Week 5 - Soils, Nutrients & trace elements

what is soil

= mineral/organic material on the earth’s surface

what 3 functions do soil play

• Diverse habitat, many diff organisms

• Nutrient cycling, carbon sequestration

• good quality soil to grow plants that are fed to animals e.g., pasture, crops

why is soil quality important

• Need to maintain soil quality to allow us to grow plants

• If we have unhealthy, degraded soils, this will impact our ability to grow food (for us & for our animals)

what are 5 management pratices that reduce biodiversity & nutrients in soil

• Overuse of fertilizer

• Monoculture crops

• Harvesting

• Inappropriate tilling, ploughing

• Pollution (e.g. oil, chemicals, pesticides)

what does soil degradation refer to

= change in the soil health status resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries

what are 5 types of soil degradation issues

(hint: e.g. what happens when there’s not enough water)

• desertfication

• erosion

• compaction

• nutrient depletion

• pollution

desertification

• where does it occur

• what happesn

• = in dryland areas, land can’t be used for its original use

what does erosion refer to (what can cause this)

= loss of topsoil & nutrient by water or wind

what is compaction

= mechanical pressure → creating impermeable layers that limit nutrient & water cycles

what is nutrient depletion?

in what areas is this most common

= no replenishment of nutrients taken out of the soil (esp in areas w/ intensive agricultural crop-growing)

why is soil moisture important

Essential for plant growth

• Diff plants have diff preference (e.g. wetland vs drylands)

how is moisure stored in soil

• Depends on the soil type

In what types of soil is moisture not stored well?

• Slopes → causing run-off

• Hard crust

• Non-wetting sands

• High evaporation

how is soil important to animal health (vets)?

• Farmers consult soil science or agronomy experts (the science of soil management and crop production)

  • Importance of soil for pasture/growth 

• Vets focus on trace elements & mineral deficiencies 

  • Advising farmers on nutrition for their animals

what are trace elements

= minerals required in very small quantities but essential for normal function (~20 need for animals)

which 8 trace elements are important for ruminants

 cobalt, selenium, iodine, copper, zinc, manganese, iron

(cciimsz)

how do animals get trace elements

Eaten in the pasture/forage or supplemented 

role of vets in ensuring trace element levels in production animal

prevention & treatment of deficiencies and/or toxicities

(T/F) There is a lot of science available for trace element requriements in animals

True. There is LOTS of science available, particularly regarding cattle & sheep

• BUT: Still see frequent over-use of supplements (i.e.,unnecessary use) & sub-clinical deficiencies still occur (i.e. the deficiency is not severe enough to present definite or readily observable symptoms)

what 6 factors do trace element requirements depend on?

• current reserves

• Metabolic demands (e.g. growth rate, age, repro)

• Disease status 

• Genetic variability (species, speeds, individuals)

• Physical nature of the diet

• Chemical composition of the diet

  • Form and concentration of the element

  • Complexing compounds that enhance absorption

  • Antagonists that decrease absorption

how does the chemical composition of the diet affect trace element requirements?

• Form and concentration of the element

• Complexing compounds that enhance absorption

• Antagonists that decrease absorption

why is cobalt important

• Constituent of Vitamin B12, converted by rumen microbes

• Part of a co-enzyme in the propionate to glucose pathway = energy metabolism

• Thus, deficiency = shortage of glucose

Which animals do you think would be particularly susceptible to a glucose shortage?

• Young growing animals 

• Dairy cows

what happens when sheep are deficent in cobalt

Washy wool = easily breakable wool 

what are some risk factors for cobalt deficiency

• Geographical location

  • Diff in soil & forage content (Fertilizers may reduce availability of cobalt)

  • Countries have maps to indicate deficiencies → farmers can plan

• Species & age of animal

importance of selenium

• Antioxidant enzymes: Protects cells against free radicals

• Resistance to infections

• Reproductive performance

what happens to ruminant animals if they are deficient in selenium

• reproductive performance

  • Poor growth

  • Early embryonic death

  • Retained fetal membranes

• Reduced resistance to infection (e.g. mastitis)

• antioxidant properties: White muscle disease

what is white muscle disease

oxidative damage and degeneration of skeletal and/or cardiac muscles → muscle looks white

is selenium safe in over dose?

No. it is toxic in overdose

risk factors for selenium deficiency

(how does forage content affect selenium content in soil)

• Geographical location

  • Diff in soil & forage content

    • Lush rapid growing pastures

    • Legume dominant pasture

    • Fertilizer (e.g. sulfur containing or superphosphate fertilizers)

    • High rainfall

• Species, age & physiological state of animal

why is iodine important

= used to synthesize thyroid hormones

Which physiological states do you think would be most susceptible to iodine deficiency?

Pregnancy

what happens if animal is deficient in iodine

• Goitre = enlarged thyroid glands 

  • May happen to fetus when the mother doesn’t have enough iodine

• Increased perinatal mortality

risk factors for iodine deficiency

• animal diet interact with iodine metabolism

  • Brassica crops increases risk of deficiency (e.g. turnips, kale). Low iodine concentration. contain glucosinolates that are goitrogenic

• Soil concentration

• Physiological state → pregnant animals most at risk

why is copper important

= important part of diff enzymes

(e.g. myelin formation, collagen synthesis, erythropoiesis)

which 2 elements are toxic in overdose

selenium & copper

is the requirement level for coppper the same for all ruminant animals

False. Large variation in requirement & absorption ability

• Cattle more prone to deficiency than sheep

• Texel sheep more prone to toxicity (they have very efficient absorption)

what happens when ruminant animals are deficient in copper

• Gait abnormalities & osteoporosis

• Reduced fertility

• ill-thrift/poor growth

• Poor coat condition

risk factors for copper deficiency

• primary & secondary deficiency

• seasonality (copper status in the body chanegs over the year, lowest in winter, so need to ensure adequate stores in the autumn)

• diet (some supplements that may be used for food contain copper that the farmers may not be aware of ) e.g. PKE

what is PKE

Palm kernel extract/PKE (by-product of palm oil production) - can be used as supplementation of copper

where in the body is copper stored

in the liver

primary vs secondary copper deficiency

• Primary = not enough copper in diet

• Secondary = competing elements result in deficiency

  • E.g. molybdenum & iron

  • High level of these can induce copper deficiency (reduce copper absorption)

what are some reasons for deficiencies in trace elements

• Regional issues/risks for pasture-based system

• change in farm policy

  • type of animal is changed (stock classes)

  • animal management changed (pasture → alternative forage)

what does stock classes refer to

categorizing animal based on species (cattle, sheep, swine, poultry), age (calf, weaner, yearling, adult), sex/production status (steer, heifer, cow, bull, ewe, ram, gilt, barrow), and intended use/quality (feeder, market, breeding, prime)

• diff stock class will have diff nutritional requirements