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What is the environmental signal that regulates secretory activity of the Pineal Gland?
Variation in photoperiod
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part 1 What is the precursor for endocrine function in the pineal gland?
tryptophan
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part 2 what is the end result or secretory product?
melatonin
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What is the target tissue and action in a ewe or goat?
hypothalamus--> increase frequency of LHRH 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 in parous animals?
BCS or body fat. threshold for fat must be achieved for puberty or seasonal reproduction.
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what does parous mean?
having given birth one or more times
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EXCLUDING reproduction, describe 3 effects of long days on whole animal performance?
- inc. ADG- average daily gain
- dec. fat and inc. lean
- inc. mammary parenchyma- comprises the functional parts of an organ
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In North America, what months during a year do mares experience estrus and ovulation?
March-->June
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Describe the photoperiod that stimulates estrus and ovulation in mares.
inc. light (>12hrs.) and decr. dark 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.
inc. light -->eye-->optic nerve-->superior cervical ganglia-->pineal gland-->decr. melatonin-->inc. LHRH pulses-->inc. LH--> Ovulation
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Defend or refute. With underfeeding energy, such as a 20% deficiency to pregnant beef cows, it is possible to reduce incidence of dystocia. EXPLAIN
Refute---> in cattle, fetal growth not affected by dietary energy for pregnant cow. Low NET may weaken cow at calving.
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Defend or refute. with underfeeding dietary energy, such as a 20% deficit to pregnant ewes, fetal growth will be reduced compared to pregnant ewes that are fed accurate energy.
Defend---> Net energy for ewe has higher priority than NE for fetus so low NET will decrease fetal lamb growth.
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Select a species of mammalian livestock. Identify the 3 phases of growth and indicate body weight at the end of each phase.
- Phase of growth body weight Beef
- Prenatal 80
- preweaning 500
- postweaning 1000
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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 temp. when ambient>UCT-upper critical temp
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Define cold stress.
Adjustments to maintain body temp when ambient <LCT-lower critical temp
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Independent of the species cause of death, what aspect of thermoregulation determines that an animal will die from hyperthermia?
ambient temp> UCT and animal cannot dissipate more heat.
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Defend or Refute. Animals exposed to very different wind speeds but same ambient temp will have the same thermoregulatory challenge. EXPLAIN
Wind--> inc. convection loss and will inc. LCT
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Excluding numbers, define the thermal neutral zone for mammalian livestock.
range of ambient temp when animal can maintain body temp without active HP or HD
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Lower Critical Temperature (LCT) is decreased. Explain whether this change is good for an animal.
more cold tolerant(less sensitive)= good
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Describe 2 animal or environmental factors that will increase Upper Critical Temperature (UCT).
- ⇧Humidity
- ⇧Conduction
- End lactation
- shearing
- ⇧Ventilation
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Upper Critical Temp. (UCT) is decreased. Explain whether this change is good for an animal.
less heat tolerant(more sensitive)= not good
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Excluding animal products and with total attention to live animals, discuss why growth is important to livestock.
- social order
- Dystocia
- DMI
- Insulation
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Discuss endocrine benefits and liabilities of fat to a live heifer, ewe, gilt, or mare.
↑ BCS---> ↓ age at puberty and can ↓ mammary development
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You measured growth of kidney in fetal pigs monthly across time during gestation form 30 to 110 days. Use increased, decreased, or no change to describe the slope of the lines for these data.
- 1) Weight of Kidney- ↑
- 2) DNA content of kidney- ↑
- 3) Ratio of Nucleus to Cytoplasm volume of kidney- →
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Defend or Refute. Heat stress will reduce growth in only the post-weaning phase of growth. EXPLAIN>
Heat stress will ↓ 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 ↑ HP and ↓HD
- only hypothermic when animal has maximal HP
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WHen ambient temp. declines below LCT, waht are the metabolic and physiological responses to maintain thermal homeostasis?
1) ↥TRH-->↑ TSH--> ↑ T3 + T4--> ↑ BMR
- 2) ↑ blood to muscle
- 3) ↓ blood to skin
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what factor has a major impact on effectiveness and efficiency of active methods to dissipate heat?
Humidity-- as increases--> ↓ evaporation so ↓cooling
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Defend or refute. In mammalian livestock that are in temperate zones, compared to thermogenesis, thermolysis is more important for thermoregulation.
Defend. HP> ambient so animal virtually always loses 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.
No effect. Acutal calories lost not changed through passive mechanisms.
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List two animal based factors that will increase LCT of a sheep.
Shearing, end lactation, ↓ dietary energy of fiber
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list two animal based factors that will increase UCT in a dairy cow.
prevent dehydration, ↓ blood to muscle, ↓BCS
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Name tow livestock species in which behavioral/social weaning occur simultaneously with nutritional weaning
Beef, Sheep, Swine, Horse
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what is a nutritional guideline for successful weaning?
DMI > NET
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describe the principle of compensatory growth.
Feed at NEm for period then ↑ feed to > NEm+NEg will cause faster growth
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Defend or Refute. During cold stress and heat stress, there is decreased growth, at least in part, because there is increased NEm, decreased NEg and but no change in NEt
Refute. NEm↑; NEg →; NEt ↑
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Name a hormone that is mitogen in growing bone.
- mitogen- stimulates mitosis
- IGF-1
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in growing bone, what type of cell experiences hyperplasia?
Chondrocytes
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when muscle grows with hyperplasia, what type of cells experience hyperplasia?
presumptive myoblasts
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excluding death, what event terminates or slows severely hyperplasia in muscle?
birth- all mitosis of muscle ends before birth
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What is the normal action of myostatin?
stop/slow mitosis of presumptive myoblasts
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when during the life of animals is myostatin active?
Mid to late gestation- fetal life
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what is the most significant negative effect of "doubled muscles" calves?
dystocia
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Defend or Refute. Meat from "double muscled" animals is less tender compared to meat from normal animals.
Refute. connective tissue diluted with more muscle so ↑ tenderness
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List environmental factors that affect livestock.
- 1. temperature
- 2. photoperiod
- 3. humidity
- 4. density of animals
- 5. homogeneity of animals-size, species, gender
- 6. Nutrition
- 7. cleanliness
- 8. surface traction
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what 3 environmental factors are hard to control?
Temp, photoperiod, and humidity
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What is photoperiod?
hours of light and hours of dark per 24 hours
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Long day=
more than 12 hours of light and less than 12 hours of dark per 24 hours.
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short day=
more than 12 hours of dark and less than 12 hours of light per 24 hours.
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effects of variation in photoperiod depend on species and what aspect of production is considered
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has to be a period of light and dark to maintain biological clock
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Effects of variation in photoperiod dependent on species and production.
A. Reproduction
- 1. "short day' breeders- Ewes and does--actual cue is longest day.
- 2. 'long day' breeders- Mares, cats, and dogs
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B. Lactation
- 1. long days (16hr light/24hr)
- -↑ yield of milk
- -↑ persistency of yield
- --->composition of milk
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C. Growth--most data form cattle
- 1. long days
- - ↑ average daily gain
- - ↑ Carcass protein and ↓ carcass fat
- - ↓ age at puberty of heifers
- - ↓ length of hair
- 2. short days
- - ↑ % fat in carcass
- - ↑ length of hair
- - ↓ mammary parenchyma
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define leptin.
forms excess fat messengers that is associated with mammary glands
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Ewes and Does:
↓photoperiod-->↑ melatonin--> ↑LHRH-->↑LH--> ovulation
- Mares:
- ↑photoperiod-->↓ Melatonin-->↑LHRH-->↑LH--> Ovulation
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Homeotherms
Mammals and birds. Generally maintain same body temp indepentent of ambient temp.
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Poikilotherms
Reptiles and amphibians. Body temp varies widely according to ambient temp.
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What happens to proteins when the environment gets too hot?
They denature
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Heat exchange goes from what to what?
- animal --> environment
- environment--> Animal
- -generally animal hotter than environment
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Define energy balance.
animal does not experience net gain of heat form environment and no net loss of heat to the environment
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Define optimal performance.
Environment is compatible with physiological requirements for energy. THus, no energy used specifically to generate or to dissipate heat
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Examples of thermal Environment.
- 1. radiation
- 2. humidity
- 3. wind speed
- 4. air temperature
- 5. Altitude
- 6. Photoperiod
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Define ambient temperature.
temperature of the environment outside an animal.
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What is thermal regulation.
goal to avoid thermal stress due to heat or cold.
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what happens during heat stress?
DECREASED appetite, feed efficiency, growth, milk yield, fertility of males and females
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What happens during cold stress?
Increase net energy requirement for maintenance, decreased feed efficiency
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What are the 5 things that affect production of Heat (HP)
Neurocontrol, Hormonal effects, Body size, Species and breed, and environmental factors
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Thermal homeostasis.
heat produced by animal or gained from the environment must equal the heat lost from the animal to the environment.
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What is Conduction?
diffusion of heat from skin to surfaces that are contacted and cooler than skin.
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Define Convection.
diffusion from skin to air that is contacting skin. regulated by air movement.
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Radiation.
general net transfer of heat away form animal
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Evaporation or Active. The 2 ways.
- 1. Panting- maximal rate of respiration inverse to body size of the animal.
- 2. Sweating- activated when energy cost to pant exceeds the amount of heat lost from evaporation
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Thermal Neutral zone.
Range of ambient temperature in which metabolic rate is minimal and temp. of an animal is regulated strictly with non-evaporative and physical processes
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Lower Critical Temperature(LCT).
ambient temperature that stimulates metabolic rate and increases Heat Production.
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Upper Critical Temperature (UCT)
ambient temperature that stimulates increased evaporative cooling.
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