend  

in  the  other  four  pregnancies  for  which  data  is  available.    

 

 

Figure  10:  Follicular  development  during  pregnancy.  A:  6  mm  (purple)  and  5  mm  (white)  follicles  on  the  left  ovary  on  Day  20  of  pregnancy.  B:  7  mm  follicle  (orange)  and  multiple  small  follicles  on  the  left  ovary  (green)  on  Day  6  of  

pregnancy.  C:  12  mm  corpus  luteum  (blue)  and  7  mm  follicle  (red)  on  the  left  ovary  on  Day  25  of  pregnancy.  

Figure  11:  Development  of  the  corpus  luteum  during  pregnancy.  A:  Pregnancy  survived  past  forty  days.  B:  Early  embryonic  death  occurred  approximately  Day  30.  

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!"#$%$$ !"#$&$$ !"#$'($$

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  11  

 

The  corpus  luteum  was  found  on  the  right  ovary  on  five  of  the  pregnancies  and  on  

the  left  ovary  in  four  pregnancies,  shown  in  

Figure  12.  The  tenth  pregnancy  (not  shown)  

resulted  in  twins  and  had  a  corpus  luteum  

present  on  each  ovary.  This  contrasts  with  

data  found  by  Olivera  (2003)  that  the  CL  is  

more  prevalent  on  the  left  ovary.  This  data  

does  support  the  findings  from  Brown  

(1999)  that  pregnancies  originating  from  the  right  ovary  migrate  to  the  left  uterine  horn.  

Out  of  the  eight  pregnancies  for  which  both  embryonic  vesicle  location  and  corpus  luteum  

location  is  available,  four  pregnancies  originated  from  the  right  ovary  and  moved  to  the  left  

uterine  horn  (50%)  (Figure  13).  Of  the  three  pregnancies  from  the  left  ovary,  two  remained  

in  the  left  horn  (67%),  while  one  traveled  to  the  right  uterine  horn  (33%).  One  pregnancy  

from  the  right  ovary  stayed  in  the  right  uterine  horn.  

Figure  12:  Location  of  the  Corpus  Luteum.  

Figure  13:  Location  of  Corpus  Luteum  and  Uterine  Horn  in  Which  the  Embryonic  Vesicle  is  First  Seen.  

  12  

 

It  has  also  been  suggested  by  Ratto  (2011)  that  the  location  of  the  corpus  luteum  

could  have  an  effect  on  embryo  survivability.  While  the  data  from  that  study  did  not  

support  this  hypothesis,  our  data  does.  Of  the  four  pregnancies  resulting  in  early  

embryonic  death,  three  originated  from  the  right  ovary  and  one  from  the  left.  In  contrast,  

three  of  the  successful  pregnancies  came  from  the  left  ovary  and  two  from  the  right.  It  

would  appear  that  early  embryonic  death  occurs  more  frequently  when  the  ovulatory  

follicle  is  located  on  the  right  ovary,  while  successful  pregnancies  have  a  relatively  equal  

chance  of  originating  from  the  left  or  right  ovary.    

An  observation  of  note  is  that  the  curvature  of  the  uterine  horns  increased  during  

pregnancy,  most  likely  due  to  the  influence  of  progesterone.  The  amount  by  which  the  horn  

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+(,*./**

  13  

curved  varied  with  each  observation  (Figure  14),  and  it  did  not  appear  that  the  curvature  

increased  as  pregnancy  progressed.  

 

 

According  to  Allen  (2001),  the  embryo  of  the  horse  remains  spherical  in  shape  until  

implantation  occurs.  This  was  not  found  in  the  alpaca.  The  contractility  of  the  uterine  horns  

caused  the  embryonic  vesicle  to  constantly  mutate  and  change  shape,  demonstrated  in  

Figure  15.    

 

 

 

 

 

 

 

Figure  14:  Curvature  of  the  Uterine  Horn.  A:  Nonpregnancy  right  uterine  horn  (25  mm  diameter).  B:  Pregnant  right  uterine  horn  at  Day  7  (22  mm  diameter).  C:  

Pregnant  right  uterine  horn  at  Day  12  (19  mm  diameter).  

Figure  15:  Embryonic  vesicle  at  Day  23  in  the  left  uterine  horn.  Picture  A  was  taken  two  minutes  before  Picture  B.  

  14  

 

Using  the  data  collected  during  our  observations,  we  were  able  to  create  a  timeline  

of  the  events  that  occur  during  early  pregnancy  (Figure  16).  The  corpus  hemorrhagicum  is  

present  at  Day  2  before  becoming  the  corpus  luteum  by  Day  4.  The  embryonic  vesicle  can  

be  seen  as  early  as  Day  7  of  pregnancy,  while  the  embryo  proper  is  not  evident  until  Day  

25.  The  heartbeat  appears  at  Day  27.  

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Individual  Animals:  

Female  A:  

Pregnancy  1:  Bred  to  Male  A:  September  12-‐October  17:  Early  Embryonic  Death  

Pregnancy  2:  Bred  to  Male  B:  November  3-‐December  16:  Successful  Pregnancy  

Figure  16:  Timeline  of  Early  Pregnancy  Events.  

  15  

 

 

Figure  17:  Uterine  Contractility  During  Pregnancy,  Female  A.  

 

  16  

Female  A  was  bred  successfully  twice  during  the  course  the  study.  The  first  

pregnancy  resulted  in  early  embryonic  death,  while  the  second  was  successfully  carried  

past  forty  days.  Uterine  contractility  was  consistent  throughout  both  of  her  pregnancies  

(Figure  17).  In  Pregnancy  1,  contractility  stayed  at  Grade  1.  In  Pregnancy  2,  uterine  

contractility  was  Grade  1,  except  for  Days  18  and  20,  when  it  was  Grade  2.  Significant  

follicular  development  was  observed  during  both  of  these  pregnancies.  During  the  first  

pregnancy,  there  were  significant  follicles  consistently  found  on  both  ovaries,  while  in  the  

second  pregnancy,  significant  follicles  were  found  mostly  on  the  left  ovary,  as  shown  in  

Figure  18.  It  should  be  noted  that  the  corpus  luteum  was  also  present  on  the  left  ovary.  The  

corpus  luteum  was  also  located  on  the  left  ovary  during  the  first  pregnancy.  It  was  found  

that  the  embryonic  vesicle  appeared  in  the  left  uterine  horn  first  in  Female  A’s  first  

pregnancy  at  Day  7,  but  appeared  in  the  right  uterine  horn  first  at  Day  25  in  the  second  

pregnancy.  In  the  first  pregnancy,  the  embryonic  vesicle  spread  into  the  right  horn  by  Day  

18,  and  in  the  second  pregnancy,  it  was  seen  in  the  left  horn  on  Day  34.  

Figure  18:  Follicular  Development  During  Pregnancy,  Female  A.  

 

  17  

Female  B:  

Pregnancy  1:  Bred  to  Male  C:  June  20-‐  August  3:  Early  Embryonic  Death  

Pregnancy  2:  Bred  to  Male  D:  August  12-‐  September  9:  Early  Embryonic  Death  

  Female  B  was  successfully  bred  twice  during  the  study.  Both  of  the  pregnancies  

resulted  in  early  embryonic  death.  As  seen  in  Figure  19,  uterine  contractility  in  the  first  

pregnancy  increased  dramatically  from  Grade  0  to  Grade  3,  while  contractility  during  the  

second  pregnancy  had  an  overall  decrease  from  Grade  3  to  Grade  1.  Follicular  development  

was  not  followed  closely  in  this  female,  though  several  follicles  of  significant  size  were  

noted  throughout  both  pregnancies.  The  corpora  lutea  for  both  pregnancies  were  located  

on  the  right  ovaries.  The  embryonic  vesicle  was  seen  in  the  left  uterine  horn  first  in  both  

Pregnancy  1  and  2,  at  Days  18  and  12,  respectively.  The  embryonic  vesicle  appeared  in  the  

right  uterine  horn  at  Day  29  in  the  first  pregnancy,  but  the  second  pregnancy  was  lost  

before  the  vesicle  could  be  seen  in  the  right  uterine  horn.  

Female  C:  

Pregnancy  1:  Bred  to  Male  E:  January  28-‐  March  2:  Early  Embryonic  Death  

Figure  19:  Uterine  Contractility  During  Pregnancy,  Female  B.  

 

  18  

Pregnancy  2:  Bred  to  Male  E:  April  13-‐  May  24:  Successful  Pregnancy  

Pregnancy  3:  Bred  to  Male  D:  October  4-‐  November  16:  Successful  Pregnancy  

  Female  C  had  three  successfully  pregnancies  during  the  study  period.  The  first  

resulted  in  early  embryonic  death,  but  the  second  and  third  were  both  carried  past  the  

forty-‐day  mark.  As  shown  in  Figure  20,  the  uterine  contractility  for  Pregnancies  1  and  3  

varied  between  Grade  1  and  Grade  2,  with  one  day  recorded  as  Grade  3,  on  Days  24  and  

Figure  20:  Uterine  Contractility  During  Pregnancy,  Female  C.  

Figure  21:  Follicular  Development  During  Pregnancy  from  Pregnancy  1,  Female  C.  

  19  

30,  respectively.  The  contractility  for  Pregnancy  2  was  not  consistently  recorded.  Female  C  

consistently  had  follicles  present  on  both  the  left  and  right  ovaries  during  her  first  

pregnancy  (Figure  21).  The  corpus  luteum  was  located  on  the  right  ovary,  which  may  

account  for  the  greater  follicle  size  on  the  left  ovary.  The  follicular  development  was  not  

closely  monitored  during  the  second  and  third  pregnancies,  though  significant  follicles  

were  seen  on  several  occasions.  The  corpora  lutea  for  these  pregnancies  were  located  on  

the  left  ovary.  The  embryonic  vesicle  was  observed  in  the  left  uterine  horn  first  in  

Pregnancy  1  at  Day  19  and  Pregnancy  3  at  Day  16.  It  spread  into  the  right  horn  at  Day  19  in  

Pregnancy  3,  but  Pregnancy  1  was  lost  before  this  occurred.  The  location  of  the  embryonic  

vesicle  was  not  recorded  during  the  second  pregnancy.  

Female  D:  

Pregnancy  1:  Bred  to  Male  D:  August  1-‐  September  9:  Successful  Pregnancy  

 

Figure  22:  Uterine  Contractility  During  Pregnancy,  Female  D.  

  20  

  Female  D  was  bred  once  during  the  study  period,  which  resulted  in  a  successful  

pregnancy  carried  past  forty  days.  The  uterine  contractility  for  this  pregnancy,  as  seen  in  

Figure  22,  increased  greatly  from  Grade  0  to  Grade  3.  There  was  some  follicular  

development  during  the  pregnancy,  particularly  on  the  left  ovary  (Figure  23).  This  might  

have  been  due  to  the  location  of  the  corpus  luteum  on  the  right  ovary.  The  embryonic  

vesicle  appeared  in  the  right  uterine  horn  first  at  Day  15  and  spread  into  the  left  horn  by  

Day  20.  

Female  E:  

Pregnancy  1:  Bred  to  Male  F:  January  31-‐  March  14:  Successful  Pregnancy  

Pregnancy  2:  Bred  to  Male  G:  August  22-‐  September  30:  Successful  Pregnancy  

Figure  23:  Follicular  Development  During  Pregnancy,  Female  D.  

 

Figure  24:  Uterine  Contractility  During  Pregnancy,  Female  E.  

  21  

  Female  E  carried  both  pregnancies  past  forty  days.  Uterine  contractility  for  the  first  

pregnancy  varied  between  Grade  1  and  Grade  3,  as  seen  in  Figure  24.  There  was  a  slight  

decrease  in  contractility  in  the  second  pregnancy,  from  Grade  3  to  Grades  1  and  2.  Female  E  

did  not  have  as  many  significant  follicles  as  the  other  females.  She  did  however  have  

multiple  small  follicles  in  almost  every  observation,  represented  by  the  data  points  at  zero  

on  the  y-‐axis  in  Figure  25.  The  first  pregnancy  resulted  in  twins,  with  a  corpus  luteum  

located  on  each  ovary.  In  the  second  pregnancy,  the  corpus  luteum  was  on  the  right  ovary.  

In  both  of  the  pregnancies,  the  embryonic  vesicle  was  first  seen  in  the  left  uterine  horn  at  

Days  18  and  29  and  in  the  right  uterine  horn  at  Days  21  and  36.  

Figure  25:  Follicular  Development  During  Pregnancy,  Female  E.  

 

  22  

Conclusion:  

  The  observations  made  in  this  study  tend  to  disagree  with  some  of  the  published  

literature.  The  rate  of  early  embryonic  death  has  been  reported  as  being  58%  by  

Fernandez-‐Baca  (1970),  while  our  rate  was  lower  at  40%.  It  was  stated  by  Ratto  (2011)  

that  lactating  females  had  less  occurrence  of  early  embryonic  death  than  females  who  were  

not  currently  nursing  a  cria  (30%  compared  to  46%).  The  rates  for  these  two  groups  found  

here  were  both  also  40%.  Ratto  (2011)  also  stated  that  44%  of  embryo  loss  occurs  before  

Day  27  of  pregnancy.  Our  observations  disagree  here  as  well,  as  only  25%  of  embryo  loss  

occurred  before  Day  27.  Established  literature  also  states  that  98%  of  pregnancies  implant  

in  the  left  uterine  horn  (Brown  2000).  In  contrast,  out  study  found  the  embryonic  vesicle  to  

first  appear  in  the  left  horn  only  78%  of  the  time.  

  Discrepancies  in  data  were  additionally  seen  when  observing  the  corpus  luteum.  

Olivera  (2003)  stated  that  the  corpus  luteum  occurs  on  the  left  ovary  more  often  than  the  

right.  Our  observations  found  that  it  appears  to  occur  on  the  either  ovary  approximately  

half  of  the  time  and  actually  occurred  slightly  more  on  the  right  ovary  than  on  the  left  (56%  

to  44%).  This  does  however  support  the  idea  that  embryos  originating  from  the  right  ovary  

must  migrate  to  the  left  uterine  horn,  as  four  out  of  the  eight  pregnancies  for  which  this  

data  was  recorded  originated  from  the  right  ovary  and  were  first  seen  in  the  left  horn.  

However,  three  of  these  four  pregnancies  resulted  in  early  embryonic  death,  contrasting  

with  findings  by  Ratto  (2011)  that  the  location  of  the  corpus  luteum  does  not  have  an  

impact  of  the  rate  of  embryo  mortality.  During  our  observations  of  the  corpus  luteum,  it  

was  detected  that  the  CL  changes  in  appearance  throughout  the  pregnancy  and  develops  a  

blackish,  fluid-‐filled  outer  ring  with  a  white  echodense  line  of  tissue  in  the  middle.  When  

  23  

early  embryonic  death  occurred,  however,  the  black  ring  did  not  develop  and  the  CL  

instead  remained  homogeneously  white  in  color.  

  Due  to  the  similarities  in  gestation  and  type  of  placenta  between  the  alpaca  and  the  

horse,  we  compared  some  observations  between  the  two  species.  While  Allen  (2001)  found  

that  the  equine  embryonic  vesicle  appears  in  the  uterine  horns  between  Days  12  and  14,  

the  range  in  which  we  detected  the  alpaca  embryonic  vesicle  was  wider,  from  7  to  29  days.  

We  also  found  that  the  shapes  of  the  two  embryonic  vesicles  do  not  match.  The  horse  

vesicle  was  reported  by  Allen  (2001)  to  remain  spherical  in  shape,  while  the  alpaca  vesicle  

is  constantly  deformed  by  the  contractions  of  the  uterus.  

  The  contractions  of  the  uterine  horns  were  followed  during  this  study.  We  originally  

hypothesized  that  the  influence  of  progesterone  from  the  corpus  luteum  would  cause  the  

contractility  of  the  uterus  to  increase.  No  discernable  trends  were  found.  Two  of  the  

pregnancies  did  increase  in  their  amount  of  contractility;  however  two  also  decreased  in  

their  amount,  while  three  had  no  change  and  three  pregnancies  were  too  varied  to  detect  a  

trend.  The  contractility  also  varied  between  different  pregnancies  in  the  same  female.  

There  does  not  appear  to  be  an  association  between  the  amount  of  contractility  and  the  

outcome  of  the  pregnancy.  While  observing  the  contractility  of  the  uterine  horns,  it  was  

also  noticed  that  the  horns  increase  their  curvature  during  pregnancy.  

  Interestingly,  follicles  were  seen  to  develop  throughout  all  of  the  pregnancies  in  this  

study.  Significantly  sized  follicles  greater  than  or  equal  to  5  mm  in  size  were  observed  on  

several  occasions,  as  well  as  multiple  small  follicles.  More  than  one  significant  follicle  was  

found  on  the  same  ovary,  in  addition  to  the  same  ovary  as  the  corpus  luteum.  Unlike  the  

nonpregnant  female  as  reported  by  Donovan  (2011),  there  do  appear  to  be  waves  of  

  24  

follicular  growth,  maturation,  and  regression  in  the  pregnant  female.  It  is  a  possibility  that  

having  a  larger  amount  of  significant  sized  follicles  is  a  sign  of  early  embryonic  death.  

  This  research  has  a  great  deal  of  potential  for  future  uses.  If  signs  of  early  embryonic  

death  can  be  recognized,  the  breeder  could  prepare  appropriately  in  case  the  pregnancy  is  

indeed  lost.  Knowing  the  parameters  for  a  successful  breeding  versus  an  unsuccessful  one  

will  also  help  alpaca  owners  determine  the  optimal  time  to  breed  their  females.  Having  this  

information  available  will  not  only  improve  the  alpaca  industry  here  in  the  United  States  

but  also  in  South  America,  where  people’s  livelihoods  rely  on  the  alpaca.  Future  studies  are  

currently  in  progress  at  the  University  of  Massachusetts  Amherst  to  answer  these  

questions  and  more.  

 

 

 

 

 

 

 

 

 

 

 

 

 

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Sources:  

Allen,  WR.  “Fetomaternal  interactions  and  influences  during  equine  pregnancy.”

  Reproduction  (2001)  121,  513-‐527.  

Brown,  B.  “A  review  on  reproduction  in  South  American  camelids.”  Animal  Reproduction

  Science  (2000)  58,  169-‐195.  

Donovan,  C.  “Correlating  Female  Alpaca  Behavioral  Receptivity  with  Cervical   Relaxation

  and  Ovarian  Follicle  Growth.”  Senior  Thesis,  University  of  Massachusetts  2011.  

Fernandez-‐Baca,  S,  Hansel,  W,  Novoa,  C.  “Corpus  luteum  function  in  the  alpaca.”  

Biology  of  Reproduction  (1970)  3,  252-‐261.  

Olivera,  LVM,  Zago,  DA,  Jones,  JP,  Bevilacqua,  E.  “Developmental  changes  at  the  

materno-‐embryonic  interface  in  early  pregnancy  of  the  alpaca,  Lamos  pacos.”  

Anatomy  and  Embryology  (2003)  207,  317-‐331.  DOI:  10.1007/s00429-‐0030346-‐1.  

Ratto,  M  et  al.  “Effect  of  location  and  stage  of  development  of  dominant  follicle  on

  ovulation  and  embryo  survival  rate  in  alpacas.”  Animal  Reproduction  Science  (2011)

  127,  100-‐105.