Influence of calcium and phosphorus feeding on markers of bone metabolism in transition cows

Abstract

A study was carried out to verify the effect of Ca and P levels on production, digestibility, and serum bone metabolism biomarkers in dairy cows. Fifty-two nonlactating multiparous cows (>or=3 lactations) were confined in a free-stall barn approximately 20 d before calving. A standard close-up diet was fed to cows once daily until d 2 postpartum. Cows were randomly assigned to 1 of 4 dietary treatments arranged in a 2 x 2 factorial approach averaging 0.64% Ca for high Ca (HCa), 0.46% Ca for low Ca (LCa), 0.47% P for high P (HP), and 0.38% P for low P (LP) on a dry matter basis. Experimental diets were fed twice daily from 3 d in milk (DIM) until 31 DIM. Intake and milk yield were recorded daily. Milk samples were collected on d 28, 29, and 30 postpartum for components analyses. Blood samples were drawn 10 d before expected calving, at calving, and at 15 and 30 DIM for serum analyses of osteocalcin, a biomarker of bone accretion, and pyridinoline, a biomarker of bone resorption. Total fecal collection was conducted when cows in a block averaged 20 DIM. Intake and production traits were not significantly affected by any of the dietary treatments. Cows averaged nearly 21 kg/d dry matter intake and 44 kg/d milk yield from 6 to 31 DIM. There were no significant differences across treatments in body weight or body condition score loss. Phosphorus intake, P fecal output, P digestibility, and P apparent absorption were affected by dietary P content. Calcium intake was higher with HCa, but Ca fecal output, digestibility, and apparent absorption showed an interaction between dietary Ca and dietary P. Calcium fecal output was 100.6 g/d for cows fed HCaHP, intermediate for cows on the HCaLP diet (89 g/d), and similar among cows fed the 2 LCa diets (70 g/d with LCaHP and 75 with LCaLP). There was no significant effect of Ca or P on osteocalcin measurements. Pyridinoline concentrations were affected by dietary Ca levels and tended to have a significant dietary Ca x dietary P interaction. Phosphorus apparent digestibility occurred independently of dietary Ca levels. Results of this study suggest that more bone was mobilized in cows fed LCa diets, but excess dietary P caused greater and prolonged bone mobilization regardless of dietary Ca content.

Meta-analysis of factors that affect the utilization efficiency of phosphorus in lactating dairy cows

“…This database subset comprised data from lactating dairy cows from 25 studies (Martz et al, 1990;Morse et al, 1992;Spiekers et al, 1993;Delaquis and Block, 1995;Khorasani et al, 1997;Knowlton et al, 2001Wu et al, 2001Wu et al, , 2003Knowlton and Herbein, 2002;Guyton et al, 2003;Kebreab et al, 2005;Kincaid et al, 2005;Shore et al, 2005;Wu, 2005;Ekelund et al, 2006;Kamiya et al, 2006a;Knowlton et al, 2007;Dann et al, 2008;Moreira et al, 2009;Myers and Beede, 2009;Taylor et al, 2009;Van Straalen et al, 2009;Herrera et al, 2010;Puggaard et al, 2011) and included 130 treatment means. The response variable of interest was P excretion in the feces, both in grams per day and as a fraction of P intake.…”

Effect of calcium intake and dietary cation anion difference in early lactation on bone mobilization dynamics all over lactation in dairy cows

“…For this purpose, the dietary Ca supply was limited to 70% of the recommended supply to cover the cows’ requirements according to the expected milk production and intake according to the INRA feeding system (INRA, 2010). With such restriction of Ca supply, some studies highlighted a decrease in the body retention of Ca at the beginning of lactation in dairy cows, with this decrease in body Ca retention later reaching negative values (11,31), whereas some studies highlighted an increase in the serum concentration of pyridinoline, which is a biomarker of bone resorption (16). Both results suggested an increase in mobilization of Ca from bones.…”

“…Incomplete bone reconstitution at the end of the lactation can result in a higher susceptibility of cows to the restricted supply of P during the following lactation, with suboptimal production performances, as highlighted for sucker cows by Dixon et al (6), or maybe to higher susceptibility of milk fever at the beginning of the next lactation (14). The effects of dietary Ca and P content and strategies for the supplementation of Ca and P on the amplitude and the completeness of the cycle of bone formation and resorption have been quantified in several experiments in lactating ruminants (10–13,15,16).…”

An extended model of phosphorus metabolism in growing ruminants1

“…Differences between resnlts could be due to the different experimental methods, type of animals or dietary P intakes used in each experiment. Several studies have shown that excess dietary P is associated with decreased P retention in bone in swine (Reinhart and Mahan, 1986), mice (Yuen and Draper, 1983), and dogs (Laflamme and Jowsey, 1972), and greater and prolonged bone mobilization in transition cows (Moreira et al, 2009). Excess P in relation to Ga can lead to skeletal softening, and a maximum tolerable dietary P of 0.6% in the ration has been recommended (NRG, 2007).…”