Abstract
One hundred ninety two swine were used in a trial to assess the relative bioavailability of phosphorus (RBP) in six phosphate sources. Phosphates were three feed grade phosphates (FP), two made in Brasil, and one USA made, and three rock phosphate samples (RP) originated from two mines sites in Brasil, and one mine site in Israel. Levels of calcium, phosphorus and fluorine in RP were 29, 12 and 1.7% (RP source 1), 33, 14 and 1.4% (RP source 2), and 30, 14 and 3.6% (RP source 3), respectively. Pigs were fed a corn-soybean meal basal diet (18% CP, 0.95% Lys, 0.75% Ca, 0.37% P) or the basal diet with 0.15% P from a standard purified grade calcium phosphate (SP), or with 0.15% P from experimental FP or RP. Each diet was fed to six pen replicates of four pigs per pen for 35 days (14.4 to 39.9 kg). Weight gain (WG), feed/gain (FG), plasma P (PP), bone ash (BA), and breaking strength of metacarpals and metatarsals (BS-MM) and femurs (BS-F) were improved by phosphorus addition. However, performance and bone parameters were depressed by RP, as compared to FP dietary supplementation. WG, BA, BS-MM and BS-F were regressed to P added, and slope-ratios were calculated to assess RBP in the FP and RP sources. The average bioavailability of P in the FP and RP sources, relative to SP, were 89 and 49% (WG), 112 and 49% (BA), 78 and 28% (BS-MM), and 101 and 52% (BS-F), respectively. Low animal performance and bone strength related to toxicity should be expected if rock phosphates are used to feed pigs.
Highlights
Animal diets based on corn and soybean meal are very deficient in available phosphorus (P) to the point that supplementation is necessary using sources of high P availability
Calcitic limestone was found in large proportions in all three commercial dicalcium phosphate products and may be the result of excess calcium carbonate added to neutralize the phosphoric acid during the industrial processing
Similar results were recorded for broilers by Fernandes et al (1999), who studied four feed-grade, and four agricultural-grade phosphates, as well as one standard purified grade P source, and reported that the performance was improved by 31% for BW, 34% for BW gain, 7% for FI, and 20% for FG, in response to increasing dietary P (0.08 or 0.16% P added to a 0.48% P basal diet)
Summary
Animal diets based on corn and soybean meal are very deficient in available phosphorus (P) to the point that supplementation is necessary using sources of high P availability. Dicalcium phosphate is commonly used as a source of supplemental P. Some animal production technicians point out that rock phosphates is an alternative dietary P source in animal nutrition due to their very low price compared to feed grade phosphates. It is well known that rock phosphates are not intended to be used in animal diets for not being submitted to manufacturing procedures to guarantee the adequate purity degree for feeding foodproducing animals, and to their very low P bioavailability. High levels of certain mineral elements can be toxic to the animal
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