乳牛栄養の野外実態調査

Abstract

Since 1955, field surveys have been conducted by this regional laboratory on the state of nutrition of dairy cows. As a part of these surveys, vitamin C levels in the blood and milk were determined, by the DNP method, in pure and hybrid Holsteins and pure Jerseys kept in crop and dairy farms in Niigata and Nagano Prefectures.The average value of blood levels was 0.490mg/dl in pure and hybrid Holsteins in Niigata Prefecture, 0.657mg/dl in Jerseys in Nagano Prefecture, and 0.637mg/dl in cows kept in the Nagano Breeding Stock Farm, Ministry of Agriculture and Forestry. In cows kept by crop farms in Niigata and Nagano Prefectures, no seasonal changes were present in blood levels, but negative correlations were observed, though a little, among blood sugar, serum protein, age, and blood level. In those kept by the Nagano Breeding Stock Farm, however, where feeding conditions and the circumstances under which examinations were performed were perfectly the same with those for the foregoing cows, the blood level showed seasonal changes and very distinct correlations with blood sugar and other factors, being high in winter and spring and low in summer. In short, there was a tendency of high blood sugar and low vitamin C level among them.In no areas of both prefectures, blood level of vitamin C was related to reproductive disorders, acetone in the urine, sugar in the urine, results of Gross test, yield of milk, and feedstuffs.It is assumed that the change of vitamin C level is influenced more deeply by the movement of the whole body than by any individual factor, as vitamin C level varies easily by stress.The average value of milk levels was 2.073mg/dl in the pure and hybrid Holsteins and 2.856mg/dl in the Jerseys, showing no correlations with blood levels.According to the results of examinations in the Nagano Breeding Stock Farm, there was a tendency that milk levels were high in winter and spring and low in summer, as well as blood levels. Milk levels of mastitic milk samples, except thoe showing separation of the components, were not so conspicuously different from those of normal milk samples and revealed no correlations with leukocyte counts in the milk.