248 Effects of feeding finishing pig diets differing in Ca:P ratio, added phytase and 25(OH)D3 on growth performance, serum 25(OH)D3, carcass characteristics, and bone characteristics

Abstract

Abstract A total of 2,160 pigs [337 × 1050, PIC; initial body weight (BW) = 33.2 ± 1.4 kg] were used in a 114-d trial to determine the effects of feeding diets differing in Ca:P ratio and added phytase or phytase and 25(OH)D3 (Hy-D, DM Nutritional Products, Parsippany, NJ) on growth performance, carcass characteristics, serum 25(OH)D3, and bone characteristics. Pigs were housed in mixed sex pens with 27 pigs per pen and 20 pens per treatment. The four treatments were assigned to pens in a randomized complete block design and consisted of 1) a high phosphorus (HP) diet with standardized total tract digestibility (STTD) P at 115% of NRC (2012) requirement estimate without added phytase and formulated to a 1.25:1 Ca to P ratio; 2) low phosphorus (LP) diet with STTD P at 80% of NRC requirement without added phytase and formulated to a 1.25:1 Ca to P ratio; 3) HP with phytase (HP+phytase) diet with STTD P at 115% of NRC requirement using 0.125% STTD P release from 600 FYT/kg HiPhorius and 1.1:1 Ca to P ratio; and 4) Diet 3 except 25(OH)D3 replaced most of the vitamin D3 in the diet (HP+25(OH)D3). Diets were fed in 4 phases from 32 to 50, 50 to 75, 75 to 100, and 100 to 133 kg. For overall growth performance, source of vitamin D had no impact on performance. Pigs fed HP diets had improved (P < 0.05) average daily gain (ADG), average daily feed intake (ADFI) and gain to feed ratio (G:F) compared with those fed LP diets, and increased ADFI compared with those fed the HP+phytase diets (Table 1). For 25(OH)D3 measured on d 50, pigs fed the HP diets had increased (P < 0.05) serum 25(OH)D3 compared with pigs fed the LP diets and pigs fed the HP+25(OH)D3 diets had increased (P < 0.05) serum 25(OH)D3 compared with pigs fed the HP+phytase diets. Pigs fed the HP diets had greater (P < 0.05) HCW and percentage lean than those fed LP diets. For bone analysis, pigs fed HP diets had greater (P < 0.05) bone ash (g) and breaking strength than pigs fed LP or HP+phytase and 1.1:1 Ca to P ratio. In conclusion, compared with pigs fed LP diets, HP-fed pigs had improved performance and HCW. Dietary 25(OH)D3 replacing D3 did not impact performance but increased circulating 25(OH)D3.