Dietary phosphorus (P) should be fed in adequate amounts to sustain body weight gain and bone growth while being avoided due to environmental concern and to limited global phosphate resources. In addition, different genetic lines may have different daily P requirements, emphasizing that P recommendations need to be adjusted to individual situations. The objective of the present study was to assess the long-term effect of low, medium and high dietary P on the absorption, retention and utilization of P, calcium (Ca), and protein during the growing-finishing phase (40 to 100 kg BW) in addition to productive performance. For this purpose, 18 female pigs (approx. 40 kg) were randomized and distributed into three treatment groups: low P (LP; 4.1 g/kg dry matter (DM)), medium P (MP; 6.2 g/kg DM) and high P (HP; 8.9 g/kg DM). All pigs were fed with the same basic diet formulated according to the current nutrient recommendations for growing-finishing pigs (45- 105 kg BW).
Pigs fed with the LP diet showed a reduced feed intake compared to the MP diet, and lower Ca, P and N absorption, excretion and retention compared to pigs fed the MP and HP diets. Oppositely, pigs fed the HP diet showed an increased retention and excretion of P and Ca compared to the MP fed pigs. The absorptive capacity of P, Ca and N increased with age whereas the ATTD of P, Ca and N remained constant irrespective of P supply. Bone length and weight were not affected by dietary P supply, though the defatted dry bone weight was significantly reduced in the LP fed pigs, but similar between MP and HP fed pigs. A dietary ratio of 1.4:1 may be tentatively suggested as a proper dietary Ca:P based on both digestible P and Ca and not total P and Ca.
In conclusion, a daily supply of about 4.6 and 6.7 g digestible P seemed to be sufficient to fulfil the physiological need for P to sustain a growth rate of 800-1100 g/day in lean young and growing-finishing pigs, respectively. Deficient as well as excessive P supply resulted in low P utilization and a relatively higher total P excretion compared to the sufficient dietary P supply. The relative distribution of P excreted through the urine or the faeces depended on the dietary P content.
Sørensen, K. U., Tauson, A. H., & Poulsen, H. D. "Long term differentiated phosphorus supply from below to above requirement affects nutrient balance and retention, body weight gain and bone growth in growing-finishing pigs." Livestock Science 211 (2018): 14-20. https://doi.org/10.1016/j.livsci.2018.03.002