The influence of sodium supplementation of two phosphorus sources on performance and bone mineralization of growing-finishing swine evaluated at two geographical locations

Abstract

Crossbred pigs (n = 144) were used at two geographical locations (mountain and coastal) to evaluate the effects of varied Na intake on growth performance, serum minerals and bone characteristics of growing-finishing swine (average initial body weight 24.5 kg) fed either defluorinated phosphate (DFP) which contained 5% Na or dicalcium phosphate (DCP) which contained < 0.1% Na. The six dietary treatments were DFP with 0, 0.07, 0.14 and 0.28% added Na and DCP with 0 and 0.14% added Na. The basal corn-soybean meal diet contained 0.01% Na, and the Cl content was held constant at 0.25% in all diets. Drinking water at the mountain location contained 4 mg L−1 Na and 194 mg L−1 Na at the coastal location. Growth performance did not differ among treatments, with the exception of pigs fed the DCP diet without added Na (total Na, 0.01%) at the mountain location which had depressed daily gain, daily feed intake and feed per gain compared with all other diets. When metacarpals (MC) and metatarsals (MT) taken from barrows at slaughter were examined on a body weight-corrected basis, Na intake and P source did not consistently influence bone dimensional and strength characteristics. Pigs fed the DCP diet without added Na at the mountain location had a lower Na and higher Mg content of MC and MT, and serum Na and Ca concentrations were reduced while serum P, Mg and K concentrations were unchanged. Varying Na intake did not influence bone strength and mineralization, and the Na in defluorinated phosphate and drinking water is readily available for growing pigs. Key words: Sodium, phosphates, bone mineralization, pigs