Spirometric variables recorded after lobeline administration in healthy Friesian and Belgian White and blue calves: Normal values and effects of somatic growth

The purposes of the present study were: (I) to develop original equations t o predict spirometric variables (SV) in healthy Friesian and Belgian White and Blue (BWB) calves <1 year of age; and (2) to determine the effects of s omatic growth on SV. Sixty-seven Friesian and 500 BWB calves were investiga ted. For each calf, the following SV were calculated: (1) the average minut e volume derived using all the ventilatory cycles recorded during the 15 s of maximal ventilatory changes induced by lobeline administration (0.25 mg/ kg, i.v.) (15-s LMV); (2) the maximal tidal volume, the maximal peak expira tory flow and the maximal peak inspiratory flow recorded from single breath s after lobeline administration (MVTL, MPEFL and MPIFL, respectively); (3) the ventilatory reserve (VRL = 15-s LMV - V-Er; V-Er = minute volume at res t). Mass specific (s) values were also calculated. All SV changed linearly with somatic growth in both Friesian and BWB calves. Since the rise in SV w as more related to body weight than the age of calves, equations for refere nce values of SV always had body weight as the only independent variable. I n the youngest calves, sSV were lower in the BWB breed. In the oldest calve s (i.e. 1 year of age), sMPEF(L) and sMPIF(L) remained small in BWB calves whereas sMV(TL), s15-s LMV and sVR(L) were almost equal in both breeds. The se results could be related to the lower resistance to respiratory disorder s in BWB calves < 1 year of age than in Friesian calves < 1 year of age.