Interactive effects of high temperature and crude protein levels on growth performance, nitrogen excretion, and fecal characteristics of broilers

In the present study, we aimed to explore the interactive effects of high temperature (HT) and dietary crude protein (CP) levels on nitrogen (N) excretion, fecal characteristics, and growth performance of broilers. A total of 288 broilers (Arbor Acres) were divided into six groups with eight replicates (six broilers per replicate). Two temperatures (ambient temperature: AT, 23 °C; HT: 28 ~ 32 ~ 28 °C) and three diets (CP: 14.90%, 18.18%, or 21.19%, with equal amounts of essential amino acids) were examined in a 2 × 3 factorial design. The experiment arrangement was from 4 to 6 weeks of age. The results showed that HT led to a significant decrease in the N excretion ( P < 0.0001), average daily feed intake ( P < 0.0001), and weight gain of broilers ( P < 0.0001), while it markedly increased the fecal pH ( P = 0.015), fecal moisture ( P = 0.0014), uric acid (UA) contents ( P = 0.0018), and feed/gain ratio ( P < 0.0001). A low CP diet significantly decreased the N excretion ( P < 0.001), fecal pH ( P = 0.016), fecal moisture ( P < 0.0001), and UA contents ( P < 0.0001), while it markedly increased the feed/gain ratio ( P < 0.001). In conclusion, HT had a negative impact on the fecal characteristics and growth performance of broilers but showed positive effects on N excretion. Moreover, decreased CP levels had a positive effect on the N excretion and fecal characteristics in broilers.