The effect of phosphorus restriction during the weaner-grower phase on compensatory growth, serum osteocalcin and bone mineralization in gilts

Ninety-six female pigs with an initial body weight (BW) of 10.0 ± 1.6 kg were assigned to 4 dietary treatments to determine the effects of restricting dietary phosphorus (P) level during the weaner-grower [approximately 10 to 50 kg BW; day (d) 0 to 59] and finisher (approximately 50 to 100 kg BW; d 59 to 131) period on growth performance, serum osteocalcin concentration, bone development and calculated P utilization. The dietary treatments were: (1) 4.0 g total P (tP)/kg from d 0 to 131 (LL); (2) 4.0 g tP/kg from d 0 to d 59 and 6.0 g tP/kg from d 59 to 131 (LH); (3) 6.0 g tP/kg from d 0 to 131 (HH) and (4) 6.0 g tP/kg from d 0 to 59 and 4.0 g tP/kg from d 59 to 131 (HL). During the weaner-grower period (d 0 to 59), pigs offered high P diets had higher daily gain (P < 0.001), feed intake (P < 0.05), P intake (P < 0.001), bone ash (P < 0.05) and serum osteocalcin concentration (P < 0.05) compared to pigs offered low-P diets. Pigs offered LH, HH and HL diets had higher average daily gain compared to pigs offered LL diet from d 59 to 131 (P < 0.01). Pigs offered LL diet had a lower carcass weight compared to pigs offered LH, HH and HL diets on d 131 (P < 0.05). Pigs offered LL diet had a lower bone ash (P < 0.05), bone P (P < 0.01) and bone calcium (P < 0.05) concentration than pigs offered LH, HL and HH diets on d 131. Pigs offered LH diet had higher concentration of osteocalcin compared to pigs offered LL (P < 0.01), HH (P < 0.05) and HL (P < 0.05) diets on d 88 and 108. In conclusion, compensatory effect occurred in growth performance and bone mineral concentration at the termination of the finisher stage when high P was introduced at the initiation of the finisher stage, following consumption of a low-P diet during the weaner-grower stage. However, pigs offered LH diet did not surpass the level of growth performance or bone mineralization achieved by pigs offered HH diet.