Abstract Recycling phosphorus (P) from swine lagoon sludge offers an opportunity to recover nutrients and offset lagoon-cleanout costs; however, its nutritional and economic value requires validation. This study evaluated dried (DSLS) and ashed swine lagoon sludge (ASLS) as alternative P sources compared with monocalcium phosphate (MCP) in nursery pig diets. A total of 192 pigs (weaned at 21 d and adjusted to feed for 1 week; 6. 99±0. 79 kg BW) were allotted by sex and BW to 48 pens (4 pigs/pen) in 16 blocks and randomly assigned within block to 3 diets. Diets were fed in 2 feeding phases (d0–14 and d14–28) and consisted of MCP (control), ASLS, or DSLS as the sole inorganic P source and were formulated to 80% of the available P requirement. Pigs were sampled on d14 and d28 for serum P analysis, and P digestibility was determined using titanium dioxide as a marker. Data were analyzed as a randomized complete block design with pen as the experimental unit and block based on sex and initial BW. Body weight and ADG did not differ among treatments in Phase 1 (P = 0. 47) ; however pigs fed DSLS had greater ADFI (P = 0. 006) and lower gain: feed (P 0. 001) than those fed MCP or ASLS. During Phase 2, pigs fed ASLS had lower BW, ADG, and gain: feed (P 0. 05) compared with MCP and DSLS and ADFI was greater for DSLS (P 0. 05) compared with ASLS but not MCP. Overall, pigs fed ASLS had lower BW (21. 77a, 20. 46b, and 21. 77a kg, for MCP, ASLS, and DSLS, respectively) and ADG (528a, 481b, 528a g/d) compared with MCP and DSLS, whereas ADFI was higher for DSLS (770. 9b, 750. 8b, 832. 5a g/d) compared with MCP and ASLS, and reduced gain: feed (0. 68a, 0. 64b, and 0. 64b) for ASLS and DSLS compared with MCP (P 0. 05). Serum P tended to be lower (P = 0. 06) for ASLS on d14 and was reduced (P 0. 001) on d28 (7. 31 mg/dL; P 0. 05) compared with MCP (9. 16 mg/dL) and DSLS (9. 35 mg/dL). The standardized total tract digestibility of P was lower (P 0. 05) for ASLS (31. 6%) than for MCP (36. 0%) and DSLS (39. 2%; P 0. 05). When DSLS was fed instead of land-applied, the net sludge-management cost decreased from 98. 00 to 75. 60 per metric ton of DM, depending on drying cost, hauling distance, and MCP price. Both ASLS and DSLS supported early growth, but prolonged ASLS use reduced BW, serum P, and digestibility of P indicating lower P availability. Feeding DSLS resulted in higher ADFI and lower feed efficiency. Despite a higher P cost, DSLS use reduced lagoon-cleanout expenses and improved nutrient recycling, offering greater value than land application. Further research is needed to optimize inclusion rates and improve the utilization of sludge-derived P in swine diets.
Soler et al. (2026) studied this question.