Appendix 1 Specific contaminants and the potential impact on livestock
This Appendix provides more detailed information on some specific issues related to water contamination.
Salinity and Total dissolved solids
The following table summarises the literature on the impact of total dissolved solid content of water on performance. It should be noted that all of these studies were carried out in semi-arid, hot climates. No studies were found that tested the effects of TDS in more temperate or cold climates with lactating dairy cattle in grazing situations.
Appendix Table 1.1: Literature covering salinity and TDS effects in dairy cows
| Work | Effect | Level |
| Beede and Myers (2000) | Nominated limiting threshold based on just a couple of conflicting studies | 3000 ppm (salinity – total soluble salts) |
| Jaster et al. (1978) | Decrease in milk production observed | 2500 mg/litre NaCl + 196 mg/litre TDS tap water compared with tap water |
| Challis et al. (1987) | Trend towards decreased milk production observed | 4300 mg/litre TDS versus 450 mg/litre |
| Bahman et al. (1993) | No effect on milk production observed | 3500 mg/litre TDS |
| Solomon et al. (1995) | Decrease in milk production observed |
One study with feedlot steer calves suggested that body weight gains tended to decline more during periods of heat stress (summer) than in winter when cattle consumed water with 6000 mg/litre TDS; although, the season by water source interaction was not significant (Ray 1989). Weeth and Haverland (1961) found that growing heifers tolerated 1.75% NaCl in drinking water during the winter, but tolerated only 1.2% NaCl in the summer before toxicity signs occurred and stated that "therefore, it may be beneficial to study the interaction between environmental temperature and drinking water salinity to determine effects on lactational performance."
The experiments mentioned in the previous paragraph do not address other potential substances that may be more problematic than TDS alone. Most research has studied added sodium chloride to a water source to increase the TDS concentration. However, sodium chloride may not be the most important compound in some natural water sources. In this respect, in some studies it is not clear whether TDS or specific mineral elements, such as magnesium or sulfates, were more responsible for reduced water intake and milk production (Challis et al. 1987; Bahman et al. 1993). However, Ray and Wegner (1989) found that steers fed a high energy finishing diet could consume 6000 ppm saline water without detrimental effects on performance during summer or winter conditions. Looper and Waldner (2002) stated that "Research has shown feedlot cattle drinking saline water (TDS = 6000 ppm) had lower weight gains than cattle drinking normal water (TDS = 1300 ppm), when the ration energy content was low and during heat stress. High-energy rations and cold environmental temperatures negated the detrimental effects of high-saline water consumption. Likewise, milk production of dairy cows drinking saline water (TDS = 4,400 ppm) was not different from that of cows drinking normal water during periods of low environmental temperature. But it was significantly lower during summer months. Cows offered salty water drank more water per day (36 versus 32 gallons per cow) over a 12-month period than cows drinking normal water."
Mineral contamination of water supplies
A U.S. study investigating the variability of water composition (focussing mainly on the impact of mineral content of water on acceptability and animal performance) collected over 3600 water samples from livestock operations throughout the U.S. (Socha et al. 2001). There was considerable variability in water composition between and within regions. The average concentration in water did not exceed the upper desired level as shown in Table 7 for calcium, chlorine, copper, magnesium, sodium, sulfate, or zinc. However 15 to 30% of the samples exceeded the desired livestock levels for calcium, sodium and sulfates. The average iron and manganese content of samples exceeded the desired livestock levels and more than 40% of samples contained iron and manganese concentrations above desired levels. Sulfates and chlorides were a concern in 15 to 25% of samples, but the minerals that tended to be of greatest concern in California water were manganese and sodium, which exceeded desired livestock levels in 41 and 64% of samples, respectively.
The trials of Willms et al. (2000) have been summarised in this report. However they noted that salt contents were within the tolerance range, even though one of the properties in one year having pumped dam water with levels of around 2500 ppm sodium. This level is much higher than the maximum upper level of 300 ppm in the water quality guidelines produced by Socha et al. (2003), but not excessive according to the data in Appendix Table 1.1. However they also noted instances where sulfates exceeded 8000 ppm, a much higher level than that the guidelines in Table 7.
Nitrate and nitrite
Winks (1963) reported death of calves and cattle in Queensland from drinking water containing 2200 mg/litre nitrate. He suggested a toxic nitrate concentration for cattle as somewhere between 300 mg/litre and 2200 mg/litre. In dairy cows, nitrate concentrations up to 180 mg/litre in drinking water did not increase the concentration of nitrate in milk (Kammerer et al. 1992).
Seerly et al. (1965) concluded that drinking water containing approximately 300 mg/litre nitrate-N had no effect on the health of pigs or sheep and that levels of nitrite-N less than 100 mg/litre over 105 days did not adversely affect pig health. Anderson and Stothers (1978) similarly reported no ill effects in weanling pigs after 6 weeks of drinking water containing around 1300 mg/litre nitrate. Sorensen et al. (1994) found no effect on early weaned piglets and growing pigs from water containing up to 2000 mg/litre nitrate or up to 17 mg/litre nitrite. In experiments carried out in Queensland, pigs raised from 20 to 80 kg showed no decrease in performance and no adverse effects on health, when given water containing up to 500 mg/litre nitrate or up to 50 mg/litre nitrite (McIntosh 1981). A national survey of pig farms in the US showed no association between animal health or performance and drinking water containing up to 460 mg/litre nitrate (Bruning-Fann et al. 1996).
As ingestion of nitrite leads to a more rapid onset of toxic effects than nitrate, the guideline value for nitrite must be correspondingly lower than that for nitrate. The total dietary intake of nitrate by livestock needs to be considered when interpreting the trigger values. High nitrate concentrations in the water supply may indicate that nitrate levels in locally-grown feed may also be elevated. Trigger values of 400 mg/litre nitrate and 30 mg/litre nitrite are recommended for livestock drinking water (ANZECC 2000). Depending on the nitrate content of feed, the type of livestock and other factors such as animal age and condition, concentrations up to 1500 mg/litre nitrate may be tolerated, at least for short-term exposure. These recommended trigger values are consistent with present Canadian guidelines for livestock drinking water (100 mg/litre nitrate-N; 10 mg/litre nitrite-N) (CCREM 1987). In South Africa, trigger values range from 100 to 400 mg/litre nitrate, depending on the type of livestock, animal condition and period of exposure (DWAF 1996b).
According to Grant (1996), nitrate levels over 100 to 150ppm may cause reproductive problems in adult cattle and replacement heifers will experience reduced growth rates but generally, there is no significant effect of mildly elevated water nitrate levels on milk production. He also stated that nitrite levels in water that are over 4 ppm may be toxic to cattle; symptoms include infertility, reduced gains, abortions, respiratory distress and eventually death.
Beede and Myers (2000) cited a study, which investigated cows given tap water (19 mg nitrate/litre) or drinking water containing 374 mg of nitrate/litre added as potassium nitrate (which is at a level that most North American publications have considered could be harmful if consumed over long periods of time). This was a 35-month study looking at the influence of nitrates on reproductive and productive efficiency. They found that during the first 20 months of the study, there was no difference reproductive performance. However, in the last 15 months cows drinking the higher concentration of nitrate had more services per conception and lower first service conception rates. Although there was not a significant difference in milk yield overall, cows consuming the high nitrate water had a slightly lower total milk production during the 2-year study than cows consuming tap water, due to a longer dry period.
Ensley (2000) collected water samples from 128 dairies in Iowa to assess the effect of water quality on dairy cow performance. Drinking water coliform, nitrate, sulfate, total dissolved solids and 21 additional minerals were measured in the drinking water and correlated with 26 production parameters. Results of that study indicated that an elevation in the nitrate concentration of drinking water increased length of calving intervals. Those findings substantiated Crowley's report of a negative impact of elevated drinking water nitrate on reproduction (Crowley et al. 1974). There was also a negative relationship between nitrate concentration of drinking water and the Rolling Herd Average for Milk production (RHAmilk) and Rolling Herd Average for Protein Production (RHAprotein).
According to Adams and Sharpe (1995), nitrate levels over 100 ppm as NO3 may adversely affect cattle. Levels of 500-1000 ppm NO3 may cause moderate symptoms of toxicity in cattle while those over 1000 ppm may result in acute symptoms and death. These guidelines for cattle assume normal levels of nitrate in the diet.
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