Dietary Calcium to Digestible Phosphorus Ratio for Optimal Growth Performance and Bone Mineralization in Growing and Finishing Pigs

Abstract

Within the context of maximizing the use of dietary phosphorus, a growing-finishing pig study was conducted to determine the optimal total dietary calcium (Ca) to digestible phosphorus (dP) ratio and to verify the possibility of mineral phosphate removal during the finishing period on growth performance and mineral status. The potential for replacing chemical and mechanical bone properties by dual energy X-ray absorptiometry (DXA) measures on non-dissected feet was also verified. Three Ca to dP ratios (2.2:1, 2.5:1 and 2.8:1) within two dP levels (P+, P–) were fed during 91 days to 84 pigs. The grower and finisher P+ diets contained 3.0 and 2.4 and P– diets contained 2.5 and 1.7 g dP/kg, respectively. Growth performance and blood serum mineral content were independent of treatments, except that 2.2:1 impaired finisher feed conversion ratio compared to 2.5:1 and 2.8:1. Urinary P concentration increased by 37% in 2.2:1 compared to 2.5:1 and 2.8:1. Maximal load on bone and DXA mineral density were reduced in 2.2:1 compared to 2.8:1. Bone ash and volumetric density were reduced in 2.2:1 and 2.5:1 compared to 2.8:1. Diet P– reduced bone ash, maximal load, volumetric density and DXA bone mineral content and density. No interaction was observed between Ca and dP level. Therefore, 2.2:1 was insufficient for an efficient metabolic use of P, 2.5:1 was sufficient to maximize growth performance and 2.8:1 further improved bone mineralization. Increasing dietary Ca did not impair bone zinc content. Diets P– without supplemented mineral phosphates during the finisher period resulted, per pig, in a decrease of its use by 65% and of the calculated P excretion by 41%, without impaired growth performance. Finally, DXA data responded to dietary treatments as did labor intensive chemical and mechanical bone properties.

Phenotyping of the Visceral Adipose Tissue Using Dual Energy X-ray Absorptiometry (DXA) and Magnetic Resonance Imaging (MRI) in Pigs

“…In pigs, MRI and DXA (including pure bone mineral analysis [30,31]) are also used for body composition analyses and achieve acceptable results compared to chemical analyses or dissection [32][33][34][35][36]. Our study shows that DXA overestimates VAT compared to MRI and the deviation rises with increasing VAT levels in accordance with other porcine and human studies, where DXA tends to overestimate the amount of fat [33,[37][38][39][40].…”

Accuracy of predicting chemical body composition of growing pigs using dual-energy X-ray absorptiometry

“…Thus, BMC is expected to be lower than body ash. When comparing BMC with ash in single bones, the correspondence of the values was greatly improved (Schlegel and Gutzwiller, 2020). Fat tissue mass was 24% lower (P < 0.05) than lipid content in the EB but comparable (P > 0.05) in the carcass.…”

Adverse effects on growth performance and bone development in nursery pigs fed diets marginally deficient in phosphorus with increasing calcium to available phosphorus ratios

“…In other words, is the relationship completely linear or is the expected negative impact intensified at very high ratios? While numerous studies have compared narrow vs. wide Ca:aP when P is deficient ( Schlegel and Gutzwiller, 2020 ), only one other study utilized sufficient dietary treatments to define the slope of the curve ( González-Vega et al, 2016b ); in this instance, the evaluation involved pigs that were heavier (25 to 50 kg) than those employed in this experiment (6 to 15 kg). In the study reported herein, seven ratios of Ca:aP from 1.25 to 2.75 were evaluated.…”