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Two experiments (digestibility and slaughter trial) involving 102 piglets between 15 kg to 30 kg body weight (bw) were conducted to assess the bioavailiability of dicalcium phosphate, monocalcium phosphate, sodium-calcium-magnesium phosphate, dicalcium-magnesium phosphate and disodium phosphate, respectively.In the 4-weeks trial piglets fed a diet supplemented with phosphate of mineral sources gained more body weight, 527 g to 548 g per day, compared to piglets, 517 g per day, receiving the basal diet.At the beginning and at the end of the feeding period 5 pigs of each group were slaughtered for chemical analysis.
At 14.2 kg of body weight the mean body contained 431 g ash, 112 g calcium, and 75 g phosphate, respectively. At the end of the period at 28.2 kg body weight, the body of pigs fed the supplemented diets contained between 721 g to 764 g ash, 183 g to 191 g calcium. The phosphate content of the total body differed significantly from 130 g to 137 g per pig in the phosphate supplemented groups to 119 g per pig in the group receiving the basal diet.Phosphate content per kilogram body weight of pigs supplemented with sodium-calciummagnesium phosphate and monocalcium phosphate differed significantly, 4.86 g/kg bw and 4.76 g/kg bw versus 4.20 g/kg bw for pigs fed the basal diet containing only the phosphate of plant origin.Within the supplemented groups no similar response were observed concerning the ash-, calcium- and phosphate content per kg body weight. Pigs fed the supplemented diet with phosphate mineral origin gained on average 119 ash, 2.7 g calcium and 2.1 g phosphate per day, respectively. The sodium-calcium-magnesium phosphate group gained most. Daily weight gain of piglets without supplementation was significantly less, 8.3 g ash, 2.1 g calcium and 1.5 g phosphate per day, respectively. Phosphate content per kg body weight gain differed from 3.84 g to 4.38 g within the supplemented groups.
Pigs fed with the basal diet containing only phosphate of plant origin gained significantly less, 3.03 g per kg body weight.Digestibility of the total diet phosphate investigated in the slaughtered pigs varied from 44% for dicalcium phosphate to 50% for sodium-calcium-magnesium phosphate compared to the basal diet with 34%. Based on the digestibility of the phosphate of plant origin of 21.7% observed in the digestibility trial, digestibility values of the supplemented phosphate was assessed as follows: monocalcium-phosphate 92.3%, sodium-calcium-magnesium phosphate 91.7%, disodium phosphate 91.3%, dicalcium phosphate 79.7% and dicalcium-magnesium phosphate 81.9%. Based on the intake of digestible phosphate in the diet and the phosphate retention in the body a bioavailability from 90.3% to 93.0% was assessed for the treated groups.Based on the results of the digestibility and the phosphate retention in the basal diet group a etto conversion of the plant origin phosphate of 26.5% was found. Based on this value, conversion rates of supplemented phosphate were determined from 79% to 91%. Sodiumcalcium-magnesium phosphate and monocalcium phosphate showed significantly higher values compared to dicalcium phosphate.
The use of the tibia bone as criteria for the conversion rate of the supplemented phosphorus was investigated. The phosphate retention in the bone was significantly influenced by the source of phopshorus added to the diet. The phosphate retention in the tibia was similar to the phosphate retention in the total body of the piglet.