Content area
Full Text
SUMMARY
Physiological processes that take place during incubation of eggs often resulted in changes in egg weight during the period. This study investigated the effects of breed, age of hen and egg size on weight loss at three points between incubation and hatching viz: pre-incubation, 18th day of incubation, chick weight at hatching. A total of 1002 hatching eggs from three strains; Anak (n=361), Marshall (n=359) and Ross (n=282) of broiler breeders were weighed and measured using digital weighing scale and digital calliper. Weight, length and width were taken prior to incubation, while shape index was also computed. Weight losses from incubation to 18 days (WtLoss1), 18th day to hatching (WtLoss2) and incubation to hatch (WtLoss3)] were computed. The JMP(R) statistical software was used for basic descriptives, regression analyses and statistical modelling of the data. The model used for the regression analysis was described by Yij = µ + αi + βj + εij describing each of the three response variables. Egg weight was between 44.60g and 81.70g, while egg length ranged between 49.99mm and 69.98mm, and egg width was between 38.54mm and 56.75mm, while shape index was between 61.44% and 99.02% across the three strains studied. The largest source of variation was breed effect which was highly significant (P<0.001) on all four variables. Similarly, breed significantly (P<0.001) impacted on WtLoss1 and WtLoss3 but was not a significant (P>0.05) source of variation on WtLoss2. All the predictor variables were significantly (P<0.05) correlated to the response variables except shape index which had negative and non-significant (P>0.05) correlation with the weight losses. The very low negative and non-significant correlation between egg weight and egg weight loss up to the 18th day of incubation indicated that weight loss was slower in bigger eggs compared to relatively smaller eggs. The study revealed that breed was a significant source of variation on weight loss at the 18th day of incubation (WtLoss1) and throughout the entire period of incubation and hatching (WtLoss3) but was not significant on weight loss after the 18th day (WtLoss2). The study also revealed that hatchability of eggs has an inverse relationship with weight loss.
Keywords: breed, broiler, egg, incubation, weight loss, Nigeria
INTRODUCTION
Meat and eggs being acceptable forms of animal protein to most people,...