Genetics of linear type traits scored on young foals belonging to the Italian Heavy Draught Horse breed

Abstract

In small horse breeds, the small size of stud-farms can bias genetic parameters’ estimations, excluding many breeders from the selection. The study aimed to find a method to include small stud-farms in genetic analysis and to estimate genetic parameters for linear type traits in Italian Heavy Draught Horse (IHDH). Stud-farms were grouped according to an increasing number of criteria: (i) geographical location and housing system; (ii) target productions and vaccination of foal; (iii) stud's body condition. These groups allowed 6 contemporary groups (CG) of environmental units (CG1-CG6) in a dataset of 11,357 scores of young foals and 17,441 subjects in pedigree. Model fitting increased with the number of CG levels. Considering the CG6, heritability varied from 0.149 (upper line direction) to 0.375 (head size/expression). The greatest genetic correlations (from 0.810 to 0.887) involved fleshiness, fore, and rear diameters. The use of CG allowed retaining many records. Genetic estimates indicated a possible genetic improvement for heavy draught and meat production.