Guanidinoacetic acid supplementation and stocking density effects on broiler performance: behavior, biochemistry, immunity, and small intestinal histomorphology

Abstract

Background: Rearing poultry under stressful high stocking density (HSD) conditions is a common commercial practice to increase profitability, despite its negative effects on broiler physiology and welfare. Many feed additives are used to alleviate the negative impact of such practices. This study investigated the ameliorative effects of guanidinoacetic acid (GAA) on growth performance, ingestive behavior, immune response, antioxidant status, stress indicators, and intestinal histomorphometry of broilers subjected to HSD. A total of 364 male broilers were randomly allocated into four treatments with 7 replicates each in a 2 × 2 factorial arrangement: two stocking densities (SD) (10 and 16 birds/m²) and two GAA levels (0 and 0.6 g/kg feed).

Results: Body weight, weight gain, feed intake, feed conversion ratio, production efficiency factor, dressing yield, and ingestive behavior were negatively affected by HSD, whereas the mortality rate was unaffected (P > 0.05). GAA improved the overall growth performance and dressing percentage (P < 0.05). In the HSD group, the immune response decreased at d 21 (P < 0.05). Creatine kinase, glutathione peroxidase (GPX), superoxide dismutase, catalase, triglycerides, and villus length and width (ileum) were reduced, whereas corticosterone (CORT) was increased (P < 0.05). Moreover, GAA increased the hemagglutination-inhibition titer at 21 days and the levels of lactate dehydrogenase, GPX, and catalase and decreased the levels of creatinine, alanine aminotransferase, nitrite, triglycerides, and CORT (P < 0.05). SD and GAA did not affect malondialdehyde or other biochemical parameters (P > 0.05).

Conclusions: Dietary GAA supplementation can improve productivity and antioxidant status and reduce stress in broilers reared in a HSD environment.

Keywords: Broiler chickens; GAA; Hemagglutination-inhibition test; Ingestive behavior; Oxidative stress; Performance; Stress indicators.

Fig. 1

Feeding and drinking behavior of broiler chickens. Values are expressed as the mean proportion and standard error of a Feeding behavior and (b) Drinking behavior. LSD: low stocking density (10 birds/m²) + basal diet only, HSD: high stocking density (16 birds/m²) + basal diet only, LSD + GAA: low stocking density + (basal diet + GAA (0.6 g/kg) feed), HSD + GAA: high stocking density + (basal diet  + GAA (0.6 g/ kg) feed). ^a,bIndicates statistical significance (P < 0.05)

Fig. 2

Antibody titers after NDV vaccination in the sera of broiler chickens (days 21 and 35). Values are expressed as the mean HI titer (log 2) and standard error at a Day 21 and b Day 35. LSD: low stocking density (10 birds/m²) + basal diet only, HSD: high stocking density (16 birds/m²) + basal diet only, LSD + GAA: low stocking density + (basal diet + GAA (0.6 g/kg) feed), HSD + GAA: high stocking density + (basal diet + GAA (0.6 g/kg) feed) . ^a,bIndicates statistical significance (P < 0.05)

Fig. 3

Serum total protein and albumin levels of broiler chickens. Values are expressed as the mean and standard error of a total protein and b albumin levels. LSD: low stocking density (10 birds/m²) + basal diet only, HSD: high stocking density (16 birds/m²) + basal diet only, LSD+GAA: low stocking density + (basal diet + GAA (0.6 g/kg) feed), HSD + GAA: high stocking density + (basal diet + GAA (0.6 g/kg) feed)

Fig. 4

Serum cholesterol and high-density lipoprotein (HDL) levels of broiler chickens. Values are expressed as the mean and standard error of a cholesterol (SDs) and b HDL levels. LSD: low stocking density (10 birds/m²) + basal diet only, HSD: high stocking density (16 birds/m²) + basal diet only, LSD + GAA: low stocking density + (basal diet + GAA (0.6 g/kg) feed), HSD + GAA: high stocking density + (basal diet + GAA (0.6 g/ kg) feed)

Fig. 5

Serum triacylglycerol (TAG) and low-density lipoprotein (LDL) levels of broiler chickens. Values are expressed as the mean and standard error of a TAG and b LDL levels. LSD: low stocking density (10 birds/m²) + basal diet only, HSD: high stocking density (16 birds/m²) + basal diet only, LSD + GAA: low stocking density + (basal diet + GAA (0.6 g/kg) feed), HSD + GAA: high stocking density + (basal diet + GAA (0.6 g/kg) feed). ^a,bDifferent superscript letters indicate a significant difference (P < 0.05)

Fig. 6

Photomicrographs of duodenum, jejunum, and ileum of broiler chickens treated with 2 × 2 factorial management. LSD: low stocking density with basal diet only . LSD + GAA: low stocking density with (0.6 g/kg feed) GAA. HSD: high stocking density with basal diet only.  HSD + GAA: high stocking density with GAA (0.6 g/kg feed). (H&E, small intestine; 4×, scale bar 200 mm)