Reproduction in Farm Animals PDF

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???