growth, phosphorus, nursery pigs
A total of 1,080 barrows and gilts (PIC; 337 × Camborough, initial pen average BW of 25.2 ± 0.64 lb) were used in a 21-d trial to determine the standardized total tract digestible (STTD) P requirement of nursery pigs from 25 to 50 lb. Two groups of pigs were weaned at approximately 21 d and allotted to pens according to BW and gender. There were 6 replicate pens per treatment and 23 to 27 pigs per pen. Pens of pigs were randomly allotted to experimental diets based on average BW at d 21 and 24 post-weaning, in a randomized complete block design. The 7 dietary treatments consisted of 0.26, 0.30, 0.33, 0.38, 0.43, 0.48, and 0.53% STTD P. These values represented 80, 90, 100, 115, 130, 145, and 160% of the NRC (2012) requirement estimate for STTD P for pigs weighing between 25 to 55 lb, respectively. Two corn-soybean meal-based diets were formulated to contain 0.26 and 0.53% STTD P by increasing the inclusion of limestone and monocalcium phosphate at the expense of corn, maintaining a similar 1.17:1 to 1.18:1 total Ca:P ratio, with no phytase added to the diets. Diets were blended using a robotic feeding system to achieve the intermediate STTD P levels.
Increasing STTD P improved ADG, ADFI, F/G, and final BW (linear, P < 0.001). There was also a marginally significant quadratic response for F/G (P = 0.067), with the greatest improvement as STTD P was increased from 0.26% to 0.33%. Income over feed cost also improved linearly through 0.53% STTD P (P < 0.001). The grams of STTD P intake per day and grams of STTD P intake per kilogram of gain where growth rate reached a point of diminishing returns in response to increased STTD P were higher than the NRC requirement estimates. For ADG, the linear model demonstrated best fit, estimating the maximum response at greater than 0.53% STTD P. For feed efficiency, modeled as G:F, the best-fitting models were the quadratic polynomial (QP) and broken-line linear (BLL). The QP model estimated the maximum at 0.43%, with 99% of maximum G:F achieved at 0.36% STTD P. The BLL plateau was estimated at 0.34% STTD P.
In conclusion, the estimated STTD P requirement for nursery pigs from 25 to 50 lb ranged from 0.34 to at least 0.53% depending on the response criteria and statistical model used, which indicates that the NRC (2012) requirement estimate is lower than what is needed to optimize performance and economic return.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Vier, C. M.; Wu, F.; Dritz, S. S.; Tokach, M. D.; Goncalves, M. A.; Orlando, U. A.; Woodworth, J. C.; Goodband, R. D.; and DeRouchey, J. M.
"Standardized Total Tract Digestible Phosphorus Requirement of 25- to 50-lb Pigs,"
Kansas Agricultural Experiment Station Research Reports: