Determining critical atmospheric ammonia levels for cattle, sheep and goats - a literature review
| Project start date: | 01 January 2001 |
| Project end date: | 01 December 2003 |
| Publication date: | 01 December 2003 |
| Project status: | Completed |
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Summary
The principal findings from the literature are:
• Ammonia gas is volatilised into the atmosphere by the action of bacterial urease enzymes in the bedding or manure pads, breaking down urea in urine and also undigested protein in faeces.
• Volatilisation of ammonia from the bedding or pad increases when pH rises above 7.0 and with increasing ambient temperature.
• Atmospheric ammonia concentration is typically 15 ppm (with a range of 10 to 50 ppm) onboard vessels during transport of cattle and sheep. Common readings below decks reach 20 to 30 ppm. In cattle feedlots in eastern Australia, typical atmospheric ammonia concentrations are 14 to 16 ppm. Thus, the average atmospheric ammonia concentrations are comparable in these two production systems. Of even greater interest for feedlots, is that atmospheric ammonia is 25 to 30 ppm at heights of 0.25 m from the ground. Thus, even the upper ranges of atmospheric ammonia for the two systems are comparable.
• The Australian National Occupational Health and Safety Commission has three standards for exposure to atmospheric contaminants such as ammonia gas in the occupational environment: the time-weight average (TWA) exposure limit for humans working for up to eight-hour shifts on a 40-hour week; the short-term exposure limit (STEL) which is a time-weight average measured over 15 minutes and should not be exceeded in any working day; and the permissible exposure limit which is the maximum concentration that humans are permitted to enter. The time-weighted average (TWA) exposure limit for atmospheric ammonia for humans is 25 ppm. The short-term exposure limit (STEL) is 35 ppm. The permissible exposure limit (PEL) for ammonia is 50 ppm.
• Under Australian legislation and workplace conditions, atmospheric ammonia concentrations should be below the TWA, STEL and PEL concentrations. However, each of these concentration limits could be exceeded under usual conditions recorded on vessels used for live export and in Australian feedlots.
• Atmospheric ammonia can be reduced by a number of atmospheric and nutritional means:
• Establishing adequate ventilation rates onboard vessels.
• Feeding diets that contain good quality cereal hay, lower protein (12% or less) or a greater proportion of rumen by-pass (RBP) or undegraded intake protein (UIP) (25% of the ration protein) will decrease the urea-N substrate for ammonia production.
• Using salts such as calcium chloride or ammonium chloride at 1% in rations to acidify urine and decrease the pH of bedding. The lower pH reduces volatilisation of ammonia.
• Adding bedding agents that reduce the pH (eg gypsum) to reduce ammonia volatilisation.
Objectives
collaborate with producers to obtain information on current husbandry practices and challenges with calf welfare to inform research findings and the evaluation of the prototype ALMS.
More information
| Project manager: | Sharon Dundon |
| Primary researcher: | Murdoch University |
