Reproduction in Farm Animals PDF
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Summary
This document provides a comprehensive overview of reproduction in farm animals, focusing on female physiology. It details the anatomy of various reproductive organs, hormonal control mechanisms, and different types of reproductive cycles. The document also discusses pregnancy, parturition, and management strategies.
Full Transcript
REPRODUCTION Chapter 10 Why talk about reproduction? ◦2x more important than carcass performance and growth on economic returns ◦Efficiency of reproduction measured by: ◦ Number of calves ◦ Lambs per 100 breeding females ◦ Number of pigs per litter ◦Need to understand the process of creati...
REPRODUCTION Chapter 10 Why talk about reproduction? ◦2x more important than carcass performance and growth on economic returns ◦Efficiency of reproduction measured by: ◦ Number of calves ◦ Lambs per 100 breeding females ◦ Number of pigs per litter ◦Need to understand the process of creating new life to try and reach optimal reproductive rates ANATOMY Repro Organs - Female ◦ Ovaries – pair of structures, suspended by ligament ◦ Oviducts (Fallopian tubes) – open ended tubes that lead to uterus ◦ Uterus – has two uterine horns that merge in lower part to form uterine body ◦ Cervix – gate between uterus and vagina ◦ Vagina – where cervix opens to external structures, urinary bladder empties here Ovaries ◦Primary Functions: 1. Produce ova (eggs) 2. Produce hormones: ◦ Estrogen – produced by follicles ◦ Progesterone – produced by Corpus Luteum Ovaries ◦ Follicles: found on the ovary; where the egg develops ◦ Graafian Follicle: Mature follicle ◦ Estrogen: produced by the Graafian Follicle ◦ Ovulation: Graafian follicles rupture and release egg ◦ Corpus luteum (CL): found on the ovary; After ovulation, follicle becomes a corpus luteum ◦ Progesterone: produced by the corpus luteum ◦ Progesterone – maintains pregnancy! Oviducts ◦Infundibulum: “Catchers mitt” ◦ Guide the egg into the oviduct ◦Sperm are transported to the oviduct after female is inseminated ◦Oviduct: where the magic happens, Location where egg and sperm meet to fertilize egg ◦Several days after fertilization, embryo passes to uterus for attachment to lining Uterus ◦ “Womb” ◦ Varies in shape between species ◦ Sow: long, slender horns ◦ Mare: short horns and large uterine body ◦ Cow: large uterine horns, small uterine body ◦ Each surviving embryo develops to fetus and remains in uterus until parturition (birth) Cervix ◦Cervix: Gates to the uterus ◦Posterior outlet between uterus and vagina ◦Cervix undergoes changes during estrus and parturition Vagina ◦Vagina: ◦ Organ of copulation in females ◦ Birth canal at parturition ◦ Dual passage role for urinary and reproductive systems Reproduction in Poultry Females ◦Hen differs greatly from other farm animals: ◦ Young are not suckled (no milk production) ◦ Egg is laid outside the body ◦ No well defined estrous cycles or pregnancy Hen Repro Anatomy ◦ Hatched with two ovaries and oviducts ◦ BUT right ovary and oviduct do not develop ◦ Mature hen only has left ovary and oviduct ◦ Ovary appears as cluster of yolks in front of left kidney ◦ Oviduct is long glandular tube leading from ovary to cloaca (common opening for reproductive and GI tract) Egg production in hen ◦ Hen’s oviduct is divided into five sections: 1. Infundibulum – receives yolk 2. Magnum – secretes thick albumen, or white of egg 3. Isthmus – adds shell membrane 4. Uterus (shell gland) – secretes thin white albumen, shell and shell pigments 5. Vagina Hen reproduction ◦ Entire time from ovulation to laying is 24 hours! ◦ 30 minutes after laying egg, another yolk is released ◦ After fertilized, egg is incubated for 21 days, chick is hatched ◦ Egg supports chick during incubation and for 3-4 days after hatching HORMONES AND CYCLES Hormonal Control of Ovarian Function ◦Hypothalamus and anterior pituitary (AP) – Releases hormones that control the cycling nature of sexually mature females Hormonal control of ovarian function ◦ Hypothalamus ◦ Releases GnRH - gonadotropin releasing hormone ◦ GnRH goes to the AP ◦ Anterior Pituitary ◦ Release FSH (follicle stimulating hormone) ◦ FSH stimulates follicle development ◦ Release LH (luteinzing hormone) ◦ A surge of LH then causes ovulation ◦ Follicles mature, estrogen(estradiol) is released from ovary which stimulates GnRH and sexual behavior of female Estrous Cycle ◦ Estrous cycle: Pattern of predictable reproductive events in female farm animals ◦ Cycle starts with expression of heat (estrus) and concludes at the following estrus (assuming she does not become pregnant) ◦ Three main types of cycles: ◦ Polyestrus – cycle all throughout the year (cattle and swine) ◦ Seasonally polyestrus – cycle seasonally, triggered by day light length (sheep, goat, horse) ◦ Can be manipulated by artificial sun light and melatonin ◦ Monoestrus – single cycle (dog) Estrous cycle ◦ FSH responsible for increase in size of ovarian follicle which in turn produces estrogen ◦ Estrus or heat is the period of time when a female will accept the male for breeding (due to estrogen) ◦ Ovulation occurs after estrus behavior has stopped (follicle ruptures due to LH surge) ◦ LH also triggers luteal cells (corpus luteum-site of ovulation) to start producing progesterone Pregnant or Not ◦If Pregnant – Corpus luteum continues to make progesterone ◦If Not Pregnant – uterus releases PGF2a (prostaglandin) to shrink CL, which drops progesterone levels and starts another cycle PREGNANCY Pregnancy ◦When fertilization occurs, begins gestation period (pregnancy) ◦Fertilized egg begins series of divisions ◦Maternal recognition of pregnancy signals presence of embryo and attachment begins ◦Placentation - Formation of placenta occurs with maternal recognition Pregnancy ◦ Placenta is temporary organ for connection between dam and fetus ◦ Allows transfer of nutrients, waste and produces hormones ◦ There are four types of placental attachment: ◦ Diffuse: cover whole surface - sows and mare ◦ Cotyledonary:– placentomes “buttons” on surface - cows, ewes and does ◦ Zonary: band of attachment - dogs and cats ◦ Discoid: disc-like structure of attachment - primates and rats Gestation Lengths ◦Gestation length = length of pregnancy ◦ Mare : 336 days ◦ Humans: 253-303 days ◦ Cow: 285 days ◦ Does: 150 days ◦ Ewe: 147 days ◦ Sow: 114 days Parturition ◦The end of pregnancy ◦Initiated by cortisol release from fetus (baby starts it!) ◦Three phases: 1. Preparation 2. Expulsion 3. Passing after birth 1. Preparation ◦12 to 24 hours ◦Moves away from the herd ◦Start of contractions ◦Cervix dilates ◦Fetus gets in position ◦Mucous discharge 2. Expulsion of the Fetus ◦ Rupture of the membranes (water breaking) ◦ Fetus is expelled ◦ Normal position – Superman or diving ◦ Abnormal positions or large fetuses lead to dystocia (difficult birth) ◦ “Normal timing” – varies greatly ◦ 45-60 minutes from water breaking to delivery ◦ Front legs visible should be 30-45 minutes ◦ Subsequent offspring within 30-45 minutes Problems…… 3. Passing Placenta ◦Placenta is expelled from the body ◦Uterine involution (Uterus returns to normal size) ◦ Takes more than a month Reproduction management ◦Producers can manage for high reproductive rates: ◦ Selection of superior animals for breeding ◦ Adequate nutrition ◦ Paying attention to parturition ◦ Good herd health program ◦ Clean birthing facilities ◦ Any others you can think of???