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Abstract
Four groups of Friesian bull calves, each containing nine animals, were reared to the age of 14 weeks on different levels of whole milk— 12%, 15%, and 18% of body weight, and to appetite, to Groups A, B, C, and D respectively.
Calves in Group A consumed their ration throughout the trial period. Intakes declined following the age of six weeks in Groups C and D and after 10 weeks in Group B. The decline was greatest in Group D and least in Group B.
Growth rate increased with advancing age while animals were on full rations. Total live weight gain over the entire 14-week period rose with increasing level of intake.
Feed conversion for the 14-week period did not differ between groups, although increases were noted after the age of 10 weeks in Group A, eight weeks in Group B, and six weeks in Groups C and D.
Scours were most prevalent before the fourth and after the eighth week of age. During the first four weeks of life scours appeared to be microbial in nature, and after the eighth week of age were peculiar to animals suffering from severe iron deficiency anaemia.
A progressive decline in blood haemoglobin concentrations was noted in all groups and was greatest in Groups C and D and least in Group A. The reduced feed intakes and decreased live weight gains were related to the decline in haemoglobin concentration.
Blood serum magnesium concentrations declined after the age of six weeks in Group D and eight weeks in Groups B and C. This decline was not associated with the reduced feed intakes or the decreased live weight gains.