Measures of Bone Mineral Content in Mature Dairy Cows

Abstract

The objectives of this investigation were to assess the relationship between chemical measures and imaging estimates (radiographic photometry and dual-energy x-ray absorptiometry) of bone mineral content in dairy cows and to evaluate the effects of parity, stage of lactation, and site of measurement (fused third and fourth metacarpal bone vs. caudal vertebrae 14 and 15) on bone mineral content. In a preliminary study, the caudal vertebrae were excised from 33 cows following slaughter. Samples were analyzed by radiographic photometry and then analyzed for mineral content chemically. In a second experiment, the caudal vertebrae and right front metacarpal (sample pairs) were excised from 107 Holstein cull cows following slaughter. Parity and days in milk (DIM) of the donor animals were obtained for 43 pairs of samples. Samples were grouped by parity (1, 2, 3, and >or=4) stage of lactation (Stage 1: <90 DIM, Stage 2: 90 to 150 DIM, Stage 3: 151 to 250 DIM, and Stage 4: >250 DIM). Samples were analyzed by radiographic photometry and dual-energy x-ray absorptiometry and then analyzed for mineral content chemically. In both experiments, the relationship between mineral content estimated via the imaging techniques and mineral content measured chemically was poor, likely because of the relative maturity of animals in the sample set and lack of variation in mineral content. Ash content was higher in the metacarpal than in the caudal vertebrae, as were concentrations of Mg (expressed as a proportion of bone ash). No effects of stage of lactation were observed on bone mineral in the caudal vertebrae, but in the metacarpal, P content (proportion of total mineral) was highest in second lactation cows. Total bone mineral content (ash) was not affected by parity in the metacarpal or caudal vertebra, but Ca and P content of the metacarpal increased with parity. Noninvasive imaging techniques are not sufficiently sensitive to detect changes in mineral content or composition of mature cows, and only modest changes in bone mineral were observed with stage of lactation and parity.

Blood Mineral, Hormone, and Osteocalcin Responses of Multiparous Jersey Cows to an Oral Dose of 25-Hydroxyvitamin D3 or Vitamin D3 Before Parturition

“…The results from the present study and the Moore et al (2000) and Kamiya et al (2005) studies taken together would suggest that although primiparous cows resorb more bone compared with multiparous cows, they also replace that bone throughout lactation. Keene et al (2004) measured bone mineral content (BMC) in cadaver Holstein metacarpal and caudal vertebrae to evaluate effects of parity. Total BMC concentration (ash, % of bone DM) was not affected by parity but Ca and P concentration of the metacarpal vertebrae increased with parity.…”

ORIGINAL ARTICLE: Physiological values and factors affecting the metacarpal bone density of healthy feedlot beef cattle as measured by dual-energy X-ray absorptiometry

“…During the last decade, the dual‐energy X‐ray absorptiometry technique (DXA) has been considered ‘the gold standard’ to evaluate BMD in human beings (Fogelman and Blake, 2000). It has also been increasingly applied, among the various areas of large animal medicine, for both ex vivo and in vivo studies in pigs (Mitchell et al., 2001), sheep (Pouilles et al., 2000), horses (McClure et al., 2001; Carstanjen et al., 2003a, b), bovine calves (Scholz et al., 2003) and dairy cows (Keene et al., 2004).…”

“…Likewise, variations in bone mineralization have been reported in relation to diet in dogs (Lauten et al., 2002), horses (Hoffman et al., 1999;Shea Porr et al., 2000) and beef cattle (Shupe et al., 1988; Williams et al., 1990; Beighle et al., 1995, 1997; Motsei and Beighle, 2006). Lastly, the stages of lactation and parity have been reported to affect BMD in both mares (Glade, 1993) and dairy cows (Beighle, 1999; Keene et al., 2004).…”

Factors affecting the faecal P status of lactating beef cattle in Northern Australia

“…Little (1972) described a method that surgically removes a small disc (biopsy) from the 11 th or 12 th rib, usually 20 cm from the spine. This method has consistently demonstrated significant differences between cattle fed different dietary P intakes, and so this has become the main method used for measuring P status (Little, 1972;Little and Shaw, 1979;Hoey et al, 1982;Read et al, 1986b;Ternouth, 1990;de Waal and Koekemoer, 1997;Keene et al, 2004). Units of measure have developed and changed over time.…”

“…However, this technology is still limited by the aforementioned limitations on rib CBT in that parts of the skeleton accrete and metabolise differently and correlations with whole skeletal phosphorus have not been identified. Keene et al (2004) stated that "non-invasive imaging techniques are not sufficiently sensitive to detect changes in mineral content or composition of mature cows, and only modest changes in bone mineral can be observed with stage of lactation and parity". Zotti et al (2010) suggested that the main limitation to absorptiometry technology is the lack of reference values for bone mineral density in cattle, as it is the "gold standard" for evaluating the bone mineral density in humans.…”