EGG WEIGHT, SHELL THICKNESS AND CHOLESTEROL CONCENTRATION IN SPECIALIZED BREEDS OF EGG-TYPE CHICKENS AS INFLUENCED BY LAYER AGE

Abstract

The effect of breeds on egg quality of egg-type chickens from Plymouth Rock and White Leghorn commercial laying hens was investigated. The aim was to determine the egg weight, cholesterol levels and shell thickness on a commercial poultry farm over twelve weeks. A total of 408 laying hens were evaluated for the two breeds, which commenced from the fifth week into lay for twelve weeks. The birds were aged 24 weeks at the commencement of the study. The biological material consisted of 50 randomly collected eggs per week, and all eggs laid during the study period were weighed. Conventional AOAC methods were used to analyze the eggs. All data were analyzed using the R-core statistical package, and results were presented graphically. The results showed that the White leghorn breed (red, breed 1) had a heavy and significant average egg weight (50-60g) over Plymouth rock (blue, breed 2), which recorded a mean average of 20-37g.  Shell thickness was the same for the two breeds at week 1 (47mm). White leghorn had consistent shell thickness between 49 and 53mm, while the Plymouth rock breed increased from 41 to 50mm. Eggs from the Plymouth rock breed had a cholesterol concentration of 0.57 – 0.65 mmol/L, while the White leghorn breed ranged from 0.51 – 0.55 mmol/L. It can be concluded that since the two breeds performed differently under similar dietary and management conditions, the White leghorn breed influenced better and had higher egg weight and shell thickness, while the nutritive value component from cholesterol was higher in the Plymouth rock.