Comparative assessment of mortality in different strains of broilers at the starter phase

Abstract

Mortality in broilers has been a major setback and source of economic losses associated with broiler production. A total of 600 day-old chicks consisting of 200 each from three strains (Arbor Acre, Cobb 500 and Ross 308) were procured from a reputable hatchery to investigate and evaluate mortality rates among the strains. Non-parametric tests including Chi-Squared tests of goodness-of-fit and independence were conducted to evaluate mortality within and across the strains studied. The Chi-Square value for test of independence between strain and weekly mortality was 3.020 with a df of 6, was not significant (P>0.05), while the Likelihood Ratio Chi-Square of 2.953 at df of 6 had a p-value of 0.815, which was equally not significant (P>0.05). The Chi-Square Goodness-of-fit for observed counts were respectively 0.5, 0.61, 2.64 and 3.38 for weeks 1 – 4, and all were not statistically significant (P>0.05). Mortality recorded in the first week was lowest for all strains with risk ranging from 1.5 to 2.5 percent, while risks rose to between 3.08 and 8.00 percent in subsequent weeks across the strains. The Arbor Acre strain despite the highest first week mortality had a steady and consistent value compared to the other two strains in subsequent weeks.  The risk ratio of comparison between Arbor Acre and Cobb 500 ranged between 0.60 and 2.42 on a weekly basis, with a cumulative of 1.70 across the entire study, while the weekly odds ratio was between 0.58 and 2.56 with cumulative of 1.86 for the entire study.  The study revealed that the Arbor Acre can be adopted as the baseline strain for mortality evaluation during the starter phase of broiler rearing.