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The previous article, shared the nutritional physiological role of fat in broiler chickens, the application of functional lipids in broiler production, and fatty acid needs and utilization in broilers. The middle part will focus on the digestion and absorption of fat in laying hens, fat metabolism diseases in laying hens, PUFA-fortified egg development, and the application of short- and medium-chain fatty acids and phospholipids in laying hens’ production.
Here are the highlights shared in this post.
Laying hens and lipid nutrition
Characteristics of fat metabolism in laying hens
More than 90% of fatty acids in laying hens are synthesized in the liver. The fat content in the diet of laying hens is low compared with that of broilers, so more than 60% of the fat deposited in the body and in the eggs needs to be synthesized by itself, which puts a great burden on the liver.
Healthy, high-producing laying hens are low in body fat. Higher fat content in eggs enhances the chances of offspring survival. Laying hens absorb 3~4g of fat from the intestines every day, while 5~7g of fat is needed to form an egg, and most of the fat absorbed from the intestines and synthesized in the body is used for yolk formation.
Diets with appropriate energy levels promote the health and performance of laying hens. Excess energy will lead to excessive fat deposition in the liver and abdomen, reducing the efficiency of energy utilization, and easy to induce fatty liver, overweight and other diseases, resulting in increased mortality.
Ability of Laying Hens to Digest and Absorb Fats and Oils
The ability of poultry to digest and absorb fats and oils is mainly influenced by factors such as age, type and content of fats and oils (see inside of this book for details).
Age: Laying hens are more capable of fat digestion and absorption than fast and large broilers of the same age. In terms of intestinal lipase activity, adult laying hens are more powerful in fat digestion than broilers and egg-laying hens.
Types of fats: There were significant differences in the utilization of energy from different fat sources by laying hens. In general, laying hens have the highest utilization of energy from PUFA-rich fats and oils, followed by monounsaturated fatty acid-rich fats and oils, and the lowest utilization of energy from saturated fats, mainly due to the fact that saturated fatty acids do not emulsify readily into lipid droplets in the intestine. Addition of fats and oils to energy-deficient or critically deficient diets can significantly improve the performance of laying hens.
The addition of fats and oils to the diet of laying hens under heat stress conditions has a significant mitigating effect on heat stress and can significantly improve performance and egg quality.
Oxidized fats and oils reduce nutrient utilization by laying hens, which ultimately leads to decreased production performance.
Nutritional requirements for essential fatty acids in laying hens
Research on essential fatty acid requirements in laying hens has focused on linoleic acid. A combination of several studies (see the inside cover of this book for details) suggests increasing dietary linoleic acid levels to 1.50% to 2.00% during the pre-laying and peak laying periods.
Diseases related to fat metabolism in laying hens: Fatty liver hemorrhagic syndrome
Fatty liver hemorrhagic syndrome (FLHS) in laying hens often occurs in high laying hens, with clinical signs of individual obesity, decreased egg production, and increased mortality during stress. Nutritional (e.g., dietary energy level, egg-to-energy ratio, micronutrients, etc.), genetic, hormonal, and environmental management factors can contribute to FLHS in laying hens.
Gut microorganisms play an important role in the development and course of FLHS. The intestinal flora that colonize the host can affect host health in a number of ways.
The key to preventing the occurrence of FLHS in laying hens lies in the energy level and fat level of the diet, and the addition of extra 6%~8% oil and fat to the diet for more than 6 consecutive weeks can significantly induce FLHS. the occurrence of FLHS during the laying period may even be affected by the nutrient level of the diets during the brooding and rearing period.
Bile acids, plant extracts, and probiotics can improve lipid metabolism and alleviate inflammation, thereby preventing FLHS in laying hens.
Low Cholesterol Egg Development
Cholesterol is an essential structural component of the human body, but hypercholesterolemia is a major contributor to atherosclerosis and an important cause of cardiovascular disease.
The liver and ovary are the main organs that synthesize cholesterol in laying hens. Laying hens mainly consume plant-based feeds, with very low cholesterol intake, and almost all cholesterol in the body is synthesized by themselves. Laying hens synthesize about 300mg of cholesterol per day, of which about 2/3 is deposited in the egg and 10mg is excreted directly into the intestinal tract (see the inside of this book for details).
It is of great practical significance to utilize the principle of nutritional regulation to reduce the cholesterol content in eggs and give them new quality characteristics. Relevant studies (see the inside of this book for details) have focused on cellulosics, micronutrients, β-cyclodextrin, chitosan, PUFA, and prebiotics.
PUFA Enhanced Egg Development
PUFA has an important role for humans in the prevention of cardiovascular diseases, among others. Increasing the PUFA content of eggs by modifying the diet of laying hens is a consistent and stable way to increase the PUFA content of human food.
Lipids in laying hen diets affect the fatty acid composition of egg yolks, and ω-3 PUFA-rich eggs can be produced by feeding ω-3 PUFA-rich diets to laying hens.
The addition of PUFA to the diet also increased the vitamin E requirement of the animal organism and products (see inside of this book for details). It was found that rats fed eggs enriched with omega-3 PUFA had significantly lower plasma and liver total cholesterol, and the fatty acid composition of total liver lipids and phospholipids had increased proportions of ALA, EPA, and DHA, and decreased proportions of arachidonic acid.
Application of short- and medium-chain fatty acids and phospholipids in the production of laying hens
Like PUFA, medium and short chain fatty acids and phospholipids are also very important for the nutrition of laying hens.
Short-chain fatty acids
Short-chain fatty acids are easily absorbed by intestinal cells and are important energy substances for intestinal cells. Short-chain fatty acids are rapidly absorbed by the hindgut, not only to store energy and reduce osmotic pressure, and for the maintenance of the normal function of the large intestine and colon epithelial cell morphology and function has an important role. Among them, butyric acid is more used in laying hens.
Adding butyric acid to the diet of laying hens can improve the egg production rate, feed conversion rate, energy utilization, production performance, reduce intestinal PH and the number of Escherichia coli, and increase the number of Lactobacillus coelicolor in each intestinal segment, which is conducive to improving the balance of intestinal microorganisms, and promoting the intestinal health of laying hens.
Medium Chain Fatty Acid
MCFA has unique physiological and biochemical functions, which can reduce fat deposition, improve insulin sensitivity, regulate energy metabolism, and also inhibit bacteria. Research shows (see the inside of this book for details) that MCFA can increase the egg production and egg weight of laying hens from 35 to 47 weeks of age, reduce the rate of shell breaking, improve feed utilization, reduce the cholesterol content of serum and eggs, and at the same time inhibit the proliferation of E. coli.
Phospholipids
Phospholipids play an important role in activating cells, maintaining metabolism, basic metabolism and enhancing immunity. In addition, phospholipids can form lipoproteins with proteins, cholesterol and triglycerides, which are involved in the regulation of fat metabolism.
The results of a number of tests (see the inside of this book for details) show that the addition of phospholipids to the diet of laying hens can increase egg weight, improve feed utilization, reduce the cholesterol content of egg yolks, and have a significant prevention and control effect on FLHS.
