In a longitudinal investigation (3 points of time n = 214, 206 resp. 202) the hemoglobin quota (Hb), the hematocrit (Hct) resp. the average corpuscular hemoglobin concentration (MCHC) were analysed at male calves receiving semi-liquid feed in the transitional period from pre-ruminal to ruminal digestion (56d). Breed, live weight development, consumption of milk, concentrated feed resp. dried forage, diseases of the calves as well as the father and the milk yield resp. the lactation age of the mother were registered as reference conditions. The percentage of calves with an Hb less than 10.5 g/dl was at the three points of time 50.00%, 86.41% resp. 41.58%, of calves with an Hct less than 33,5% it was 43.46%, 66.02% resp. 31.68% and of calves with an MCHC less than 30.5 g Hg/dl erythrocytes 51.87%, 76,21 resp. 47,03%. 21.50%, 33.50% resp. 4.46% of all test animals even had an Hb of less than 8.5 g/dl.

With 195 male rearing calves which received concentrates ad libitum beside fluid feed with milk from their 5th day of life onward, investigations were made if and how far the characteristics of the development of the calves while they are fed on colostrum (body weight at birth, live weight increase and duration of keeping or stalling age) correlate with the hemoglobin content (Hb), the hematocrit (Hc) and the average corpuscular hemoglobin concentration (MCHC) of the animals on the 3rd, 28th resp. 56th day of keeping in the weaning period. There was a significant simple dependence particularly between body weight at birth, live weight increase and stalling age on the one hand and the hematologic values on the 3rd day of keeping in the weaning period on the other. A partial correlation analysis showed that the live weight increase while the calves were fed on colostrum was the main variable for all three hematologic parameters at the beginning of the weaning period of the calves. With increasing live weight, Hb, Hc and MCHC were diminished. This analysis was supplemented by the results of a cross--section investigation of the development of the milk and concentrate consumption and the Fe-intake of the calves fed on colostrum. The calculation of the Fe-balance showed that the mere ad libitum supply with feed supplements rich in Fe cannot prevent Fe-deficiency. Anaemia developing in the first month of the calves' lives is not a physiologic one but essentially caused by Fe-deficiency.

195 calves were at random divided into 3 test groups and received oral (200 mg Fe/d) or intramuscular (1.0 and 1.5 g Fe on the 3rd and 36th day of the period of fluid feeding) applications of ferridextrane or no additional quotas of iron (control group) and a limited supply of milk replacer and skim milk as well as ad libitum supply with concentrated feed and dried green fodder during their 56-day period in the range of the rearing farm where the calves receive fluid feed. Iron intervention was carried out without considering the individual iron content of tissue. Its effect was evaluated according to the hemoglobin content (Hb), the hematocrit (Hc) and the mean corpuscular hemoglobin concentration (MCHC) in venous puncture blood. There was no difference between the test groups as to the stabling conditions (affiliation to race and genotype, birth weight, age and live weight resp. at the beginning of the experiment, live weight gain before the beginning of the experiment). In the control group Hb, Hc and MCHC were analogous to previous epidemiologic investigations concerning the anaemia of calves. The ferridextrane interventions carried out resulted in a raised level of Hb and Hc and diminished anaemia frequency as well as the shortened duration of anaemia in this rearing period.

The average hemoglobin (Hb) and hematocrit (Hc) values determined in our own investigations with 491 rearing calves in the first five months of their lives were compared with the nationally and internationally published data of the dependence of these hematologic values on the age or rearing resp. milk fattening calves. The main influencing factors on the ageing development were the initial level of Hb and Hc, the length of the milk feeding period, the time of the beginning of feed supplementing, the development of dry matter consumption resp. the supply with milk, the iron content of the milk exchanger and the live weight increase achieved under the respective nutritional conditions. This dependence on the development proves that anaemia occurring with rearing calves in the first few weeks of their lives is mainly caused by iron deficiency. From the similarity of the average Hb resp. Hc values one can derive the conclusion that the considerable anaemia frequencies observed in one's investigations are not a phenomenon specific of one farm or of time but represent a general problem of the rearing of calves without iron substitution.

The hamoglobin content (Hb), the hematocrit (Hc) resp. the mean corpuscular hemoglobin concentration (MCHC) were determined resp. calculated of the blood samples (1 to 6 per animal) taken from 491 rearing calves during the first 23 weeks of their lives. Hb, Hc and MCHC were graphed as arithmetic means with standard deviation, as quartiles and as frequency distributions on an interval scale in dependence on live weight (20 ... 160 kg) resp. age (1 ... 161 days). It follows that the period of development from birth up to 28 days of keeping in the weaning area of the rearing farm, up to an age of 63 days resp. a live weight of 80 kg must, under the reference conditions, be considered the minimal period in which the supply of iron covering the needs by iron intervention in the whole stock of calves seems advisable.