Dietary calcium and phosphorus levels in lactating Shenxian sows regulate growth performance and bone metabolism in suckling piglets.

Abstract

Optimal dietary calcium and phosphorus levels are critical for maximizing milk production in highly prolific sow breeds and subsequent bone development in suckling piglets. However, specific nutritional recommendations for the Shenxian sow are lacking. This study aimed to evaluate the effects of graded dietary Ca and P levels during lactation on growth performance, mineral metabolism, and the OPG/RANKL/RANK signaling pathway in nursing piglets. Forty-five multiparous Shenxian sows were randomly assigned to one of five dietary treatments in a completely randomized design (n = 9 sows/treatment). Treatments consisted of a control diet (C: 0.63% Ca, 0.31% available P), a low Ca-P diet (L: 0.55% Ca, 0.27% available P), and three high Ca-P diets (H1: 0.71%/0.35%; H2: 0.79%/0.39%; H3: 0.87%/0.43%). Piglet blood samples were collected via anterior vena cava puncture on days 17 and 35 of lactation for serum biochemical and hormonal analysis. High dietary Ca-P supplementation linearly improved indicators of mineral retention and bone regulation. Compared with the control group, apparent Ca digestibility increased in H1, H2, and H3 groups by 15.18%, 19.86%, and 16.08%, respectively ( P < 0.05). Serum P and milk Ca concentrations were elevated in all high Ca-P groups ( P < 0.05). Notably, the OPG/RANKL ratio, a key marker of inhibited bone resorption, increased by 32.73% and 41.82% in the H2 and H3 groups, respectively ( P < 0.01). While FGF-23 levels increased on Day 17 in the L, H2, and H3 groups, the H2 group exhibited a subsequent 15.05% reduction by Day 35 ( P < 0.05), suggesting a time dependent normalization of phosphaturic response. The H2 group also demonstrated superior nitrogen efficiency, with a 26.21% reduction in average daily fecal N excretion ( P < 0.05). Elevating dietary Ca and P levels to 0.79% and 0.39%, respectively, optimally enhances piglet growth performance by modulating the OPG/RANKL/RANK axis and reducing postnatal bone resorption. These findings establish evidence based nutritional thresholds for high-yielding Shenxian sows. Future research should investigate the long term effects of these mineral levels on sow longevity and subsequent reproductive cycles.