Calcium balance and bone density in immature horses fed a high protein diet

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Title: Calcium balance and bone density in immature horses fed a high protein diet
Author: Spooner, Holly Sue
Abstract: Studies in other species indicate high protein diets increase urinary calcium (Ca ) excretion and may lead to negative calcium balance and reduced bone density . As overfeeding of protein is commonplace in the horse industry , this study was undertaken to determine the effects of excess dietary protein on growth , physiologic response , mineral balance , bone density , and bone geometry in immature horses . Sixteen 10 -month -old American Quarter Horses were blocked by age and sex into two dietary treatments . The control diet was formulated to provide the NRC (1989 ) recommended concentration of crude protein , while the high protein diet provided 130 % of NRC (1989 ) recommendations . All other nutrients were formulated at or slightly above NRC (1989 ) recommendations . Blood samples , feces , and urine were collected during the 116 -day study to determine any diet effect on pH and mineral balance . Radiographs were made of the left third metacarpal (MCIII ) to determine bone density via radiographic bone aluminum equivalence (RBAE ) , and bone geometry was determined metrically from the radiographs . Urine pH decreased over time (p < 0 .001 ) , but there were no diet effects on blood pH or urine pH . Conversely , when normalized to day 0 values , fecal pH was reduced by feeding the high protein treatment (p < 0 .02 ) . Density of dorsal and palmar cortices increased over time (p < 0 .001 ) , but no differences were observed between diets . But , normalized total medial -lateral (ML ) width of the MCIII was higher in the control diet (p < 0 .05 ) . Fecal Ca loss was greater in horses fed the high protein diet (p < 0 .005 ) , while Ca absorption and retention were lower for horses on the high protein treatment (p < 0 .02 ) . Phosphorus (P ) balance was not different between diets , although feeding the high protein diet resulted in higher P intake overall (p < 0 .001 ) . While excess dietary protein may decrease fecal pH , increase fecal Ca excretion , and decrease Ca absorption and retention , there was no consistent effect of the high protein diet on bone density over the course of this study . Further research is necessary to determine if feeding high -protein diets is detrimental to bone quality in the growing horse .
URI: http : / /hdl .handle .net /1969 .1 /4378
Date: 2006-10-30


Calcium balance and bone density in immature horses fed a high protein diet. Available electronically from http : / /hdl .handle .net /1969 .1 /4378 .

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