225 The Effect of Different Analytical Methods on Assessment of Bone Mineralization of Various Rib Bones in Response to Dietary P, Phytase, and Vitamin D in Nursery Pigs

Abstract

Abstract Pigs (n = 350; initial body weight = 11.9 ± 0.56 kg) were used to evaluate the effects of different bones and analytical methods on the assessment of rib bone mineralization response to dietary P and vitamin D in nursery pigs. Currently, there is little information available describing the effect of rib location (2nd through 10th) on measures of bone mineralization including density and ash. Pens of pigs (5 pigs/pen) were randomized to 6 dietary treatments in a randomized complete block design with 10 pens/treatment. Pens of pigs were assigned dietary treatments consisting of: 1) P at 0.19% STTD P (deficient); 2) P at 0.33% STTD P (NRC requirement) using monocalcium phosphate; 3) P at 0.33% STTD P using monocalcium phosphate and phytase; 4) P at 0.44% STTD P (industry level) using monocalcium phosphate, phytase, no vitamin D; 5) diet 4 with vitamin D (1,653 IU/kg), and 6) diet 5 with additional 2,000 IU/kg 25(OH)D3 (HyD). After feeding diets for 28-days, eight pigs/treatment were harvested for bone analysis. The 2nd, 3rd, 5th, 7th, and 10th ribs were collected from each pig and analyzed for bone density and non-defatted bone ash. All bones were cleaned of tissue and then dried at 105°C for 7 d and then ashed in a muffle furnace at 600°C for 24 h. Bone density was measured on each bone based on Archimedes principle. There was no interaction between bone and dietary treatment for bone density and non-defatted bone ash (P > 0.05; Table). Therefore, interpretation of results will focus on the effect of bone and treatment on measures of mineralization. Pigs fed deficient P (0.19%) had less bone density and ash percent compared with treatments fed NRC and industry levels of P. For bone density, there was a significant main effect of bone (P = 0.001), with the 10th rib having greater bone density than all other treatments and the 3rd rib having greater bone density than the 5th rib. Bone density of the 2nd and 7th ribs did not differ (P >0.05) from either the 3rd or 5th ribs. For non-defat bone ash, 10th rib had the greatest (P < 0.05) bone ash, followed by the 2nd rib which was greater (P < 0.05) than the 3rd rib, with the 5th and 7th ribs having the least non-defat bone ash percent. In summary, bone density and ash responses varied depending on the bone being measured. When measuring all of the bones, the 10th rib has the greatest value for bone density and bone ash percent, while the 5th rib has the least value for both bone density and bone ash percent compared with the rest of the bones analyzed. These results can help guide diagnostic investigations and aid in comparing results across different bones used to measure bone mineralization.