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

Abstract

The objective of this study was to determine the effects of 25-hydroxycholecalciferol (25OHD3) 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 25OHD3/kg diet (C + 25OHD3); low-P diet + 1000 U phytase/kg diet +50 μg 25OHD3/kg diet (C + phytase + 25OHD3). Dietary 25OHD3 supplementation decreased (P < 0.05) feed conversion ratio (FCR) in phase 1 and overall phase. Phytase increased (P < 0.05) carcass yield, and 25OHD3 enhanced (P < 0.05) a* value of the longissimus dorsi muscle. 25OHD3 or phytase improved (P < 0.05) total antioxidant capacity (T-AOC) content and superoxide dismutase (SOD) activity in the longissimus dorsi muscle. 25OHD3 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 25OHD3 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 25OHD3 or phytase supplementation. 25OHD3 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, 25OHD3 slightly improved the efficiency of growth. 25OHD3 and phytase supplementation enhanced some carcass traits and meat quality, especially for higher antioxidant capacity and lower n-6:n-3 PUFA ratio.