Mdoda, Bayanda2025-05-212023-07Mdoda, Bayanda. (2023). Effects of Supplemental Zingerone on Cobb 500 Broiler Chicken (Gallus gallus domesticus) Growth Performance, Health and Meat Quality. [PhD thesis, University of the Witwatersrand, Johannesburg]. WIReDSpace. https://hdl.handle.net/10539/44940https://hdl.handle.net/10539/44940A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy., to the Faculty of Health Sciences, School of Physiology, University of the Witwatersrand, Johannesburg, 2023.Commercial broiler and pullet chicken producers supplement chicken diets with sub-therapeutic doses of antibiotics such as zinc bacitracin that act as growth promoters to enhance production performance, meat and egg quality. Use of these antibiotics as growth promoters, in addition to causing environmental pollution, causes the public health challenge of antibiotic resistance which compromises poultry and consumer, hence the need to search for environmentally friendly and health-friendly alternatives to antibiotics. Phytochemicals, zingerone included, display biological activities similar to those of antibiotics. This study evaluated zingerone`s potential to replace bacitracin (ZnBcn) as a growth-promoting diet supplement in broiler feed specifically determining its effects on growth performance, meat quality and bird health. One hundred and twenty unsexed 1-day-old Cobb 500 broiler chicks (10 chicks per replicate with 3 replicates per diet) were randomly assigned to four dietary treatments where zingerone replaced ZnBcn at: diet 1 – 0 mg kg-1 (control: 500 mg akg-1 of zinc bacitracin); diet 2 – 40 mg kg-1; diet 3 – 80 mg kg-1 and diet 4 – 120 mg kg-1 in the starter, grower and finisher diets. The broiler chicks were fed ad libitum for 6 weeks: starter (week 1-2), grower (week 3-4), and finisher (week 5-6). Initial and weekly body mass, daily feed intake (FI), and terminal body mass (TBM) were measured. Body mass gain (BMG), average daily gain (ADG), and feed conversion ratio (FCR) were computed. On day 42, the chickens were humanely slaughtered, blood collected and carcasses dressed. The gastrointestinal tract (GIT) and accessory GIT viscera organs were weighed and small and large intestine lengths were measured. Empty carcass masses were measured and the dressing percentages were computed. Viscera macromorphometry, long bone indices and carcass traits, the meat’s physical quality [initial and ultimate pH (pHi and pHu), colour, thawing loss (TL), cooking loss (CL), and tenderness] traits, proximate and amino acid content and fatty acid profiles were measured. Plasma malonaldehyde (MDA) concentration, glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activities, surrogate markers of liver and kidney function, liver fat content and histology were determined. Across growth phases and overall, dietary zingerone had similar effects (p > 0.05) as ZnBcn on the chicken’s TBM, BMG, ADG, FI, and FCR. It also had similar effects (p > 0.05) as ZnBcn on the chicken’s empty carcass mass, dressing percentage, long bone indices and viscera macromorphometry. Dietary zingerone had similar (p > 0.05) effects as ZnBcn on the broiler chicken meat’s pHi, pHu, CL, TL and tenderness. However, at 40 mg kg-1 of feed (diet 2) it increased the meat’s redness (a*) compared to that of counterparts fed the ZnBcn-fortified control diet. Furthermore, supplemental zingerone had a similar effect to that of ZnBcn on the meat’s crude protein content but it significantly increased the meat’s ash and fat contents (p < 0.01; p < 0.0001). Meat from chickens fed diet 2 (40 mg kg-1 of feed zingerone) had the highest concentration of essential amino acids (p < 0.05) and that from chickens fed diets 3 (80 mg kg-1 of feed zingerone) had the lowest (p > 0.001) total amino acid content. Dietary zingerone had a similar (p > 0.05) effect as ZnBcn on the chicken meat’s total saturated fatty acids, but breast meat from chickens fed diets 3 (80 mg kg-1 of feed zingerone) had significantly increased (p < 0.0001) total monounsaturated fatty acid and oleic acid content. Meat from chicken-fed diet 4 (120 mg kg-1 of feed zingerone) had the highest total polyunsaturated fatty acid and linoleic acid content and a higher PUFA:SFA ratio compared to that from counterparts fed diets 1, 2 and 3. Supplemental zingerone had similar effects (p > 0.05) as ZnBcn on the chickens’ liver masses and fat contents, plasma MDA concentration, GSH-Px, GST, SOD, CAT, alkaline phosphatase, alanine transaminase activities, albumin, total bilirubin, creatinine and urea concentrations. Chickens’ hepatic inflammation and steatosis scores were similar across diets (p > 0.05). At 120 mg kg-1 of feed zingerone, though similar to the control, supplemental zingerone decreased the chickens’ plasma globulin and total protein concentration (p < 0.01; p < 0.05) compared to counterparts supplemented at low and medium dose of zingerone. Zingerone can be used as a growth promoter in place of zinc bacitracin in broiler chicken diets without compromising growth, feed use efficiency, carcass yield, long bone and GIT viscera growth and development, the meat’s pH, CL, TL and tenderness. Furthermore, it can be used without eliciting oxidative stress in the birds and with no risk to kidneys, liver and general health of the birds. Importantly, zingerone, as a dietary supplement, can be used to enhance broiler chicken meat’s redness, positively impacting its acceptability and meat’s total monounsaturated, oleic acid, total polyunsaturated and linoleic acid fatty acid profile; thus improving its nutritional value.en©2023 University of the Witwatersrand, Johannesburg. All rights reserved. The copyright in this work vests in the University of the Witwatersrand, Johannesburg. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of University of the Witwatersrand, Johannesburg.Antibiotics growth promotersPhytochemicalsGrowth performanceProduct qualityLiver and kidney healthUCTDThesisUniversity of the Witwatersrand, JohannesburgSDG-3: Good health and well-beingSDG-4: Quality education