Abstract
The storage and preparation of corn for animal feed inevitably lead to lipid and protein peroxidation. Granulosa cells play an important role in follicular development in the ovaries, and hen laying productivity is likely to be dependent on follicle health and number. We hypothesized that oxidized oil and protein induce apoptosis via oxidative stress in laying hen granulosa cells. A sample of 360 38-week-old Lohmann commercial laying hens was used in a 2 × 2 factorial design for 8 weeks. Dietary treatments included dietary oil (fresh corn oil (FO) or oxidized corn oil (OO)) and corn gluten meal (fresh corn gluten meal (FP) or oxidized corn gluten meal (OP)). Productivity, ovarian histology, granulosa cell apoptosis, and indicators of oxidative stress were evaluated in all groups. Both dietary OO and OP decreased egg production and the average daily feed intake (ADFI) of laying hens. Flow cytometry, TUNEL, and real-time PCR revealed that both dietary OO and OP induced granulosa cell apoptosis in prehierarchical and hierarchical follicles. Furthermore, dietary OO and OP caused oxidative stress in prehierarchical and hierarchical follicles, as indicated by the downregulation of antioxidant-related-gene expression. Moreover, forkhead box O1 (FoxO1), extracellular regulated protein kinase (ERK), and c-Jun NH2 kinase (JNK) are involved in potential apoptosis regulation pathways in the granulosa cells of laying hens fed OO and OP, as indicated by the upregulation of FoxO1 expression and downregulation of ERK/JNK expression. These results indicate that OO and OP induce granulosa cell apoptosis via oxidative stress, and the combined use of OO and OP aggravates the adverse effects of oxidative stress in laying hens.
Highlights
Oils are often used in animal diets to increase their energy levels
Feeding experiments involving animals revealed that the ingestion of oxidized fats and oxidized proteins provokes a wide array of biological effects [3,4,5,6], one of the most striking of which is the induction of oxidative stress due to the absorption of lipid hydroperoxide or advanced oxidation protein products [6,7,8]
There were oxidized corn oil (OO) × OP interaction effects observed on the feed conversion rate (FCR) for the whole period and on the egg weight in weeks 5 to 8 (P < 0:05), in which the control group had lower FCR and the OO+FP group had a lower mean egg weight compared with the other groups
Summary
Protein is known to be the most important component and is the main source of nitrogen, which monogastric animals use to synthesize proteins. Both oils and proteins are often exposed to oxidants or oxidizing conditions during the preparation or storage of feeds [1, 2]. Oxidized oil in animal feed was demonstrated to decrease the concentrations of exogenous and endogenous antioxidants and increase the activity of endogenous free radical scavenging enzymes and concentrations of lipid and protein peroxidation products [1, 7, 9, 10], decreasing the productivity of laying hens and broilers. The interactions between oxidized oils and oxidized proteins and whether oxidized proteins can cause similar damage to the productivity of laying hens are unclear
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