Abstract

GALLARA, E. A.; MENICHELLI, M. L.; DIMASSO, R. J.  and  REVIDATTI, A. F.. Stocking density, hematocrit and heterophil/lymphocyte ratio in broiler chickens in thefour seasons of the year. Rev. vet. [online]. 2021, vol.32, n.2, pp.164-168. ISSN 1669-6840.  http://dx.doi.org/10.30972/vet.3225725.

Variations in poultry environment derived from stocking density influence animal welfare, whose deterioration is reflected in different hematic indicators. The objective of this study was to evaluate the effect of the reduction in stocking density on the hematocrit and the heterophile/lymphocyte ratio (H/L) in male and female broiler chickens in the four seasons of the year. Cobb500 hybrid chickens were reared in mixed batches, in dark houses tunnel forced ventilation. The stocking densities were standard (14 chickens/m2) and reduced (12 chickens/m2). At sacrifice at 42 days of age, anticoagulated blood samples were taken from 30 males and 30 females from each treatment, the hematocrit was determined by the micro method and the H/L ratio was calculated by the count of heterophile and lymphocyte by smear. Data were evaluated with the Mann-Whitney U test separately for each sex and season with density as source of variation. In females, the hematocrit value showed significant differences in winter (standard 32.5 vs reduced 31%; p=0.035) and marginally significant in spring (standard 31 vs reduced 30%; p=0.093). In males, the H/L ratio difference was marginally significant with higher value in reduced density in summer (p=0.093) and in females in summer (p=0.08) and in winter (p=0.077). It is concluded that the modification of the stocking density in winter causes environmental conditions that led to an increase in the hematocrit in chickens housed at a higher density, a response that was more evident in the case of females, while the decrease in density produces increases in H/L ratio not compatible with situations of chronic stress.

Keywords : broiler chickens; animal welfare; stress; haematology.

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