Abstract The objective of this study was to evaluate whether the addition of a blend based on α-monolaurin mono-, di- and triglycerides of butyric acid, and lysolecithin on the performance even on diets containing reduced inclusion of oil in the diet and without the use of growth-promoting antibiotics of broilers considering the effect on health, performance, and meat. Three treatments were defined: positive control (TP: with enramycin), negative control (TN: no enramycin), and blend (T-FRA: with monolaurin and glycerides of acid butyric minus 0.8% soybean oil). At 21 days, broilers treated with TP and T-FRA obtained the lower feed conversion ratio (FC); at 35 days, T-FRA broilers obtained lower FC than TN broilers. Cholesterol levels were higher in the blood of T-FRA broilers. On day 42, levels of ROS and TBARS were lower in the intestine, muscles, and liver of T-FRA broilers. Moreover, glutathione S-transferase and total non-enzymatic antioxidants were greater at the intestinal and muscular levels. The T-FRA broilers had a lower percentage of lipids in the meat. The MIC indicated that 111mg of the blend/mL inhibited the growth of E. coli; however, the counts of total coliforms and E. coli in the feces and the broilers’ litter did not differ between treatments. In conclusion, the addition of the blend T-FRA in broiler diets was able to improve the feed conversion and maintain the other performance parameters even considering a reduction of 0.8% in the inclusion of oil.

ABSTRACT: This study aimed to evaluate the effect of probiotics on performance, intestinal morphology and carcass characteristics of broiler chickens housed on lower or higher environmental challenge. Three hundred male Cobb chicks were distributed into four groups in completely randomised design with treatments arranged in a 2 x 2 factorial scheme to evaluate effects of two diets (with or without probiotics) and two environmental conditions (lower or higher challenge), totaling four treatments with five replications with 15 birds per box. Probiotics were added on diets and were composed of Lactobacillus acidophilus, Bacillus subtilis, Bifidobacterium bifidum and Enterococcus faecium. The environment with lower challenge was made up of new wood shavings used as litter, low bird density (8 birds/m2) and daily-cleaned bell drinkers. The environment with higher challenge was made up of re-used wood shavings used as litter (after three broods of broilers), bird density of 16 birds/m2 with bell drinkers cleaned every two days. No significant interaction between diet and environmental challenge was found for any of the variables evaluated. Performance, slaughterhouse variables and chemical carcass composition were not affected by the use of probiotics. Chicks receiving diets without probiotics had lower intestinal crypt depth (267.1 vs. 316.6 pm, P=0.0068). Birds raised in the environment with higher challenge decreased feed intake (4,660 vs 5,020 g, P=0.0422), weight gain (2,610 vs 2,810 g, P= 0.0054), drumstick and thigh yield (21.98 vs 24.14 %, P=0.0354), and increased crypt depth (325.2 vs 258.5 pm P=0.0009). In conclusion, the probiotic does not promote satisfactory improvements, regardless of the environmental challenge.