ABSTRACT
An experiment was conducted to determine the standardized ileal digestible (SID) calcium requirement of fast-growing broilers from hatch to d 14 post-hatch. Ross 308 (n = 360) male broilers were obtained on day of hatch and allocated to 1 of 5 treatments in battery cages. There were 6 birds per cage and 12 pens per treatment. Four treatments were formulated to contain 0.60%, 0.46%, 0.32% or 0.18% SID Ca. The final treatment was formulated using total Ca to meet or exceed all nutrient requirements, including 0.90% total Ca and 0.49% non-phytate P (nPP), using the same ingredients. This treatment was the reference diet for comparison and validation of the SID Ca diets. Birds and feed were weighed at placement and on d 14. Tibias and ileal contents were obtained on d 14 and excreta was collected per pen and pooled on d 14. Data were analyzed using JMP Pro and requirements were estimated using 3 different non-linear regression models. Increasing the SID Ca content in the diet from 0.18% to 0.60% improved (quadratic, P < 0.05) body weight gain and mortality corrected feed conversion ratio (mFCR). The estimated SID Ca requirement to optimize gain or mFCR was between 0.39% and 0.52%. Tibia ash percent and weight increased (quadratic, P < 0.05) as SID Ca content in the diet increased and the estimated SID Ca requirement was between 0.32% and 0.58%. Phosphorus utilization was improved in birds fed diets formulated using SID Ca compared with birds fed the reference diet. In conclusion, the SID Ca requirement of fast-growing broilers from hatch to d 14 was estimated between 0.534% and 0.398% when quadratic, straight-broken line, or quadratic-broken line regressions were used. These results agree with previously published data evaluating the SID Ca requirement of fast-growth broilers from hatch to d 10.
ABSTRACT
The current study presents a safety evaluation of a novel glucuronoxylan hydrolase (EC 3.2.1.136) from Bacillus subtilis produced in Bacillus licheniformis. The glucuronoxylan hydrolase preparation did not exhibit irritative potential to the eye and skin when applied in in vitro models. The glucuronoxylan hydrolase preparation was non-mutagenic and non-clastogenic in in vitro tests. Oral administration of the glucuronoxylan hydrolase preparation to rats did not cause any adverse effect in a 90-days subchronic toxicity study. A tolerance study was performed with broiler chickens and confirmed that this glucuronoxylan hydrolase is safe for broiler chickens when fed at the maximum recommended dose, as well as at the 10 times higher dose. In conclusion, there are no safety concerns with using this novel glucuronoxylan hydrolase as a feed additive as it is toxicologically inert and the glucuronoxylan hydrolase is well tolerated by broiler chickens. The beneficial safety evaluation of glucuronoxylan hydrolase is consistent with the fact that this type of enzyme is ubiquitous in nature.
