Equine Science & Technology. Unit Title: Horse Reproduction and Parturition CIP:

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1 Equine Science & Technology Unit Title: Horse Reproduction and Parturition CIP: Instructor: Objectives: After completing this unit of instruction, students will be able to: A. Describe the physiology of the reproduction tracts of stallions and mares; B. Summarize the estrus cycle and proper times to breed; C. Describe proper horse gestation management; D. Explore equine reproductive technology; Artificial insemination Embryo transfer Cloning E. Discuss proper care during pregnancy and parturition; and F. Describe the horse condition scoring system. Click here for this lesson s PowerPoint presentation Equine Science & Technology Lesson Plan Library Page 1 of 11

2 Interest approach: Ask students to name a part on a car. Ask students to briefly explain each parts function in the operation of the car. Then ask students Why is it important for a car mechanic to be able to identify and know the function of these parts? After a brief discussion, ask students Is it important for a livestock producer to know the parts of an animal? If so, why? Curriculum & Instruction Curriculum A. Describe the physiology of the reproduction tracts of stallions and mares. Reproductive organs of the stallion The primary sex organ of the stallion is the testicle, of which there are two. The testicles produce (1) sperm and a hormone called testosterone, which regulates and maintains the male reproductive tract, and is responsible for the masculine appearance and behavior of the stallion. Sperm production takes place within the testicles in the seminiferous tubules-a mass of minute, coiled tubules, the inner wall or surface of which produces the sperm. These tubules merge into a series of larger ducts, which carry the sperm to a coiled tube called the epididymis. The epididymis is the place where the sperm are stored and where they mature. The testicles and epididymis are enclosed in the scrotum, the chief function of which is thermo-regulatory- to maintain the testicles temperatures several degrees cooler than the body proper. From the epididymis the sperm move through a tube, the vas deferens, into the urethra. The urethra has a dual role; it carries (1) urine from the bladder through the penis and (2) sperm from the junction with the vas deferens to the end of the penis. Along the urethra are the accessory sex glands- the prostate, the vesicular glands (seminal vesicles), and the bulbourethral (Cowper s) glands. Their fluids nourish and preserve the sperm and provide a medium for its transport. The combined sperm and fluid is called semen. Instruction PowerPoint presentation: 09 Horse Reproduction & Parturition.ppt A1. Lecture and discussion. A2. Write the bolded terms on the board to the side. As terms are brought up in the lecture, write the definitions next to each. Equine Science & Technology Lesson Plan Library Page 2 of 11

3 Reproductive organs of the mare The primary sex organ of the mare is the ovary, of which there are two. The ovaries are bean-shaped organs, 2 to 3 in. long that produce eggs. Each egg is contained in a bubble-like sack called a follicle. There are hundreds of follicles on every ovary. When the follicle is about 1 in. in diameter a hormone causes it to rupture and discharge the egg. This process is known as ovulation. The egg is then trapped in a funnel-shaped membrane called the infundibulum, which surrounds the ovary. The infundibulum narrows into a tube called the oviduct. The oviduct then carries the egg to the uterus, or womb, the largest of the female reproductive organs. There the unborn young (the fetus) will develop. B. Summarize the estrus cycle and proper times to breed. Fillies generally start a heat cycle when 12 to 15 months. The mare is seasonally polyestrous. This means that she typically has multiple estrous cycles only during a certain time of year. During the anestrous (nonovulatory) period, most mares show no behavioral signs of sexual receptivity (estrus) and fail to develop follicles that ovulate. In the Northern Hemisphere, the anestrous period of the mare occurs most frequently during the winter (mid- November to mid-february). During the ovulatory season, the mare undergoes a series of cycles, each of which is approximately 21 days in length, with some shorter and others longer. The estrus cycle is divided into two physiological parts: estrus and diestrus. Estrus refers to the time the mare is in heat and sexually receptive to the stallion. Diestrus refers to the longest period (15 to 19 days) of the estrous cycle; it is the time the mare is not receptive to the stallion. Mares do not always follow a cycle, they can be erratic. Estrus usually lasts 3 to 7 days. Ovulation generally occurs 24 to 36 hours prior to the end of estrus. The hormones produced by the hypothalamus, anterior pituitary, and ovaries are responsible for both the release of the egg and the behavioral signs of estrus. Estrogen- the primary hormone responsible for causing the characteristic changes that occur in the mare s genital tract. B1. Lecture with discussion. Equine Science & Technology Lesson Plan Library Page 3 of 11

4 Leutenizing hormone (LH) This is the primary hormone responsible for ovulation. It is highest at ovulation. Progesterone- This hormone, which is produced in the corpus luteum, is primarily responsible for the recognition and maintenance of pregnancy. Ovulation occurs in response to increased levels of LH. If the mare is not pregnant, the corpus luteum (CL) begins to regress in response to prostaglandin. Progesterone levels decrease when the CL regresses. About the same time, FSH levels increase causing follicular growth in preparation for ovulation during the following estrus. Mares are long-day breeders, and thus the percentage of ovulating mares increases significantly as the daily photoperiod increases above the 12-hour vernal equinox. Generally, the maximum number of naturally occurring mares occurs during the maximum daylight periods of June. C. Describe proper horse gestation management. The average gestation period of mares is 340 days, or a little more than 11 months. Care of the pregnant mare Pregnant mares are often housed separately from other horses. Pregnant mares should be closely monitored for any signs of sickness or possible abortion. Mares should receive routine health care, including worming, vaccinations, and care of the teeth and feet. Which vaccinations are given depends on the farm and location and should be determined after consultation with a local veterinarian. Approximately ten days before the foal is to be expected arrangements for the place of foaling should be completed. During the spring, summer, and fall months when the weather is warm, the most natural and ideal place for foaling is a clean, open pasture away from other livestock. C1. Compare the gestation periods of various agricultural animals. C2. Why are some gestations longer than others? C3. Note the relationships between market cycles and gestation periods. Market cycles: Poultry Months Swine 3 years Cattle 8 to 10 years It takes longer for markets to adjust according to the time to reproduce a herd. Equine Science & Technology Lesson Plan Library Page 4 of 11

5 D. Explore equine reproductive technology. Artificial Insemination Artificial Insemination (AI) is less widely practiced in horses than in dairy cattle. AI permits more mares to be bred to a stallion, makes for a higher conception rate, lessens the hazard of transmitting an infection or a disease, and lessens the risk of injury to the stallion or the mare. D1. Allow the class to share information about technology being used in their agricultural homes & businesses. Kinds of Processed Semen Three kinds of processed semen are used in horses: Fresh semen-fresh semen is collected, and an extender is usually added. The semen may be stored in a refrigerator at about 55 F and used within 24 hours. Cooled Semen-Cooled semen is slowly cooled from body temperature down to 41 F. Cooled semen is usually viable for 24 to 72 hours, depending on the stallion. Frozen semen-following collection, an extender is added to semen that is to be frozen. The semen can be stored indefinitely. The drawback is that pregnancy rates in horses using frozen semen are only approximately 35 %. Embryo Transfer An embryo can be nonsurgically removed from the uterus of one mare, transferred, and inserted into the uterus of another mare. Embryo transfer allows reproduction by older, less fertile mares, reproduction by two-year-old mares, and increased production of foals from genetically superior mares. This method is very expensive, and the yield is not high. Cloning A cell, group of cells, or organism descended from and genetically identical to a single common ancestor. In cloning, a cell is propagated from a host cell. Equine Science & Technology Lesson Plan Library Page 5 of 11

6 E. Discuss proper care during pregnancy and parturition. When rendering assistance to a mare that is about to foal the following precautions should be followed: Cleanliness Quietness Gentleness Perseverance Knowledge, skill, and experience If foaling has been normal, the attendant should enter the stall to make certain that the foal is breathing and that the membranes have been removed from its mouth and nostrils. E1. Parturition The act or process of giving birth F. Describe the horse condition scoring system. Condition score is a method used to quantify the amount of subcutaneous fat cover. If a mare is not in acceptable condition, her diet must be changed to move her in the direction of a five score. Thin mares must gain weight since poor nutrition causes mares not to cycle normally. F1. Horse Condition Scores: A scale of 1 to 9 with 1 Poor/thin 9 Extremely fat Refer to Table 1 Equine Science & Technology Lesson Plan Library Page 6 of 11

7 Review & Evaluation Objectives will be reviewed before examinations. Exams will be developed based on objectives as taught in class. Instructional Support A. References Ensminger, M. E. (2004). Equine Science (8 th ed.). Upper Saddle River, N.J: Prentice Hall B. Teaching Aids and Equipment - Overhead projector - Board with chalk/marker C. Facilities - Room Equine Science & Technology Lesson Plan Library Page 7 of 11

8 Score TABLE 1: Description of individual condition scores Description 1. Poor Animal extremely emaciated. Spinous processes, ribs, tailhead, tuber coxae and ischii projecting prominently. Bone structure of withers, shoulders and neck easily noticeable. No fatty tissue can be felt 2. Very thin Animal emaciated. Slight fat covering over base of spinous processes, transverse processes of lumbar vertebrae feel rounded. Spinous processes, ribs, tailhead, tuber coxae and ischii prominent. Withers, shoulders and neck structures faintly discernable 3. Thin Fat build up about halfway on spinous processes, transverse processes cannot be felt. Slight fat cover over ribs. Spinous processes and ribs easily discernable. Tailhead prominent, but individual vertebrae cannot be visually identified. Tuber coxae appear rounded, but easily discernable. Tuber ischii not distinguishable. Withers, shoulders and neck accentuated 4. Moderately thin Negative crease along back. Faint outline of nbs thin discernable. Tailhead prominence depends on con formation, fat can be felt around it. Tuber coxae not discernable. Withers, shoulders and neck not obviously thin 5. Moderate Back level. Ribs cannot be visually distinguished but can be easily felt. Fat around tailhead beginning to feel spongy. Withers appear rounded over spinous processes. Shoulders and neck blend smoothly into body 6. Moderately fleshy May have slight crease down back. Fat over ribs fleshy feels spongy. Fat around tailhead feels soft. Fat beginning to be deposited along the side of the withers, behind the shoulders and along the sides of the neck 7. Fleshy May have crease down back. Individual ribs can be felt, but noticeable filling between ribs with fat. Fat around tailhead is soft. Fat deposited along withers, behind shoulders and along the neck 8. Fat Crease down back. Difficult to feel ribs. Fat around tailhead very soft. Area along withers filled with fat. Area behind shoulder filled with fat. Noticeable thickening of neck. Fat deposited along inner thighs 9. Extremely fat Obvious crease down back. Patchy fat appearing over ribs. Bulging fat around tailhead, along withers, behind shoulders and along neck. Fat along inner thighs may rub together. Flank filled with fat Information found at Equine Science & Technology Lesson Plan Library Page 8 of 11

9 Name Date Multiple Choice. Circle the correct answer. Equine Science and Technology Horse Reproduction Quiz 1. All of the following are kinds of semen used in artificial insemination EXCEPT A. Boiled semen B. Cooled semen C. Fresh semen D. Frozen semen 2. What is the process of recovering a fertilized egg from the uterus of one mare and transferring it to the uterus of another for gestation? A. Artificial insemination B. Cloning C. Embryo transfer D. Estrus manipulation 3. What is the method used to quantify the amount of subcutaneous fat cover? A. Condition score B. Conformation formula C. Edward s formula D. Skin palpation 4. The average gestation period of mares is A. 175 days B. 260 days C. 340 days D. 380 days 5. The primary sex organ of the stallion is the A. Epididymis B. Gonad C. Sperm D. Testicle Equine Science & Technology Lesson Plan Library Page 9 of 11

10 6. What is the primary sex organ of the mare? A. Egg B. Estrus C. Follicle D. Ovary Matching. Write the correct letter of the term next to the description. The term may be used once, more than once, or not at all. Description 7. Each egg is contained in a bubble-like sack called a(n). 8. Fillies generally start coming into heat when they are months of age. 9. Refers to the time the mare is in heat and sexually receptive to the stallion. 10. Rupture of the follicle and discharge of the egg is known as. 11. This term is when the mare has multiple estrous cycles during the year. 12. The primary hormone responsible for ovulation. 13. The testicles produce this hormone. 14. The three kinds of semen used in horses cooled, frozen and. Item A. 12 to 15 B. 18 to 20 C. Anestrous D. Diestrus E. Estrus F. Follicle G. Fresh H. Leutenizing I. Ovary J. Ovulation K. Polyestrous L. Testosterone Equine Science & Technology Lesson Plan Library Page 10 of 11

11 Equine Science and Technology Horse Reproduction Key Multiple Choice 1. A 2. C 3. A 4. C 5. D 6. D Matching 7. F 8. A 9. E 10. J 11. K 12. H 13. L 14. G Equine Science & Technology Lesson Plan Library Page 11 of 11