The long-term oral administration of thyroxine: effects on blood hematological and biochemical features in broiler breeder hens

Revisiting glucose regulation in birds - A negative model of diabetes complications

Birds naturally have blood glucose concentrations that are nearly double levels measured for mammals of similar body size and studies have shown that birds are resistant to insulin-mediated glucose uptake into tissues. While a combination of high blood glucose and insulin resistance is associated with diabetes-related pathologies in mammals, birds do not develop such complications. Moreover, studies have shown that birds are resistant to oxidative stress and protein glycation and in fact, live longer than similar-sized mammals. This review seeks to explore how birds regulate blood glucose as well as various theories that might explain their apparent resistance to insulin-mediated glucose uptake and adaptations that enable them to thrive in a state of relative hyperglycemia.

Effects of genetic selection on activity of corticotropic and thyrotropic axes in modern broiler chickens

Commercial selection for meat-type (broiler) chickens has produced economically valuable birds with fast growth rates, enhanced muscle mass, and highly efficient feed utilization. The physiological changes that account for this improvement and unintended consequences associated with them remain largely unexplored, despite their potential to guide further advancements in broiler production efficiency. To identify effects of genetic selection on hormonal signaling in the adrenocorticotropic and thyrotropic axes, gene expression in muscle and liver and post-hatch circulating hormone concentrations were measured in legacy [Athens Canadian Random Bred (ACRB)] and modern (Ross 308) male broilers between embryonic days (e) 10 and e18 and post-hatch days (d) 10 and d40. No interactive effects or main effects of line were observed for adrenocorticotropic gene expression during either developmental period, although age effects appeared for corticosteroid-binding globulin in liver during embryogenesis and post-hatch and glucocorticoid receptor in both tissues post-hatch. There was a main line effect for circulating corticosterone, with levels in ACRB greater than those in Ross. Several thyrotropic genes exhibited line-by-age interactions during embryonic or post-hatch development. In liver, embryonic expression of thyroid hormone receptor beta was greater in ACRB on e12, and deiodinase 3 (DIO3) levels were greater in Ross on e14 and e16. In juvenile liver, deiodinase 2 (DIO2) expression was greater in ACRB on d10 but greater in Ross on d20, while DIO3 was higher in ACRB on d30 and d40. Levels of thyroid hormone receptor alpha mRNA exhibited a main line effect, with levels greater in ACRB juvenile breast muscle. Several thyrotropic genes exhibited main age effects, including DIO2 and DIO3 in embryonic breast muscle, thyroid hormone receptor alpha and thyroid hormone receptor beta in post-hatch liver, and DIO2 in post-hatch breast muscle. Circulating triiodothyronine displayed a main line effect, with levels in Ross significantly reduced as compared to ACRB. These findings suggest that in modern broilers, a decrease in levels of hormones that control basal metabolism triiodothyronine and the stress response circulating corticosterone, as well as altered expression of genes regulating thyroid hormone activity, could contribute to lower heat production, reduced stress response, and altered nutrient partitioning, leading to more efficient feed utilization and faster, more productive growth.

Transcriptomic Analysis of Laying Hens Revealed the Role of Aging-Related Genes during Forced Molting

Molting in birds provides us with an ideal genetic model for understanding aging and rejuvenation since birds present younger characteristics for reproduction and appearance after molting. Forced molting (FM) by fasting in chickens causes aging of their reproductive system and then promotes cell redevelopment by providing water and feed again. To reveal the genetic mechanism of rejuvenation, we detected blood hormone indexes and gene expression levels in the hypothalamus and ovary of hens from five different periods during FM. Three hormones were identified as participating in FM. Furthermore, the variation trends of gene expression levels in the hypothalamus and ovary at five different stages were found to be basically similar using transcriptome analysis. Among them, 45 genes were found to regulate cell aging during fasting stress and 12 genes were found to promote cell development during the recovery period in the hypothalamus. In addition, five hub genes (INO80D, HELZ, AGO4, ROCK2, and RFX7) were identified by WGCNA. FM can restart the reproductive function of aged hens by regulating expression levels of genes associated with aging and development. Our study not only enriches the theoretical basis of FM but also provides insights for the study of antiaging in humans and the conception mechanism in elderly women.

The effect of methionine and folic acid administered in ovo on the hematological parameters of chickens (Gallus gallus domesticus)

Methionine (Met), an essential amino acid in poultry diets, when overdosed may cause hyperhomocysteinemia, which is mainly a trigger for cardiovascular diseases in humans. Homocysteine is neutralized (remethylated) in the presence of folic acid (FA), which also plays an important role in hematopoiesis and participates in the synthesis of DNA, and its deficiencies may result in the development of neural tube defects. One of the basic tools in studying the impact of both xenobiotics and nutrients on the animal organism is hematological analysis. Thus, the aim of this study was to determine the effect of in ovo supplementation with Met and FA on the hematological parameters of broiler chickens. On the 17th day of incubation, embryonated eggs (Ross 308) were injected with 5 or 25 mg of Met per egg (M5 and M25), 3 and 15 mg of FA per egg (F3 and F15), or a mixture of these 2 compounds (M5/F3 and M25/F15). The broilers were reared in accordance with welfare regulations and fed with commercial diets ad libitum. Blood samples were collected on the first, seventh, and 35th day of rearing (D1, D7, and D35), and complete hematological analysis was performed. The observed changes in red blood cell parameters probably result from physiological changes occurring during bird growth. Mean erythrocyte volume decreased with the age of chickens in the control, M5, and M25 groups, but not in those supplied with FA. Among supplemented groups, the number of white blood cells on D1 was lower only in group M5 than in the sham (C) group. The analysis of leukograms showed no significant differences between the groups. Comparing D1 with D7 in the group injected with a higher dose of Met and FA (MF25/15), a statistically significant increase in the percentage of lymphocytes and a significant decrease in the percentage of heterophils were observed. In addition, in the group injected with a higher FA dose (F15), there was statistically significant reduction in the percentage of eosinophils and a significant increase in the percentage of monocytes at day 7 compared with day 1. It seems that Met supplementation led to temporary immunosuppression in the animals.