Digestion

• Feed additives

  Added to feed for a number of reasons to effectively improve production levels, improve efficiency, and improve animal health
• Feed additives

  • Decrease the incidence of coccidiosis, bloat and acidosis
  • Suppress oestrus and control other health issues like parasites
  • Increase palatability encouraging the animal to eat more
• Ionophores


  Antimicrobial compounds (not antibiotics but similar) that modify microbial fermentation in the rumen, allowing cattle/sheep to get more energy from the food they consume
• Ionophores


  • Improve feed efficiency by capturing feed energy during rumen fermentation and therefore decreasing the amount of methane produced
  • Increase the absorption of nitrogen, magnesium, zinc and selenium
  • Decrease the breakdown of protein in the rumen, increasing bypass protein in the small intestine where it can be better used by the animal
• Ionophores


  • Monensin
  • Bovatec
• Buffers


  Added to ruminant diets to reduce fluctuations in rumen pH
• Buffers


  • Sodium carbonate (a base which raises pH)
  • Acid Buf (derived from marine algae)
• Acidosis (Grain Toxicity)


  Caused by a build up of lactic acid in the rumen, most often occurs when animals are first put onto a high grain diet
• Antibiotics


  Controls a range of bacterial diseases, only to be used on order by a licensed veterinarian, not to be used in calves to be processed for veal or animals that are intended on breeding
• Controversy on overuse of antibiotics - antibiotic resistance is a serious human health issue
• NPN - non protein nitrogen - Urea


  Supplementation can increase the rate of digestion of dead and decaying grass which becomes more fibrous and difficult to digest over time
• Urea


  • Contains no by-pass protein and is commonly supplemented in the dry season as it is a cost-effective source of nitrogen
  • It stops weight loss but will not result in weight gain
• Hormone Growth Promotants


  Increases growth rate, feed efficiency, profit, consistency of line, decreased impact on environment, labour, resources fuel, feed etc
• Oestrus suppressors


  Melengestrol Acetate (MGA) can be mixed into feed to prevent heifers cycling, it will increase the rate of weight gain and improve feed efficiency
• Growth promotants are only concerned with increasing the rate of growth, while feed additives are used to improve the quality of the feed/rectify nutrient deficiencies or similar or increase palatability to increase feed intake
• Meat meal cannot be fed to ruminants because it is a restricted animal material (RAM) and is banned due to its link to the occurrence to mad cow disease
• Functions of feed additives

  1. Reducing disease risk

  2. Altering rumen microflora to reduce waste

  3. Improve efficiency of digestion/metabolism of feed

  4. Correcting vitamin/mineral deficiencies
• Feed additives

  • Antibiotics, coccidiostats, probiotics, vitamin/mineral premixes
• Functions of antibiotic growth promotants

  1. Altering rumen microflora to reduce waste

  2. Improve efficiency of digestion/metabolism of feed
• Functions of hormonal growth promotants

  Accelerate animal's metabolic processes, leading to faster growth rates
• Growth promotants

  • Antibiotics, oestrogen, testosterone, synthetic androgens
• Effects of feed additives and growth promotants on efficiency and profitability

  • Increased growth and production due to better use of feed and reduced losses due to nutrient deficiencies/health issues/waste (e.g. methane emissions) with little change in feed requirements
  • Increased income with costs maintained/reduced = greater profit
  • Possible reduction in health issues = reduced costs of treatment/lost production
  • Cost of additive/implant and its application must be taken into consideration
• Why do animals need food?

  • Livestock require good quality feed for 4 main reasons:
  • Supply of energy for day to day life processes (respiration, movement, circulation etc.)
  • Maintenance and growth of body tissues
  • Regulation of vital bodily processes
  • Meet additional energy demands required for wool growth, milk production etc.
• Nutrients


  • Water
  • Energy
  • Protein
  • Minerals
  • Vitamins
• Water


  • Required by animals for:
  • Transportation of nutrients around the body
  • Removal or excretion of waste products
  • Control of body temperature
  • Milk production
  • Production of blood
  • An animal can last up to 60 days without food but only 7 seven days without water
• Carbohydrates


  • Monosaccharides: glucose, fructose
  • Disaccharides: sucrose, maltose and lactose
  • Polysaccharides: starch, glycogen and cellulose
• Ruminants


  The only animals that can break down cellulose to obtain protein
• Protein


  • Essential for energy production and makes up almost 50% of an animals dry mass (bones, tissue, muscles, nerves, blood and hormones)
  • Used to make wool, muscle, tissue and hair
  • Especially important for growing animals, pregnant animals and for milk production
• Protein in ruminants


  • Obtained through various feedstuffs but is also created in the rumen
  • The creation of protein in the rumen is dependent on the crude protein of food remaining above 7%
• Macro minerals


  • Calcium
  • Phosphorous
  • Potassium
  • Sodium
  • Chlorine
  • Sulphur
  • Magnesium
• Micro minerals


  • Iron
  • Zinc
  • Copper
  • Manganese
  • Iodine
  • Cobalt
  • Molybdenum
  • Selenium
  • Fluorine
• Fats


  • Required in relatively small amounts by all animals
  • They contain more energy than carbohydrates
  • Can be found in plants and seeds
  • Fatty acids are important as they regulate body metabolism
  • Too much fat can be detrimental
  • Oily plants contain higher levels of fats
• Vitamins


  • Fat soluble – A, D, E and K
  • Water soluble – B vitamins and vitamin C
  • Green feed generally contains adequate levels of these vitamins
• Plant components


  • Water
  • Carbohydrates: Structural – cellulose, Non-structural – simple sugars and starches
  • Protein
  • Minerals
  • Fat
• Products of plant digestion

  • Volatile fatty acids (VFAs): Acetic, Propionic, Butyric
  • Proteins: Microbial amino acids, Plant amino acids
  • Fat: Fatty acids, Triglycerides
  • Carbohydrates: Glucose
• Energy


  Energy content for animals represents the capacity of various components of feed to allow the animal to perform its regular functions. For instance move muscles, to metabolise nutrients and produce heat.
• Energy flow through animal

  1. Gross energy (GE)

  2. Energy in faeces: Digestible energy (DE)

  3. Energy from urine

  4. Energy in rumen gasses: Metabolisable energy (ME)

  5. Heat losses – panting, radiation: Net energy (NE)

  6. Maintenance

  7. Production: growth, lactation
• Dry matter


  The component of feed that remains after all the water has been removed
• Dry matter digestibility


  Provides an indication of the proportion of energy in a feed that is able to be digested
• Metabolisable energy


  The amount of energy that is available to the beast for its metabolism or body functions