Quelques facteurs de variation de la teneur en calcium des laits de vaches

Abstract

SummaryA study was made of the effect of various factors which may influence the calcium content of milk. The basic data consisted of the calcium content of 20840 samples of individual milks, taken once a month, during the course of 2300 lactations of Montbeliarde cows. For each lactation, a weighted average figure for the calcium concentration was calculated, taking into account the milk quantities recorded on each sampling day. The calcium content has been expressed in g/kg of milk.The stage of lactation caused significant variations in calcium content mainly during the first month and the last three months. Expressed as percentages of the arithmetic mean for the whole lactation period, these variations were always within the limits —4 to +8% (Fig. 1).The season of calving did not greatly affect the weighted lactational average content of calcium but caused some important changes in the average value with advancing lactation (Fig. 2). The minimum values were always observed in July, whatever the month of calving (Fig. 3).The age of the cow, as well as the age at first calving (Table 1), had very small effects on the calcium content.