Factors to improve chicken uniformity

Edgar Orlando Oviedo-Rondón, professor of the University Faculty Scholar Prestage Department of Poultry Science for North Carolina State University, was in charge of the presentation on “Factors to Improve Chicken Uniformity” during LPN 2021.

Uniformity of broiler flocks is an indicator parameter of performance, health and welfare. It can be measured as the coefficient of variation (CV) of the average weight or as a percentage of similarity of target weight for each age. There is always variation among birds, but the goal is to have between 10% and maximum 12% CV at 42 days of age. But values fluctuate between 11 and 18% among flocks of the same genetics, sex, management and age at slaughter.

The factors that can alter uniformity are multiple and the effects start before chick hatching.

Logically, the best evaluation of uniformity should be done in sexed flocks, since sexual dimorphism is a source of biological variation that is impossible to control.

Each factor adds up impacts on the bird’s development, but there are some that are crucial and cause irreversible effects. Therefore, improving uniformity requires action on many aspects of production.

To begin with, uniformity, good nutrition, and low stress during the proper rearing of breeder flocks ensures hens that will produce eggs that are uniform in size, with progeny that are better able to adapt to the environment.

Good broiler egg temperature management from nest collection to the start of incubation ensures that embryonic development will not become disuniform.

Prolonged storage of the hatching egg can also reduce flock uniformity by extending the hatch window, reducing the growth rate of some embryos and multiple post-hatch developmental defects due to cell death.

Other factors such as ambient humidity of not less than 25% or greater than 65%, or water temperature and access to feed also have an effect on uniformity. Rapid access to water and feed is key to uniformity.

Some on-farm hatching methods such as Vencomatic’s X-Treck have shown improvements of up to one percent in CV (12.7 vs. 11.6%).

Flocks that suffer from any factor during the first few days of life tend to have higher first week mortality and poor final uniformity, lower final weight, higher total mortality, poorer feed conversion, and increased carcass defects.

Poor uniformity may indicate problems with the house environment, problems with access to water and feed, locomotion problems, and immune challenges or diseases during growth. Houses are seldom totally homogenous. Maintaining uniformity of environmental conditions is a challenge from hen growth to delivery to the slaughter line.

Heat or cold stress, which can occur from the first days of life, limits feed intake and bird growth. Heat in conjunction with high humidity or lack of air velocity can be the most negative aspects throughout the life of the birds.

Nutrient concentration in diets also plays a major role in uniformity. Generally, the more nutrient-dense the diet, the better uniformities can be obtained. But, for example, high amino acid density must be maintained throughout life to maintain good flock uniformity. Also the particle size resulting from grain milling and pellet hardness affects uniformity.

Finally, any pathogen has a negative effect on bird development, metabolism and growth. The challenges of any pathogen and the immune response to intestinal or external microorganism infections are variable for each individual within a flock. Among the most common causes of non-uniformity are coccidiosis and dysbacteriosis, which can be complicated by necrotic enteritis.

In conclusion, the factors to improve uniformity are multiple and we must pay attention to all of them to obtain the desired results.