This Is AuburnElectronic Theses and Dissertations

Effect of Dietary Energy, Synthetic Amino Acids, Enzymes, Antibiotics, and Molting Method on Commercial Leghorns




Wu, Guangbing

Type of Degree



Poultry Science


A series of experiments were conducted to investigate the effect of dietary energy, antibiotics, and molting method on performance, egg composition, egg solids, egg quality, and profits of current strains of commercial Leghorns. Two experiments were conducted to investigate the effect of adding synthetic amino acids on performance and nutrient utilization of commercial layers. One experiment was conducted to compare the effects of two sources of phytase on performance of commercial Leghorns. The results showed that increasing dietary energy by the addition of poultry oil to a dietary energy level of 2,877 kcal ME/kg maximized egg weight during Phase I (from 21 to 36 wk of age). Based on feed conversion, increasing dietary energy to 2,864 kcal ME/kg by the addition of poultry oil gave optimal performance of laying hens during Phase II (from 40 to 51 wk of age). An ideal dietary energy level for optimal performance could not be determined during early post-molt production period (from 70 to 81 wk of age). Based on improved feed conversion, a dietary energy of 2,846 kcal ME/kg gave optimal performance during second cycle phase 2 (from 86 to 95 wk of age). Based on body weight of hens, dietary energy level for optimal performance should be less than 2,936 kcal ME/kg during second cycle phase 3 (from 101 to 110 wk of age). There can be no fixed ideal dietary energy level for optimal profits, due to varying feed ingredient prices and egg price. When protein level of a corn-soy diet is below 15% (supplying less than approximately 15 g protein/hen per d) or lysine intake is less than 720 mg/hen per d, the addition of synthetic lysine while maintaining a 0.75 Met+Cys/Lys ratio significantly improved performance of laying hens. Although adding synthetic lysine to diets containing less than approximately 15% protein can improve performance and profits depending on value of performance improvements gained and cost of protein and lysine, these results give no indication as to whether or not diets containing less than 15% protein would be economical. While antibiotic supplementation had no effect on performance, antibiotic supplementation significantly reduced body checks and dirty eggs, and increased yolk color, resulting in positive effects on egg quality of laying hens. The addition of phytase significantly increased egg production and egg mass of hens fed the phosphorus deficient diet (0.11% NPP) to levels that were similar to hens fed the control diet containing 0.38% NPP. There was no significant difference in performance between hens fed two phytases. Feeding a no salt diet can produce an acceptable long-term post-molt performance and egg quality, and may be considered as an effective alternative molt method for conventional feed withdrawal.