Evaluation of serum parameters to predict the dietary intake of calcium and available phosphorus in growing pigs

Abstract

Adequate provision of calcium (Ca) and phosphorus (P) is essential for bone formation and high growth performance in pigs. Nevertheless, reliable serum biomarkers for pig’s Ca and P intake are still missing. Here, we used phytase supplementation to alter the dietary available P (aP) level in order to investigate the effect of differences in dietary aP levels on serum parameters related to the Ca and P homeostasis in pigs. Moreover, we assessed whether serum parameters can be used to predict the Ca, total P (tP) and aP intake in barrows and gilts throughout the fattening period. In total, 216 pigs (115 gilts and 101 barrows) were randomly allotted to 1 of 2 diets in 3 replicate batches, each lasting 56 days (n =108/diet). Pigs had free a, ccess to the diets without (Con) or with phytase (Phy; 650 phytase units/kg) via a transponder-based feeding system. Blood samples were collected on days 2, 23 and 52 and serum parameters were correlated to the daily Ca, tP, and aP intake. The intake of tP, aP, and Ca was overall 14.2, 13.8, and 14.2% higher in barrows compared to gilts, respectively (P < 0.001). Concurrently, phytase decreased the intake of tP and Ca by 8.4 and 6.7%, respectively, whereas it raised the intake of aP by 16.3% compared to Con diet (P < 0.001). Serum levels of fibroblast growth factor 23, alkaline phosphatase (ALP), vitamin D (VitD) and osteocalcin (OCN) decreased with age (P < 0.05). The higher aP intake of pigs fed Phy diet increased serum P on days 2 and 23 but decreased it on day 52 compared to Con diet (P = 0.004). Pigs fed Phy diet had higher serum ALP compared to pigs fed Con diet on days 23 and 52 (P < 0.05). Correlation analysis between serum parameters and Ca, tP and aP intake showed age- and sex-related associations. With 12 weeks of age serum P in both sexes, serum VitD in barrows and serum OCN and ALP in gilts correlated with aP intake (|r| > 0.38), whereas serum OCN correlated with Ca in both sexes’ intake (r > 0.50). At 20 weeks, serum Ca and ALP in gilts correlated with aP intake, whereas serum P, Ca and VitD correlated with Ca intake in both sexes (|r| > 0.39). In conclusion, present results showed that the daily Ca and aP intake could be most reliably estimated from serum parameters for an approximate age of 12 and 20 weeks. Serum P and the Ca:P ratio at 12 weeks of age and serum VitD at 20 weeks of age may be used to predict pig’s daily aP intake in both sexes.

Available phosphorus levels modulate gene expression related to intestinal calcium and phosphorus absorption and bone parameters differently in gilts and barrows

“…The data presented here were derived from a subset of 24 pigs from the first and two replicate batches of a published study evaluating serum parameters to predict dietary intake of Ca and aP presented in Vötterl et al [5]. The institutional ethics committee of the University of Veterinary Medicine Vienna and the National authority approved all procedures involving animal handling and treatment according to the Law for Animal Experiments, Tierversuchsgesetz (BMWFW-68.205/01221-WF/V/3b/2017).…”

“…In the first and second replicate batch of the previously published study Vötterl et al [ 5 ], 144 (75 gilts and 69 barrows; 11 weeks of age; 37.9±6.2 kg) fattening pigs (Swiss Large White× Piétrain) from 13 litters were used. Data from this feeding trial were already presented for the entire group of pigs in Vötterl et al [ 5 ].…”

“…In the first and second replicate batch of the previously published study Vötterl et al [ 5 ], 144 (75 gilts and 69 barrows; 11 weeks of age; 37.9±6.2 kg) fattening pigs (Swiss Large White× Piétrain) from 13 litters were used. Data from this feeding trial were already presented for the entire group of pigs in Vötterl et al [ 5 ]. The outdoor climate-fattening unit consisted of six pens for 12 pigs each (3.50 m×5.48 m/pen) with slatted flooring, two nipple drinkers, and one automatic feeding station per pen.…”

“…Assumable from the results of all pigs used in this research [5], linking the daily intake of Ca, tP, and aP with serum parameters proved to be difficult in the subset of 24 pigs at the time point of sampling.…”

“…Overall, at 12 weeks of age, serum P and serum Ca/P ratio, and at 20 weeks of age serum 25-hydroxyvitamin D3 and D2 (VitD) were the most reliable parameters to predict aP intake. Active VitD, parathormone, and bone-synthesized fibroblast growth factor 23 (FGF23) regulate the Ca and P homeostasis via actions in the intestine, kidney, and bone [ 5 , 6 ]. The intestinal absorption of Ca and P comprises two absorption routes.…”