Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2004
Publication Date: 6/15/2004
Citation: Peebles, E.D., Burnham, M.R., Walzem, R.L., Branton, S.L., Gerard, P.D. 2004. Effects of fasting on serum lipids and lipoprotein profiles in the egg-laying hen (gallus domesticus). Comparative Biochemistry and Physiology. Part A 138:305-311. Interpretive Summary: Very low density lipoproteins (VLDL) are the main carriers of cholesterol in chickens. Egg production depends on the hen's capacity to initiate and sustain the assembly of VLDLy, a relatively small (30 nm diameter) VLDL particle. Prolonged fasting is known to be accompanied by a reduction in egg production and abnormal lipoprotein profiles; however, no information is available concerning the effects of a short-term (24 hr) fast on lipoprotein profiles in laying chickens. Ultimately, understanding of this mechanism will help to discern how infection of layer chickens with the common bacterial pathogen, Mycoplasma gallisepticum (MG), causes a reduction in egg production in infected hens as cholesterol is also required by MG for the organism to survive. Results of this study suggest that the relationship between egg production and fasting was not associated with an altered capacity to initiate and sustain the assemblage of the relatively smaller diameter VLDLy from larger VLDL particles. Thus, changes in VLDL diameter do not appear to be involved in the relationship between short-term fasting and egg production.
Technical Abstract: The effects of short-term fasting on serum lipids and lipoprotein profiles in commercial laying hens were investigated. Blood was analyzed at 34 and 46 weeks of age from hens that had been either fed ad libitum or had been fasted for 24 hours prior to collection. At 12 weeks, birds were divided into 16 biological isolation units, with 8 replicate units assigned to each treatment group. Four birds out of ten in each unit were tagged for bleeding. Parameters evaluated included total serum cholesterol and triglycerides, mean diameters of very low density lipoproteins (VLDL) for the 10th, 50th, and 90th percentiles of serum total VLDL, mean total population VLDL particle diameter (MPD), and percentage serum cholesterol recovered in VLDL, low density lipoprotein (LDL), and high density lipoprotein (HDL) fractions. Fasting led to decreases in total serum cholesterol and triglycerides, and a decrease in mean serum VLDL particle diameter in the 90th population percentile. At Week 34, percentage serum cholesterol recovered from LDL was increased, whereas percentage serum cholesterol recovered from HDL was increased due to fasting. It was concluded that short-term fasting decreased serum lipids (cholesterol and triglycerides) and the size of VLDL particles in the 90th population percentile in commercial laying hens. Furthermore, bird age influenced the effects of a 24 hour fast on MPD and the redistribution of serum cholesterol among VLDL, LDL, and HDL particles.