The effects of heat stress on nutrient utilization were studied in broiler chickens using indicator method with two different markers. Chickens were divided into two research facility (RF) rooms with eight compartments (10 chickens per compartment; n=160). Beginning on day 21 of the experiment, chickens in half of the compartments (RF room 1) were exposed to a temperature of 30-32°C for 10 hours per day (warm environment group; VO), while the other half of the chickens (RF room 2) were housed in a thermoneutral environment (TNO). Three days before the end of the experiment, titanium oxide (TiO2) was added to the feed as an external marker. On day 42, the excreta were collected and the apparent utilization of nutrients was calculated using the TiO2 indicator method (NI-Ti). The internal marker lignin, defined as acid detergent lignin (ADL), was also used as an indicator and apparent nutrient utilization (NI-KDL) was calculated. Data were processed using SAS statistical software with the GLM procedure. In the analysis of the feed, we found very high mineral contents, especially microminerals, which was due to contamination of the raw materials before feed preparation. No statistical differences were found in apparent nutrient utilization between the TNO and VO group, regardless of the indicator method used. However, there were differences in nutrient utilization when comparing indicator methods, and virtually all values of NI-KDL were lower than those of the NI-Ti method. This suggests that the excreta were contaminated with litter, which increased the ADL content of the excreta and thus decreased the calculated apparent nutrient utilization of the NI-ADL method.
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