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)

• 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

Bovine somatotropin (BST) is a protein naturally produced by cows:

• 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)

1. Animal welfareMay make cows more vulnerable to hoof-splitting, udder infections and reproductive problems

Reasons for the ban:

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 worriesSmall 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)

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

Will drinking milk from BST – treated cows also increase ourlevels of IGF-1 and therefore the chances of developing cancer?

Will drinking milk from BST – treated cows also increase ourlevels of IGF-1 and therefore the chances of developing 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

Severe undernutrition

Adequate nutrition

Moderate undernutrition

Basal

BST

0

50

100

150

200

BST (ng/ml)

1. Why are BST-treated cows likely to need greater quantities of high-nutrition 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.