Synthetic and phytogenic antioxidants improve productive performance, antioxidant activity, gene expression, and offspring quality in breeder hens subjected to heat stress.

This study aimed to investigate the efficacy of a synthetic source (a combination of vitamin E, vitamin C, selenium, and L-carnitine) and phytogenic sources (a combination of clove, green tea pomace, and Vietnamese coriander) in overcoming heat stress (HS) damage in female breeder hens on production, blood chemistry, sperm survival in the oviduct, antioxidant properties, gene expression, and quality of offspring. One hundred SUT female breeder hens were housed in individual cages and divided into 4 treatment groups: T1) basal diets in the thermoneutral (TN) zone; T2) basal diets under HS; 3) basal diets with synthetic antioxidants under HS; and T4) basal diets with phytochemical antioxidants under HS. The result revealed that HS condition had a negative effect on reducing final body weight, egg weight, and 1-day-old chick weight while increasing water intake and FCR and altered blood chemicals in breeder hens compared to TN breeder hens (P < 0.05). However, either synthetic or phytogenic antioxidants resulted in increased egg production and hatchability, while decreasing the number of late stages of embryo death during the incubation (P < 0.05). Furthermore, the synthetic antioxidants also improved the uniformity of chicks and reduced late-stage embryo death compared with phytogenic antioxidants (P < 0.05). HS breeder hens fed with either of the antioxidant sources exhibited higher antioxidant capacity in terms of DPPH and ABTS radical scavenging (in yolk, liver, and breast meat) and FRAP radical scavenging (in yolk and liver) and lower liver malondialdehyde than HS breeder hens fed with the control diet (P < 0.05). Additionally, the gene expression of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in the liver was upregulated, whereas the expression of proinflammatory cytokines (nuclear factor-κB) and heat shock proteins (HSP70 and HSP90) was downregulated in breeder hens that received both antioxidant sources (P < 0.05). Future investigations should focus on the potential for combinations of synthetic and phytogenic antioxidants in diets for HS breeder hens.

Transcriptome analysis of the uterovaginal junction containing sperm storage tubules in heat-stressed breeder hens.

Sperm storage tubules (SSTs) in the uterovaginal junction (UVJ) of the oviduct are major sites of sperm storage after artificial insemination or mating. Female birds may regulate sperm motility in the UVJ. Heat stress can decrease the reproductive ability of broiler breeder hens. However, its effects on UVJ remain unclear. Changes in gene expression aid in understanding heat stress-affected molecular mechanisms. Herein, we wanted to conduct a comparative transcriptomic analysis to identify the differentially expressed genes (DEGs) in the UVJ of breeder hens under thermoneutral (23°C) and heat stress (36°C for 6 h) conditions. The results indicated that cloacal temperatures and respiratory rates were significantly increased in heat-stressed breeder hens (P < 0.05). Total RNA was extracted from the hen UVJ tissues containing SSTs after heat exposure. Transcriptome analysis identified 561 DEGs, including 181 upregulated DEGs containing heat shock protein (HSP) transcripts and 380 downregulated DEGs containing immune-related genes, such as interleukin 4-induced 1, radical S-adenosyl methionine domain containing 2, and 2'-5'-oligoadenylate synthetase like, in heat-stressed hens. Gene Ontology analysis revealed the significantly enriched terms involving HSPs. Kyoto Encyclopedia of Genes and Genomes analysis identified 9 significant pathways, including the protein processing in endoplasmic reticulum (11 genes including HSPs), neuroactive ligand-receptor interaction (13 genes including luteinizing hormone/choriogonadotropin receptor), biosynthesis of amino acids (4 genes including tyrosine aminotransferase), ferroptosis (3 genes including heme oxygenase 1), and nitrogen metabolism (carbonic anhydrase [CA]-12 and CA6) pathways. Protein-protein interaction network analysis of DEGs revealed 2 large networks, one containing upregulated HSPs and the other containing downregulated interferon-stimulating genes. Overall, heat stress inhibits innate immunity in the UVJ tissues of broiler chickens, and heat-stressed chickens protect their cells by increasing the expression levels of HSPs. The identified genes are potential candidates for further exploration of the UVJ in heat-stressed hens. The identified molecular pathways and networks increase our understanding of the sperm storage reservoirs (UVJ containing SSTs) within the reproductive tract and may be used to prevent heat stress-induced fertility loss in breeder hens.