Summary Feed and environmental issues

BLGY1211 Feed and environmental issues

Pollutants
 Slurries are liquid and can be pumped and manures are solid and can be stacked
 Pigs excreta 5kg per day (0.03kg N and 0.01 kg P), dairy cows excreta 53kg per day
(0.14kg N and 0.03kg P)
 13 billion tonnes of waste per annum  21 billion by 2030
 Extensive (e.g. ranching); ratio of animals per unit of land is low, diffuse pollution
 Intensive (e.g. feedlots); ratio of animals per unit of land high, point source pollution
 Nitrogen (nitrate - NO3-, ammonia - NH3, nitrous oxide (270x warming ability) - N2O);
20 million tonnes/annum, 44% of global ammonia output to increase by 60% over
next 30 years, produce 17% of nitrous oxide to increase by 50% over next 30 years
 eutrophication (marine), methaemoglobinemia (caused by decreased ability of
blood to carry oxygen as methaemoglobin is a form of haemoglobin that doesn’t
bind to oxygen  tends to effect bottle fed infant where water is drawn from wells
in rural areas (nitrate in water reduced to nitrite in gut which is then absorbed) and
enzyme deficiency), global warming, vegetation biodiversity  heathlands
particularly sensitive and can cause them to be taken over by grass, moss-dominated
heathlands are reduced and species of vegetation that only require low levels of
nutrients are lost
 Phosphorus (phosphate - H2PO4- ) ; 11 million tonnes/annum, found in weakly acidic
conditions, macronutrient  eutrophication (fresh water)
 Methane (greenhouse gas 21x warming ability); 15% of global emissions to increase
by 60% over next 30 years
 Heavy metals (Cu, Zn)
 Eutrophication – enrichment of an ecosystem with chemical nutrients
 Increase in the transport and trade of animals will result in more pollution
 Excreta from ruminants tends to be N-rich and excreta from non-ruminants tends to
be P-rich on a LW basis  largely due to differences in digestive physiology
 By improving the utilization of dietary N and P the output of these pollutants from
animals into the environment is reduced

Gut fermentation
 Sites of gut fermentation; foregut fermenters (Ruminants, Camelids, Sloths, Colobus
monkeys, Kangaroos, Hoatzins), hindgut fermenters (All animals but some are
specialists; non-ruminant herbivores  Elephants, Horses, Rabbits, Rodents)
 Hindgut fermenters
 Feed enters the mouth where it is chewed (masticated) and mixed with saliva
secreted from salivary glands (submaxillary, sublingual and parotid glands)
containing amylase which begins the digestion of starch and dextrins
(products from starch hydrolysis)  food passes down oesophagus to
stomach where its mixed with secretions from the stomach glands (gastric
juice) consisting of HCl, mucin, pepsin, rennin and lipase  small intestine
divided into 3 regions (duodenum, jejunum and ileum); duodenum (main site
of digestion)feed is mixed with intestinal juice, pancreatic juice and bile,
jejunum and ileum major sites of nutrient absorption (absorbed into hepatic
portal vein and lymph)  digesta goes into large intestine divided into 3

, regions (caecum, colon and rectum); concentrated populations of enteric
microorganisms (mainly bacteria but also fungi and protozoa) exist in a
symbiotic relationship with the host (they digest and ferment the dietary
constituents that escaped digestion further up the gut, mainly plant fiber
composed of cellulose, hemicellulose and lignin)
 Fermentation takes place after the stomach and the small intestine 
enlarged hindgut (caecum and/or colon)
 Microorganisms get what the animal doesn’t use  better if higher quality
diet
 VFA’S (acetate, propionate, butyrate) are absorbed straight through hindgut
walls and are an important source of energy
 Microorganisms are defecated  hindgut fermenters miss out on microbial
protein and vitamins
 The more fibrous an animal’s diet, the larger the population of enteric
microorganisms in the large intestine and the larger the large intestine
 All mammals are hindgut fermenters
 Carnivores have the simplest guts of all mammals as have a short
uncomplicated intestine
 Foregut fermenters
 Stomach is compartmentalized into four compartments (rumen, reticulum,
omasum and abomasum); rumen contains large populations od
microorganisms so feed is subjected to pregastric/foregut fermentation and
hindgut fermentation
 No upper incisor teeth so depend on upper dental pad and lower incisors to
bite  mixed with saliva in the mouth that doesn’t contain amylase then
passes into the rumen  rumen is a large chamber containing
microorganisms (continuous culture system for anaerobic bacteria, protozoa
and fungi)  VFAs and ammonia are absorbed across the rumen wall  feed
remains in rumen until it has been broken down into particle sizes small
enough to pass out of the rumen via the reticulum into the omasum along
with numerous microorganisms (the more fibrous the diet the longer the
feed tends to remain in the rumen)  feed is regurgitated into the mouth for
rechewing, water is extracted from digesta in the omasum which has layers
of lamellae to increase SA for absorption  digesta and microorganisms then
flow into abomasum where hindgut fermentation takes place (see above)
 Fermentation vat (rumen) comes before the stomach
 Food is entirely processed my microorganisms  not good if diet is of high
quality (will be down-graded); good if diet of low quality (will be upgraded) –
known as the leveling effect of the rumen
 VFA’s are absorbed straight through rumen walls  how ruminants get 60-
80% of their energy
 True stomach and small intestine is used to digest microorganisms  how
ruminants get about 60% of their protein
 Not all herbivores are ruminants as they aren’t as efficient as ruminants at digesting
fiber because of the absence of a holding chamber like the rumen means the transit
time of digesta in the gut is more rapid meaning there is less time for the microbes in
the large intestine to digest and ferment fiber