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Unit 2: Reproduction & Insemination
Chapters 10 & 11
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Objectives Identify and explain the functions of the male and female reproductive anatomy Knowledge of hormone function and its affect on reproductive success Understanding of the process of parturition Describe the process of semen collection and processing Influence of AI on the livestock industries Knowledge of the use of embryo transfer and its place in reproductive management
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Female Organs of Reproduction & their Function
Ovary Produces the ova & female sex hormones (estrogen & progesterone) Folliculogenesis Each follicle contains an ovum Development starts from deep within the ovary with primordial follicles As a follicle develops, it produces more estrogen, which continues its maturation
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Female Organs of Reproduction & their Function
Each follicle goes through stages of recruitment, selection, and dominance. As a follicle develops it can become: Primary Secondary Tertiary Graafian Degenerative (atresia)
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Female Organs of Reproduction & their Function
Only the Graafian follicle can be ovulated Ovulation occurs when the follicle ruptures, releasing the ovum After ovulation, follicular cells form the Corpus Luteum The Corpus Luteum “yellow body” or callous on the ovary Produces progesterone (maintains pregnancy) m_curr/histology/fr/HiFRp09.htm
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Female Organs of Reproduction & their Function
The Oviduct Collects the ovulated ovum in the Infundibulum which guides the egg into the oviduct The site of fertilization A fertilized embryo migrates to the uterus within 3- 5 d Uterus Embryo attaches to the uterine wall to begin development Some attach in the uterine horn (sow), others in the uterine body (cow/mare) Guarded by the cervix (gatekeeper)
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Female Organs of Reproduction & their Function
The Vagina The “passageway” to the reproductive tract Female organ of copulation Environment changes depending on the stage of reproductive cycle Also include the urethra
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Figure 10. 1 Reproductive organs of the cow
Figure Reproductive organs of the cow. Source: Colorado State University.
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Figure A dorsal view of the reproductive organs of the cow and the sow. The most noticeable difference is the longer uterine horns of the sow compared to the cow. Source: Colorado State University.
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Figure 10.3 Reproductive tract of the mare. Source: Sean Field.
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Figure 10. 4 Bull sperm and cow egg magnified 300
Figure Bull sperm and cow egg magnified 300. The ovum is about 1/200 in. in diameter, while the sperm is 1/6000 in. in diameter. Each is a single cell and contains half the chromosome number typical of other body cells. Courtesy of Colorado State University.
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Figure The large structure outlined with a circle of dark cells, is a follicle located on a cow’s ovary (magnified 265). The smaller circle, near the center, is the egg. The large light gray is the fluid that fills the follicle. When the follicle ruptures, the egg will move into the oviduct by anatomical action of the infundibulum. Courtesy of Colorado State University.
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Figure A cross section of the bovine ovary showing how a follicle develops of full size and than ruptures, allowing the egg to escape. The follicle then becomes a “yellow body” (corpus luteum), which is actually orange in cattle. The corpus luteum degenerates in time and disappears. Of course, many follicles cease development, stop growing, and disappear without ever reaching the mature stage. Source: J. F. Bone, Animal Anatomy and Physiology 4th ed., (Corvallis: Oregon State University Book Stores © 1975).
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Male Reproductive Organs
Testicles Suspended from the body Produce testosterone Leydig or Interstitial cells Site of spermatogenesis Sperm begin development within the seminiferous tubules
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Male Reproductive Organs
The Epididymis Stores sperm for maturation Acquire the potential for fertilization Most mature spermatozoa are nearest the Vas Deferens, while least mature are nearer the testicles Some degenerate and are reabsorbed
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Male Reproductive Organs
Vas Deferens Transport tube for sperm from epididymis to urethra. Spermatozoa are stored in the ampulla of the V.D. until the time of ejaculation Some species deposit sperm very quickly, and some slowly (8-12 min.) Bull, horse, ram Boar, dog
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Male Reproductive Organs
Urethra Canal extending from the bladder through the pelvis to the end of the penis Carries both urinary waste and sperm The Penis Male organ of copulation Virtually every species is different in form and function
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Figure 10.9 Reproductive organs of the bull.
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Figure 10. 11 A diagrammatic sketch of the structure of bull sperm
Figure A diagrammatic sketch of the structure of bull sperm. Source: Dr. Arthur S. H. Wu, Oregon State University.
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Figure Bull spermatozoa (magnified 12,000) viewed with the scanning electron microscope showing the depth of the sperm head covered by the raised acrosome. Courtesy of Oregon State University.
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Figure A cross section through the seminiferous tubules of the bovine testis (magnified 240). The tubule in the lower right-hand corner demonstrates the more advanced stages of spermatogenesis as the spermatids are formed near the lumen (opening) of the tubule. Courtesy of Colorado State University.
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Male Hormone Function Hormones stimulated and produced from the Anterior Pituitary of the brain Luteinizing Hormone (LH)-causes Leydig cells to produce testosterone Follicle-Stimulating Hormone (FSH)-stimulates the seminiferous tubules to nourish developing spermatozoa Hormone function can be influenced by photoperiod (day length)
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Female Hormone Function
Originate in the Hypothalamus and the Anterior Pituitary Gonadotropin Releasing Hormone LH FSH Some Hormones also released from the female reproductive organs Estrogen-follicle Progesterone-CL Prostaglandin-uterus
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Female Hormone Function
All these activities make up the estrous cycle Estrous cycles range from 14-29d and can last anywhere from 12 hrs. to 9d Hormone function can be altered or stimulated with hormone therapy treatments
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Figure 10.15 Events and hormone changes during the estrous cycle of the cow.
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Pregnancy Onset of gestation following fertilization
Embryonic cell division every 20 hrs. The period of attachment in the uterus is critical (20-30d cattle, 14-21d swine)-if no attachment-embryonic death occurs Embryonic stage ends around 45d after period of formation of major organs Fetal stage from 46d to birth
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Figure A bovine embryo in the six-cell stage of development (magnified 620). Courtesy of Colorado State University.
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Parturition Placenta is responsible for protecting the fetus and exchanging nutrients and waste with the mother Birthing is initiated with the release of cortisol Cortisol release causes progesterone to decrease and estrogen, PGF2a, and oxytocin to spike initiating uterine contractions Relaxin also released from the CL-stimulates the pelvis
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Figure 10. 18 Parturition in the mare
Figure Parturition in the mare. (A) The water bag (a fluid-filled bag) becomes visible. (B) The head and front legs of the foal appear. (C) The foal is forced out by the uterine contractions of the mare. (D) In a few moments, the mare is licking the foal to increase circulation and stimulate the newborn. Source: Colorado State University.
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Figure Normal and some abnormal presentations of the calf at parturition. Source: R. A. Battaglia and V. B. Mayrose, Handbook of Livestock Management Techniques (New York: Macmillan, 1981), pp. 131, 134, 135.
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Figure Live offspring are born to each breeding female in the herd or flock when the intricate mechanisms of reproduction function properly. (A) Beef cow and calf. Courtesy of the American Hereford Association. (B) Ewe and lambs.Courtesy of Colorado State University. (C) Nursing pigs. Courtesy of National Swine Registry. (D) Chicks starting on feed. Courtesy of Big Dutchman, Inc.
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Artificial Insemination
What has it done for the livestock industry? How does it fit? What are the drawbacks? Is it prominent in all of animal agriculture? First recorded in dogs in 1780, cattle & horses in the early 1900’s Can increase the number of offspring from one male Bulls – females/yr natural, units/wk for AI (avg. 1 calf/1.5 units semen) Success of AI dependent on success of estrus detection, quality semen, semen handling, high fertility
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Artificial Insemination
Semen Collection & Processing Collection of semen w/ and artificial vagina Male mounts a female in estrus, or trained to mount an object May also collect semen manually (boar, dog), or by electroejaculation Collection timing Bulls – 2x/d, 2d/wk Boars – every other day Shortening or extending the schedule may decrease number of sperm/ejaculate
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Figure 11. 1 Longitudinal section of an artificial vagina
Figure Longitudinal section of an artificial vagina. Source: Colorado State University.
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Figure 11. 3 Collecting semen from a bull using an artificial vagina
Figure Collecting semen from a bull using an artificial vagina. Courtesy of Select Sires, Inc.
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Artificial Insemination
Evaluated for: Volume, sperm concentration, motility, abnormalities Mixed w/ an extender to dilute for more volume (milk, egg yolk, buffer) 1 unit of cattle semen should contain 10m normal, motile spermatozoa Can be stored and used fresh for only hrs.
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Figure 11. 4 (A) Normal bull semen. (B) Normal stallion semen
Figure (A) Normal bull semen. (B) Normal stallion semen. Courtesy of Colorado State University.
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Artificial Insemination
Freezing semen What is it frozen in? Bull semen – can be frozen and stored for indefinite time without loss of fertility Boars, stallions, rams – only modest success w/ frozen semen Inseminating the Female Conception rates depend on: Estrus detection, properly managed semen, timing of insemination, insemination techniques, avoiding stress
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Figure Bovine semen is typically packaged in plastic straws and then stored in liquid nitrogen. The bull’s name, registration number, and inventory code are usually printed on each straw to ensure accurate identification of semen during breeding season
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Figure 11. 6 Artificial insemination of the cow
Figure Artificial insemination of the cow. Note that the insemination tube has been manipulated through the cervix. The inseminator’s forefinger is used to determine when the insemination rod has entered into the uterus. Source: Colorado State University.
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Artificial Insemination
Estrus Detection Signals time of ovulation, timing of insemination What is the best indicator? What are some other indicators of estrus? What are some technologies that might be used to detect estrus? What strategies might we use to detect estrus? Timing of Insemination Duration of estrus and timing of insemination varies w/ species Exhibition of estrus doesn’t necessarily include ovulation Sows at 3-5d after farrowing
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Estrous Synchronization
Why use estrous synchronization? Where is it the most appropriate and cost effective? Prostaglandins Causes regression of a CL Cows will be in estrus ~3d after injection Only effective in the presence of a functional CL Heifers/cows must be in d 5 – 18 of estrous cycle
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Estrous Synchronization
One-injection system Observe heats for first 5d of breeding season and AI all that exhibit heat Inject those not exhibiting heat on day 6 All animals bred by day 11 Can increase P.R. from 30-40% to 50-60% Two-injection system Inject all cows at day 1 and day 14 All cows should exhibit estrus by day 19, or breed hrs. after second shot Can be a good tool in well-managed herds What is a major risk w/ using Prostaglandin?
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Estrous Synchronization
MGA & Prostaglandin MGA – feed additive that suppresses estrus in heifers Feed MGA for 14d, give Prostaglandin 19d after last MGA feeding Most heifers should show estrus in hrs Conception rate may be >80% Select-Synch Injection of GnRH 7d following Prostaglandin Heat detect hrs to 5d after injection Should have ~70% exhibit estrus
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Estrous Synchronization
Co-Synch GnRH on day 0, Prostaglandin on day 7, second GnRH on day 9 and breed Initiates ovulation May not exhibit estrus CIDR-B Use of intravaginal progesterone implant for 7d Inject prostaglandin on day 6 Breed upon estrus detection from days 3-6 after injection
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Estrous Synchronization
PG 600 Pregnant mare serum gonadotropin Enhances fertility efficiency in swine Helps lower days returning to estrus after farrowing, schedule breeding Natural estrus synchronization Most females will suppress estrous while nursing young Removal of calf/piglet will help bring the cow into heat
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Figure The MGA-prostaglandin (PGF2a) system for synchronizing estrus. Source: Colorado State University.
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Embryo Transfer What is ET? Why use ET? Can be costly - ~$1000/hd
Superovulation Increase the number of ovulated ova May increase the number of harvested embryos How is ET performed? What components are essential?
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Figure Ten Holstein embryo transfer calves resulting from one superovulation and transfer from the Holstein cow in the background. The 10 recipient cows are shown on the left-hand side of the fence. Courtesy of Colorado State University.
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Sexed Semen What are the advantages/disadvantages?
Reliability of 85-90%
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