Effect of age on the interrelations between certain blood components and milk yield during early lactation period in Ayrshire cows injected with vitamin D3 prior to calving

Authors

• Vappu Kossila Department of Animal Husbandry, University of Helsinki

DOI: https://doi.org/10.23986/afsci.71761

Abstract

Altogether 132 blood samples were drawn from V. jugularis of 38 apparently healthy lactating Ayrshire cows during the first 75 days following parturition. Each cow had been injected twice with 5 million I. U. of vitamin D3 shortly before calving. The cows were divided into two groups, I comprising 19 cows with 1 or 2 calvings and II 19 cows with more than 2 calvings. The blood hemoglobin (Hb), and hematocrit (Hc) values, and the amounts of calcium (Ca), inorganic phosphorus (P), and magnesium (Mg) in serum were determined and coefficients of correlation between the blood components and the level of the daily milk yield were calculated. The following significant partial correlations were obtained: in group I, for Hb with Mg (0.29*) and milk yield (—0.28*), and for Ca with milk yield (0.54***); in group II, for Hb with milk yield (—0.42***), and for Mg with P (0.25*); in groups I + II, for Hb with milk yield (—0.31***). The significance of the simple and corresponding partial correlations was very similar, and it did not make much difference whether the absolute instead of the relative daily milk yield was used as a variable in the calculations. The results are discussed in detail.