Semen sexing - sex is determined by an X(female) and Y(male) chromosomes in sperm cells. A FACS machine is used to determine and separate the individual sperm based on their chromosome. They actually look at each individual sperm at a time.
Gestation Management
Day 1- Fertilization of sperm and egg, happens in the oviduct (fallopian tubes), immediately after fertilization, cell division begins.
Different stages of development (zygote, marula, blastacyt, embryo)
Days 2-5 - Zygote passes down the oviduct and enters the uterus by day 5 post breeding.
Day 6 - Cell differentiation - different organ and tissue cells begin developing.
Ectoderm - Skin, Nervous System - External Layer
Endoderm - Lungs, thyroid, pancreatic - inner layer
Mesoderm - Muscle, skeletal system - middle layer
Maternal Recognition of Pregnancy
recognition of pregnancy doesn't involve any conscious recognition by the mother, rather a chemical hormonal signal. The window for recognition is very narrow.
Interferon Tau is the hormone that signals a pregnancy. In sheep, (ovine) interferon tau is released around day 12-13 and in cattle (bovine) interferon tau is released in days 15-16.
Int. Tau inhibits the production of pgf2a (prostaglandin, which destroys the CL [corpus luteum] that maintains pregnancy) no prostaglandin means a safe CL which means a stable pregnancy.
In humans - the fetus produces chorionic gonadatropin hCG - similar to LH, it binds LH receptors on the CL and stimulates progesterone production. Pregnancy tests look for hCG.
Day 14 - Embryo elongation - the embryo helps to establish its own room or space in the uterus, especially in hogs and sheep because of the multiple embryos, by elongating the cells inside.
Day 30-35 - implantation and attachment - the embryo attaches itself to the uterine wall and can now receive nutrients directly from the mother. Before implantation, the embryo had to receive nutrients from the uterine fluids.
The First Trimester - most differentiation happens while the 2nd and 3rd trimester experience mainly growth.
Fetal Growth
Bone development - day 70
Extensive Bone Development - 180
Teeth - 110
Hair, eyes, muzzle - 150
Hair on the entire body - 230
More than 50% f fetal weight comes in the last 2 months of pregnancy
Pregnancy Detection
There are several methods to detect a pregnancy in cattle. Detecting pregnancy is essential to main a productive cow herd, as it costs money every day to feed and maintain them. Non-Productive days = days when a cow isn't raising calf or is pregnant.
Estrus detection - Cheap, easy, fairly accurate, and quick. Sometimes though, cows can display a false heat.
Rectal Palpation - most common, can be performed around day 45 of pregnancy. The vet or other person is feeling around the uterus for the fetus its self or later on can feel the weight in the uterus. Sometimes its not always accurate and can also cause abortions, not to mention it can be expensive.
Ultrasound - Detects the developing embryo as early as 25 days, extremely accurate, but the ultrasound machines are expensive.
Blood/Milk Progesterone Test - Measure the level of progesterone in in either the milk or progesterone, must be performed between 18-21 days. accuracy = 61-88 %
BioPryn - Blood pregnancy test - tests for a protein called Pregnancy Specific Protein B (PSPB) which is produced by the placenta. Can be used as early as 28 days post breeding, 90 days post calving. 99% Accurate, costs $2.40 per sample + supplies.
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