Limited incremental response to routine phytase supplementation in Hy-Line Brown laying hens fed mineral-adequate...

This study evaluated whether routine moderate phytase supplementation in adequate-phosphorus diets provides additional measurable benefits in 40-week-old Hy-Line Brown laying hens, based on laying performance, egg quality, nutrient digestibility, excreta traits, gas emission, and apparent ileal amino acid (AA) digestibility. A total of 180 hens were assigned to three dietary treatments for 8 weeks: (TRT1) a basal diet, (TRT2) the basal diet supplemented with 500 FTU/kg phytase, and (TRT3) the basal diet supplemented with 1000 FTU/kg phytase. Each treatment included five replicates with 12 hens per replicate. Body weight and laying performance were recorded throughout the experimental period, while egg quality was assessed at weeks 2, 4, 6, and 8. Nutrient digestibility, fecal score, excreta gas emission, volatile fatty acids (VFAs), and apparent ileal AA digestibility were also evaluated. Repeatedly measured variables were analyzed using a mixed model including treatment, time, and treatment × time. Phytase supplementation produced no significant overall treatment effect on body weight or laying performance (P>0.05). Body weight and egg production changed significantly over time (P = 0.008 and 0.004, respectively), whereas no significant treatment × time interactions were detected. Egg quality traits were not affected by treatment, time, or their interaction (P>0.05). Nutrient digestibility and apparent ileal digestibility of essential, nonessential, and total AAs also showed no significant treatment effects. Similarly, no treatment effects were detected for fecal score, ammonia or hydrogen sulfide emissions, or VFA concentrations; however, fecal score and butyric, valeric, and isovaleric acids changed significantly over time. In conclusion, supplementation with 500 or 1000 FTU/kg phytase did not produce statistically detectable incremental improvements in productive, nutritional, or excreta-related responses under the adequate-calcium and phosphorus conditions tested. These findings are specific to the phytase doses and nutritional conditions evaluated.