The ability of cattle to tolerate heat load varies depending on factors such as cattle breed, health status, coat colour, degree of finish, and pen conditions (i.e. whether the pen is shaded or unshaded and the manure management practices employed). For this reason the threshold at which heat load starts to accumulate also varies depending on these factors. For the purposes of forecasting, various heat load thresholds have been incorporated to account for these factors (for example – AHLU86 and AHLU95 where 86 and 95 are the heat load thresholds upper limit (UL) respectively).
The RAP calculator is used to calculate the HLI threshold to use for your particular operation. If the threshold you calculate for your operation falls between the values utilised in the forecasts, you will have to estimate the results for your situation by interpolating between the forecast values. The RAP also gives an assessment of the risk of heatload events based on the site specific data entered and historical climatic data.
The RAP automatically defaults to the industry standard animal and conditions, details of which are as follows:
|Cattle type||Bos taurus|
|Days on feed||80 130|
|Shade provision||No shade|
|Trough water temperature||20 30 degrees|
|Manure management class||Class 1|
|Extra water troughs installed||No|
|Heat load ration||No|
|Wet manure removal||No|
The parameters presented in the table above can be changed using selections from the drop-down menus and check boxes. Once the required parameters have been selected for the RAP, the results are generated by clicking on the Calculate risk button at the bottom of the table.
The resulting probability of occurrence of high and extreme risk events is presented in tabular form, along with the scenario that you have selected. The results can be generated either as overall results or on a monthly basis.
Date of analysis
The results window will always include details of the version of the RAP that has been used and the date on which it became effective. It will also detail the date on which the analysis was undertaken.
The selections you made are also displayed in tabular form as the first item on the page and will incorporate any notes made by the user.
Understanding your Risk
The results for a particular site and your selection are displayed in the second table, which follows details of the threshold HLI calculated for the class of animals being assessed.
The columns are, from left to right, the duration of the event, the probability of observing a high risk event and the probability of observing an extreme risk event.
The results consist of probabilities of specific types of events occurring. The events are classified firstly by the intensity of the event and secondly by the duration of that event. The intensity is categorised as high risk (daily maximum accumulated heat load is between 50 and 100 accumulated heat load units) or extreme risk (daily maximum accumulated heat load exceeds 100 accumulated heat load units). The duration is the number of consecutive days that the accumulated heat load maintains the specified intensity. These are classified as events of two day duration, three day duration etc. All events exceeding a duration of seven days are binned into a 7 and over category.
The probabilities consist of the number of instances that a specific event is observed, expressed as the number of events per number of years.
The results can be printed using the print button provided at the bottom of the results page.
For Registered users, the results can be saved using the save and print button provided at the bottom of the results page. You will need to provide the results a save name for easier identification for reprinting.
For Registered users, the previously saved can be viewed or deleted. You will be able to view and reprint.
Select a Site
A site should be selected to represent a location near your feedlot and consequently the climate associated with that site. The sites are organised alphabetically by state. Note that no default site is selected so you must choose a site if any calculations are to complete successfully.
Select a Period
The results can be viewed for a particular site based on either the long term statistics or a monthly basis. This allows an examination of the frequency of events for the various months as a means of assessing the period during which your site is likely to encounter problems with heat load.
Parameters can be set to define the characteristics and condition of your stock. These include the genotype, coat colour, health status and days on feed of the animals being fed.
A range of genotypes are available for selection. These include Bos taurus and Bos indicus and their crosses, European and F1 Wagyu. HLI adjustments associated with the different genotypes are:
|Bos taurus genotypes||0|
|Bos indicus cross (25%)||+4|
|Bos indicus cross (50%)||+7|
|Bos indicus cross (75%)||+8|
|Bos indicus genotypes||+10|
Three colours are available to choose from black, red and white. HLI adjustments associated with the different coat colours are:
|Coat Colour||HLI Adjustment||Coat Colour|
|Black coat colour||0||Black coat colour|
|Red coat colour||+1||Red coat colour|
|White coat colour||+3||White coat colour|
Two health categories are available Healthy and Sick/Recovering/Unacclimatised.
The Sick /Recovering / Unacclimatised category refers to animals that are either in the sick pen or have recently arrived at your feedlot and have not yet acclimatised to your site conditions. HLI adjustments associated with the different health status are:
|Health Status||HLI Adjustment|
In the case of sick animals there is no need to adjust the days on feed criteria as the RAP model assumes that these animals are likely to be consuming only small amounts of feed, because of their condition. However, for newly arrived animals the days on feed category should be set to the shortest period to allow for the fact that they will be on a ration with low energy content.
Days on Feed
Three categories can be selected that align with the usual feeding periods for the domestic and export markets. HLI adjustments associated with the different days on feed categories are:
|Days on Feed||HLI Adjustment|
|Days on feed (0 80)||+2|
|Days on feed (80 130)||0|
|Days on feed (130 +)||-3|
The management practices in place at your feedlot that impact on the heat load of an animal. These include the provision of shade, temperature of water in the water troughs and the level of manure management employed at your feedlot.
The amount of shade provided per animal can be selected. HLI adjustments associated with provision of the varying amounts of shade are:
|Shade Provision||HLI Adjustment|
|Shade (1.5m2/SCU 2m2/SCU)||+3|
|Shade (2m2/SCU 3m 2/SCU)||+5|
|Shade (3m2/SCU 5m2/SCU)||+7|
Note: SCU = Standard Cattle Units
Amount of shade should be calculated at midday
Trough Water Temperature
The HLI adjustments associated with different water temperatures are:
|Trough Water Temperature||HLI Adjustment|
|Temperature of water in troughs = 15 20°C||+1|
|Temperature of water in troughs = 20 30°C||0|
|Temperature of water in troughs = 30 35°C||-1|
|Temperature of water in troughs > 35°C||-2|
Manure Management Class
The level of manure management employed by your feedlot can play an important part in the heat loading of your cattle. Allowable values range from 1 to 4 and equate to the following levels of management, as specified in the Queensland Department of Primary Industries publication; ‘Reference Manual for the Establishment and Operation of Beef Cattle Feedlots in Queensland’. The manual details specific criteria in terms of construction and operational specifications for the different classes, but the main ones are as follows:
|Criteria||Class 1||Class 2||Class 3||Class 4|
|1. Pen foundation preparation||Compacted base, with uniform slope built in||Compacted base, with uniform slope built in||Strip topsoil and grade to a durable, uniform surface||Strip topsoil and grade to a durable, uniform surface|
|2. Pen slope||2.5 4%||2.5 4%||2 6%||2 6%|
|3. Pen cleaning by removal or mounding|
|Maximum manure removal frequency (weeks)||7||10||14||14||20||26||26||26|
|Maximum manure pack depth||50||100||200||200|
|4. Under fence cleaning||monthly||quarterly||at each pen cleaning||at each pen cleaning|
|5. Eliminate wet patches||weekly||monthly||at each pen cleaning||at each pen cleaning|
|6. Repair potholes||weekly||monthly||6 months||6 months|
Notes: Specifications outlined in Appendix F of manual
Discounts applied to the HLI as a result of the less intensive manure management practices are an indication of the potential for problems associated with high levels of manure in the pens during periods of hot and wet conditions. HLI adjustments associated with the different manure management practices are:
|Manure Management||HLI Adjustment|
There are various mitigation measures that can be implemented at your operation during periods of excessive heat load which have been shown to assist in the management of heat load during these periods.
Options available include the use of additional water troughs, use of a ration that has been specifically designed to reduce metabolic heat load and the strategic cleaning of areas within the feedlot pens where wet manure accumulates.
It should be noted that the installation of additional water troughs takes effect only if there is no shade provided.
HLI adjustments associated with the implementation of these measures are:
|Mitigation Measure||HLI Adjustment|
|Install extra water troughs||+1|
|Implement heat load feeding strategy||+2|
|Strategic clearing of high manure deposition areas||+2|
Record specific details about the analysis being performed here for your records. Examples might include the name of the feedlot and/or the type of animals being assessed.