The Effect of Stocking Density and Strain on the Performance and Physiological Adaptive Responses in Broiler Chickens

Abstract

The aim of this study was to determine the effects of stocking density and strain on the performance and physiological adaptive responses including the plasma corticosterone content and the level of mRNA expression of proinflammatory cytokines and antioxidant enzymes in broiler chicks. A total of 300 birds of two strains (150 Ross strain vs. 150 Cobb strain) aged 3-d old were allotted into two stocking densities (standard stocking density, 0.046 m 2 /bird vs. high stocking density, 0.023 m 2 /bird) in battery cages by 2×2 factorial designs with ten replicates until 35 d of age. There was no significant strain effect on body weight, feed intakes and feed to gain ratio and the relative organ weights. However body weight, feed intakes and relative organ weight were found to be significantly (P<0.05) affected by the effect of stocking density. Plasma corticosterone level was not affected by both stocking density and strain effects. Hepatic mRNA expression of pro-inflammatory cytokines including interleukin-1β (IL-1β), IL-6, IL-18 and interferon-gamma (IFN-γ) was not significantly changed by the effects of strain and stocking density. However, the mRNA expression of glutathione peroxidase (GPX) was affected by strain, showing that Ross strain decreased (P<0.05) the GPX expression. With respect to the effect of stocking density, there was a significant (P<0.05) increase in superoxide dismutase (SOD) and catalase (CAT) and GPX mRNA expression in the liver from high stocking density group. Splenic pro-inflammatory cytokine expression was not also affected by stocking density and strain, except that IL-18 mRNA significantly (P<0.05) decreased in Cobb strain under high stocking density. The mRNA expression of SOD and CAT was significantly (P<0.05) affected by the effects of stocking density and strain. In conclusion, growth performance was not affected by strain but stocking density. Although mRNA expression of major pro-inflammatory cytokines was not changed by stocking density and strain, antioxidant enzyme was significantly affected by stocking density, strain or even organ in birds under summer conditions. More detailed studies still needed to be explored to elucidate the effects of environmental conditions and genetic background on physiological responses in birds.

Effects of different stocking densities on growth performance, antioxidant ability, and immunity of finishing broilers

“…In contrast to our results, some researchers found that stress did not necessarily cause elevated levels of cytokines (Maier & Watkins, 1998). Jang et al (2014) declared that splenic proinflammatory cytokine expression was not affected by stocking density (compared with 0.023 m 2 /bird and 0.046 m 2 /bird). Owing to the fact that the secretion of cytokine is a continuous process which happens in multiple tissues, the concentration of IL-1β and IL-4 detected in serum increased with the increase in stocking density in our study.…”

“…In the liver, Jang et al. () found that there was a significant increase in superoxide dismutase (SOD), CAT and GSH‐Px mRNA expression from high stocking density group (0.023 m 2 /bird compared with 0.046 m 2 /bird). Increasing the stocking density rate from 28 to 40 kg of BW/m 2 had negative effects on hepatocellular of broiler chicken (Abudabos, Samara, Hussein, Alghadi, & Alatiyat, ).…”

Impact of stocking density and dietary nano-zinc supplementation on stress indicators, immunity, and DNA damage in broiler chickens

“…In the present study,it was determined that HSD had no significant effect on cytokine levels (IFN-γ, IL-12, and IL-18 levels). Similar results were found by Jang et al(2014) who reported that HSD (0,023 m 2 /bird) had no effect on IFN-γ, IL-6, and IL-18 levels in broiler. However, Kang et al(2011) stated that combined stress (HSD and feed restriction) reduce the levels of inducible nitric oxide synthase expression and hepatic lipopolysaccharide-induced tumor necrosis factor-α but did not affect IL-4 and IL-6 levels in laying hens.…”