Dietary protein excess does not influence calcium and phosphorus absorption and retention in Iberian pigs growing from 50 to 100 kg body weight1

Abstract

Effects of apparent total tract digestible dietary protein [expressed as apparent ileal digestible (AID) Lys in parentheses] from excessive to marginally deficient [110 (7.9), 92 (6.6), 73 (5.3) and 54 (3.8) g/kg DM] and feeding level (FL; 0.80 and 0.95 × ad libitum) upon fractional absorption and retention of Ca and P was studied in 48 purebred Iberian barrows from 50 to 100 kg BW to investigate possible detrimental effects of protein over supply on Ca and P metabolism. The diets were prepared by diluting a high-protein diet, formulated according to the ideal protein concept, with a protein-free mixture. The diets provided (per kg DM) 11.6 to 10.7 g Ca, 6.67 to 6.25 g total P, and 13.9 to 14.8 MJ ME. Intake levels with free access to feed were calculated according to individual BW and were adjusted weekly. A digestibility and balance trial was performed at 75 kg BW. The ADFI was 3104 and 2643 g for 0.95 and 0.80 × ad libitum FL. The ADG reached a maximum at 854 g (18.87 g/MJ ME intake) with the diet containing 5.3 g AID Lys/kg DM. Dietary AID Lys content did not alter Ca and P fractional apparent absorption, which attained average values of 0.417 ± 0.0109 and 0.545 ± 0.0106. The Ca and P retention as a fraction of intake remained unaffected at 0.403 ± 0.0114 and 0.403 ± 0.0120. The Ca urinary losses were not elevated by excess of dietary protein supply, remaining at 0.260 ± 0.0212 g/d. High feeding level increased (P < 0.05) the flow of absorbed Ca and P. In conclusion, long-term, high-protein (Lys) intake did not affect Ca intestinal absorption and renal excretion in the pig.