Animal Breeding and Genetics

Breeding & Genetics

• A gene is a unit of heredity that is transferred from a parent to offspring and determines some characteristic of the offspring
• DNA is shaped like a double helix
• The term used when a gene changes to cause a different outcome, such as in the case of Polled Hereford, is mutation
• The "recipe" for an organism is its DNA
• Much more genetic change comes from the sire because of widespread use of artificial insemination
• Breeding technologies that allow for some parents to be used more frequently than typical breeding cycles include artificial insemination (AI) and embryo transfer (ET)
• Selection is used in animal breeding to improve the genetic merit of the herd or flock
• Types of selection in animal breeding include natural selection and artificial selection
• A homozygous gene (allele) is when both alleles are the same (e.g., PP or pp), while a heterozygous allele has two different alleles (e.g., Pp)
• Dominance/recessive is when one allele masks the effect of the other; for example, the allele for black coat color (B) is dominant over the allele for red coat color (b)
• Over-dominance is when the heterozygous genotype results in a superior phenotype compared to either homozygous genotype; an example is seen in some cases of disease resistance
• Co-dominance is when both alleles are expressed in the heterozygote; an example is roan coat color in cattle, where both red and white hairs are present
• Heterosis is the superior performance of hybrid offspring compared to their parents; an example is increased growth rate in crossbred pigs
• Five types of qualitative traits include coat color, horn presence/absence, blood type, genetic diseases presence/absence, and polled/horned
• Three ways the environment can impact the phenotype of a calf before weaning are nutrition, disease exposure, and climate
• A trait that is highly heritable is stature, and a trait that is lowly heritable is reproduction

Growth & Development

• Hyperplasia is the increase in the number of cells in a tissue or organ
• Hypertrophy is the increase in the size of cells in a tissue or organ
• Precocial young are relatively mature and mobile from birth or hatching
• Altricial young are immature and helpless at birth or hatching
• Compensatory gain is the accelerated growth of an organism after a period of nutrient restriction
• The law of diminishing returns states that at some point, increasing one input while holding other inputs constant will lead to a smaller increase in output
• The levels of cellular organization are cells, tissues, organs, and systems
• Nutrients are partitioned in the following order of importance: maintenance, growth, reproduction, and lactation
• During the finishing period, animal management includes providing a high-energy diet, optimizing environmental conditions, and minimizing stress
• Factors that can be manipulated to increase growth include nutrition, genetics, and environment
• Economically important tissues are muscle, fat, and bone
• Physiologically important tissues include the brain, heart, and lungs
• Physiological factors that can be altered to increase nutrient delivery to the fetus during gestation include maternal nutrition, placental blood flow, and hormone levels
• The order of fat deposition is visceral, subcutaneous, intermuscular, and intramuscular
• Slaughter weights for all livestock species vary depending on the species and market demand
• Growth hormone fluctuates throughout an animal's life, with peaks during periods of rapid growth and declines during periods of maintenance

Reproduction

• Diagrams of the bovine female, swine female, and male swine reproductive tracts can be found on Canvas labelled “reproductive tract anatomy.”
• Fitness is the ability of an organism to survive and reproduce
• Polyestrus describes animals that have regular estrous cycles throughout the year
• Seasonal polyestrus describes animals that have estrous cycles only during certain times of the year
• Monoestrus describes animals that have only one estrous cycle per year
• Estrous refers to the entire reproductive cycle of a female mammal
• Estrus is the period of sexual receptivity in female mammals
• Gestation is the period of pregnancy
• Parturition is the act of giving birth
• Estrous synchronization is the process of manipulating the estrous cycle of female mammals
• Artificial insemination is the process of collecting semen from a male and manually depositing it into the reproductive tract of a female
• Embryo transfer involves collecting embryos from a donor female and transferring them to a recipient female
• In-vitro fertilization is a process where eggs are fertilized by sperm outside the body
• Intracytoplasmic sperm injection is a fertilization technique in which a single sperm is injected directly into an egg
• Sexed semen is semen that has been processed to separate sperm that carry the X chromosome (female) from sperm that carry the Y chromosome (male)
• Cloning is the process of producing a genetically identical copy of an organism
• The vestibule is the area between the vulva and the vagina
• The vagina is the elastic, muscular canal that leads from the vestibule to the cervix
• Cervical anatomy changes depending on the species to accommodate differences in insemination and gestation
• The endometrium, myometrium, and perimetrium are the three layers of the uterus; the endometrium is the inner lining, the myometrium is the muscular layer, and the perimetrium is the outer serous layer
• Fertilization occurs in the oviduct
• A Graafian follicle is a mature ovarian follicle that contains a fully developed egg
• Seminal plasma increases sperm viability by providing nutrients, protection, and motility factors
• Sertoli cells support and nourish developing sperm cells
• Leydig cells produce testosterone
• Seminiferous tubules are the site of sperm production
• The tunica dartos is a muscle that controls the position of the scrotum
• The cremaster muscle elevates the testes
• The pampiniform plexus is a network of veins that cools arterial blood entering the testes
• The inner cell mass develops into the embryo
• The trophoblast develops into the placenta
• The placenta provides nutrients and oxygen to the fetus
• The hormone produced during the follicular phase is estrogen
• The hormone produced during the luteal phase is progesterone
• Average estrus length varies by livestock species: cow (18-24 hours), ewe (24-36 hours), mare (5-7 days), sow (2-3 days), doe (24-48 hours)
• A zygote is a fertilized egg cell
• The embryonic period of gestation is when the major organs and systems develop
• The fetal period of gestation is when the organs and systems grow and mature
• Placenta type varies by livestock species: cow (cotyledonary), ewe (cotyledonary), mare (diffuse), sow (diffuse), doe (cotyledonary)
• Artificial insemination (AI) is used in livestock species to improve genetics, control disease, and increase reproductive efficiency
• The easiest way to see if an animal is producing to its potential is by monitoring its performance, such as growth rate, milk production, or reproductive success

Digestive Systems

• The four functions of the digestive tract are ingestion, digestion, absorption, and elimination
• The three types of digestion are mechanical, chemical, and enzymatic. An example of mechanical digestion is chewing, an example of chemical digestion is the breakdown of food by stomach acid, and an example of enzymatic digestion is the breakdown of food by enzymes in the small intestine
• Absorption is the process by which nutrients move from the digestive tract into the bloodstream; it occurs primarily in the small intestine
• Mastication and physical digestion of feed occur in the crop and gizzard in chickens
• Reptiles mainly use chemical digestion to digest their feedstuffs
• Cattle have a ruminant digestive tract
• Sheep have a ruminant digestive tract
• Goats have a ruminant digestive tract
• Swine have a monogastric digestive tract
• Horses have a hindgut fermenter digestive tract
• Saliva's function is to moisten food, facilitate swallowing, and begin the digestion of carbohydrates
• The epiglottis prevents food from entering the trachea
• The four chambers of the ruminant stomach are the rumen, reticulum, omasum, and abomasum. The rumen is responsible for microbial fermentation, the reticulum traps large particles, the omasum absorbs water and volatile fatty acids, and the abomasum is the true gastric stomach
• The by-product of microbial fermentation in the rumen and cecum is volatile fatty acids (VFAs)
• The three VFAs are acetate, propionate, and butyrate
• An animal with an esophageal groove is a young ruminant because it allows milk to bypass the rumen and reticulum
• The three sections of the small intestine are the duodenum, jejunum, and ileum. The duodenum is responsible for further digestion, the jejunum is responsible for nutrient absorption, and the ileum absorbs bile salts and vitamin B12
• Protein hormones have to be activated to bind to their receptors and initiate a cellular response
• Bile is produced in the liver and stored in the gallbladder
• The cecum digests fiber in some animals

Nutrients & Feeding

• The highest cost in livestock production is feed
• Feedstuff is any material used as food
• Diet is the type and amount of feed an animal eats
• Ration is the amount of feed provided to an animal over a 24-hour period
• Nutrient is a substance that provides nourishment essential for growth and the maintenance of life
• Building blocks are the essential components of nutrients
• Essential amino acids cannot be synthesized by the body and must be obtained from the diet
• Non-essential amino acids can be synthesized by the body
• Non-protein nitrogen is nitrogen that is not part of a protein molecule
• Gross energy is the total energy content of a feedstuff
• Digestible energy is the gross energy of a feedstuff minus the energy lost in the feces
• Metabolizable energy is the digestible energy of a feedstuff minus the energy lost in the urine and gases
• Net energy is the metabolizable energy of a feedstuff minus the energy lost as heat
• Feed efficiency is the amount of feed required to produce a unit of product
• A lower feed conversion value means that an animal has greater efficiency
• Five traits of a balanced ration are adequate energy, protein, vitamins, minerals, and water
• Macronutrients are required in large quantities and include carbohydrates, protein, and fats. Micronutrients are required in smaller quantities and include vitamins and minerals; both are required for life
• There are 4 calories in a gram of carbohydrate, 4 calories in a gram of protein, and 9 calories in a gram of fat
• Energy is not a nutrient but is required for life
• Saturated fats have no double bonds between carbon atoms, while unsaturated fats have one or more double bonds between carbon atoms
• Three functions of proteins in the body are building and repairing tissues, making enzymes and hormones, and supporting the immune system
• The four types of carbohydrates are monosaccharides, disaccharides, oligosaccharides, and polysaccharides
• On average, a dairy cow consumes 30-50 gallons of water per day
• On average, a beef steer consumes 8-12 gallons of water per day
• On average, a young mare consumes 5-10 gallons of water per day
• On average, a barrow consumes 3-5 gallons of water per day

Animal Health I

• Commensals are organisms that live in or on another organism without causing harm
• Opportunistic pathogens are organisms that can cause disease if the host is compromised
• True pathogens are organisms that always cause disease
• Dysbiosis is a microbial imbalance
• Fibrolytic bacteria digest fiber
• Glycolytic bacteria digest sugar
• The microbial members within most microbiomes are bacteria, archaea, fungi, and viruses
• Four factors that can influence microbial colonization and microbiome composition are diet, environment, genetics, and antibiotic use
• Dysbiosis can lead to disease by disrupting the normal functions of the microbiome
• The microbiome is a supporting organ and important for livestock production because it aids in digestion, produces vitamins, and supports the immune system

Animal Health II

• Endemic diseases are constantly present in a population
• Epidemic diseases occur in a population at a higher rate than expected
• Pandemic diseases are epidemics that spread across multiple countries or continents
• A pathogen is a biological factor that causes disease
• A vector is an organism that transmits a pathogen
• A reservoir host is a host that harbors a pathogen without getting sick
• Bio-exclusion prevents the introduction of disease agents into an area or population
• Bio-containment prevents the spread of disease agents out of an area or population
• Bio-management involves all of the practices that maintain animal health status
• A zoonotic pathogen is a pathogen that can be transmitted from animals to humans
• Passive immunity is the transfer of antibodies from one animal to another; neonates obtain it through colostrum
• There is no longer any IgG absorption in the gut after 24 hours
• An example of structural biosecurity is a fence
• An example of procedural biosecurity is hand washing
• An employee should move through an operation from clean to dirty areas on a daily basis
• The four types of injections are subcutaneous, intramuscular, intravenous, and intraperitoneal
• The quickest way to increase herd immunity and achieve optimal herd health is through vaccination
• The One Health Initiative is a collaborative, multisectoral, and transdisciplinary approach working locally, regionally, nationally, and globally to achieve optimal health outcomes recognizing the interconnection between people, animals, plants, and their shared environment