Graduate Thesis Or Dissertation


Effects of High-docosahexaenoic Acid Microalgae and Choline in the Hen Diet on Egg Production and Lipid Metabolism Public Deposited

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  • The objectives of the current study were to 1) investigate the effect a high-docosahexaenoic acid (C22:6 n-3, DHA) microalgae product (MAL), and choline dosage in diets containing MAL, on egg production performance, physical egg quality, and nutritional parameters, and 2) determine whether choline dosage influences hepatic lipid metabolism of hens fed MAL. Fifty six, 26-week-old, White Leghorn hens were kept in individual cages and randomly allocated to one of the four dietary treatments, each with seven replicates of two hens (n=7 per treatment). All diets were corn and soybean meal based, isocaloric, isonitrogenous, and contained the same amount of vitamin and mineral premix, which provided 551 mg/kg choline in the diets. Experimental diets contained 0% MAL and no supplemental choline (Control), 1% MAL and no additional choline chloride (Alg), 1% MAL and 0.1% supplemental choline chloride (Ch0.1), and 1% MAL and 0.2% supplemental choline chloride (Ch0.2). The feeding trial lasted 16 weeks after a two week adaptation period. Eggs were collected, counted and weighed daily, feed intake and egg quality were measured every two weeks, and fatty acid (FA) composition was analyzed every four weeks. Birds were euthanized for tissue collection at the end of the trial. The effects of MAL and supplemental choline on all response variables was analyzed as a general linear mixed model with repeated measures using SAS software (version 9.4) (SAS Institute). All results from this analysis were considered significant at p≤0.05. Using orthogonal contrasts, Alg was compared to Control to calculate the effect of MAL, and Ch0.1 and Ch0.2 were compared separately to Alg to calculate the effect of choline chloride dosages in diets containing MAL. Compared to Control, Alg increased egg yolk content of DHA (p<0.0001), phosphatidylethanolamine (PE) (p=0.02), and phosphatidylcholine (PC) (p<0.0001). In the liver, Alg similarly increased PE (p=0.0003) and PC (p=0.0003) concentrations, but also increased lipid peroxidation products compared to Control (p=0.01). Compared to Alg, Ch0.1 increased hen day egg production (p=0.03), daily egg mass (p=0.02), Haugh unit (p=0.04), total lipids (p=0.04) and γ-tocopherol (γT) (p=0.05) concentrations in egg yolks. Additionally, Ch0.1 increased hepatic concentrations of α-tocopherol (αT) (p=0.03) and γT (p=0.005), and decreased feed conversion ratio (p=0.005) and hepatic lipid peroxidation products (p=0.005) compared to Alg. Ch0.2 likewise increased hepatic γT (p=0.0002) and αT (p=0.001) concentrations, but did not produce any of the other changes associated with Ch0.1. These results indicate that DHA content of eggs can be greatly increased by supplementing MAL in the diets of laying hens. Furthermore, supplementing 0.1% choline chloride in hen diets containing MAL can improve production performance and egg quality, and protect the liver from oxidative stress.
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