Dietary Supplemental Chromium Yeast Improved the Antioxidant Capacity, Immunity and Liver Health in Broilers under High Stocking Density

Abstract

This study was conducted to investigate the effects of different levels of yeast chromium on growth performance, organ index, antioxidant capacity, immune performance and liver health of broilers under high stocking density. A total of 684 1-day-old Arbor Acres broilers were selected and fed a common diet from 1 to 22 days of age. At the end of 22 days, broilers with similar weight were randomly divided into six treatments, with six replications in each treatment. The broilers in control groups were fed with a control diet and raised at low stocking density of broilers (14 broilers/m2, LSD) and high stocking density (20 broilers/m2, HSD). The broilers in treatment groups were fed with diets supplemented with 200, 400, 800 and 1600 µg Cr/kg chromium yeast (Cr-yeast) under HSD, respectively. The experimental period was 23~42 days. Compared with the LSD group, the HSD group significantly decreased the liver index (ratio of liver weight to live weight of broilers) of broilers (p < 0.05), the HSD group significantly increased the content of corticosterone (CORT) and the activities of alanine aminotransferase (ALT) and alkaline phosphatase (ALP) and decreased the prealbumin (PA) level in the serum (p < 0.05). HSD decreased the total antioxidant capacity (T-AOC) contents in the serum, liver and breast, serum glutathione peroxidase (GSH-Px) activities, breast total superoxide dismutase (T-SOD) activities and liver catalase (CAT) activities of broilers (p < 0.05). The HSD group significantly increased the total histopathological score (p < 0.05). Compared with the HSD group, adding 200, 400, and 1600 Cr-yeast significantly increased the liver index of broilers (p < 0.05), all HSD + Cr-yeast groups decreased the ALT activities (p < 0.05), and the HSD + 800 group significantly decreased the CORT contents and the ALP activities of the serum (p < 0.05); the HSD + 400, 800 and 1600 groups increased the PA contents of the serum (p < 0.05); HSD + 800 group significantly reduced the tumor necrosis factor-α (TNF-α) and Interleukin-1β (IL-1β) contents of the serum (p < 0.05); moreover, the HSD + 400 group increased the GSH-Px activities of the serum (p < 0.05), the T-AOC and the T-SOD activities of the breast (p < 0.05) and the T-AOC and CAT activities of the liver (p < 0.05). Adding 800 Cr-yeast significantly decreased the total histopathological score (degree of hepatocyte edema and inflammatory cell infiltration) under HSD (p < 0.05). In summary, Cr-yeast can improve the antioxidant capacity and immune traits, and liver health of broilers under HSD. Based on the results of the linear regression analysis, the optimal supplementation of Cr-yeast in antioxidant capacity, immunity ability and liver health were at the range of 425.00−665.00, 319.30−961.00, and 800.00−1531.60 µg Cr/kg, respectively.

Keywords: antioxidant capacity; broilers; chromium yeast; immunity; liver health; stocking density.

Figure 1

Effects of Cr-yeast on serum immunity index of broilers under high stocking density. (A) TNF-α: tumor necrosis factor—α; (B) IL-1β: Interleukin-1β; (C) IL-10: Interleukin-10; (D) T3: thyroxine; (E) T4: thyrotropine.; LSD: low stocking density; HSD: high stocking density; Date was shown as the mean ± SE from six independent experiments. * Means t-test results of independent samples in group LSD and group HSD (* p < 0.05). ^a–e These bars without the same letter indicate differences significant at p < 0.05.

Figure 2

Effects of Cr-yeast on liver histopathological score of broilers under high stocking density. LSD: low stocking density; HSD: high stocking density; Date was shown as the mean ± SE from six independent experiments. * Means t-test results of independent samples in group LSD and group HSD (* p < 0.05). ^a–c These bars without the same letter indicate differences significant at p < 0.05.

Figure 3

Effects of Cr-yeast on histopathological analysis results of liver of broilers under high stocking density. The magnifications are 200×. The yellow arrows point to inflammatory cells and the red scissors point to the edema of hepatocytes. (A) the LSD group; (B) the HSD group; (C) the HSD + 200 Cr-yeast group; (D) the HSD + 400 Cr-yeast group; (E) the HSD + 800 Cr-yeast group; (F) the HSD + 1600 Cr-yeast group. LSD: low stocking density; HSD: high stocking density.