Effect of phosphorus and calcium precision feeding on reproductive performances and mineral status in gestating sows

Precision feeding can enhance amino acid utilization efficiency in swine, but precision phosphorus (P) feeding on gestating sows has not yet been tested. Therefore, the aim of the study was to evaluate the effects of a P and calcium (Ca) precision feeding strategy during gestation on the phosphocalcic status and performance of sows compared with constant dietary contents over two gestation cycles. A total of 120 sows were monitored over two consecutive cycles (C1 and C2) to study the effects of three dietary treatments: Canadian (CAN; 0.32% digestible P; 0.83% Ca), European (EU; 0.25% digestible P; 0.68% Ca), and precision feeding (PR; 0.15-0.32% digestible P; 0.46-0.83% Ca). Phosphocalcic status was studied during two cycles on days 30 (d30) and 90 (d90) or 110 postweaning (d110) by the 24-h total urine collection using the catheter method and blood analyses. The BW and backfat thickness were measured at mating, on d110, and at weaning. The only performance trait affected by the dietary treatments was a higher backfat thickness on d110 in sows fed PR compared to those one of EU and CAN (P < 0.05). Lactation performances were similar across all treatments. Dietary treatments, stage of gestation, and cycle did not influence urinary Ca excretion. A three-way interaction was observed for urinary P excretion and urinary Ca:P ratio (Treatment × Stage × Cycle, P < 0.05). The PR sows excreted more P in urine than the CAN sows, although the CAN sows were fed a higher P amount. High P losses were associated with a low Ca:P ratio (less than 0.5), indicating a lack of Ca supply to retained P. At d30 of C2, EU sows excreted more P than CAN sows (P < 0.05) and numerically more than PR sows, likely due to insufficient Ca supply to retain P. On d90 of C2, PR sows still lack Ca (urinary Ca:P ratio less than 0.5). This study highlights the importance of controlling the digestible Ca:P ratio when applying precision feeding in order to obtain maximal dietary P efficiency. This ratio was probably too low in the PR feeding treatment. Monitoring across multiple cycles is essential to validate this strategy and support its adoption on commercial farms.