SAFETY STUDY WITH LOW PHOSPHORUS LEVELS
There are several reports in the scientific literature indicating that some clay-based adsorbents will interfere with an animal’s ability to utilize nutrients. Also, it is a well-known fact among animal nutritionists that aluminum (Al) will complex with P in the digestive tract causing decreased bone mineralization and increased bone reabsorption. Ledoux et al. (1999) was able to demonstrate that when 1.0% Improved Milbond-TX® (IMTX) was supplemented to broiler diets nutrient utilization was not impaired when performance of birds fed IMTX was compared to control birds fed diets containing no IMTX. Miles and Henry (2007a) fed up to 2.0% IMTX to broilers in a study designed to specifically determine its safety at high levels of dietary inclusion. Even at a dietary concentration which was twice the amount included in the diet by Ledoux et al. (1999) no indication of impaired nutrient utilization was reported. In their study, Miles and Henry (2007a) also reported that serum P concentration and percent bone ash (as measured by toe ash) were not affected by IMTX. A normal serum P concentration in broilers was also documented in the publication of Ledoux et al. (1999) when IMTX was fed at a dietary concentration of 1.0%. Therefore, it was concluded by these investigators that dietary P was not being sequestered by the aluminum (Al) in IMTX since IMTX contains between 100 to 136 gm Al/kg as Al2O3.
Even though Ledoux et al. (1999) and Miles and Henry (2007a) were able to show that feeding high dietary concentrations of IMTX in diets adequate in all nutrients(including P) and metabolizable energy did not inhibit P utilization, the question arose: would IMTX have a negative effect on overall bird performance and bone mineralization if it were fed to broilers at high dietary concentrations in diets containing low P. This would be extremely important to know since less inorganic P is used in formulating poultry diets when phytase is used to enhance the utilization of the organically bound phytate P. Thus, a study was initiated at the University of Florida, using diets containing low P, in order to determine if supplementing high concentrations of IMTX would indeed bind P and decrease its utilization as reflected in poor overall broiler performance and/or decreased bone ash.
In this low phosphorus safety study, 450 Ross X Ross male broilers were selected from a larger group of chicks, weighed and allotted randomly with 5 birds per pen, 10 pens per treatment, in Petersime battery brooders. Each pen contained approximately the same total weight of chicks to eliminate extremes in initial body weight variability. IMTX was added at 0, 1.0 and 2.0% to each of 3 corn-soybean meal diets formulated to be isocaloric and isonitrogenous and contain 0.22, 0.32 or 0.42% available P. The diets and water were available ad-libitum throughout the entire 21-day experimental period. All birds and feed were weighed every 7 days and average treatment body weight, feed consumption and feed conversion were summarized.
Percent toe ash was selected as a measure of bone mineralization since it is a well-established method of determining bone mineralization rather than tibia ash because of the simplicity of toe collection and preparation compared with that required for bone ash. Hence, no ether extraction or removal of flesh tissue is required when using toe ash as the measure of bone mineralization. At the end of the 21 day experimental period for each experiment all chicks were killed and the middle toes of each chick were removed at the tarsometatarsal/P3 joint with the skin intact. The toe tip containing the nail was removed and discarded, then each toe was cleaned of any adhering foreign material with a wet paper towel and pooled by pen for toe ash analysis. Each set of toes was dried in an oven for 48 hours at 100◦C, then ashed in a muffle furnace at 550◦C for 14 hours to determine percent toe ash.
Results indicated that the effect of P in this study was highly significant. This meant that in the control and IMTX treatments when P in the diet increased feed consumption and body weight of chicks also increased. Feed conversion also improved as dietary P increased. There was no effect on body weight, feed consumption or feed conversion from feeding IMTX at 1.0 or 2.0% of the diet at any dietary P concentration. Toe ash was significantly lower when available P was deficient in the diet but was not affected by the addition of IMTX at any dietary P concentration. Even though, IMTX contains Al in its structural matrix, the data collected in this study clearly alidate the fact that the Al in IMTX is not free to bind P in the digestive tract. Thus, if a feed mixing error occurs and IMTX is added to poultry diets at up to 8 times the recommended level no detrimental effects on bird performance should be expected (Miles and Henry, 2007b).
Note: A complete description of this experiment conducted at the University of Florida and the
data collected in the experiment can be found in the referenced publication (Miles and Henry, 2007b) located in
the footnote below. The information presented in this issue of MILWHITE’S INFORMATION PAGE was compiled by
Dr. Orlando Osuna, Director of Health Science at Milwhite, Inc. and Dr. Richard Miles, Professor Emeritus,
University of Florida, Gainesville, FL, USA.
Miles, R.D. and P.R. Henry. 2007a. Safety of Improved Milbond-TX® when fed in broiler diets at greater than
recommend levels. Animal Feed Science and Technology. 138:309-317.
Miles, R.D. and P.R. Henry. 2007b. Safety of Improved Milbond-TX® when fed in broiler diets limiting in available
phosphorus or containing variable levels of metabolizable energy. Journal of Applied Poultry Research. 16:412-
Ledoux, D.R., G.E. Rottinghaus, A.J. Bermudez and M. Alonso-Debolt. 1999. Efficacy of a hydrated sodium
calcium aluminosilicate to ameliorate the toxic effects of aflatoxin in broiler chicks. Poultry Science 78:204-210.