Dietary supplementation with 25-hydroxycholecalciferol and phytase in growing-finishing pigs: I. Effects on performance, carcass traits, muscle antioxidant capacity and fatty acid profile

The objective of this study was to determine the effects of 25-hydroxycholecalciferol (25OHD 3 ) and phytase on carcass traits, muscle antioxidant capacity and fatty acid profile of growing-finishing pigs fed low-phosphorus (P) diets. Eighty crossbred pigs [Duroc × (Landrace × Yorkshire)] with initial body weight (BW) of 49.38 ± 4.31 kg were allotted to 4 diets with 5 replicate pens per treatment (2 barrows and 2 gilts per pen) according to BW and sex. The whole experiment lasted for 88 days from the beginning of feeding to the end of slaughter, including phase 1 (days 1–28), phase 2 (days 29–60), and phase 3 (days 61–88). The treatments were designed as a 2 × 2 factorial arrangement: low-P diet (C); low-P diet + 1000 U phytase/kg diet (C + phytase); low-P diet +50 μg 25OHD 3 /kg diet (C + 25OHD 3 ); low-P diet + 1000 U phytase/kg diet +50 μg 25OHD 3 /kg diet (C + phytase + 25OHD 3 ). Dietary 25OHD 3 supplementation decreased (P < 0.05) feed conversion ratio (FCR) in phase 1 and overall phase. Phytase increased (P < 0.05) carcass yield, and 25OHD 3 enhanced (P < 0.05) a* value of the longissimus dorsi muscle. 25OHD 3 or phytase improved (P < 0.05) total antioxidant capacity (T-AOC) content and superoxide dismutase (SOD) activity in the longissimus dorsi muscle. 25OHD 3 decreased (P < 0.05) n-6:n-3 polyunsaturated fatty acid (PUFA) ratio and iodine value, phytase tended to decrease (P = 0.094) n-6:n-3 PUFA ratio and decreased (P < 0.05) iodine value in the longissimus dorsi muscle. In addition, significant interaction between 25OHD 3 and phytase was observed for SOD activity and n-6:n-3 PUFA ratio (P < 0.05). The mRNA expressions of copper/zinc superoxide dismutase (Cu/Zn SOD) and nuclear factor E2-related factor 2 (Nrf2) were increased (P < 0.05) by 25OHD 3 or phytase supplementation. 25OHD 3 increased (P < 0.05) the mRNA expression of peroxisome proliferator activated receptor gamma (PPARγ), phytase increased (P < 0.05) the mRNA expression of PPARγ and tended to increase (P = 0.052) the mRNA expression of fatty acid synthase (FAS) in the longissimus dorsi muscle. Collectively, 25OHD 3 slightly improved the efficiency of growth. 25OHD 3 and phytase supplementation enhanced some carcass traits and meat quality, especially for higher antioxidant capacity and lower n-6:n-3 PUFA ratio.