Net feed intake information is used to calculate the Net Feed Intake (Feedlot) EBV within the TransTasman Angus Cattle Evaluation (TACE).
Recording Net Feed Intake Information
Collection of net feed intake information can be conducted either ‘on-farm’, or at a ‘central-test’ facility (e.g. Tullimba Research Feedlot), and involves:
The use of commercial feeding systems that automatically record feed intake of individually electronically identified animals is recommended. Currently most feed intake data is collected using GrowSafe feeding systems, however there are other collection systems such as the Calan Broadbent Feeding System that can effectively capture feed intake data.
How Much Effort is Involved?
Those who are considering collecting net feed intake information for TACE need to be aware that the collection of feed intake measurements must be collected in a standardised way, and can be challenging, expensive, and time consuming.
However, if effective net feed intake information can be collected and analysed through TACE, the benefits can be considerable.
What Animals Should Be Tested?
It is essential that animals are weighed regularly during the feed intake test period as net feed intake is calculated by adjusting daily feed intake for an animal’s live weight and rate of weight gain across the duration of the test.
Each animal must be weighed at the start and end of the test period, and at 14 day intervals during the test period.
All animals in a pen should be weighed as the one group, with animals weighed as promptly as possible after removal from the pen.
There should not be any delay in weighing due to other procedures being conducted (e.g. ultrasound scanning). If other procedures are to be conducted, all animals in a pen should be weighed, and then animals run through a second time for the completion of the other procedure.
When collating net feed intake information for submission to Angus Australia, the following information needs to be recorded for each animal:
Having collected daily feed intake measurements for each animal during the test period, the average daily intake across the duration of the test needs to be calculated.
It is essential that only valid daily feed intake measurements are included in the calculation of average daily intake. That is, invalid feed intake records should be removed.
A feed intake measurement may be identified as being invalid on a particular day (for either a single animal, a single pen or across all pens) in the trial if:
If there are too many invalid records for an animal, a pen or across all pens, the test period may need to be extended to ensure a minimum of 60 valid daily feed intake measurements for each individual animal, or alternatively, the feed intake measurements should be excluded for any individual animal with less than 60 valid measurements.
The start and end test weights that need to be submitted to Angus Australia for each animal ARE NOT the actual weights recorded at the start and end of the test period, but rather need to be calculated by fitting a linear regression line across all weights collected for an individual animal during the test period. Fitting a regression line enables the animal’s weight and rate of weight gain across the entire duration of the test to be measured more accurately.
When fitting the regression line, it is important that the relationship between the different weights that have been taken on each individual animal is carefully
scrutinised, and any weights that are clearly incorrect (i.e. vary considerably from the regression line) excluded from the linear regression calculation. A minimum of 5 weights should be used when fitting the regression line.
A simple way of analysing the relationship between the different weights is the R squared value. Start and end weights should not be submitted for animals if the R squared value is not 0.9 or above.
A spreadsheet that can be used to fit the linear regression line, calculate the start and end test weights, and calculate the R squared value is available from the TACE section of the Angus Australia website.
Specifying the Test Station
Standard codes should be specified to identify the test station in which the net feed intake information has been collected.
Specifying Management Groups
A management group should be specified to identify any animals within a contemporary group whose net feed intake information (i.e. average daily feed intake / weights) may have been affected by considerable nongenetic factors.
Specifically, a different management group should be specified for animals in different pens, and pen differences will generally have an effect on feed intake
performance. This is particularly important for animals that start their feed intake test on the same day in the same location.
Specifying the Test Type
The test type (P = post weaning / F = finishing) is used to determine whether the net feed intake information corresponds to the NFI-F EBV and needs to be specified when submitting net feed intake information.