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what is the environmental signal that regulates activity of the pineal gland?
variation in photoperiod
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for the endocrine function of the pineal gland what is the precursor?
tryptophan
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what is the end result for endocrine function of pineal gland?
melatonin
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for the endocrine product of the [pineal gland, what is the target tissue and action in a ewe or goat?
hypothalamus- increase frequency of Luteinizing hormone releasing hormone pulses
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excluding photoperiod, nerves, and pineal gland, what factors can significantly modify achievement of puberty in seasonal breeders and onset of seasonality on parous animals?
body condition score, or body fat, threshold for fat must be achieved for puberty or seasonal reproduction.
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excluding reproduction describe three effects of long days on whole animal performance.
- increased average daily gain
- decreased fat increased lean
- increased mammary parenchyma
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in north America what months during the year do mares experience ovulation?
March through June
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describe the photoperiod that stimulates estrus and ovulation in mares.
increased light (more than 12 hours a day) and decreased dark period per 24 hour period
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starting with external signal describe all active components in the neural and endocrine sequence of events that cause a mare to experience estrus and to ovulate. use cryptic text or labeled diagram
increased light hits eye, goes through optic nerve, travels to superior cervical ganglia, then goes to pineal gland, leads to decreased melatonin, leads to incresed LHRH from hypothalamus, leads to increased LH from gonadotrope, leads to ovulation.
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defend or refute. with underfeeding energy, such as 20% deficiency to pregnant beef cows, it is possible to reduce incident of dystocia. EXPLAIN.
REFUTE. in cattle fetal growth is not effected by deficiency in energy for pregnant cow. low net energy may lead to weakness at calving however.
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defend or refute. with underfeeding dietary energy, such as 20% deficit to pregnant ewes, fetal growth will reduce compared to pregnant ewes that are fed adequate energy. EXPLAIN.
DEFEND. net energy for maintenance for a ewe has a higher priority than net energy for fetus, do low total net energy in will decrease fetal lamb growth.
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define ambient temperature.
environmental temperature (not animal)
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define heat stress.
physiological and metabolic adjustments to maintain constant body temperature when ambient temp is higher than upper critical temperature.
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define cold stress
physiological and metabolic adjustments to maintain constant body temperature when ambient temp is lower than low critical temp.
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what aspect of thermal regulation determines that an animal will die from hyperthermia?
ambient temp is higher than upper critical temp and animal can not dissipate heat quickly enough
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defend or refute. animals exposed to very different wind speeds but same ambient temperature will have the same thermoregulatory challenge. EXPLAIN.
REFUTE. wind will increase heat dissipation via convection, and will increase the lower critical temperature
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excluding numbers define the thermal regulatory zone fro mammalian livestock.
range of temp where animal can maintain body temp without active heat production or heat dissipation.
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lower critical temp is decreased explain whether this change is good for an animal.
they are more cold tolerant which means they are less sensitive to cold which is good
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describe two animal or environmental factors that will increase upper critical temp.
- decreased humidity
- increased conduction
- end lactation
- increase ventilation
- shearing
- decreased body condition score
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upper critical temp is decreased explain whether this is good for the animal or not
this is bad as it makes the animals less heat tolerant or more sensitive to heat change
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excluding animal products and with total attention to live animals discuss why growth is important to livestock.
- social order
- dystocia
- intake of feed and energy reserves
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discuss endocrine benefits and liabilities of fat to a live heifer, ewe, gilt, or mare.
increased body conditioning score decrease age at puberty and can decrease mammary development.
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you measured growth of kidney in fetal pigs monthly across time during gestation from 30 to 110 days. use increase decrease or no change to describe the slope of lines for weight of kidney, DNA content of kidney and ratio of nucleus to cytoplasm volume of kidney.
- weight of kidney: increase
- DNA content of kidney: increase
- ratio nucleus to cytoplasm volume: no change
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defend or refute. heat stress will reduce growth in only the post weaning phase of growth EXPLAIN.
REFUTE. heat stress will reduce growth in all phases of growth
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defend or refute. animals that are experiencing cold stress will be hypothermic EXPLAIN.
REFUTE. cold stress involves increased heat production and decreased heat dissipation, an animal is only hypothermic when heat production is maximal
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when ambient temperature declines below lower critical temp, what are maetabolic and physiological responses to maintain thermal homeostasis? no more than one hormonal among responses.
- increased blood to muscle
- decreased blood to skin
- increased catabolism (fat to glucose)
- increased appetite
- increase in tyroid releasing hormone which increases thyroid stimulationg hormone which increases triiodothyronine and thyroxine which increases basal metabolic rate
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what factor has a major impact on the effectivness and efficiency of active methods to dissipate heat EXPLAIN.
humidity, as it increases evaporation decreases which decreases cooling.
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defend or refute. in mammalian livestock that are temperate zones compared to thermogenesis thermolysis is more important for thermoregulation, EXPLAIN.
DEFEND. heat production is greater than ambient temp, so animal is virtually always losing heat.
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as ambient temp increases what is the influence on actual amount of heat lost through passive mechanisms to dissipate heat EXPLAIN.
there is no effect, actual calories lost does not change through passive methods but percent of heat dissipation due to passive methods decreases.
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list two animal based factors that will increase lower critical temp of a sheep
- shearing
- decreased dietary energy from fiber
- end lactation
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list two animal based factors that will increase upper critical temp in dairy cattle
- shearing
- decreased blood to muscle
- decreased body condition score
- prevent dehydration
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name the livestock species in which social and nutritional weaning occur at the same time.
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what is the nutritional guideline for sucessful weaning?
dry matter intake is greater than or equal to total net energy
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describe the principal of compensatory growth
feed at maintenance net energy for a period then increase feed to exceed or equal net energy for growth and maintenance and this will cause faster growth
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defend or refute. during cold stress and heat stress there is a decreased growth at least in part because there is increased net energy for maintenance.
REFUTE. maintenance net energy goes up while net energy for growth stays the same, and total net energy goes up.
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name a hormone that is a mitogen in growing bone.
insulin like growth factor-1
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in growing bone, what type of cell experiences hyperplasia?
chondrocyte
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when muscle grows with hyperplasia what type of cell experiences hyperplasia?
presumptive myoblast
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excluding death, what terminates or slows severely hyperplasia in muscles
birth, all mitosis of muscles ends before birth.
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what is the normal action of myostatin
stop or slow mitosis of presumptive myoblasts
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when during the life of an animal is myoststin active?
mid to late gestation, fetal life
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what is the most significant negative effect of double muscled calves?
dystocia
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defend or refute. meat from double muscled animals is less tender compared to meat from normal animals EXPLAIN.
REFUTE. connective tissue is diluted with more muscle which makes it more tender.
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Describe three (3) factors that will increase the magnitude of response oftarget cells to prolactin (PRL). The factors listed must be after theendocrine tissue and outside of the cytoplasm of the target cells. Describemeans that in addition to listing factors, your response must include anarrow to indicate the direction of change in the factor that will increaseaction of PRL.
- [PRL] in blood increases ---> # of receptors for PRL increases
- Blood flow to target increases ---> affinity of receptor for PRL increases
- [PRL] in interstitial fluid increases ---> # of target cells increases
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Describe three (3) factors that will decrease the magnitude of response oftarget cells to prolactin (PRL). The factors listed must occur between themedial plasma membrane and the cytoplasm of target cells. Describe meansthat in addition to listing factors, your response must include an arrow toindicate the direction of change in the factor that will decrease action ofPRL.
- Activation of Adenylate cyclase decreases ---> increase phosphatase
- Amount of cAMP decreases ---> increase phosphatase
- Increase phosphodiesterase ---> increase phosphatase
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During and possibly after activation with PRL, describe how target cellachieves and sustains homeostasis.
Phosphatase --> remove phosphate from enzymes --> deactivate Phosphodiesterase --> metabolism of cAMP
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Excluding reproduction, describe 3 (effects) of long days on whole animalperformance
- Increase ADG
- Increase protein accretion
- Increase fat accretion
- Increase lactation persistency
- Decrease age at puberty
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In North America, what months during a year do mares experience estrusand ovulation? Describe the photoperiod that stimulates estrus andovulation in mares
- Increase light per day
- Broad Window: March to September
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Based on your response above (3.b.), starting with external signal describethe neural and endocrine sequence of events that cause a mare toexperience estrus and to ovulate. Use text or labeled diagram
Increase L:D --> Eye, Optic Nerve, SCG --> Pineal --> DecreasedMelatonin --> Increased LHRH --> Increased LH --> Ovulation
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For estradiol, name a target cell that is in the reproductive tract anddescribe an action of estradiol on that target cell
- Endometrium --> Mitosis/Secretion
- Myometrium --> Contraction
- Grannulosa --> Mitosis
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An animal is lactating, suckled, and diet is less than NET. What is thegeneral effect of this metabolic and physiological status on biologicalactivity of estradiol? EXPLAIN
Decreased steroid binding protein --> Increased E2 --> Increased! biological action of E2
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Describe two situations/factors that will increase the magnitude ofresponse of target cells to testosterone. Limit attention to situations/factors that are inside the target cell
- Increase translocation of HR from cytosol to nucleus
- Increase affinity for hormone
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Excluding any aspect of negative feedback and any aspect ofspermatogenesis, name a target cell for testosterone and describe anaction of testosterone on that type of cell
- Sex accessory glands --> Increase seminal fluid
- Hypothalamus/Brain --> Libido
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Define ambient temperature
Environmental temperature
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Define heat stress
Physiological and metabolic adjustments to high ambient temperatures! that allow for a constant body temperature
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Define cold stress
Adjustments to low ambient temperatures that allow for a constant! body temperature
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What aspect of thermal regulation determines that an animal will die fromhyperthermia? This is not about specific cause for death
Have achieved maximal capacity to dissipate heat
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Defend or Refute. Animals exposed to very different windspeeds but same ambient temperature will have the samethermoregulatory challenge. EXPLAIN
REFUTE. Wind --> Increased convection loss of heat. So will cold ambient temperature, wind will increase LCT
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Excluding numbers, define the thermal neutral zone for mammalianlivestock
Ambient temperature where the animal can sustain body temperature! with no effort or energy
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Lower Critical Temperature (LCT) is decreased. Explain whether this changeis good for an animal
Decreased LCT --> Increased cold tolerance --> GOOD for the animal
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Describe some animal or environmental factors that will increase UpperCritical Temperature (UCT)
- Ventilation increases
- Shade (+)
- Decrease hair
- Decrease BCS
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Upper Critical Temperature (UCT) is decreased. Explain whether thischange is good for an animal
Decreased UCT --> Decreased heat tolerance --> NOT GOOD for animal
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Including the initial environmental signal, describe the neural regulation ofpineal secretory activity
Increased duration of dark --> Optic Nerve --> SCG --> Increased! pineal activities (Melatonin)
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For the endocrine function of the pineal gland, what is the precursor andwhat is the end result or product?
Tryptophan --> Serotonin --> Melatonin
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For the endocrine product of the pineal gland, what is the target tissueand action in a ewe or goat?
Increased Melatonin --> Hypothalamus --> Increased LHRH
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Excluding photoperiod, nerves, and pineal gland, what factors cansignificantly modify achievement in seasonal breeders and onset ofseasonality in parous animals?
Growth rate and accumulation of body fat/energy
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Defend or Refute. Animals that are experiencing cold stresswill be hypothermic
REFUTE. During cold stress --> Increased HP and decreased HL --> constant body! temperature
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When ambient temperatures declines below LCT, what are the metabolic and physiological responses to maintain thermal homeostasis? Among responses no more than one hormonal
- Increased blood to viscera and skeletal muscle
- Decreased blood to skin
- Increase vertical posture of hair
- Increase intake of feed
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What factor has a major impact on effectiveness and efficiency of activemethods to dissipate heat? EXPLAIN
Humidity --> Increase humidity --> Decrease evaporation
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Define Upper Critical Temperature (UCT)
Ambient temperature that activates active heat dissipation
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Describe factors that will decrease UCT in mature sows
- No shade
- Low ventilation
- High body fat
- Lactation
- Full feed
- Humidity increased
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Define Lower Critical Temperature (LCT)
Ambient temperature that activates heat production and heat sparing
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Describe factors that will decrease LCT in adult beef cow
- Long, dry hair
- Moderate or greater BCS
- Feed forage
- Shelter
- Lactation
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Defend or Refute (circle choice). In mammalian livestock that are intemperate zones (not tropical or arctic), compared to thermogenesis,thermolysis is more important for thermoregulation. EXPLAIN
Thermolysis is dissipation of heat. Heat production is inherent product of! metabolism. < 100% efficiency to retain heat
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As ambient temperature increases, what is the influence on effectivenessand efficiency of passive mechanisms to dissipate heat. EXPLAIN
Decreased gradient between animal and environment! ! --> Decreased effectiveness of passive heat loss
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List two animal-based factors that will increase LCT of a sheep
- Shearing wet wool
- Low dietary fiber
- No shelter
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List two animal-based factors that will increase UCT in a dairy cow
- End lactation
- Good ventilation
- Low BCS
- Shade
- Low humidity
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How does the chemical nature of TSH affect the mechanism of action for TSH?
TSH protein cannot enter target cell. Must act through receptor and! second messenger
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How does the chemical nature of testosterone affect the mechanism ofaction for testosterone
T is non-polar and can enter cell. Acts at nucleus to affect transcription! and translation
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Given any target cell for cortisol and with cortisol in the cytoplasm,describe four major events that lead to the first synthetic product thatcortisol stimulates
- Tow molecules of C bind to receptor (cytoplasm)
- HR complex translocated to nucleus
- Beta subunit bind to N-H protein of chromatin (specificity)
- Alpha subunit binds to DNA to affect transcription (mRNA)
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A woman is using oral contraceptives such as progesterone and estradiol.This same woman starts taking an antibiotic. THe antibiotic blockstranscription. Discuss the consequences, if any, to effectiveness of the oralcontraceptive
Decreased or no transcription means that steroid hormones cannot act. Thus, oral contraceptives will be less effective
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for beef cattle name the growth phases and weights for each
- prenatal: 80lbs
- preweaning: 500lbs
- postweaning: 1000lbs
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for dairy cattle name the phases of growth and weights for each
- prenatal: 100
- preweaning: 250
- postweaning: 1200
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for equine name the phases of growth and weights for each
- prenatal: 115
- preweaning: 250
- postweaning: 1100
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for ovine name the phases of growth and weights for each
- prenatal: 10
- preweaning: 75
- postweaning: 130
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for swine name the three phases of growth and weights for each
- prenatal: 3
- preweaning: 25
- postweaning: 300
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