Growth performance and intestinal morphology in broiler chickens produced from hyperthyroid breeder hens

An association between induced maternal hyperthyroidism and a decreased incidence of cold-induced ascites in broiler chickens has been reported recently. There are also reports suggesting that thyroid hormones have an effect on intestine, a high oxygen-demanding organ. The present study aimed to determine whether the ascites-attenuating effect of maternal hyperthyroidism is associated with morphological changes in intestine and with probable adverse effects on growth performance in progeny chicks. Eighty-eight broiler breeder hens were allotted to control or hyperthyroid [HYPER; thyroxine-treated] groups, and artificially inseminated. Hatching eggs (n = 924) were incubated and day-old male chicks (n = 288) were reared for 42 days under standard or low ambient temperature. Plasma thyroxine was higher in the HYPER hens and their embryos at internal pipping. Maternal hyperthyroidism did not adversely affect the feed : gain ratio and carcass weight, whereas cold stress impaired them. A higher relative weight was found at 42 days of age for all intestinal regions at low ambient temperature. The duodenal and jejunal crypt depths (CD) were lower in HYPER group at 7 days of age. Cold exposure decreased the duodenal and jejunal villus height and CD, and increased the ileal goblet cell number at 21 days. On Day 42, higher values were recorded for CD, goblet cell number, and epithelial thickness of different intestinal regions in cold-exposed birds. In conclusion, growth performance was not adversely influenced by maternal hyperthyroidism and its minimal early effect on intestinal morphology does not appear to be the underlying mechanism for decreased incidence of ascites in broilers.