Influence of triiodothyronine and growth hormone on growth of dwarf and normal chickens: Interactions of hormones and genotype

Abstract

1. 1. The effects of dietary triiodothyronine (T 3), injections of a preparation of growth hormone (GH) (purified from chicken pituitary tissue) and their combination on growth were investigated in three lines of chickens. The three lines were the Cornell K strain (K) (a Single Comb White Leghorn strain), the Cornell K strain hemizygous for the sex-linked dwarfing gene (SLD), and the Cornell K strain homozygous recessive for the autosomal dwarfing gene (ADW). 2. 2. A dietary T 3 treatment by genotype interaction was observed. Dietary T 3 (0.1 ppm) decreased growth in the K line, tended to decrease growth in the ADW line while it tended to increase growth in the SLD line. 3. 3. Chicken growth hormone (100 μg/kg body wt) alone did not affect growth in any of the lines studied. There was, however, a GH treatment by T 3 treatment interaction. Chicken GH overcame the growth-depressing effects of T 3 in the K and ADW lines while it tended to promote growth in T 3 treated SLD birds. 4. 4. Dwarf (SLD) chickens had higher basal circulating GH concentrations, lower circulating immunoreactive somatomedin C concentrations, and lower circulating T 3 concentrations than the K or ADW chickens.