Effect of the dw gene on growth, plasma hormone concentrations and hepatic enzyme activity in a randombred population of chickens.

The effect of the dw gene on growth, lipid deposition, plasma hormone concentration, and enzyme activity in a randombred population of chickens was studied. The reciprocal crosses were examined as well as purebred dwarf and normal populations. Body weight, carcass fat, plasma growth hormone (GH), triiodothyronine (T3), thyroxine (T4), hepatic malic enzyme (ME) and citrate cleavage enzyme (CCE) activities were determined at 0, 2, 4 and 6 weeks. Body weights of dwarf birds were less than normal birds and, unexpectedly, Dwdw males had greater body weights than DwDw males. Percent carcass fat was greater in dwarf birds in comparison to phenotypically normal birds. All males carrying the dw gene had greater fat pad weights than homozygous normal males. The dw- females from cross 3 had less abdominal fat than cross 4 Dw- females, while dw- females from the dwarf parental mating had fat pad weights similar to Dw- females. Plasma T4 levels were elevated in all birds carrying the dw gene in comparison to normal birds. Plasma T3 levels were depressed in all birds carrying the dw gene versus normals, although the T3 levels of Dwdw males were intermediate to dwdw and DwDw males. The homozygous dwarf progeny exhibited elevated GH levels versus normals and Dwdw males exhibited GH concentrations intermediate to dwdw and DwDw males. Malic enzyme activity was lower in all birds carrying the dw gene, while CCE activity was not effected by genotype.