Week 6 and 7 Notes
Week 6 and 7 Notes ANSC 1000
Popular in Introduction to Animal Sciences
Popular in Animal Science and Zoology
This 5 page Class Notes was uploaded by Olivia Schweikart on Sunday March 6, 2016. The Class Notes belongs to ANSC 1000 at Auburn University taught by Dr. Carolyn Huntington in Spring 2016. Since its upload, it has received 31 views. For similar materials see Introduction to Animal Sciences in Animal Science and Zoology at Auburn University.
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Date Created: 03/06/16
Animal Breeding & Reproduction Week 6 and 7 Notes Genetic Variation • Producers like to have animals that can all be vaccinated at the same time, moved at the same time, appear the same way, etc. o The animals are very similar in action, as well as appearance o Allows for the animals to be raised the same way, as well as handled the same way § Leads to a moderately constant harvest yield Accuracy • How well the heritable traits are transferred to the offspring o Important to recognize for exams which traits have higher/lower levels of heritability § Example: Reproductive traits are known to have low heritability • If the environment of the animals is standardized, then the environment will have the same effect on how the animals grow o This allows for other genetic variations the animals may have to show through Selection Intensity • Selection pressure- • Selection differential- a comparison of the average mating results for a heard of animals and two animals from the herd that have been mated o If the animals mated end up above the average for the herd, these will be chosen to be the mating animals o Can often be abbreviated SD, not to be confused with standard deviation • Example problem: If a group of heifers has an average weaning weight of 460 pounds, and the replacement heifers for the group carry a weaning weight of 490 pounds, what is the selection differential? o Solution: Subtract the average for the group from the weaning weight of the replacement heifers: 490 – 460 = 30 Generation Interval • The offspring of animals with a lower turnover for offspring are able to reach sexual maturity at a faster rate o Prove to be good in terms of fast generations where breeders can notice improvements § Example: Poultry have a 1-year generation interval whereas horses have 10 years before their offspring are sexually mature Tandem Method • When placing a lot of pressure on an individual trait, also influences other traits o Example: In the dairy industry, the Jersey does not yield as much milk as other breeds, such as Holstein, but do have a higher percentage of milk fat § Increasing the milk production would decrease the milk fat • Not efficient and not common in industry Independent Culling Levels • A common practice in industry where producers may set a minimum level a trait may be present • Two main issues with this method o Discrepancies emerge when deciding what animals are to be culled because the producers have to decide what traits are considered more desirable than others o An animal may be culled because of a certain characteristic when the producers would not take into consideration any other possible traits that could set the animal on top Breeding Decisions • Producers have to determine which superior animals to match • Artificial insemination or superovulation become decisions a producer has to make when determining rate of production • When looking at a breeding pedigree, the top portion refers to the parental lineage and the bottom refers to maternal lineage o If looking at an individual bracket within the pedigree, the top line represents a sire and the bottom represents a man • Inbreeding results in animals that are more similar in genotype and phenotype due to being crossed down their lineage o Results in a wide increase of amount of homozygous genes the animals hold § Producers must be aware about possible recessive genes o Decreases the size of the gene-pool o Can be used to develop new breeds by using nearly identical genetic pools o Not common in industry o Linebreeding § Can be done in industry § Considered to be less intense than traditional inbreeding § If males that are superior genetically are difficult to come by, can be a viable option § When an animal shows up in a pedigree multiple times, but is farther up the pedigree • Deemed linebreeding because you are concentrating ancestry for this animal of interest • Outbreeding results in animals that come from two different gene pools o Brings about a wider range of genotypes that have different performance traits § Species cross • Form of outbreeding that results from the crossing of two different species • Often, the offspring are infertile due to varying numbers of chromosomes o Example: Mule as a result of a Jack and a Mare § Outcrossing • Form of outbreeding where two individuals of the same species are mated • Previously unrelated • Most common procedure in industry § Grading up • Form of outbreeding where highly superior sires are used to ensure their purebred genes are getting passed along • Most common practice in the cattle industry § Crossbreeding • Form of outbreeding where animals of different breeds are crossed in order to bring out superior characteristics • Usually to bring about high performance • Producers must find breeds that compliment each other • Types of crossbreeding: o Terminal Cross § o Rotational Cross Reproduction • Timing is key in ensuring reproduction is successful o Otherwise, a lot of energy has been invested with nothing in return o Estrous cycles vary with species, as well as when the animal is actually in estrus § Ewe average 17 days • Estrus lasts 1 to 2 days § Mare average 21 days • Estrus lasts 4 to 6 days § Sow average 21 days • Estrus lasts 1 to 3 days § Cow average 21 days • Estrus lasts 16 to 20 hours • Crucial in industry o Can be harmful to production if reproduction declines • Embryo transfer o Transferring an embryo to another mother o The mother receiving the embryo must be in the exact stage of ovulation • Transgenic animals o Implementation of genes from one animal into another • Artificial Insemination o Taking semen from a superior sire and placing it inside of an accepting mother Sexual Development • The primary sex cell for the female is known as oogonia o The antrum is a fluid filled space around an egg while in a follicle § The tertiary follicle will mature and its lining cells will secrete estrogen • The corpus luteum in females is responsible for producing progesterone o Ensures a pregnancy continues • While females have a set amount of eggs, males are constantly undergoing the development of new sperm • Males o Testes § Responsible for the production of sperm § Involved in the production of testosterone § Stag- animal whose testicles have been removed after reaching sexual maturity • In vasectomies, the vas deferens tube is snipped § The scrotum, due to muscle action, will move either toward or away from the body depending on the temperature of the environment • Temperatures that are too high can result in non-functional sperm • Muscles include the cremaster and tunica dartos muscle • Producers take this into consideration and have set factors in order to handle it: o Fans, drip coolers, fans, water sources § Seminiferous tubules are what give the testicles their mass and size • Fill the testicle with sperm after producing it § Seminal vesicles make sure sperm have the nutrients they need in order to have the energy to swim throughout the female reproductive tract § In the epididymis, sperm will mature and will also have their pH changed, as the vagina is more acidic • If the sperm were to directly go into the vagina without this pH change, they would disintegrate § The bulbourethral gland functions on the sexual reproduction side, as it secretes a mucous to go along with the sperm; But, it also functions with the urinary system as it makes sure the urethra has no friction to it, will secrete a lubricant • The prostate gland will clean the urethra in order to remove the acidity o Males with lower hanging sheaths are susceptible to infection, as well as scraping Fertilization and attachment • An egg will be ovulated due to an LH hormone release from the pituitary gland • Once fertilized, this egg will attach to the endometrium, which is the lining of the uterus wall • The baby will receive nutrients through placenta o Made of three types of membranes: amniotic, allantoic, and chorionic