Comparative study of gastrointestinal tract size in three parent breeds for the production of dual‐purpose organic chickens

An alternative to culling male hatchlings of layers is breeding dual‐purpose chickens. One breeding objective is the ability to digest low‐quality feed. Certain measurements of the gastrointestinal tract may be useful indicators of this ability. The present study compared the gastrointestinal tract of adult hens of two layer‐type breeds (White Rock (WR), New Hampshire (NH)) and the meat‐type ÖTZ (Ökologische Tierzucht gGmbH) Bresse Gauloise (BR), used for the production of dual‐purpose organic chickens. Flocks had the same housing and feeding conditions. At slaughter at 19 months, the body weight and gastrointestinal organs of 134 hens (51 WR, 55 NH and 28 BR) were measured. The muscle thickness of the proventriculus and ventriculus and the length and width of the duodenum, jejunoileum, caeca and colorectum were measured and variances between the groups were analysed using a one‐factor covariance analysis. Significant differences between the breeds were found in total intestine length and the lengths and/or widths of single gastrointestinal segments. For example NH showed the highest mean total intestinal length and BR showed the lowest mean (NH: 186.73 cm, WR 185.86 cm, BR 157.91 cm; p = 0.001). To our knowledge, this is the first study comparing the gastrointestinal tract size of adult female layer‐ and meat‐type chicken breeds kept under the same feeding and housing conditions. Given the possible relationship between intestinal length parameters and chicken performance, measurement of the gastrointestinal tract may be a simple, quick and inexpensive additional method to help select layer‐, meat‐type and dual‐purpose chickens suitable for organic production when a selection process using genetic markers is not possible.