Study Questions Dairy Section BAP1 Week 3 Quiz 2022

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Feb 20, 2024

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Study questions for the third quiz Dairy Section BAP1 Spring 2022 Artificial insemination What is the name of the device that is used to collect semen from a bull? Bovine Artificial Vagina What five criteria are used in semen evaluation? Motility, morphology, total sperm per ejaculate, volume, and concentration What are the components of a semen extender and what is their purpose? Milk or egg (yolk) base with: Salt, glucose or fructose, glycerol, antibiotic, and buffer. How is semen packaged and stored for long-term storage? Liquid Nitrogen What is “sire conception rate”? Fertility test on bull after breeding What is “gender-selected semen”? Semen selected for x (female) or y (male) chromosomes to get a specific gender What are the advantages and disadvantages of gender-selected semen? An advantage is that you can get what you are needing and won’t have to worry about what to do if you get a male or female that is not wanted (based on if you need replacement heifers or are creating dairy beef to discontinue a dam’s genes). A disadvantage is that gender-selected semen is more costly. What is the basis for separating X and Y semen using a flow cytometer? X chromosomes are bigger than Y chromosomes, so a stain can spot the x chromosome with a darker stain and clearer, and the y chromosome has a lighter stain. A laser then sorts out the semen based on that stain dye into x, y, uncertain, or no sperm. Synchronization of estrus in heifers What is estrus synchronization? Estrus synchronization is synching a herd to go into heat at the same time with the injection of PGF 2α What are three important things to know about PGF 2α treatment for estrus synchronization? 1. PGF 2α will not regress the CL if the cow/heifer is on the first 5 days of her estrous cycle 2. Heifers will come into heat 2-3 days after injection 3. Cows will come into heat 3-5 days after injection Diagram/understand a program that uses two PGF 2α treatments for estrus synchronization in heifers. Inject PGF 2a then wait 2-3 days, check heat and AI. That is a 14-day period. At the start of a new 14 days, redo the process. Fertilization, early embryonic development, and pregnancy testing When (relative to estrus and ovulation) do we AI heifers and cows? Why? If she was in heat in the morning, breed in the afternoon (am – pm rule). This is because we have to AI before ovulation, so the sperm cells can mature and make their way through the tract to fertilize. Where is semen placed in the repro tract when a cow or heifer is AI? The body of the uterus. Where does fertilization occur in the female repro tract? 1

Oviduct. When does the fertilized embryo enter the uterus? The 16-32 cell stage, or the morula stage, is when the embryo enters the uterus. Know the stages of early embryonic development from one cell to tubular embryo. 1, 2, 4, 8, 16 cell stages, then morula (16-32 cell stage), then a blastocyst (day 7-8, when the blastocoel cavity is formed which signals differentiation from placental and fetal cells, next a hatched blastocyst where it breaks out of the zona pellucida coating, spherical, and finally tubular. Define blastocoel, inner cell mass and trophoblast. Blastocoel: fluid-filled cavity in blastocysts (differentiate placental and fetal cells) Trophoblast: placenta forming Inner cell mass: fetus forming What are the two cellular layers of the uterus? Myometrium (muscle layer that surrounds uterus) and endometrium (lining of uterus) - Uterine lumen is the center of the uterus where embryo develops What do uterine glands do to help the embryo survive? They secrete histotroph which provides nutrients to the embryo, “uterine milk” What is meant by the term “maternal recognition of pregnancy”? Maternal recognition of pregnancy is the hormone that is Interferon Tau, embryo makes this and signals to the mother that she is preg. What is interferon tau and how does it act to maintain the CL? Interferon Tau is made by the embryo to signal to the mother that she is pregnant and stops the release of PGF 2α to stop the CL from regressing so that it can make progesterone and maintain the pregnancy. Know the parts of the 80-day placenta. Clear fetus along with: clear cotyledons, placental arteries and veins, amnion and amniotic fluid, the chorion, and the allantois. How are the bovine placenta and the human placenta different? Humans implant with a discoid placenta, the bovine placenta is cotyledonary, so it has the placentomes that act as Velcro patches to connect maternal and fetal tissues. Why doesn’t a pregnant cow come back into heat 21 days after breeding? Progesterone blocks estrus, LH surge, and ovulation, so a pregnant cow stops cycling. What are three ways that you could diagnose pregnancy in a cow? Palpate, ultrasound, or blood/milk test What are pregnancy-associated glycoproteins (PAG)? Pregnancy-associated glycoproteins are found in the blood or milk of pregnant cows and are secreted by trophoblast cells in the placenta. When (day of pregnancy) can you test for PAG and where (what biological fluids) do you look for them? 28 days, look at blood or milk. When can you use ultrasound for pregnancy diagnosis (day of pregnancy)? 35 days. When talking about pregnancy diagnosis, what is a “recheck”? A recheck is testing for pregnancy again 60-80 days after AI with blood/milk, palpation, or ultrasound. What is the difference between implantation in the human and placentation in the cow? 2

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