Abstract
Chickens are exposed to numerous types of stress from hatching to shipping, influencing poultry production. Embryonic manipulation may develop resistance against several stressors. This study investigates the effects of thermoneutral temperature (T0; 37.8°C) with no injection (N0) (T0N0), T0 with 0.6 ml of 10% in ovo gamma-aminobutyric acid (GABA) supplementation (N1) at 17.5th embryonic day (ED) (T0N1), thermal manipulation (T1) at 39.6°C from the 10th to 18th ED (6 h/day) with N0 (T1N0), and T1 with N1 (T1N1) on hatchability parameters and hepatic expression of stress-related genes in day-old Arbor Acres chicks. The parameters determined were hatchability, body weight (BW), organ weight, hepatic malondialdehyde (MDA), and antioxidant-related gene expression. Percent hatchability was calculated on a fertile egg basis. Growth performance was analyzed using each chick as an experimental unit. Eight birds per group were used for organ weight. Two-way ANOVA was used taking temperature and GABA as the main effect for growth performance and gene expression studies. Analysis was performed using an IBM SPSS statistics software package 25.0 (IBM software, Chicago, IL, USA). Hatchability was similar in all the groups and was slightly lower in the T1N1. Higher BW was recorded in both T1 and N1. Intestinal weight and MDA were higher in T0N1 against T0N0 and T1N1, respectively. The expression of HSP70, HSP90, NOX1, and NOX4 genes was higher and SOD and CAT genes were lower in the T1 group. The present results show that T1 and N1 independently improve the BW of broiler chicks at hatch, but T1 strongly regulates stress-related gene expression and suggests that both T1 and N1 during incubation can improve performance and alleviate stress after hatch.
Highlights
Chicken producers face numerous stressful conditions that include high ambient temperature, transportation, delayed feeding, infection, noise, and stocking density [1,2,3]
There was a significant interaction between temperature and gamma-aminobutyric acid (GABA) (p = 0.029), as MDA was higher in T1 with N1 (T1N1) compared to T0N0
The current study was conducted to examine the impact of embryonic Embryonic thermal manipulation (ETM) with or without GABA on hatching performance and hepatic gene expression of stress- and antioxidant-related enzymes in newly hatched broiler chicks
Summary
Chicken producers face numerous stressful conditions that include high ambient temperature, transportation, delayed feeding, infection, noise, and stocking density [1,2,3]. All these conditions collectively or individually may lead to the generation of reactive oxygen species (ROS). Previous studies have shown increment in ROS, antioxidants, HSPs, and MDA under heat stress conditions [4, 5]. Evaluation of these genes may help identify the intensity of stress and the preparation of chickens to withstand stress. Manipulation of chicken embryos either by tweaking temperature or feeding supplements may develop tolerance to heat stress during the rearing period
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