PENGARUH HEAT STRESS INDEX TERHADAP PERFORMA AYAM LAYER DI KANDANG CLOSED HOUSE UMUR 7-10 MINGGU PADA AREA YANG BERBEDA

This research aimed to evaluate the effect of the Heat Stress Index (HSI) on the Average Daily Gain (ADG) and uniformity of laying hens. The mean Average Daily Gain (ADG) of laying hens in the front area was 14.8±1.24ns, while in the rear area it was 14.2±4.74ns. Although the mean values were similar, the larger standard deviation in the rear area indicated greater daily growth variation, suggesting more fluctuating performance compared to the front area. The T-test results (P>0.05) showed no significant difference in ADG between the two areas. This outcome may be influenced by other factors, such as genetic variation (Wolc et al., 2009) and differences in gut gene expression, as reported by Akram et al. (2024). Using Partial Least Squares Regression (PLSR), the study identified gene combinations highly predictive of body weight phenotypes, particularly during early growth stages. The findings indicate that differences in average body weight are partly driven by variations in the expression of intestinal function genes, suggesting that ADG is likely influenced by internal rather than external factors, despite differences in HSI values. Regarding uniformity, hens in the front area recorded 93.29±0.50a, while those in the rear area recorded 95.2±1.31b, indicating better body weight uniformity in the rear area. However, a higher standard deviation in the rear also suggested slightly greater individual variation. Additional data showed that average HSI values were higher in the front area than in the rear. The T-test results (P<0.05) showed significant difference in uniformity between the two areas. This confirms that HSI significantly affects chicken comfort through physiological responses, as heat stress can trigger the release of cortisol and corticosterone, which, when prolonged, negatively impact growth, reproduction, and immune function (Romero et al., 2015).