Water and energy Flashcards
Water is how important
Major important nutrients to life, participating in all major physiological functions
Major constituent of animal’s body (75% at birth, 60% in adult age)
Classified as a macronutrient
Required in large amounts
Unlike protein, fat or carbohydrates, does not provide a source of energy
How does water help the body
Disperses nutrients and waste
Promotes optimal environment for biochemical reactions
Regulates body temperature
Lubricates joints, eyes and inner ear (transmits sound)
3 natural sources of water
Drinking
Food (variable amounts of water depending on food type)
Oxidation reactions in nutrients
Water provision is
Free choice fresh water is the general recommendation for all species
Recognized that cattle at maintenance (includes early and mid pregnancy) can obtain their water needs from snow (not ice)
Lack of water can casue
Thirst and dehydration
Reduced heat tolerance
Poor performance
Poor production
Death (3 to 10 d.)
Colic (especially horses)
Sources of water
Big problem in North America is usually quality, not availability
Surface water
Open (flowing)
Closed (salt lakes)
Well water
Water quality affects and how
Water quality affects feed intake
Poor water quality decreases water consumption and food intake, which decreases performance
How does water intake vary
Water intake can vary depending on the physiological status of the animal
Beef cow can drink 5% of her body weight per day
Dairy cow producing milk may drink four times that much
Allowing animals to enter water source to drink is poor practice because
Results in fecal contamination of water
Many enteric bacteria, protozoa and parasites can be transmitted by fecal contamination of water
Animals that routinely enter stagnant watering sources are at risk for bacterial infections
Trials have shown that most times animals will preferentially select to drink water from alternative sources, if given the choice
Fencing water sources are
Use pump to deliver water to a nearby trough
Can be combined with aeration
Windmills can use wind energy to pump water from sources
Less microbial contamination
benefits to fencing water sources
Preserves banks
Less nutrients in water from saliva (K, P, N) so less algal growth.
Less disease
Better growth of calves
Less algal blooms
Blue green algae poisoning is
Cyanobacteria are common inhabitants of ponds and lakes
Multiply if:
Warm weather
Organic nutrients suddenly increase due to run off from slurry (liquid waste) from lagoons or fertilizers (N, P)
Steady, gentle wind may concentrate
Many species float and may be visible as a scum (makes water turbid)
A few species produce toxins
CNS signs and death (often sudden with little warning)
Fence off and aerate water
Mineral concentration is particularly a problem in
Arid areas
Closed surface waters
Wells
How does arid areas affect mineral contamination
High air temperature and low soil moisture results in high soil temperatures which stimulate bacterial respiration
Results in soils with 10x lower organic carbon and nitrogen
How does closed waters affect mineral concentration
Flows in and evaporates
Especially late summer
Great Salt Lake
How do wells affect mineral contamination
Shallow to medium depth
Minerals can contaminate a private well through groundwater movement and surface water seepage and water run-off
Mineral contamination in prairie sloughs
Typically lowest mineral content in spring following runoff
Highest in late summer
Most sloughs dry up in summer (1/3 of then disappear by mid-July in driest regions)
Evaporation plus desiccating winds concentrate the nutrients that get washed into sloughs
Two main profiles of mineral contamination
Calcium and Magnesium plus Carbonates and Bicarbonates (Shell Remnants, Hard water)
These are the most common type
Sodium and Potassium plus Chloride and Sulfates (Dried out seas)
Total dissolved solids is
Most Useful Overall Indicator
Sometimes measured as sum of ions
Sometimes measured as conductance
Easy to measure but not quite as accurate as directly measuring TDS
What do waters with high TDS commonly contain
Waters with high TDS typically have high Na and K ions (because these are highly soluble)
Problems caused by salinity
Water refusal
Lower feed intake
Decreased production
Diarrhea
TDS < 1000 ppm are always safe
TDS > 10,000 ppm are very dangerous
Sulphate toxicity is
In general, the tolerance to sulfates in water depends on total dietary intake (depends on the levels in feed) and total water consumption
Total water consumption influenced by
Environmental temperatures
Moisture levels in feed
Stage of production
Some ability to become accustomed to sulfates (rumen microflora can slowly shift over time)
Linked to development of polioencephalomalacia in ruminants
Disease of cerebral cortex
Clinical signs and prognosis of sulphate toxicity
Signs include
Blindness
Head Pressing
Sulfate related form has a poor prognosis
Water hardness is
Tendency to form insoluble precipitates with boiling or soaps
Related to presence of Ca, Mg, CO3 and HCO3.
Hard waters do not impair health
Hardness and Total Dissolved Solids are poorly related
Water pH is
pH not usually important
Alkali waters
Early settler misnomer for high total dissolved solids
Nitrates in water is
A big concern to farmers
Comes from fertilizer, manure
Feed is the main risk
Poisoning especially likely in ruminants
Rumen flora can rapidly reduce nitrates to nitrites
Nitrate (NO3) reduces to nitrite (NO2), rapidly absorbed and leads to reduction of Hb to metHb
Inhibits oxygen transport
Chocolate brown blood that cannot carry oxygen causes
Chocolate brown blood that cannot carry oxygen
Dyspnea
Cyanotic mucus membranes
Weakness
Death (if severe)
How much water should SA get
50-60 ml/kg/day
Cats have lower physiological thirst drive than dogs
Able to concentrate urine to conserve water
Dogs drink and replace water deficit more rapidly than cats
Free drinking influenced by
Water Content of Diet
Wet food 80-85% water
Dry food <10% water
Meal Frequency
Typically drink after eating
Increasing frequency can increase water intake
Nutrient Composition
Dogs increase free intake when fed higher carbs
Cats increase free intake when fed higher protein
Nutrient enriched water is
Novel approach to increase total water intake in cats through feeding nutrient-enriched water
Increase in free liquid intake increased 60% from baseline
Cats preferred the new water
Different ways to measure energy
Energy Content of a food can be measured in different ways
Gross Energy
Digestible Energy
Metabolizable Energy
Net Energy
Gross energy means
total energy content of food
Digestible energy is
GE-fecal energy
Metabolizable enrgy
DE- urinary energy- gas energy
Net energy is
Energy available to tissues
ME-energy lost in absorption, movement, and use of food (heat)
Gross energy is in
The energy liberated when the food is burnt to ash
Highest for fats
Least accurate measurement of a food’s energy content as seen by an animal
Never used to calculate diets
Digestible energy is dependent on
Amount of energy absorbed from the digestive tract
Amount of energy in the feed minus the amount of energy lost in the feces
Depends on the fiber (cellulose and related plant fibers) content of the diet.
Used to calculate horse and beef cow rations
Metabolize energy is in
Excludes the energy required for urinary and gas functions
Net energy remaining after fecal and energy losses
Represents the energy available for growth or reproduction and for supporting metabolic processes (work, locomotion) and respiration (thermoregulation, maintenance metabolism,etc)
Differs from digestible energy (DE) mainly when it comes to protein
When amino acids are used as an energy source
They have to be deaminated
Nitrogen is excreted in the urine as urea.
ME takes this energy loss into account
ME is used in pet foods
Net energy is for
Excludes the energy lost in absorption movement and use of food (ie, heat)
The energy available to the cell (mainly as ATP)
Different values depending on the use of the energy
NEm: maintenance
NEg: growth (production)
NEl: lactation
Used in formulating feedlot and dairy cow rations
Very accurate
ME calculations
In the later 1890’s Atwater developed a simple system to calculate ME based on the fat, protein and carbohydrate (excluding fiber) components of the diet
ME
Protein and carbohydrate, ME = 3.5 kcal/g
Fat, ME = 8.5 kcal/g
Can use these values to calculate the ME available in a diet
When diet formulated to meet AAFCO standards
Calculated ME values
Energy is measured as
Calories
Kcalories(kcals) = 1000 calories
Confusingly, sometimes called the large calorie or simply the Calorie
Mcalories(Mcals) = 1000 kcal
Mcalories(Mcals) = 1,000,000 calories
kJoules, SI measurement of energy
1 Mcal= 4.2 MJ
Energy and physiologic states
Energy requirements are specific for physiologic state
Resting Energy
Maintenance Energy
Energy for Production
Growth
Lactation
Work
Resting Energy Requirement (RER) is
Normal adult animal (not pregnant, growing or lactating)
At rest
Fed
Energy to maintain body functions and digest food
Works reasonably well within a species but over a wide range of weights requirement is actually proportional to Kg0.75
Take home message:
For very small or very large animals in a given species requirements expressed /kg may be inaccurate.
Universal RER formula
RER = 70x(BWkg)^0.75
Simplified RER formula
RER = (30xBWkg) + 70
Maintenance energy requirement is
Maintenance energy requirement (MER)
Resting energy requirement
Plus an allowance for normal daily activity
Production-Defined as energy needed for
Lactation
Pregnancy (fetal growth)
Growth
Special physical activity
Working horse or sled dog
Energy for production is
Added to Maintenance Requirement to get overall energy requirement
The total is the Daily Energy Requirement (DER)
