The document summarizes the avian reproductive system. It describes the major components including the testes, epididymis, ductus deferens, and papilla. It discusses spermatogenesis, semen production and transport, and the roles of hormones like testosterone. The timing of artificial insemination and techniques like semen collection, evaluation, and storage are also outlined. Caponization is described as the surgical removal of testes in male chickens to improve meat quality.

1. By
Zaib-Ur-Rehman
Lecturer
Department of Poultry Science
PMAS,Arid Agriculture University,Rawalpindi,Pakistan

2.  Avian Reproductive system differs
 Reproduction is organized into distinct developmental and
functional phases
 Male, it include
 Fertilization
 formation of a patent reproductive tract
 production of sperms
 maniifestation of male-specific behavioral patterns
 expulsion of sperm from the body
 It consist of testes, epididymis, ductus deferens, papilla and
phallus

4. TESTES
 Two elliptical testes lie along the back, near the anterior end of
kidneys
 Weight at birth is 2-4g & at maturity 25-35g
 Left testis is heavier 0.5-3g
 Mesorchium connects testes with the body wall
 Serves as conduit for blood vessels and nerves
 Each teste is made up of two types of parenchymal tissue,
interstitial and seminephrus epithelium
 Interstitial tissue contain
 Lyding cells
 Peritubular epithelial cells
 Nerves
 Lymphatic vessels
 Blood vessels

5. TESTES
 Seminephras epithelium consist of
 Fibroblast
 Myoepitheilial cells
 Connective tissue over basal lamina
 Sertoli cells and developing germ cell stages are present
within seminephrus tubules
 Their size varies depending upon the age and reproductive
stage

9. EPIDIDYMIS
 The series of ducts opening into deferent duct are referred as
epididymis
 It is present on the dorso-medial aspect of kidney known as
hilus
 Epididymis consists of
 rete testes
 connecting ducts
 efferent ducts
 epididymal duct
 Rete testes are lined by simple cuboidal and simple squamous
epithelium
 Efferent dusts have pseudostratified clumner ciliated and non-
ciliated epithelium

10. EPIDIDYMIS
 Connecting Ducts The epithelium of connecting ducts is also
pseudostratified columnar
 Ductus deferens
 It is the continuity of epididymis having low mucosal folds
covered with non-ciliated pseudostratified columnar
epithelium
 From cranial epididymis toward ductus deferens the luminal
diameter increase gradually up-to three times and dense
connective tissue along with smooth muscles surround the
mucosa
 It runs towards cloaca for opening

11. PAPILLA
 The deferens ductus straitens towards cloaca
 Abruptly widens making receptacle a bean shaped structure
 It terminates into cloacal urodeum (on dorsal wall) as papilla
(copulatory organ), immediately below the opening of ureter

12. ACCESSORY ORGANS
 Accessory reproductive organs consist of
 Paracloacal vascular bodies
 lymphatic folds
 dorsal proctodeal gland
 They are integral part of cloaca
 Paracloacal vascular body lies alongside the receptacles
 Lymphatic folds are present in proctodium wall
 A non-intromittent phallus (used for sex identification) forms
tumescence of lymphatic folds that is seen everted immediately
after ejaculation
 And the lymph is formed inside vascular bodies by the
ultrafiltration of blood

13. ONTOGENY OF REPRODUCTIVE
ORGANS
 Pronephros, mesonephros and metanephros are the three pairs
of primary excretory organs formed after incubation
 Pronephros (wollifian duct) disappear after 4 days of
incubation
 Pronephros gives rise to mesonephros tubule, Mullarian duct,
connect mesonephros and cloaca and eventually persist as
deferent duct in males
 Gonads arise from germinal ridge of mesonephros
 Primary sex cords and rete cords are present in
undifferentiated gonad

14. ONTOGENY OF REPRODUCTIVE
ORGANS
 Gonadal differentiation takes place around 6.5-7 day of
incubation
 Progenitors of sertoli cells in sex cords are responsible for the
production of mullarian inhibiting substance (hormone) which
is responsible for regression of Mullarian ducts
 Acromatase is an enzyme responsible for conversion of
testosterone into estradiol, so it is the key factor for gonadal
differentiation and development of female phenotype

16. HORMONAL PROFILES AND
SPERMATOGENESIS

17. CONTINUE……
 The LC being dispersed between the tubules, produce several
androgens, primarily testosterone
 As sexual maturity approaches, production of testosterone is
stimulated by increased plasma concentrations of
gonadotrophins, especially, LH
 In mature males, blood levels of LH is maintained by the
following negative feedback loop :
 increased testosterone levels decreased secretion of
GnRH -, inhibits secretion of LH decreased concentration
of LH decreased concentration of androgens
increased secretion of GnRH --) increased secretion of
LH.

18. SEMEN PRODUCTION
 Number of sperms per gram of testes produced per day is
known as daily sperm production
 In case of gallus it is 80–120 million sperm per gram of testis
 This value denotes number of sperms released from
seminephrous epithelium to seminephrous tubule lumen per
day
 This phenomenon is known as spermiation
 Galliform sperms are 0.5–0.7 µm wide and 75–90 µm in length

19. SEMEN PRODUCTION
 Acrosome of sperm is conical, nucleus is moderately bent
cylindrical, and flagellum (84% of cell length) is surrounded by
helix having 25-30 mitochondrion
 Following spermiation sperms are suspended in seminephrus
fluid that results in formation of seminal plasma
 Male ejaculate 0.1-1 cc semen with 1.5-8x109 sperms in a single
mating

20. SEMEN
 Volume and concentration
 Number of SC and daily sperm production depend on testicular
size
 large-sized males will have larger testes and produce more semen
 Up to 87% of daily sperm may be collected by abdominal massage
method provided that the males are mating frequently or
ejaculated 5 times a week in artificial insemination (Al) program
 In the absence of ejaculation, spermatozoa from lower vas deferens
are reabsorbed
 Volume and concentration of sperms decrease if ejaculate is
collected frequently
 Color of semen will be pearly white with a pH of 7.0 to 7.2

21. VOLUME AND CONCENTRATION OF THE
SEMEN

22. NUMBER OF SPERMS VS NO OF EJACULATIONS

23. MOTILITY OF SPERMS AT DIFFERENT
REGIONS

24. TRANSPORT AND STORAGE
 Fluids from ST move SZ released into the lumen to RT
 Re-absorption of the fluids at RT and vasa efferentia resulting in
concentration of SZ which then pass through ED to vas deferens
(VD), reservoir of semen
 In Coturnix, sperm concentration is enhanced by 60 folds and
transport through excurrent ducts takes about 24 hr (several
days in chicken)
 Cells of RT and ED synthesize and secrete proteins which help
SZ to gain motility and fertilizability
 Release of fully formed SZ into lumen of ST is called as
spermiation.

25. CONTINUE….
 SZ can reach lower VD from ED in 24 hr and most of SZ in ED
would have been transported within 72 hr
 40-60% of SZ/semen is given out in the first ejaculate on
abdominal massage
 At ejaculation, semen from VD flows out, on contraction of well-
developed muscles in the lower region, through papillae into
urodeum, lymph-engorged lateral phallic folds of proctodeum
and to cloaca in that order; it exits with such a force that it
seldom touches cloaca

26. SECONDARY SEX GLANDS
 Domestic birds lack secondary sex glands
 Seminal fluid is derived entirely from testes and/or excurrent
ducts
 Lymphatic exudates may be added to the semen in case of
abdominal massage for collection of semen
 Chicken, turkeys and Japanese quails have a gland in the dorsal
proctodeum
 This gland can be considered an accessory sex gland in case of
Japanese quails

27. METABOLISM
 In vivo, fertilizing capacity of SZ lasts for 7 to 14 d whereas, in vitro, it
decreases within 15 min
 From testes up to ED, SZ do not receive energy nor dispatch waste directly
to blood stream.
 Cock can utilize glucose both aerobically and anaerobically
 Tom semen only aerobically
 Fowl SZ can utilize PL when glucose is not available; but it cannot
metabolize glutamate although it is available at high concentrations
 Therefore, glutamate is not an essential component in any semen diluent
 but it is beneficial as a preservative probably as an alternative for Cl- ions
 Seminal fluid is a poor reservoir of glucose and hence cannot cater to the
energy requirements of SZ
 If lymphatic fluid is present in semen (as in case of abdominal massage)

28. MATING/ ARTIFICIAL INSEMINATION
 Natural Mating
 Courtship
 Male
 Waltz (drops one wing and approaches the hen with short shuffling
side-steps)
 Tidbitting
 Cornerning
 Female

29. MATING
 Semen is ejaculated through the engorged phallic folds into
everted cloaca
 The male quickly retracts and slides off the female
 The female assumes a characteristic stance and in about 3 to 4
sec shakes vigorously while the male may circle and waltz
around the female
 Males prefer to mate with females having a phenotype
 In small flocks, females mate with the same male in the
absence of morphological differences in the male
 Courtship in case of turkeys is called strutting

30. ARTIFICIAL INSEMINATION
Advantages
 Less number of males
 Pedigree mating
 Unlimited number of single male matings
 Prefential mating
 Problems of trap nesting
 Pooled semen
 Old males (with good characteristics)
 Cage system
 Turkey & broiler breeders
 Male to female ratio in Muscovy ducks
 Sexually transmitted diseases

31. CONTINUE……
Disadvantages
 Labor consuming
 Chances of cross contamination
 Involves handling of birds

32. MATING
 Male chicken attempts to mate 10-30 times a day and 70%
mating is successful
 Male birds prefer to mate with pullets in the middle of social
order and may mate with the same hen many times in a day
 Competition, availability of female, social order, light,
temperature and many other factors effect courting behavior

33. SEMEN COLLECTION
 In chicken, turkeys, Guinea fowl, Pheasants and Quails, semen
collection can be done by abdominal massage method
 In case of Ducks and Geese, semen is usually collected by
intercepting the flow of semen during natural mating.

34. ABDOMINAL MASSAGE METHOD
 Semen can be collected from male chicken by massaging the
soft part under pelvic bone
 Papilla protrudes out and semen is gently milked out in a vial
 An experienced practitioner can collect semen from 145 birds
in an hour
 Semen collected at morning is more efficient because of
 Greater volume
 High sperm motility
 Concentration
 Semen is collected by aspiration into an ampoule containing
semen diluent at 15°C

35. CONTINUE…
 Advantages of using diluents are
a) prevents cold-shock to the SZ since the vial itself will be
cooler
b) diluents buffer the acidic products of metabolism of SZ and
c) volume of semen to be handled will be practical and
convenient commercially
 Since Avian SZ can metabolize glucose/fructose
 TES, BFS and PO4
- - act as buffers in the range of pH 6.8 to 7.5.
 Milk powder and albumen are added to help freezing

36. SEMEN EVALUATION
 Fertilizability of the SZ
 To fix dilution rate to ensure 108 sperms/Al.
 Color of semen must be white to pearly white; yellow (fecal
contamination) and brownish red (presence of RBCs) colors are not
acceptable
 Neat semen can be viewed under microscope for swirling mass of
cells sweeping across the field
 Volume is found to fix dilution rate later and if weigh of semen is
fund, density can be calculated as the ratio of weight to volume;
density of semen is expected to be 1 mg/µL
 Concentration can be assessed by automatic counters
(spermatocrit)
 Transmittance (spectrometric)
 Integrity of SZ can be estimated by staining technique

37. INSEMINATION DOSE
 Theoretically, 5 x 107 SZ appear to be sufficient; but, under
commercial conditions, 108 (chicken) to 2 x 108 (turkeys) SZ are
recommended
 5 to 20 AI can be done per collection
 Each male can yield semen 4 to 5 times/week
 40 to 200 hens can be inseminated over a week out of semen
from a cock

38. TIMING OF AI
 Timing of Al changes according to oviposition of the species
 In chicken, AI done at or within 2 hr after oviposition resulted in
20 to 40% fewer fertile eggs
 This is presumably because of fewer contractions of shell gland
and vagina
 High fertility can be expected for 7 d (chicken) and 14 d
(turkeys) after Al
 It is highly recommended to repeat AI after 5 d (chicken) or 7 d
(turkeys) to ensure high fertility
 Under commercial conditions, some poultry breeders do
perform AI twice a week.

39. PLACEMENT OF SEMEN
 Cloaca is everted by securing the bird and applying a gentle
pressure on the abdomen towards the vent;
 White Leghorns commonly evert the cloaca with little effort
whereas, broiler breeders may require training and careful
handling for satisfactory results
 Vaginal entry is exposed (constricted opening can be seen on
the left side of the bird)
 Al pipette is inserted to about 3 cm (chicken) or 6 cm (turkeys)
depth
 It is highly desirable that the Al is performed within 30 min of
collection of semen

40. IN VITRO STORAGE OF SEMEN
 Avian semen is more fragile than that of mammals
 Therefore, whenever AI is not possible to be completed within
30 min, in vitro storage becomes a necessity
 Semen can either be held in a liquid medium or be frozen; the
latter is not commercial because of fragility of Avian SZ (98 to
99% of SZ are Lost due to freezing and thawing) as well as cost
and availability of liquid nitrogen
 Liquid semen can be stored up to 48 hr with sufficient supply of
oxygen and glucose with sufficient buffering to maintain pH
and an ambient temperature of 5 to 7°C
 Hence, it is possible to hold diluted semen for 24 hr (turkeys) to
48 hr (chicken) at 5°C with minimum loss

41. CAPONIZATION
 Surgical removal of testes to castrate a male chickens resulting
the cockerel fail to develop
 certain male characteristics
 tends to lose them if they are developed
 Castration eliminate the production for male sex hormones
 capons are usually docile and quiet, and their head seem small
because comb and wattles cease growing after castration but
the feathers of hackle, tail and saddle grow unusually long

42. CAPONIZATION
 These males do not waste energy in courting behavior, fighting
and territorial protection
 Feed conversion ratio becomes better, fat deposition increases
and meat quality improves
 Capon meat has more fat, so this meat is more tender, juicier
and flavorful than that of intact male
 Caponization is usually done at two to four weeks of age
 Capons are marketed at the age of 15 to 18 weeks
 A good practitioner can caponize 200 birds per hour

43. FERTILITY IN CHICKENS
 Goal of a chicken breeder is to produce hatching eggs
 Flock fertility is dependent (the level of egg and semen production)
 Combined with the chickens' interest in and capability of mating
 Fertility decrease as the chickens get older
 For females, it is decline in fertility is due to
 faster release of sperm from the sperm storage tubules
 meaning that the hen cannot store sperm as long
 For males, it is presumed that although roosters continue to produce sperm
for many years, sperm quality declines and mating activity decreases as a
rooster ages
 Increase in early embryo deaths occurs when incubated eggs come from
chickens in the second half of their reproduction cycle. These early deaths
often appear as clears and may be mistaken for infertile eggs during
candling or breaking out of unhatched eggs.

44. REFERENCES
 Reece, W.O., 2005. Dukes Physiology of Domestic Animals, Panima
publishing corporation New Delhi,Banglore,India.
 Whittow, G.C., 2000. Sturkie’s Avian Physiology. 5th Edition.
Academic Press,NewYork,USA.
 Bell, D.D. and W.D. Weaver. 2007. Commercial Chicken Meat and
Egg Production.5th Edition.Springer (India) Private,Limited.
 Sreenivasaih, P.V. 2006. Scientific Poultry Production. 3rd Revised
Edition, International Book Distributing Company, Lucknow, India.
Pages,134-146.