- - AGRICULTURE CORE CURRICULUM - - (CLF3000) Advanced Core Cluster: ANIMAL SCIENCE (CLF3250) Unit Title: LIVESTOCK BREEDING AND GENETICS ____________________________________________________________________________ (CLF3259) Topic: GESTATION AND Time Year(s) PARTURITION 3 hours 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (D-15) - List the three stages of parturition, explain when each stage begins and ends, describe the proper fetus presentation, and list possible problems that may occur during delivery. (D-16) - Verbally outline the development of a prenatal farm animal from fertilization to birth using slides. (D-18) - List the gestation periods of the mare, cow, sow, ewe, and doe rabbit. (D-19) - Define the term freemartin and identify the problems that can occur with freemartins in bovine breeding programs (genetic level). Special Materials and Equipment: VEP Filmstrip, "Calving Management", a handout showing proper fetus presentation and problem situations (See Vo-Ag Curriculum Guidelines, "Anatomy and Physiology of Farm Animals"), slides showing embryo development, and Supplemental Handout #5 and Supplemental Worksheet #6. References: Ensminger, M.E. (1983). STOCKMAN'S HANDBOOK. Hafez, E.S. (1973). REPRODUCTION IN FARM ANIMALS. Ronning, Magnar and Cole, H.H. (1974). ANIMAL AGRICULTURE. LIVESTOCK BREEDING. (1977). Ohio Ag Ed Curriculum Materials Service. VOCATIONAL AGRICULTURE CURRICULUM GUIDELINES, Vol.1A "Anatomy and Physiology of Farm Animals". Evaluation: Quiz by instructor and completion of Supplemental Worksheet #6. TOPIC PRESENTATION: GESTATION AND PARTURITION A. Gestation is the term for length of pregnancy. __________________________________________________________ ACTIVITY: 1. Review and discuss Supplemental Handout #5. __________________________________________________________ B. Prenatal developmental stages in the calf 1. Fertilization - a. Usually occurs in the upper third of the fallopian tube (oviduct), and b. Occurs within 6-8 hours after the egg is shed. 2. Cleavage - a. Is when the fertilized cell (zygote) begins to divide. b. Occurs about 20 hours after fertilization. 3. Implantation - a. Usually occurs between day 4 to 12, depending on the species. b. The zygote or embryo forms a weak attachment to the uterine wall. 4. Amnion/Chorion development - a. Occurs when prenatal membranes form to develop the placenta. b. By day 18 to 21, the heart begins to beat in the new baby. 5. Differentiation - a. Body parts such as the head and limbs become discernable at 4-6 weeks. b. The embryo is now called a fetus. 6. Continued development - a. day 60 - eyes open and close b. day 100 - horn pits are visible c. day 110 - tooth development begins d. day 230 - hair development begins e. day 280 - birth __________________________________________________________ ACTIVITY: 1. Observe slides of fetal development or look at preserved samples. __________________________________________________________ C. Freemartins are sterile heifers born twin to a bull calves. 1. Occurrence - a. This condition prevails in about 90-95 percent of twin births, and b. when a calf of each sex is born. 2. Cause - a. The fetal circulations fuse, and the male hormones get into the circulation of the unborn female. b. They interfere with the normal development of the sex and modify the female embryo in the direction of the male. 3. Detection - a. At birth the animals appear normal and healthy. b. The freemartin heifer will continue to develop normally until puberty when she does not cycle. External genitalia may be abnormally small. c. Upon examination by a veterinarian, the vagina may be 1/3 the normal length. 4. Production practices - a. Only about 10-15 percent of heifers born twin to bull calves are fertile so it is best to assume they are sterile and to market them. b. For potentially very valuable animals, a blood test can be done at birth that will tell whether or not the female will be a freemartin. D. Parturition 1. This is the process of giving birth. 2. Before parturition: a. One week - mammary glands fill with milk, tailhead ligaments relax, and you will see a waxing of teats. b. 12-24 hours - frequent defecation and urination, anorexia, looking for young, makes a nest or seeks out an isolated area. This all depends on the species. 3. Stages of parturition: a. Stage 1 - preparatory stage - 1) characterized by dilation of the cervix, 2) rhythmic contractions of the uterus, and 3) at the end of this stage, the cervix expands, allowing the uterus and vagina to become a continuous canal. b. Stage 2 - expulsion of the fetus - 1) increase in contractions with abdominal pressing, 2) the placenta, along with the head and forelegs, are forced into the vagina (birth canal), and 3) the fetal extremities appear through the vulva. 4) In ruminants, the fetus is expelled while still attached to the fetal membranes so the fetus has oxygen from the mother, even if the birth is prolonged. 5) In swine and horses, the placental connections are broken soon after the first stage of parturition, so it is imperative that this second stage be fairly rapid or the fetus will suffocate. c. Stage 3 - expulsion of the placenta - 1) This process is associated with uterine contractions. 2) Normally, the placenta should be expelled within 12 hours following parturition. In cases of abortion, dystocia, premature birth, or twin births, the placenta may be retained and should be removed or treated by a vet. The following time periods are by when the placenta should be expelled. a) mare - one hour b) cow - 8-12 hours d. Stage 4 - period of rest. 3. Proper Presentation: a. Presentation depends on the species. However, the most common presentation is forelegs first with the nose resting on the forelegs. This is called an "anterior" presentation and means "head first". b. In swine, piglets may be born anteriorly or posteriorly (front or rear first). In small species, rear end delivery (backwards) is common, and is called breech presentation. 4. Dystocia: a. Is a general term for difficulty during parturition. b. Fetal dystocia problems - 1) Over-sized fetus - This may occur because a genetically large male was bred to a small or immature female. 2) Multiple births - Seen in both sheep and cattle where both fetuses may be presented at the same time. 3) Breech presentation - With sheep, cattle, and horses, the fetus is presented posteriorly. 4) Deviations in normal presentation - For example, one leg may be pushed back or the head may be turned. c. Maternal dystocia problems - 1) Narrowing of the birth canal due to fractures of the pelvis. 2) Uterine torsion reducing the size of the birth canal. 3) The cervix may fail to dilate. 4) Hypocalcemia may occur which is primary uterine inertia. 5) Absence of uterine contractions can occur in all species and may occur because the uterus is stretched due to a large litter or the uterine muscle in exhausted due to fetal dystocia. d. Questions to ask yourself regarding parturition: 1) What is the due date? 2) How long has the animal been trying to give birth? 3) Has the animal given birth before? 4) Have some offspring already been delivered? 5) Has anyone attempted to assist yet? e. At a certain point in time it is critical to answer these questions to decide whether to assist or call in a veterinarian. __________________________________________________________ ACTIVITY: 1. Observe the filmstrip "Calving Management" by VEP. 2. Complete Supplemental Handout #6 "Gestation and Parturition". __________________________________________________________ Supplemental Handout #5 GESTATION LENGTHS SPECIES GESTATION PERIOD ============================================================================ Range Average ____________________________________________________________________________ Cattle 274 - 294 days 283 days Sheep 144 - 152 days 148 days Swine 110 - 118 days 114 days Horses 310 - 370 days 336 days Rabbits 30 - 31 days 30 days ============================================================================ Supplemental Worksheet #6 GESTATION AND PARTURITION NAME___________________ DATE___________________ PER.___________________ 1. Describe the length of the estrous cycle and the breeding seasons for the mare, cow, ewe, and sow: ==================================================================== species | length of estrous cycle | breeding season __________|______________________________|__________________________ mare | | __________|______________________________|__________________________ cow | | __________|______________________________|__________________________ ewe | | __________|______________________________|__________________________ sow | | ==================================================================== 2. Give the average gestation lengths in months and days for the following: =================================================================== Species | Avg. Gestation Length (days) | (months) _____________|_____________________________________|_______________ cow | | _____________|_____________________________________|_______________ mare | | _____________|_____________________________________|_______________ sow | | _____________|_____________________________________|_______________ ewe | | ____________|_____________________________________|_______________ doe | | =================================================================== 3. Where does fertilization occur in the cow? 4. What do the following terms mean? Cleavage - Implantation - Differentiation - 5. What is a "freemartin"? 6. Why are they usually sterile? 7. What should be done with most freemartin heifers? 8. Describe, in detail, the 3 main stages of parturition (do not include the rest period): a. b. c. 9. Describe the proper fetal presentation of a calf: 10. What is dystocia? 11. Give 5 causes of dystocia: 5/2/90sg #%&C