Changes in hormone profiles, growth factors, and mRNA expression of the related receptors in crop tissue, relative organ weight, and serum biochemical parameters in the domestic pigeon (Columba livia) during incubation and chick-rearing periods under artificial farming conditions

Abstract

The present study was conducted to determine the changes in concentrations of hormones and growth factors and their related receptor gene expressions in crop tissue, relative organ weight, and serum biochemical parameters in male and female pigeons during incubation and chick-rearing periods under artificial farming conditions. Seventy-eight pairs of 60-week-old White King pigeons with 2 fertile eggs per pair were randomly divided into 13 groups by different breeding stages. Serum prolactin and insulin-like growth factor-1 (IGF-1) concentrations in crop tissue homogenates were the highest in both male and female pigeons at 1 d of chick-rearing (R1), while epidermal growth factor (EGF) in female pigeons peaked at d 17 of incubation (I17) (P < 0.05). mRNA expression of the prolactin and EGF receptors in the crop tissue increased at the end of incubation and the early chick-rearing stage in both sexes. However, estrogen, progesterone, and growth hormone receptor expression each decreased during the early chick-rearing stage (P < 0.05). In male pigeons, IGF-1 receptor gene expression reached its peak at R7, while in female pigeons, it increased at the end of incubation. The relative weight of breast and abdominal fat in both sexes and thighs in the males was lowest at R7, and then gradually increased to the incubation period level. Serum total protein, albumin, and globulin concentrations increased to the highest levels at I17 (P < 0.05). Total cholesterol, triglyceride, and low-density lipoprotein reached their highest values at I17 in male pigeons and R25 in female pigeons (P < 0.05). In conclusion, hormones, growth factors, and their receptors potentially underlie pigeon crop tissue development. Changes in organs and serum biochemical profiles suggested their different breeding-cycle patterns with sexual effects.

Effects of incubation and chick rearing on intestinal morphology, digestive enzyme activities, and mRNA expression of nutrient transporter genes in the pigeon (Columba livia) under artificial farming conditions

“…Intestinal adaptation in different breeding stages was speculated to be regulated by specific hormones ( Baksheev and Fuller, 2000 ), such as glucocorticoids, cortisol, and triiodothyronine, which were already found to affect the digestive enzymes in animals ( Chapple et al., 1989 ; Khangembam et al., 2017 ). Our previous study showed that the prolactin concentration rapidly reached the peak value in both sexes on the first day of chick-rearing, but the estradiol concentration in female pigeons remained low until the late chick-rearing period ( Xie et al., 2018 ). Whether digestive enzymes in pigeons are influenced by these hormones warrants further investigation.…”

“…Our results showed that pancreatic amylase activity gradually decreased from I4 to R1 but then recovered to the beginning level in the late chick-rearing period. Pigeon serum glucose concentration was stable from egg incubation to chick rearing ( Xie et al., 2018 ), but hepatic glycogen content was reported to decrease significantly during the incubation period and then recovered when feeding nestlings ( Wan et al., 2018 ). In addition, our present study indicated that the activities of maltase and sucrose in mucosa also maintained a relatively lower level from I17 to R1.…”

“…Similarly, jejunum SGLT1 and GLUT2 in males and duodenum GLUT2 in females in our present results also maintained a lower level at I17. It is suggested that glucose absorption in the intestine may partly keep pace with glucose metabolism in the liver, which maintains the blood sugar levels stable in pigeons during the whole breeding stages ( Xie et al., 2018 ). However, similar to fatty acid transporters, the effects of intestine segments and sexes also existed in SGLT1 and GLUT2 expression.…”

“…The whole study consisted of 50 D: a 7-D acclimation and a 43-D experimental period, including an 18-D incubation period and a 25-D chick-rearing period. As described previously ( Xie et al., 2017 , Xie et al., 2018 ), plastic eggs were placed into cages only after the second egg was laid to avoid egg breakage and maintain the broodiness of the parent pigeon. Baby pigeons hatched from the incubator were reared by parents after 18 D of incubation.…”

“…However, few studies have focused on the organ and metabolic changes in breeding birds, except during the migration and molting processes ( Christians and Williams, 1999 , Landys-Ciannelli et al., 2003 , Vézina and Williams, 2003 ). In our previous study, the body and organs of parental pigeons, shown to be a nutrient reserve, fluctuated in weight during incubation and chick-rearing period, and serum biochemical profiles and enzyme expression in the liver of breeding pigeons also changed significantly ( Wan et al., 2018 ; Xie et al., 2018 ). Dietary intake of parent pigeons was found to increase significantly when feeding squabs ( Xie et al., 2016 ); therefore, will the pigeon intestine vary in its morphology or digestive and absorption function, similar to mammals, for dealing with these changes?…”