Abstract
Our objective was to determine the effects of high phytase levels and feeding duration on performance of growing finishing pigs. A total of 1,215 barrows and gilts (PIC 359×Camborough, initially 28.0±0.47 kg) were used in a 126-d growth trial with 27 pigs per pen and 15 pens per treatment in a randomized complete block design. Diets were corn-soybean meal-dried distillers grains with solubles-based.Treatments were: 1) Control (no added phytase); 2) Grower phytase (1,500 FYT/kg added phytase fed from d 0 to 57, then no phytase from d 57 to market); and 3) Grow-finish phytase (1,500 FYT/kg added phytase fed throughout the study). Phytase (Ronozyme Hiphos GT 2500, heat-stable; DSM Nutritional Products, Inc., Parsippany, NJ) was assumed to release 0.146% digestible phosphorus (P), 0.166% available P, 0.102% STTD calcium, 53 kcal/kg of metabolizable energy, 42 kcal/kg of net energy (NE), and 0.0217, 0.0003, 0.00886, 0.0224, 0.0056, 0.0122, and 0.0163% standardized ileal digestible lysine, methionine, methionine+cysteine, threonine, tryptophan, isoleucine, and valine, respectively. Beef tallow and feed grade amino acids (AA) were added to the diets without phytase to balance NE and AA across treatments. Data were analyzed using generalized linear mixed models with pen as the experimental unit.Overall, pigs fed diets with no phytase and pigs that were only fed phytase in the grower period had greater (P< 0.05) average daily gain (ADG) and feed efficiency (G:F) than pigs fed the phytase-containing diets until market. Pigs fed the control and grower phytase treatments had greater (P< 0.10) hot carcass weight (HCW) than the phytase throughout treatment. No evidence of differences (P >0.10) were observed for other carcass characteristics. In summary, adding 1,500 FYT/kg of phytase and using full matrix values for minerals, AA, and energy had detrimental effects on ADG, G:F, and HCW in this study when applied to the entire grow-finish period.
Effects of the standardized ileal digestible lysine to metabolizable energy ratio on performance and carcass characteristics of growing-finishing pigs
