Abstract
Simple SummaryEggs are a valuable source of protein and fat in the human diet. Due to continuous improvement in the production performance of laying hens, the requirements regarding the feed energy of laying hens are increasing. Oils, which are the main energy sources in feed, exert a substantial effect on the production performance and egg quality of laying hens. In this review, we discuss the classification of oils commonly used in the diets of laying hens and the process of lipid metabolism in laying hens. We further look at the effects of adding different oils on the nutritional composition of eggs with a focus on the mechanism through which dietary oils affect the production performance and egg quality of laying hens, the effects of adding different types of animal and plant oils to the diets, and the potential effects of different types of oils on the health of laying hens.With the development of a large-scale and intensive production industry, the number of laying hens in China is rapidly increasing. Oils, as an important source of essential fatty acids, can be added to the diet to effectively improve the production performance and absorption of other nutrients. The present review discusses the practical application of different types and qualities of oils in poultry diets and studies the critical effects of these oils on production performance, such as the egg weight, feed intake, feed conversion ratio (FCR), and various egg quality parameters, including the albumen height, Haugh units, yolk color, and saturated/unsaturated fatty acids. This article reviews the effects of different dietary oil sources on the production performance and egg quality of laying hens and their potential functional mechanisms and provides a reference for the selection of different sources of oils to include in the diet with the aim of improving egg production. This review thus provides a reference for the application of oils to the diets of laying hens. Future studies are needed to determine how poultry products can be produced with the appropriate proper oils in the diet and without negative effects on production performance and egg quality.
Highlights
Oils are the most commonly applied sources of energy in feed diets for laying hens and exert multiple effects, such as improving palatability, feed intake, animal immunity, and reducing morbidity [1,2,3]
A diet including rapeseed oil with a low amount of erucic acid reduces the serum lipid content and liver fat deposition in laying hens, and these effects may be related to the increases in the expression of the apolipoprotein synthesis genes apoB-100 and apoBVLDL-II observed with this diet, which lead to increased lipid transport
Cottonseed contains free gossypol (FG), cyclopropylene fatty acid (CPFA), and other toxic and harmful substances [168,169] that inevitably remain in cottonseed cake, meal, and Cottonseed oil (CSO) after processing, which limits the use of this oil in livestock and poultry feed
Summary
Oils are the most commonly applied sources of energy in feed diets for laying hens and exert multiple effects, such as improving palatability, feed intake, animal immunity, and reducing morbidity [1,2,3]. The appropriate proportion and type of oil addition is important for the production performance, lipid metabolism, and egg quality of laying hens. The addition of oils to the diets of laying hens has become an effective method to promote animal growth, increase the FCR, and improve poultry health. Hyland brown chickens has no significant effect on the egg weight [13], but the addition of 2%, 4%, and 6% rapeseed oil to the diet of 40-week-old brown chickens reduces feed intake, egg production, and egg weight [12]. Compared with the results obtained with the addition of 3% fish oil, olive oil, grape seed oil, or soybean oil, the addition of equal amounts of canola oil to the diets of laying hens does not significantly change the egg production, egg weight, feed intake, or FCR but increases the linolenic acid content in the egg yolk [14]. This study focuses on the effects of the type, quality, and proportion of oils in the diet on the production performance and egg quality of laying hens and provides a reference for the selection of different types of oils in the egg production process with the aim of improving egg quality and economic efficiency
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