Responses of broilers to dietary zinc bacitracin at two different planes of nutrition

The cereal type in feed influences gut wall morphology and intestinal immune cell infiltration in broiler chickens

In broiler chickens, a diet where the major cereal types are wheat, rye and/or barley has a lower digestibility compared with a diet in which maize is the major cereal type. In the present study, the effects of two different dietary cereal types, maizev.wheat/rye, on host factors (inflammation and gut integrity) and gut microbiota composition were studied. In addition, the effects of low-dose Zn-bacitracin supplementation were examined. Broilers given a wheat/rye-based diet showed more villus fusion, a thinner tunica muscularis, more T-lymphocyte infiltration, higher amount of immune cell aggregates in the mucosa, more and larger goblet cells and more apoptosis of epithelial cells in the mucosa than those given a maize-based diet. Adding Zn-bacitracin generally reversed these alterations. The microbiota composition was analysed by the use of terminal-restriction fragment length polymorphism, showing changes in the microbiota composition depending on the cereal type used in the diets. The effect of the change of cereal type on the gut microbiota composition was larger than that of Zn-bacitracin supplementation. In conclusion, a wheat/rye-based diet evoked mucosal damage, an alteration in the composition of the microbiota and an inflammatory bowel type of condition.

Influence of zinc bacitracin, light regimen and dustbathing on the health and welfare of broiler chickens

1. The influence of zinc bacitracin, an antibiotic growth promoter, and the combined influence of two environmental factors (8 h of darkness and access to sand) on health and welfare variables were studied in 96 broiler chickens (kept as pairs). 2. Chickens fed with zinc bacitracin (ZB) had a higher frequency of tibial dyschondroplasia (TD) and a higher frequency of dustbathing than chickens fed without zinc bacitracin. 3. When 42 d old, chickens exposed to 8 h of darkness and access to sand were heavier than chickens reared under continuous light and with no access to sand. 4. Fluctuating asymmetry was higher in the 'light/no sand' groups than in the 'night/sand + ZB' group. 5. There was a negative correlation between tonic immobility and weight and a positive correlation between weight and TD.

The bioefficacy of zinc bacitracin in practical diets for broilers and laying hens

Two balance trials were conducted to examine the response in metabolizable energy and metabolizability of both fat and amino acids to graded levels of zinc bacitracin (ZnB; Albac registered trade name of Alpharma, Oslo, Norway) in practical broiler and layer diets varying in their nutrient density. Broiler diets were supplemented with either 0, 20, or 50 mg ZnB/kg and layer diets were supplemented with either 0, 50, or 100 mg ZnB/kg. Each experimental diet was fed to five replicates of four broiler chicks each or nine replicates of individually housed laying hens, respectively. All balance parameters were significantly influenced by nutrient density, age, and dietary ZnB level. No significant interactions between ZnB by nutrient density were found. Addition of ZnB resulted in a lower excreta:feed ratio and an improved N retention; there was a nearly linear relationship between these effects and dietary ZnB levels. Moreover, dietary MEn content was linearly enhanced by ZnB supplementation. As a consequence, the bioefficacy of ZnB can be expressed in terms of MEn units: the average MEn equivalency of ZnB was 2,080 and 1,184 Mcal/kg, for broiler chicks and laying hens, respectively.