No abstract

(Co)variance components for milk, fat, and protein yield of 8075 first-parity Danish Holsteins (DH) were estimated in random regression models by REML. For all analyses, the fixed part of the model was held constant, whereas four different functions were applied to model the additive genetic effect and the permanent environment effect. Homogeneous residual variance was assumed throughout lactation. Univariate models were compared using a minimum of -2 ln(restricted likelihood) as the criterion for best fit. Heritabilities as a function of time were calculated from the estimated curve parameters from univariate analyses. Independent of the function applied and the trait in question, heritabilities were lowest in the beginning of the lactation. Heritabilities for persistency of fat yield were slightly higher than heritabilities for persistency of milk and protein yield. Genetic correlations between persistency and 305-d production were higher for protein and milk yield than for fat yield. Bivariate analyses between the production traits were carried out in sire models using the models with the best 3-parameter curve fit in the univariate analyses. Correlations between traits were calculated from covariance components for curve parameters estimated in bivariate analyses. Genetic correlations between milk and protein yield were higher than between milk and fat yield.

The European Fifth Framework Programme (Contract No. QLK1-CT-2000-00623).

The effect of vitamin D supplementation on bone mineral augmentation in 212 adolescent girls with adequate calcium intake was studied in a randomized placebo-controlled setting. Bone mineral augmentation determined by DXA increased with supplementation both in the femur and the lumbar vertebrae in a dose-responsive manner. Supplementation decreased the urinary excretion of resorption markers, but had no impact on formation markers.Introduction: Adequate vitamin D intake protects the elderly against osteoporosis, but there exists no indisputable evidence that vitamin D supplementation would benefit bone mineral augmentation. The aim of this 1-year study was to determine in a randomized double-blinded trial the effect of 5 and 10 g vitamin D 3 supplementation on bone mineral augmentation in adolescent girls with adequate dietary calcium intake. Materials and Methods: Altogether, 228 girls (mean age, 11.4 ± 0.4 years) participated. Their BMC was measured by DXA from the femur and lumbar spine. Serum 25-hydroxyvitamin D [S-25(OH)D], intact PTH (S-iPTH), osteocalcin (S-OC), and urinary pyridinoline (U-Pyr) and deoxypyridinoline (U-Dpyr) were measured. Statistical analysis was performed both with the intention-to-treat (IT) and compliance-based (CB) method. Results: In the CB analysis, vitamin D supplementation increased femoral BMC augmentation by 14.3% with 5 g and by 17.2% with 10 g compared with the placebo group (ANCOVA, p ‫ס‬ 0.012). A dose-response effect was observed in the vertebrae (ANCOVA, p ‫ס‬ 0.039), although only with the highest dose. The mean concentration of S-25(OH)D increased (p < 0.001) in the 5-g group by 5.7 ± 15.7 nM and in the 10-g group by 12.4 ± 13.7 nM, whereas it decreased by 6.7 ± 11.3 nM in the placebo group. Supplementation had no effect on S-iPTH or S-OC, but it decreased U-DPyr (p ‫ס‬ 0.042). Conclusions: Bone mineral augmentation in the femur was 14.3% and 17.2% higher in the groups receiving 5 and 10 g of vitamin D, respectively, compared with the placebo group, but only 10 g increased lumbar spine BMC augmentation significantly. Vitamin D supplementation decreased the concentration of bone resorption markers, but had no impact on bone formation markers, thus explaining increased bone mineral augmentation. However, the positive effects were noted with the CB method but not with IT.

Dr Lars Ovesen, fax +45 33 95 11 19, email lov@fdir.dk Vitamin D is produced endogenously when the skin is exposed to sunlight and can be obtained exogenously from a few natural food sources, from food fortification and from supplements. Generally, vitamin D intake is low ≤ 2-3 µg/d in Europe. Casual exposure to sunlight is thought to provide most of the vitamin D requirement of the human population. However, skin synthesis of vitamin D may not compensate for the low nutritional intake in Europe, even in countries with high supplies from food fortification and supplements.