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972
Digestible calcium requirement for 100 to 130 kg pigs
An experiment was conducted to determine the digestible calcium requirement by pigs from 100 to 130 kg. Ninety pigs (average initial BW = 99.89 ± 3.34 kg) were randomly allotted to 15 experimental diets. Each diet was fed to 6 replicate pens using a randomized complete block design. Fifteen corn and soybean meal-based diets were formulated and all diets had the same concentrations of phytate and Na. Diets were formulated using a 3 x 5 factorial design with diets containing 0.11, 0.21, or 0.31% standardized total tract digestible (STTD) P and 0.12, 0.29, 0.46, 0.61, or 0.78% total Ca (0.08, 0.18, 0.29, 0.38, or 0.49% STTD Ca). The P concentrations ranged from 48 to 152% of the STTD P requirement and the Ca concentrations ranged from 27 to 173% of the total Ca requirement. Experimental diets were fed for 28 d and pigs were individually housed. Pig and feeder weights were recorded at the beginning and at the conclusion of the experiment to calculate ADFI, ADG, and G:F. On d 28, all pigs were euthanized and the right femur was extracted. Ash, Ca, and P concentrations were determined from the de-fatted, dried femurs. Results indicated that as dietary concentrations of STTD Ca increased, the ADFI and ADG decreased (main effects of Ca, P < 0.05), regardless of the dietary concentration of P. Models to predict ADFI [ADFI = 3.6782 – 1.2722 x STTD Ca (%); P = 0.001] and ADG [ADG = 1.2141 – 0.6230 x STTD Ca (%); P = 0.008] were dependent only on the concentration of STTD Ca, but not on the STTD of P. There were no effects by STTD Ca or STTD P on G:F indicating that the negative effects of STTD Ca on ADG was a result of reduced ADFI. Linear increases were observed for bone ash, bone Ca, and bone P as dietary concentrations of STTD Ca increased for all levels of STTD P (interaction, P < 0.001). In conclusion, results from the experiment support the current requirements (NRC, 2012) for Ca and STTD P, and feeding beyond the requirements for Ca (0.46% total Ca; 0.29% STTD Ca) or STTD P (0.21) is detrimental to growth performance of pigs.
Keywords: bone ash, calcium, pigs, phosphorus