Published online by Cambridge University Press: 27 March 2009
1. In an experiment conducted with eight pairs of monozygous twin heifer calves aged from 7 to 9 months, it was shown that the mean haemoglobin concentration of those reared on a high plane of nutrition was higher than the corresponding value of those reared on low-plane rations.
2. The relative anaemia of the low-plane animals was microcytic but normochromic in type. Its cause must await further investigation, but these features would not be inconsistent with a deficiency of iron.
3. For this type of haematological study, monozygous twins proved more efficient than unrelated animals, as shown by the smaller variability within than between pairs.
4. Day-to-day variation in the same animal must be considered an important possible source of sampling error.