ANIMAL SCIENCE 200 Introductory

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ANIMAL SCIENCE 200 Introductory Powered By Docstoc
					                              Reproduction

MOST ECONOMICALLY IMPORTANT
     TRAIT IN FARM ANIMAL
         PRODUCTION

 determines number of saleable animals
 determines number of replacement females
 initiates lactation
 determines number of eggs sold
                                   Reproduction
• reproductive efficiency
  = # animals born/100 breeding females
  = # pigs per litter; lambs/ewe; eggs/hen
          See table 11-1, page 215


          Reproduction terminology

SPECIES        MATURE FEMALE YOUNG FEMALE

Cattle                COW              HEIFER
Sheep                  EWE            EWE LAMB
Swine                  SOW              GILT
Horse                 MARE              FILLY
Birds                  HEN             PULLET;
                                     POULT;CHICK
          See table 11-1, page 215


          Reproduction terminology

SPECIES        MATURE MALE           CASTRATE MALE

Cattle                BULL              STEER
Sheep                  RAM             WETHER
Swine                 BOAR             BARROW
Horse              STALLION            GELDING
Birds           Rooster/cock/tom        CAPON
Figure 11–4: Female reproductive tract. [Source: (a) Bearden and Fuquay,
1997; (b) Texas A&M University. Used with permission.]
  Cow reproductive tract – see Figure 11-4a in text




University of Kentucky; AgriPedia
Sow reproductive tract
              Reproductive Organs
Oviduct
     a. Transport egg & sperm
     b. Site of fertilization
Uterus
     a. Transport of spermatozoa from cervix to oviduct
     b. Site of embryo attachment – nourishment
     c. produces hormone prostaglandin
         lyses (kills) a corpus luteum; restarts estrous
           cycle
                Reproductive Organs

Cervix
     a. Passageway for sperm & fetus
     b. Barrier between uterus & vagina; protects uterus
Vagina
     a. Copulatory (sexual union) organ
         a. Semen deposition (all livestock species?)
     b. Birth canal
  Ovaries

Follicles contain eggs
(oocyte/ova)
-produce estrogen,
induces heat/estrus


Corpus Luteum (CL)
forms from follicle
-produce progesterone
maintains pregnancy
  Estradiol and Progesterone during the Estrous Cycle




                               CL        Progesterone
  Ovulation                                              Ovulation



                             Follicles       Estradiol
               Uterus     Prostaglandin



               5                10                 15
Estrus                                                   Estrus
                   Days Relative to Estrus
                   See Figure 11-2 page 217
                     Estrous Cycle


   Estrus – period of time when female is sexually
    receptive to male (aka. heat)
      - Due to increased concentrations of estradiol
      - Signals approaching ovulation
   Estrous cycle – period of time from one estrus to the next



    ESTRUS = NOUN              ESTROUS=ADJECTIVE
             Reproductive characteristics
                       of female animals

Animal   Estrous cycle    Estrus        Time of        Gestation
         length (days)   duration      ovulation     length (days)
 Cow                                10-14 h after        281
             21           14 h      end of estrus
                                                        (9 mo)
 Sow                                18-60 h after        114
             21           60 h      estrus onset
                                                     (3mo,3wk,3 d)
 Mare                               24-48 h before       336
             21           6 d?       end of estrus
                                                        (11 mo)
 Ewe                                1 h before end       150
             16           30 h         of estrus
                                                        (5 mo)


            See table 11-1, page 208
    Terminology for giving birth – “Parturition”


•   Cattle – calve
•   Sheep – lamb
•   Swine – farrow
•   Horses – foal
•   Dogs – whelp
•   Cats – queen
•   Goats – kid
           Hormones of female reproduction



Hormone           Source          Function
estrogen          follicle        estrus; mating behavior
                                  uterine growth, mucus
progesterone      corpus luteum   maintain pregnancy
prostaglandin     uterus          kills corpus luteum
FSH               pituitary       follicle development
LH                pituitary       ovulation
                                  formation of CL
   LH and FSH During the Estrous Cycle
                                              LH




                          Progesterone




                  FSH




           5             10              15
Estrus         Days Relative to Estrus             Estrus
             The Estrous Cycle in Cattle
                                                     LH



                 1st    Progesterone               2nd
                 Wave                              Wave




                                       Estradiol
                FSH




         5              10                    15
Estrus       Days Relative to Estrus                      Estrus
     Avian
 Reproductive
Tract See Figure
     11-13




     Purdue University;
     Avian Sciences Net
               Reproduction in Poultry

• Female
  – Right ovary & oviduct fail to develop after
    hatching
  – ovulate starting at puberty starting at 20-25 weeks
  – 24+ hours from one ovulation to next
Chicken reproductive tract




                                        Oviduct


            Ovum
Ovary
             (University of Alberta & CBHEMA, 1999)
Chicken ovary




  (University of Alberta & CBHEMA, 1999)
   Oviduct:

   infundibulum – 30 min
   – egg pickup; sperm
   storage, fertilization
   magnum - 3 hrs
    – secretes albumen
   isthmus – 1.5 hrs
   – adds shell membranes
   Uterus – 18-20 hrs
    – shell formation

   New yolk is ovulated 30
   min after laying egg

   Purdue University; Avian Sciences Net



Fig 11-13 and 11-14 in book
Boar reproductive tract
                       Male reproduction
 Organs
  1. Gonads – testicles
         supported by scrotum (none in poultry)


     a. Temperature regulation in testes
         blood vessel system to exchange heat in blood
          – pampiniform plexus
         muscle to raise and lower testes – cremaster
          muscle
         muscles in scrotum contract and expand
Ram Reproductive Tract
                     Male reproduction
 Organs
  1. Testicles-cont.
     b. Produce gametes; spermatozoa
         spermatogenesis – process of production
          & development of male gametes
         occurs in seminiferous tubules
     c. Produce male sex hormones (androgens)
         testosterone by interstitial cells
 Cross – section of testes – Seminiferous Tubules
No figure in text
Spermatozoa
See Fig. 11-6
                                     Bull reproductive tract




 University of Kentucky; AgriPedia
    Organs
                             Male reproduction
    2. Epididymis
       Concentration, storage, maturation, & transport of
       spermatozoa
    3. Vas deferens – transport of spermatozoa from
       epididymis to urethra
    4. Urethra – common excretory duct for urine & semen
       (not present in birds)
    5. Accessory glands
        add fluid volume, nutrients, and buffers to semen
        sperm + accessory gland fluid = SEMEN
        3 Accessory glands:
           1 prostate gland
           2 seminal vesicles
           2 bulbourethral (Cowper’s) gland
                        Male reproduction
 Organs
  6. Penis – organ of copulation
      Types include:
     a. fibroelastic –
        - sigmoid flexure (S-shaped portion) straightens upon
        erection; allows for extension
        - bull, ram, boar
     b. vascular – increased blood flow causes
        engorgement/erection
        - stallion
Bull Reproductive Tract
                       Penis types

       FIBROELASTIC



BULL       BOAR




RAM         STALLION
                       VASCULAR
Semen characteristics of male animals
  Reproductive management tools

 Artificial insemination
  Why is AI used?
     1. maximize genetic improvement
        - greater access to superior genetics; individual
           matings
     2. reduce mating costs
     3. control reproductive diseases
     4. use of dead or injured sires
     5. Safety
Semen Collection in Males




• Electroejaculation
• Massage accessory glands
• Hand pressure (boars)
         Reproductive management
 Artificial insemination
  Species use of AI
     Dairy - 70% of all cows
     Poultry – 95% turkeys; difficult natural mating: chickens
                   use natural mating
     Swine – >80%
     Horses – increasing with greater use of extended semen
     Beef - < 10% of all cows, increasing
     Sheep – increasing but limited; flocks dispersed
                AI procedures in females
Sheep
-surgical or
   speculum

Swine
-corkscrew

Horses
- like cattle




                See Figure 11-9 in text – much better!
              Reproductive management
 Estrous synchronization – controlling estrous
      cycle so females express estrus around same time
  •    Reasons to use:
    1. with AI - decrease expense of time & labor for detection
    of estrus
    2. for success of embryo transfer
  •    Methods:
    1. hormonal – induce ovulation; restart estrous cycle;
      suppress estrus
    2. natural – weaning (sows & beef cattle)
             Reproductive management
    Embryo transfer (ET) – transferring fertilized
     embryos from one female to another
     How is ET used?
    1.   superovulate and inseminate donor cow
    2.   synchronize estrus of recipient females
    3.   flush embryos of donor and transfer to recipient or
         freeze
     Why is ET used?
          maximize use of superior genetics (females)
         - many offspring/female/year
Figure 11–7: Specific cleavage stages at given times after fertilization in the
cow (281-day gestation) and the sow (114-day gestation). (Source: Bearden and
Fuquay, 1997, p. 91. Used with permission.)
    Parturition
• Initiated by the fetus – stress
   – Corticosterone from Adrenal
   – Decreased progesterone

• Foals and lambs – like cattle

• Piglets – either way

• Oxytocin – contractions

• Relaxin – birth canal expansion

• Estrogen, Prostaglandin
                    Reproductive management
        Breeding Soundness Exams
          •     to determine physical ability of an animal to breed
          •     typically males
    •         Evaluates:
    1.      Physical attributes
          •    body condition, health,
    2.      Reproductive Anatomy
          •    testicle size; organ abnormalities (ie. penis)
    3.      Semen Quality
          •    semen color & volume; sperm concentration & abnormalities
    Reproductive management tools
    Artificial insemination
    Some keys to success are:
       1.   detection of estrus
            -   behavioral changes
            -   standing to be mounted; restless
       2.   proper timing of insemination
            -   viable sperm available at time of ovulation
            -   breed ~12 hours before ovulation
       3.   technician skill
            -   correct placement of semen in reproductive tract
            -   cervix

				
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