Comparison of production parameters and meat quality characteristics of South African indigenous chickens

Thesis (MScAgric)--Stellenbosch University, 2014.

ENGLISH ABSTRACT: This study quantified the growth performance, carcass and meat characteristics of South African slow-growing chicken lines. Two slow-growing lines developed outside South Africa, the Black Australorp and New-Hampshire, two native lines including the Naked-Neck and Potchefstroom Koekoek, as well as a hybrid between a Cobb 500 broiler and Potchefstroom Koekoek were evaluated. Fifty birds of each line were randomly allocated to cages of five birds per cage where they were fed a standard broiler diet ad libitum to an average weight of 2kg. Twenty cockerels of each line were then slaughtered for further analyses. For the carcass characteristics: live weight at slaughter, hot carcass weight, and chilled carcass weight were determined. Portion yields and dissection characteristics were measured, and the deboned meat from the breast, thigh and drumstick analysed for proximate analysis and fatty acids. Average daily gain (ADG), feed conversion ratio (FCR), and European Production Efficiency Factor (EPEF) were calculated and analyzed for line differences. No significant differences were observed between the indigenous lines with regards to feed intake ADG (~22g), FCR (~3.65), and EPEF (~57). The Hybrid outperformed the indigenous lines for all of the growth performance parameters measured. No differences were observed for dressing %. The breast yield obtained by the Hybrid was significantly higher (45.56%) than that of the indigenous lines which had similar breast yield values (~41%). The naked-Neck had the highest thigh yield and the lowest drumstick percentage yield, 27.7% and 17.3%, respectively. A similar pattern was observed for drumstick yield with the Australorp, New-Hampshire and Koekoek lines having significantly higher yields than those of the Hybrid. For the tissue characteristics, similar values were seen for breast skin (~20%), breast bone (~22%), drumstick skin (~4.3%), and drumstick muscle (~27%). The Hybrid had significantly higher breast muscle, thigh muscle, and total muscle percentage yield (22.67%, 26.17% and 43.51%, respectively). Proximate chemical composition of the breast samples did not differ (P>0.05) for any parameters. Differences (P<0.05) were recorded for thigh moisture, protein and ash content. The Naked-Neck recorded the lowest moisture (72.3%) and the highest protein (18.6%) and ash (1.1%) values. Differences were also recorded for drumstick moisture protein and fat. The highest moisture content was measured for the Hybrid (75.9%) and the lowest for the Naked-Neck (73.6%). The indigenous lines had higher protein content (~19.5%) when compared to the Hybrid (18.9%). The drumstick fat content for the Nakednecks (4.4%) was higher than the remaining lines. Differences were observed for the fatty acid profile. Total PUFA differed (P<0.05) with the Australorp (28.2%) showing the highest proportion. The relative contributions of total SFA, total MUFA and TUFA did not differ significantly between lines. The ratio of polyunsaturated and saturated fatty acids, the proportion of n-6 fatty acids and the ratio of n-6/n-3 differed, higher values were recorded for the indigenous lines. The proportion of n-3 fatty acids did not differ. The Hybrid performed significantly better than the indigenous lines but did not reach the performance potential expected for commercial broilers. Despite this, the Hybrid does show potential for use in alternative practices that make use of slower growing lines.

AFRIKAANSE OPSOMMING: Hierdie studie het die groei-prestasie, karkas- en vleiskwaliteitseienskappe van Suid Afrikaanse inheemse hoenders gekwantifiseer. Vier plaaslike lyne, die Swart Ostralorp, New Hampshire, Kaalnek en Potchefstroomse Koekoek, sowel as ʼn kruising van die Koekoek henne met Cobb 500 braaikuikenhane is evalueer. Vyftig voëls van elke genotipe is ewekansig ingedeel in hokke met vyf voëls per hok. ʼn Standaard braaikuiken dieet is gevoer totdat die gemiddelde massa van die kuikens 2kg bereik het. Daarna is 20 hane van elke genotipe geslag vir verdere analise. Vir karkaseienskappe is lewendige massa voor slag, warm karkasmassa en koue karkasmassa bepaal. Daarna is porsie opbrengs en disseksie eienskappe bepaal en, en die ontbeende vleis van die bors, dy en been is ontleed vir proksimale en vetsuur analises. Gemiddelde daaglikse toename (GDT), voeromsetverhouding (VOV), en Europese produksie effektiwiteits faktor (EPEF) is vir die verskillende genotipes bereken en getoets vir verskille. Geen betekenisvolle verskille is waargeneem vir inname, GDT (~22g), VOV (~3.65), en EPEF (~57) nie. Die kruisras het in alle gevalle beter produksieparameters gelewer as die plaaslike lyne. Geen verskille is opgemerk vir uitslagpersentasie nie. Die borsopbrengs van die kruisras was betekenisvol hoër (45.66%) as die van die plaaslike lyne (~41%). Die Kaalnek het die hoogste dyopbrengs (27.7%) en die laagste beenopbrengs (17.3%) gelewer. ʼn Soortgelyke patroon is waargeneem vir die beenopbrengs van Australorp, New-Hampshire en Koekoek met betekenisvol hoër opbrengste as dié van die kruisras. Weefsel eienskappe het dieselfde opbrengs gelewe vir die plaaslike lyne met borsvel (~20%), borsbeen (~22%), beenvel (~4.3%) en beenspier (~27%). Die kruisras het betekenisvol meer borsvleis, dyspier en totale spierpersentasie gelewer as al die ander genotipes (onderskeidelik 22.67%, 26.17% en 43.51%). Proksimale analise van die borsmonsters het geen verskille (P>0.05) gelewer vir enige van die parameters wat bepaal is nie. Verskille is opgemerk vir die vog-, proteïen- en asinhoud van die dyspier. Die Kaalnek het die laagste voginhoud (72,3%) en die hoogste proteïen- (18.6%) en as-inhoud (1.1%) gehad. Verskille is ook opgemerk vir been vog-, proteïen- en vetinhoud. Die hoogste voginhoud is gemeet in die kruisras (75.9%) en die laagste in die Kaalnek (73.6%). Die plaaslike lyne het ʼn hoër proteïeninhoud (~19.5%) as die kruisras (18.9%) gehad. Die vetinhoud van die beenspier was ook die hoogste vir die Kaalnek (4.4%). Verskille is waargeneem vir die vetsuurprofiele van vleis. Die PUFA het verskil, met die hoogste persentasie waargeneem vir die Australorp (28.2%). Die verhoudelike bydrae van die totale SFA, totale MUFA en TUFA het nie betekenisvol tussen genotipes verskil nie. Die verhouding van n-3 vetsure het ook nie verskil nie. Die verhouding van die PUFA:SFA, die verhouding van n-6 vetsure en die verhouding van n-6/n-3 vetsure het verskil, met hoër waardes vir die plaaslike lyne. Die verhouding van n-3 vetsure het nie verskil nie. Die kruisras het oor die algemeen betekenisvol beter gevaar as die plaaslike lyne, maar het steeds nie die produksie potensiaal van die kommersiële braaikuiken bereik nie.

Masters