Well-planned, carefully designed whole-house broiler trials offer customers significant benefits through comparative testing of breeds, nutrition, environmental factors or management procedures. Along with providing valuable product performance information, trials allow customers to make important economic decisions which may impact the company.
Trial protocols must be designed with clear objectives, a focus on minimising variation between the treatments and detail-oriented management. Failure to properly plan a trial, or strictly follow the instructions outlined in the protocol, can result in incorrect data, poor breed comparisons and possible economic losses.
Birds should be sampled from at least three evenly distributed locations throughout each house, with sample points away from doors and walls. Photo: Tim Scrivener
Once a clear objective for the trial has been determined, it is essential to have a control treatment (a standard group with no changes made) to compare to the treatment group(s). It is recommended to only change the attribute you are interested in investigating in your treatments, and to use paired house testing. The more paired houses used, the smaller the difference between treatment and control that can be distinguished. In order for results to be consistent, it is strongly recommended to run multiple trials (at least 5 trials in a series) testing the same parameters, before final conclusions are made. When running paired house trials, multiple paired placements can be made over time, removing any farm bias. Also, the houses used should be side by side on the same farm and have similar house design, equipment, management programme and stocking density.
To design a successful broiler trial, the following points should be considered:
- Communication between all personnel involved to ensure the objective and procedures are clearly understood.
- Use blind testing to remove breed or nutrition bias (depending on the subject of testing).
- Have recorded measurements of live weight and mortality at selected intervals during grow-out. Record feed delivery, body weight and mortality on each house separately so that feed conversion and liveability can be calculated by breed or treatment. Avoid using houses that share feed bins with other houses; these houses cannot be used for FCR calculation.
- Avoid using broiler flocks with multiple breeder sources and confirm the source flock age of each breed cross is not more than 2 weeks apart in age.
- Maintain breed cross integrity by ensuring that parent females are the same breed cross and no male replacement has occurred using a different strain of male. If there are any questions about flock integrity, the trial should not proceed.
- Control factors such as hatching and housing conditions, farm management, nutrition and withdrawal time.
- Ensure that seasonal impacts will not influence the result, e.g., by spreading the trials over seasons.
- Use houses that best represent the normal commercial programme in terms of equipment.
- Determine if the flocks had any problems in the field such as poor liveability, disease, feed / water issues or wet litter. This could provide valuable information if issues are seen during the trial.
- Never use sick or injured birds for processing.
- Deplete and process trial houses on the same days.
- Have the same feed withdrawal time for trial broilers.
- Ensure that the processing plant will be able to process the entire trial within a shift.
Measurements during grow-out
During grow-out it is recommended to weigh a sample of birds at selected intervals to determine weight-to-age comparisons of the treatments and to alert to potential issues within the trial flocks. Weighing intervals will depend on the trial protocol and final processing age, but weights should always be taken at days 0 and 7. Subsequently, weights can be sampled on the usual ages for the operation, either weekly or on feed change days. The more weighing’s conducted and the greater the sample of birds weighed, the more accurate the predictions of live weight and uniformity (CV%) will be.
Correctly measuring FCR will provide information on flock cost and/or profit. To determine FCR, it is necessary to have an accurately measured quantity of feed consumed by the birds, and to ensure the amount of feed delivered into each house is measured precisely. For this reason, each of the paired houses must have its own feed bin and the amount of feed delivered to that bin weighed exactly- not estimated. If the feeding equipment is not able to accurately measure the amount of feed moved from the feed bin into the feeders, it will only be possible to determine FCR over the entire growing period.
Thinning is not recommended for trial flocks. The broilers must be grown to either the thin age or the grow-out age only, because thinning significantly affects FCR. If flocks must be thinned, the percentage of birds thinned must be the same in each house on trial and they must be thinned at the same age. To be able to compare flocks, mortality records should be kept daily, beginning at placement, and be recorded separately by house and sex. Euthanised broilers should be recorded separately from mortality and, if possible, the reason for euthanasia recorded. If higher than expected mortality occurs, it will be necessary to investigate possible causes.
Processing the trial
Broilers sampled for processing should be chosen at random, and enough birds sampled so that a sufficient representation of the flock population is achieved. The sample size should be at least 100 birds per house (50 males and 50 females); this ensures that there are enough birds in the sample to account for mortalities, and still have good representation of the flock. Birds should again be sampled from at least three evenly distributed locations throughout each house, with sample points away from doors and walls.
Coops or crates should be labelled with house, sex and treatment. Ideally each combination will have a unique range of barcoded or numbered bands. The following information should be recorded:
- Time of loading at farm
- House number
- Flock identification
- Breed code
- Number of birds sampled per sex
- Number of birds banded (band range for each house)
- Time of arrival at the processing plant
- Number of dead on arrivals (DOAs)
When sampling, banding and weighing the broilers, it is important to equalise the sampling and feed withdrawal time for each treatment. Once birds are caught for sampling, band, sex and weigh all the birds and record their weights to unique band numbers; then load them into a clearly marked live transport crates. Birds should have access to water until they are loaded into crates for transport, and the transport time to the processing plant should be kept to a minimum.
Trial birds should be kept separate from all other birds on the processing line to ensure that data capture is reliable to the gram. Photo: Aviagen
Broilers should be processed at the same time to obtain consistent yield results. Notify the processing plant beforehand with the protocol and detailed processing instructions. Trial birds should be kept separate from all other birds on the line. Air chilling is recommended over water chilling due to the possibility of increased water uptake. If it is only possible to water chill, the carcasses must be weighed before they are chilled and as soon as they are removed from the chiller to determine the amount of variability. If it is not possible to fully process trial birds in one day, send all birds through first processing on one day and debone all birds the next day. If data are missing or the carcass band number is incorrect, that bird and its measurements must be discarded from the trial.
Data collection and analysis
Collect whole carcass and carcass component weights on an individual bird basis. Specific cuts should be reflective of the product mix of the company. Cuts can vary dramatically between deboners and it is strongly recommended that each deboner be given an equal quantity of each treatment in order to remove any possible bias. Once data has been collected, it should be analysed. But not before all outliers or incorrect data is removed. It is good to keep in mind that rounding numbers can have an impact on results; live weights should be reported to the nearest gram, and carcass yield should be reported to at least 2 decimal places. Extremes should be excluded from the data set, values exceeding ± 3 standard deviations are out. Parts yield should be calculated as a percentage of live weight, with the mean, standard deviation and CV% .
Specific cuts should be reflective of the product mix of the company. Photo: Aviagen
A well-planned and executed commercial trial can provide valuable information, as well as assist the company in making important economic decisions. To guarantee the best possible outcome it is essential to make sure to handle and test all birds in a similar way to avoid introducing bias to either sex or breed and pay attention to detail throughout the trial. It is important that all parties involved communicate with each other guarantee the success of the trial and the reliability of the results. For reliable results random sampling, sufficient sample size and consistent testing procedures are essential as is correct data collection and analysis procedures. Only then can you make direct comparisons of different breeds.