ALFS nutrition

• the components of food are water, dry matter, inorganic (minerals), organic (proteins, lipids, carbohydrates) and vitamins
• nutrition can prevent or control metabolic syndromes such as pregnancy toxaemia, hyperinsulinemia, hypocalcaemia and hypoglycaemia
• copper toxicity is common in sheep as excess is stored in the liver
• examples of vitamin and mineral deficiencies in nutrition include swayback (copper deficiency in mid to late pregnancy), white muscle disease (a deficiency in selenium and/or vitamin E) and pining (retarded growth from cobalt and/or Vitamin B12 deficiency)
• nutrition plays a role in fertility, public health and behavioural management
• nutrition can control and prevent deficiencies, toxicity, metabolic syndromes and obesity/ weight loss
• nutrition drives growth, milk production, wool/ hair growth, food production and production quality
• nutrition accounts for 80% of production costs on average
• terms used in food analysis:

  • moisture
  • ash
  • crude protein
  • ether extract
  • lipid content
  • crude fibre
  • nitrogen-free extracts
• Ash is measured by igniting feed at 550c and the remaining residue is ash
• crude protein is measured by multiplying the nitrogen content of the feed by 6.25
• Crude fibre is measured by boiling residue from ether extract in acid or alkali
• Nitrogen-free extracts are measured by 1000 - (moisture + ash + CP + EE + CF)
• modern methods used instead of crude fibre include neutral detergent fibre (cell wall material which doesn't dissolve in neutral detergent = lignin + cellulose + hemicellulose) and acid detergent fibre ( fibre insoluble in acid detergent = lignin + cellulose)
• carbohydrates can be structural (cell wall material) or non-structural (storage material)
• structural carbohydrates provide dietary fibre and are a major energy source to herbivores (due to fermentation)
• microbial degradation of the cell wall depends on the plant species, stage of growth, type of cell wall, constituents, composition of the cell wall
• the plant cell wall is made up of non-starch polysaccharides (cellulose, hemicellulose, pectin and proteins) and phenolics (lignin, water and minerals)
• lignin is a non-carbohydrate monomer which is negatively correlated to digestibility. Lignin proportion in the plant increases with maturity
• lignin reduces digestibility as it is highly resistant to chemical and microbial degradation. some plant carbohydrates and protein are bound to lignin so cannot be freed for use easily
• water soluble carbohydrate fraction (WSC) measures the proportion of fructan and simple sugars (non-structural carbohydrates)
• The proportion of non-structural carbohydrates varies by season. In early spring there is rapid growth so NSC levels are low ( being used to grow) whereas in late spring/summer there is reduced growth so NSC levels are high ( being stored)
• Non-structural carbohydrates differ by time of day. Proportion rises during the day, peaking in the late afternoon/ early evening. Proportion declines in darkness as NSCs are being used.
• NSC proportion is altered by temperature (low = increase), light (increase = increase), water (increase = increase) and fertiliser (increase = decrease)
• cereal grains, forage legumes, roots and tubers, leaves and grass stems are all rich in NSCs
• grass makes up approximately 60-65% of dairy cattle's diet
• grass makes up approximately 80-85% of beef cattle's diet
• grass makes up approximately 90-95% of sheep's diet
• grass makes up approximately 80-90% of a horse's diet
• there are two types of grassland: natural (rough/ hill grazing) and cultivated ( permanent and rotational/ grass ley)
• there is roughly 34 million acres of grassland in the uk
• natural grasslands are mainly grazed by sheep
• natural grasslands are made up of poor quality grasses, heather, rushes and mosses. quality is affected by soil type, topography and climate
• natural grassland is managed by grazing and burning
• permanent pasture is grassland managed for at least 5 years without re-seeding. permanent pasture grass is more palatable and nutritious than rough grazing
• permanent pasture is more diverse than natural grassland, containing ryegrasses, cocksfoot, fescues, timothy and meadow grass
• grass leys are rotational cultivated grasslands which are sown every few years as part of an arable crop rotation. grass is again more palatable and nutritious than permanent pasture grass
• grass leys contain mainly ryegrasses and legume mixes e.g clover
• lucerne is a grazing material (not in the UK) which is conserved. it is higher in protein and minerals than grass
• factors affecting grass growth include time of year, environment, soil status, grass species, general management and cutting/grazing strategies