Phosphorus and calcium requirements for bone mineralisation of growing pigs predicted by mechanistic modelling

Abstract

<jats:p>Phosphorus (<jats:bold>P</jats:bold>) is an essential nutrient in livestock feed but can pollute waterways. In order for pig production to become less of a threat to the environment, excreta must contain as little P as possible or be efficiently used by plants. This must be achieved without decreasing the livestock performance. Phosphorus and calcium (<jats:bold>Ca</jats:bold>) deposition in the bones of growing pigs must be optimised without affecting the muscle gain. This requires precision feeding based on cutting-edge techniques of diet formulation throughout the animal growth phase. Modelling and data mining have become important tools in this quest. In this study, a mechanistic model taking into account the distribution of P between bone and soft tissues was compared to the established factorial models (INRA (Jondreville and Dourmad, 2005) and NRC (National Research Council, 2012)) that predict P (apparent total tract digestible, <jats:bold>ATTD-P</jats:bold>; or standardised total tract digestible, <jats:bold>STTD</jats:bold>-P) and Ca (total and STTD) requirements as a function of BW and protein deposition. The requirements for different bone mineralisation scenarios, namely, 100% and 85% of the genetic potential, were compared with these two models. Sobol indices were used to estimate the relative impact of growth-related parameters on mineral requirements at 30, 60 and 120 kg of BW. The INRA showed the highest value of ATTD-P requirement between 29 and 103 kg of BW (6%) and lower for lighter and higher BW. Similarly, the model for 85% bone mineralisation showed lower STTD-P requirement than NRC between 29 and 93 kg of BW (7%) and higher for lighter and higher BW. Contrary to other models, the Ca requirement of the proposed model is not fixed in relation to P. It increases from 95 kg of BW while the others decrease. The INRA showed the highest Ca requirements. The model Ca requirements for 100% bone mineralisation are higher than NRC from 20 to 38 kg of BW similar until 70 kg of BW and then higher again. For 85% objective, the model showed lower Ca requirements from 25 to 82 kg of BW and higher for lighter and higher BW. The potential Ca deposition in bones is the most sensitive parameter (84% to 100% of the variance) of both ATTD-P and Ca at 30, 60 and 120 kg. The second most sensitive parameter is the protein deposition, explaining 1% to 15% of the ATTD-P variance. Studies such as this one will help to usher in a new era of sustainable and eco-friendly livestock production.</jats:p>

Dietary Phosphorus and Calcium Utilization in Growing Pigs: Requirements and Improvements

“… c Estimated according to Jondreville and Dourmad ( 84 ) . d estimated according to Lautrou et al ( 12 ) . …”

“…This is clear when looking at the capacity of P- and Ca-depleted pigs to rapidly replace bone mass through compensatory bone mineralization (see section 4.3). This model has been revised ( 12 ) to rectify the no dependency of bone mineral deposition on protein gain by establishing a potential for Ca deposition independent of soft tissue gain, thus allowing P and Ca requirements for soft tissue growth and bone growth to be predicted independently ( Figure 3 ).…”

“… General layout of the proposed mechanistic model predicting total calcium (Ca) and apparent and standardized digestible phosphorus (ATTD and STTD P) requirements of growing pigs ( 12 ). …”

“…This strategy can increase the animal's P digestive efficiency and metabolic utilization in growing pigs; thus it overall decreases in P intake and excretion while maintaining growth and bone mineralization ( 9 , 10 ). Finally, a mechanistic model approach predicts bone ash and then P and Ca requirement ( 11 , 12 ) and does not estimate the P and Ca requirement for bone directly from protein. This is an interesting multicriteria approach to mitigate P impact that will be essential for P precision feeding ( 13 ).…”

Bone traits and gastrointestinal tract parameters of piglets fed cholecalciferol and 1,25-dihydroxycholecalciferol glycoside

“…However, the dietary calcium content was based on commercial diets, with formulated values below the nutritional requirements (NRC, 2012;Rostagno et al, 2017), promoting different concentration values in the bone. An increase in dietary phosphorus content has limited effect on the phosphorus content in soft tissue, whereas the phosphorus retention in the bone is enhanced (Lautrou et al, 2020). In this case, bones are the default storage site for calcium and phosphorus if availability exceeds growth requirement (González-Vega et al, 2016).…”