Feeding Animals

Year 1 - Normal Animal

fresh weight

weight of food as it is prepared i.e. when fed to an animal

dry matter

weight of food without any water present

energy balance

when total energy provision of an animal is equal to the total energy it needs, if provision is greater than needs there is a positive energy balance (PEB) and if lower than needs then tehre is a negative energy balance (NEB)

gross energy

amount of energy present in food before consumption, measured using bomb calorimetry to calculate energy released by oxidation of covalent bonds

digestible energy

amount of energy present after consumption due to faecal energy loss

metabolisable energy

the energy assimilated by the animal and which is available to fuel metabolism after energy loss through urine and belching/flatulence

factors affecting metabolisable energy

digestibility (species, fibre content, plane of nutrition, feed preparation), diet quality, species (i.e. monogastric/ ruminant), nitrogen balance, food preparation, feeding levels

heat increment of feeding

heat produced by the digestion of food, as energy must be used

net energy

all of the dietary energy available to the animal when the costs of digestion, metabolism and wastage have been accounted for

practical ways to measure net energy

net energy is hard to measure so metabolisable energy is measured in ruminants, poultry, dogs and cats and digestible energy is measured in horses and pigs

formula to calculate dry matter weight

fresh weight x dry matter proportion

formula to calculate fresh weight

dry matter weight/ dry matter proportion

metabolic rate

the total conversion of energy in the body per unit time

basal metabolic rate

amount of energy expended to keep an animal alive, measured when animal is not moving, not stressed, within thermoneutral zone and post absorptive state

fasting metabolic rate

amount of energy expended when an animal has a low level of activity

maintenance metabolic rate

energy expended when an animal is eating exactly the amount of food needed to maintain a constant body mass

ways to measure metabolic rate

direct calorimetry; measure of heat production by animal in a calorimeter, indirect calorimetry; estimating the heat produced from respiratory exchanges in a calorimeter

factors affecting metabolic rate

size (smaller increases rate), age, activity

energy costs in addition to maintenance in livestock animals

growth and fattening, lactation, gestation, wool growth, egg production, thermal stress

vitamins

organic compounds required in very small quantities for normal body function, will be fat or water soluble

which vitamins are water soluble?

B and C

which vitamins are fat soluble?

A, D, E and K

vitamin C chemical name

ascorbic acid

vitamin B1 chemical name

thiamine

vitamin B2 chemical name

riboflavin

vitamin B3 chemical name

nicotinic acid/ niacin

vitamin B5 chemical name

pantothenic acid

vitamin B6 chemical name

pyridoxine

vitamin B7 chemical name

biotin

vitamin B9 chemical name

folic acid

vitamin B12 chemical name

cyanocobalamin

provitamins

compounds that act as vitamins only after undergoing chemical change to active forms in the body

avitaminosis

total absence of a vitamin

hypovitaminosis

partial lack of a vitamin, often shown by non-specific signs of ill health which don’t always relate directly to the vitamin’s metabolic function

hypervitaminosis

excessive provision of a vitamin

metabolic functions of retinol

formation and integrity of epithelia and mucous membranes, retinal function (combines with opsin to form rhodopsin), bone growth, immune function

factors affecting vitamin requirements of an animal

health, age, production, rate of growth, speed of food passage through gut

beta carotene

pro-vitamin A which is converted to retinol during absorption through the gut wall, however the ability to do this varies with age, species, breed and health

where is retinol stored?

in the liver

sources of retinol

liver, egg yolk, milk fat, beta carotene in plants

retinol deficiency in cattle

symptoms: rough scaly skin, night blindness, lachrymation, corneal opacity, infertility, abortion, retained placenta, still-birth

rare in adults as they acquire carotenoids at pasture so can provide adequate retinol over winter periods but intensively reared indoor beef cattle on cereal diets are more prone

symptoms of retinol deficiency in dogs

dry, scaly skin, night blindness, abnormal skeletal growth

symptoms of retinol deficiency in cats

foetal defects or complete infertility

retinol deficiency in poultry

symptoms: pale comb and wattles, loss of condition, slowed growth, ruffled plumage, susceptible to infectious diseases

high mortality rate

symptoms appear after 2-3 weeks

effects of hypervitaminosis A in dogs and cats

abnormal bone deposition, lameness, vertebral spondylosis, gingivitis, weight loss, poor coat

effect of hypervitaminosis A in pregnant sows

cardiac abnormalities in piglets 

biological molecules classed as vitamin D

calciferols

sources of vitamin D

sunlight, oily fish, egg yolk, hay, colostrum

metabolic functions of vitamin D

promotes calcium ion absorption from digesta in the gut lumen, enhances intestinal absorption of calcium when blood calcium concentration decreases, stimulates phosphorous uptake from gut and reabsorption of calcium and phosphorus from bones and kidneys

problems caused by vitamin D deficiency

rickets (soft weak deformed bones in young growing animals), osteomalacia in adults (weak bones), poor egg shell quality and weak bones in poultry

vitamin E chemical name

tocopherol

metabolic functions of vitamin E

biological antioxidant, acts in combination with glutathione peroxidase to protect cells from oxidative damage caused by free radicals, important for reproductive and muscular function and capillary integrity

problems caused by vitamin E deficiency

white muscle disease and mulberry heart disease in calves, stiff lamb disease in lambs, mulberry heart disease in pigs, crazy chick disease in poultry, tying-up in horses

group of molecules that are vitamin K

quinones

sources of vitamin K

green, leafy materials, egg yolk, liver, fish

metabolic functions of vitamin K

essential for normal clotting of blood, bone and kidney function

signs of vitamin K deficiency in chicks

anaemia and delayed clotting of blood

sources of vitamin E

green doffer, cereals

why are B vitamin deficiencies only seen in pre-ruminant young and sick ruminants?

rumen bacteria can synthesise B vitamins in sufficient quantities

metabolic function of vitamin B1/thiamine

initiation and propagation of nerve impulses

signs of vitamin B1/thiamine deficiency

progressive dysfunction of nervous system, paralysis, blindness, muscular dysfunction, loss of appetite, emaciation

how can adult ruminants develop vitamin B1 deficiency?

bacterial thiaminases produced in disturbed rumen microflora destory ingested and bacterial thiamine

metabolic function of vitamin B2/riboflavin

vital for oxidative phosphorylation and proton transport

signs of vitamin B2 deficiency in pigs

poor apetite and growth, skin eruptions, vomiting, eye abnormalities, infertility and abortion

metabolic function of cyanocobalamin

important coenzyme in cellular respiratory pathways

signs of vitamin B12 deficiency

poor growth in young animals mostly

sources of vitamin B12

food of animal origin, microbial as long as cobalt is present in diet

sources of vitamin C

citrus fruits, green leafy vegetables

metabolic functions of vitamin C

normal collagen formation, metabolic oxidation and reduction pathways, iron transport, antioxidant

which animals need vitamin C in their diet?

primates, guinea pigs and fruit bats (other species synthesise it from glucose)

signs of vitamin C deficiency

scurvy, lethargy, muscle and joint pain, red dots on skin, bleeding and swelling of gums, diarrhoea, weight loss, rough hair coat, reduced immune function

signs of vitamin B2 deficiency in chicks

curled toe paralysis

signs of vitamin B2 deficiency in ruminants

inappetence, diarrhoea, mouth lesions

signs of vitamin B6 deficiency

neural degeneration and jerky gait in chicks, rare due to wide distribution and gut microbial synthesis

2 types of essential minerals

macro and micro

functions of calcium

structural component of skeleton, controls cell excitability, regulates muscle contraction, regulates blood coagulation, many enzyme actions

sources of calcium and phosphorus in an ideal ratio

leafy greens, hay, animal products

corrective sources of calcium

limestone flour, soluble grit for poultry

factors affecting absorption of calcium

plant calcium can be bound as phytates which prevents absorption in monogastrics, oxalates bind to calcium to form insoluble salts, total absorption of calcium and phosphorus decreases as dietary concentration becomes excessive, high fat diets as fatty acids bind to calcium, enteritis - inflamed mucosa can’t absorb calcium

causes of hypocalcaemia

female mammals at onset or peak of lactation, laying hens due to eggshell production

milk fever

sudden hypocalcaemia in dairy cows before/shortly after calving caused by high demand for calcium due to lactation, causes flaccid paralysis, recumbency, rumen stasis, pupil dilation

chronic hypocalcaemia

occurs in growing animals due to high rate of skeletal growth which causues osteodystrophy (abnormal bone growth) and rickets (failure of bone to ossify)

causes of osteodrystrophies in puppies/kittens

excessive phosphorus causes a secondary calcium deficiency

factors affecting absorption of phosphorous

oxalates and phytates cause lots of plant phosphorus to be organically bound as salts of phytic acid, excess dietary calcium inhibits absorption of phosphorus

signs of phosphorus deficiency

abnormal bone growth, osteomalacia, reduced growth rates, abnormal appetites, infertility

functions of magnesium

most common enzyme activator, allows muscle contraction, propagation of nerve impulses

sources of magnesium

green plants, meat and bone, colostrum, magnesite, no body reserves

major presentations of hypomagnesaemia

• calves fed all-milk diets (poor source of magnesium)

• beef cattle and sheep fed on low quality roughage/fodder crops, causes dullness, hyperaesthesia, convulsions, death

• lactating cattle and sheep, hyperaesthesia, incoordination, muscle tremor, recumbency, convulsions, sudden death, ‘grass staggers’

causes of grass staggers

rapid grass growth, grass diarrhoea, bad weather, fertilisers (nitrogen increases rumen NH3 which decreases Mg uptake, potassium increases Mg excretion, liming decreases grass Mg concentration), gradual decrease in grass magnesium in autumn, stresses which decrease food intake

ways to reduce hypomagnesaemia

provide shelter, introduce to spring grass slowly, use fertilisers with care, porvide mineral licks, top dress pastures, increase clover in swards, supplement diet or water with mg, Mg rumen boluses, avoid stress

functions of copper

important for formation of plasma proteins, component of other blood proteins, plays a role in oxygen metabolism, role in many enzyme systems, essential for normal hair, wool and feather pigmentation, essential for immune function

most readily absorbed form of copper

copper sulphate

transport of copper in the body

loosely bound to albumen in plasma and stored and released from liver to meet body requirements

signs of copper deficiency

anaemia, abnormal bone growth, abnormal hair, feather and wool growth, loss of hair pigmentation, cardiovascular disease

swayback

disease affecting lambs born to copper deficient ewes which causes failure or degeneration of normal neural development in lamb or stillborn, depressed growth rate, rapid onset hind limb weakness, ataxia then paresis and death

signs of copper deficiency in calves

failure to thrive, poor growth, stiff gait/lameness, loss of hair pigment (causes a speckled appearance)

effect of molybdenum on copper absorption

rumen microbes form sulphides which combine with molybdenum to form thiomolybdate which binds copper to form copper thiomolybdate which decreases copper absorption and causes signs of copper deficiency despite adequate dietary copper provision

animals with the worst copper toxicity tolerance

sheep (then cattle, horses then pigs)

signs of copper toxicity

jaundice, appetite loss, hepatic coma and death

nutrient

any chemical element or compound in the diet that supports normal reproduction, growth, lactation or the maintenance of life processes