Abstract

The aim of this study was to evaluate phosphorus (P) kinetics in calves submitted to a single acute infection of
Cooperia punctata, using isotopic dilution and modelling techniques. Ten Holstein calves were used, with a mean live
weight of 66.05 ± 0.30 kg. Of these, five received a single dose of 45 000 infectant (L3) C. punctata larvae and the other
five were maintained in a control group without infection. Twenty one days after the infection, all animals received 29.6
MBq 32P by intravenous injection to evaluate P kinetics. Weight gain, feed consumption and excretion in the faeces and
urine were monitored and blood was collected for seven days. After the collection period, all animals were slaughtered, tissues collected and worms counted. The number of eggs per gram of faeces (EPG) reached 3 342 ± 194 and the
number of adult worms was 12 992 ± 1 470. Final live weight, mean daily live weight gain, level of P in the plasma and
its retention in control calves were higher and P excretion in the faeces less than in the infected calves. There was a
negative P balance in both the control and infected calves for soft tissues and bone. A single infection by C. punctata
negatively influenced calf performance and P kinetics, leading to lower retention of the mineral.

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