ND = not detected.
ND = not detected.
A comparison of levels of estrogens concentrations in animal waste effluents reported in overseas literature and in New Zealand (Table 2 and 3) shows that the concentration of these compounds varies significantly depending on the number of animals and their reproductive stages. For example, a studies conducted in the USA demonstrated the highest average concentrations of estradiol and its metabolites were observed in effluents from dairy holding ponds (Williams 2002; Raman et al. 2001).
In the New Zealand study, dairy effluent samples were collected from either 1- or 2-stage oxidation pond systems. The number of cattle on each farm may have had a significant influence on the concentration of estrogens found in these samples. For instance, some samples showed much higher values than others, such as the sample in Farm 4, where the total load of estradiol (a and P epimers) was a few orders of magnitude higher than the sample collected from Farm 5. Farms 2 and 4 had greater numbers of animals (250 and 262 dairy cows, respectively) than other farms, and this was reflected in the total estrogens present in the effluent. The ratio of steroid hormones excreted in faeces and urine can dramatically change during pregnancy and lactation periods (cited by Hanselman et al. 2003). The 17a-estradiol epimer is reportedly more prevalent in dairy cattle than its P-epimer (Hanselman et al. 2003) and it was therefore not surprising to find greater values of 17a-estradiol in dairy farm effluents. The a and P stereochemical distinction of estradiol might be useful for identifying the livestock species contributing to waterway contamination (cattle vs pig or poultry); however, this possibility has yet to be investigated.
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