This study aimed to evaluate the effects of phytase and tannase addition in broiler diets on the growth performance and meat quality of broilers fed sorghum-based diets. Twelve experimental diets were formulated at three sorghum levels (0, 50, and 100%) and four enzyme levels (no enzyme, 5000 FTU phytase, 25 TU tannase, and a combination of 5000 FTU phytase + 25 TU tannase). Data on voluntary feed intake, average weekly weight gain, and feed conversion ratio were recorded and used to assess growth performance. Technical and nutritional parameters were used to determine meat quality. Broilers fed total sorghum diets with phytase and tannase enzyme combination had the highest feed intake in the first (24.4 ± 0.04 g/bird/day) and second weeks of life (23.0 ± 1.06 g/bird/day), respectively. Complete sorghum diets with phytase (83.0 ± 0.88 g/bird/day) and tannase (122.0 ± 0.88 g/bird/day) showed the highest feed intake in the third and fourth weeks, respectively. Broilers fed 50% sorghum diets with tannase (135.3 ± 0.05 g/bird/day) and complete maize diets with phytase (158.1 ± 0.88 g/bird/day) had the highest feed intake during weeks five and six, respectively. Broilers fed a 50% sorghum diet without enzymes showed the highest weight gain in the final week (606.5 ± 32.39 g). Comparable feed conversion was observed in birds fed complete maize and 50% sorghum diets. Dietary treatment substantially influenced the live body, carcass, liver, kidneys, abdominal fat pad weight, and intestinal length. However, it did not affect nutritional and technical parameters or Pectoralis major meat.

ABSTRACT Free-range chicken production has significantly increased in recent years and it often entails exposing birds to cyclic environmental conditions. The objective of the current study was to investigate the effect of bird strain and sex, and rearing system on the physiological responses of Potchefstroom Koekoek (PK), Ovambo (OV) and Naked Neck (NN) chickens reared in a hot environment. Body weight (BW), rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were determined weekly for 4 weeks, in 3 slow-growing chicken strains under cyclic environmental conditions. A total of 288, 20-week old Potchefstroom Koekoek (PK), Ovambo (OV) and Naked Neck (NN) chickens were separated by sex and allocated to extensive and intensive rearing systems. Ambient temperature and relative humidity (RH) were used to compute a temperature humidity index (THI). A Proc MIXED model was used to analyze fixed effects and a linear regression model was fitted to test the relationship between THI and response parameters. All factors studied influenced (p<0.05) BW while none affected (p>0.05) RT. Higher BW (p<0.05) were obtained with OV in both rearing systems. Sex influenced (p=0.0021) HR but not RR (p>0.05). Week and rearing system affected (p>0.05) RR. THI showed significant correlation with RR and HR. THI was higher in intensive than extensive rearing. Physiological responses of PK, OV and NN are comparable under similar rearing conditions.