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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.