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Importance of broiler flock uniformity


Can uniform poultry flocks be considered healthier? Or does poor uniformity indicate poorer performance or, indeed, animal welfare? These are valid questions, especially when non-uniform chicks are received from the hatchery with no advance notice.


BY MARK KARIMI, AB NEO P


Age Day 0


Day 14 Day 28 Day 42


Uniformity (%) %CV


Uniformity (%) %CV


Uniformity (%) %CV


18


oor uniformity does affect flock performance and welfare across all chicken subspecies. When egg lay- ing birds reach sexual maturity, it’s the bird’s individ- ual weight at that time which determines the start


of production. So underweight pullets will have a delayed onset of egg production, while those that are overweight will start early. Thus, poor uniformity may cause performance issues in both breeder and layer operations. Here we will focus on commercial broilers, as uniformity issues are more common there.


Measuring uniformity To appreciate its importance, we must define and measure uniformity. Bodyweight variability is the determinant, with two ways to measure it. Firstly, there is coefficient of varia- tion, the spread of bodyweight within the flock and, secondly,


Table 1 – The effect of AlphaSoy Gold on improving uniformity in an exceedingly uneven broiler flock.


Flock variation Uniformity (%) %CV


No ASG in diet 82.0 7.48 49.0


13.46 52.0


14.75 46.0


15.56 ▶ POULTRY WORLD | No. 2, 2021


ASG in diet 71.0 9.56 56.0


12.17 53.0


13.87 55.0


14.50


uniformity (percent), the similarity of bodyweight within a flock. Coefficient of variation (CV%) is the standard deviation divided by the mean bodyweight of the flock (measures dis- persion values around the mean). Therefore, a large CV shows a wide variation, while a low CV indicates less variability. Uni- formity indicates the percentage of flock that falls within a certain range of the average flock bodyweight (mean). This certain range is usually ±10% of the mean. So, the greater the uniformity, the less variable a flock is. While there is little scientific data available, a broiler flock with 10-12% CV at 40-42 days is considered uniform. Links between high flock CV and increased week one mortality, to- tal mortality, and slaughterhouse rejection, as well as poor FCR and growth rates, have been seen in multiple global tri- als. But where does the variability come from and what is making it worse with age?


Sources of variation Poor uniformity originates from various sources, including poor farm management. However, external factors may have a greater influence, such as the breeder farm. Non-uniform breeder flocks produce uneven eggs, with larger eggs pro- ducing larger chicks and vice versa, thereby creating variable day-old chick weights and sizes. Hatcheries may be another source. They obviously receive eggs from multiple breeder farms with different production capacities, flock ages and egg quality. They then supply the chicks to multiple broiler units.


PHOTO: MARK PASVEER


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