Unraveling the Potential of Orange Pulp for Improving Laying Rate, Egg Quality, Oxidative Stability, Fatty Acids Composition, and Reproductive Tract Morphology of Laying Hens

Abstract

The current study aimed to demonstrate the effects of dietary dried orange pulp (DOP) on the laying performance, egg quality, antioxidant status, yolk fatty acid composition, serum biochemistry, and reproductive tract morphology of laying hens. A total of 200 Lohman Brown Lite laying hens were randomly allotted into 4 dietary treatments with 10 replicates each. The experimental treatment groups were the control group, a basal diet containing 50 g DOP/kg feed (DOP5%), a basal diet containing 70 g DOP/kg feed (DOP7%), and a basal diet containing 100 g DOP/kg feed (DOP10%). Data were statistically analyzed by one-way ANOVA following a completely randomized design, and the incremental levels of dietary DOP were tested by orthogonal polynomial contrasts. The body weight gain, feed intake, egg production%, egg weight, egg mass, and feed conversion ratio of laying hens fed the DOP7% and DOP10% diets were greater (p < 0.01) than those fed the control diet. Eggs obtained from the DOP7% and DOP10% groups had a heavier shell weight% and shell thickness, as well as a greater yolk color score (p < 0.01; linear, p < 0.01). Dietary DOP improved the egg yolk concentrations of PUFA, n-3 PUFA, and n-6 PUFA (linear, p < 0.001; quadratic, p < 0.05), whereas the content of SFA was reduced (p < 0.001; linear, p < 0.001). The egg yolk cholesterol and triglyceride levels were linearly decreased (p < 0.001) with the inclusion of DOP in the diets of hens. After storage for 40 days, the malondialdehyde (MDA) contents in the egg yolk were reduced, whereas the glutathione peroxidase content was increased (p < 0.01) due to dietary DOP. The DOP7% and DOP10% hens had an obvious reduction in the levels of serum total lipids, total cholesterol, triglycerides, low-density lipoprotein, and MDA, whereas high-density lipoprotein and GPx levels were increased (p < 0.01) compared with those fed the control diet. The relative weights of the ovary, oviduct, uterus, and follicle of hens receiving diets containing 7% and 10% DOP were heavier (p < 0.01) than those of the control hens. Moreover, the number of large yellow follicles was increased (p < 0.001; linear, p < 0.001) in the hens-fed diets containing 7% and 10% DOP. In conclusion, dietary DOP at up to 100 g/kg of feed improves laying performance, health status, antioxidant capacity, egg nutritive value, and egg shelf life in laying hens.