C. A. Bailey

Evaluation of high dietary phytase supplementation on performance, bone mineralization, and apparent ileal digestible energy of growing broilers

ABSTRACT The present study was conducted to evaluate four commercially available phytase sources supplemented at regular (R) and super‐dose (S) levels on live performance, bone mineralization, and apparent ileal digestible energy. Broiler chickens were allocated in stainless steel battery brooders (six birds per cage and eight pen replicates per treatment). A basal diet formulated to contain 0.2% non‐phytate phosphorus (NPP) and 0.7% Ca was subdivided to create 11 dietary treatments: (1) basal diet was kept as the negative control (NC); (2) NC + limestone and monoclacium phosphate to create positive controls 1 and 2 formulated to yield 0.3% and 0.4% NPP; (3) NC + phytase A (250 and 1,500 FTU/kg); (4) NC + phytase B (500 and 1,500 FTU/kg); (5) NC + phytase C (500 and 1,000 FTU/kg); (6) NC + phytase D (1,000 and 2,000 FYT/kg). Performance was evaluated on d 7, 14, and 22. Tibia bone ash, tibia breaking strength, bone mineral content, and bone mineral density were evaluated on d 22. Apparent energy digestibility was evaluated on d 24. At d 7, phytases A and C supplemented at S level improved (P < 0.05) body weight and weight gain when compared to the NC. At d 14 and 22, all phytase sources improved (P < 0.05) body weight, weight gain, and bone mineralization when compared to the chicks under the NC diet. Overall, phytase supplementation at S level improved 17% apparent ileal digestibility at 24 d. Throughout the grow out period, phytase super‐dose yield (P < 0.05) better performance, bone characteristics, and energy digestibility than the regular dietary level. In conclusion, all phytase sources were able to compensate the phosphorus deficiency and promote performance and bone mineralization. High levels of phytase showed a higher response when compared to the lower levels of supplementation.

Assessing effects of yeast cell wall supplementation on threonine requirements in broilers as measured by performance and intestinal morphology

ABSTRACT The objective of this study was to evaluate whether or not the use of a prebiotic yeast cell wall (YCW) affects threonine requirements in starter broilers. Two hundred and forty 1‐d‐old Ross 308 broiler chickens were distributed among 2 Petersime battery brooder units (48 pens; 5 birds per pen). Different threonine to lysine ratios (0.60, 0.65, and 0.70 to 1.0) with 1.22% available lysine with and without YCW at 250 ppm was fed to the chickens in order to evaluate performance and intestinal morphology over a 21‐d trial. A basal diet with 22% protein and 2,980 kcal/kg ME was prepared to create the 6 dietary treatments. The calculated lysine concentration was 1.34%, whereas threonine was 0.81, 0.88, and 0.94%, respectively. Pen weights and feed consumption were recorded at d 1, 7, 14, and 21 of the experiment. Jejunal and ileal samples were collected on d 21 for histology analysis to evaluate villi height (VH), crypt depth, villi width (VW), and muscularis thickness. A threonine to lysine ratio of 0.7:1.0 resulted in significant improvement of performance variables with increased jejunum VW and ileum VH compared with the other threonine to lysine ratios. Adding YCW to starter broiler did not affect the requirement for threonine.

Relative bioavailability determination of highly concentrated cholecalciferol (vitamin D3) sources employing a broiler chick bioassay

SUMMARY Cholecalciferol (D3) deficiency in animals and humans is associated with skeletal deformities and retarded growth. Hence, the evaluation of D3 sources is useful to ensure adequate biological activity. For this experiment, two sources of D3 were used to compare both biological activities using a chick bioassay. Newly hatched broiler chickens were caged in 2 battery brooders for a 17‐day trial period. Experimental treatments were created from a common basal D3‐deficient corn‐soy broiler starter diet. The basal diet was supplemented with 0 (NC), 62.5, 125, 250, 500, or 1,000 IU D3/kg of feed. All birds were fed the basal diet devoid of D3 (NC) over the first 9 d to deplete the maternal D3, followed by a 12‐hour fasting period. On d 10, the test diets were offered ad libitum for 7 days. Feed consumption, body weight (BW), and mortality were recorded to evaluate weight gain (WG) and feed efficiency (FE). Additionally, bone mineral content (BMC), bone mineral density (BMD), percent fat‐free dried tibia ash (TBA), and tibia breaking strength (TBS) were used to evaluate bone mineralization. Relative bioavailability (RBV) of D3 was determined by the slope‐ratio method using the powdered D3 as the reference standard source. Estimated RBV of the D3 beadlets source was 0.74, 0.75, 0.79, 0.80, 0.65, and 0.63 when BW, WG, TBA, TBS, BMC, and BMD were used as response criteria, respectively. In conclusion, this protocol was able to detect differences between highly concentrated D3 sources and may be employed to evaluate D3 biological activity.