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How are agrochemicals used to
manipulate the food species?
Learning Outcomes
• Describe the uses of plant hormones.
• Describe the advantages and risks of animal hormones.
• Describe the uses of BST
Agrochemicals
Hormones and other chemicals can be used to control aspects of
plant and animal growth
Hormone/substance
Effect
Indoleacetic acid (IAA)
Apical dominance
Ethylene gas
Promotes fruit ripening
Indolebutyric acid
Stimulates root growth
Zeranol
Improves unsaturated fatty acid
content of beef
BST
Improves milk yield
Progesterone
Increases growth efficiency
Hormones
Potential problems
• Steroid hormones such as Progesterone exert effects when we or
other species ingest them
• There may be a link between intake of e.g. Zeranol and incidence of
breast cancer
• Growth promoting hormones are released in manure, contaminating
surface and groundwater. Female fathead minnows downstream of
cattle feedlots have developed male characteristics and male fish have
developed abnormally small testes and almost feminized heads
Monsanto News Story
Bovine somatotropin (BST)
Bovine somatotropin (BST) is a protein naturally produced
by cows:
• Essential for growth and development of
the mammary gland and for milk
production
• Farmers in the US and 33 other countries
inject BST into cows to increase milk
production
• Some studies have suggested that BST also improves fertilization rate,
accelerates embryo development, and improves embryo quality
• But it has been banned in the EU since 1994
Bovine somatotropin (BST)
Reasons for the ban:
1. Animal welfare
May make cows more vulnerable to hoof-splitting, udder infections
and reproductive problems
2. Human health
• One concern is that the use of BST may trigger breast and prostate
cancer
• Cows given BST have more IGF-1 in their milk. High concentrations
of IGF-1 are found in the breasts of women suffering from breast
cancer
3. Socioeconomic worries
Small farmers are worried that they will be forced out of business by
bigger farms that can afford to treat their bigger herds with bigger
doses of BST
Bovine somatotropin (BST)
Will drinking milk from BST – treated cows also increase our
levels of IGF-1 and therefore the chances of developing cancer?
There are several arguments suggesting the answer is No
• There is little evidence that IGF-1 can
survive eating and cross into the
bloodstream
• Humans naturally produce IGF-1
• Three pints of milk contain less than
1 per cent of the IGF-1 that we
produce naturally
• It assumes that it is the high
concentrations of IGF-1 that is
causing the cancer
Bovine somatotropin (BST)
The graph shows the effect of different levels of nutrition on cows that
have been treated with BST and control cows not treated with BST
200
Basal
BST
150
BST (ng/ml)
100
50
0
Adequate
nutrition
Moderate
undernutrition
Severe
undernutrition
1. Why are BST-treated cows likely to need greater quantities of highnutrition food than the control cows?
2. Why might BST-treated cows be more likely to suffer hoof problems?
3. Some scientists have argued that use of BST may help stop global climate
change as fewer cows will be needed. Explain the scientific basis of this
claim.