Short communication: Genetic analysis of respiratory disease in Norwegian Red calves.

A genetic analysis of respiratory disease (RD) in Norwegian Red calves was conducted. This is the first genetic study of calf diseases based on data from the Norwegian health recording system, and RD was chosen because it is the most frequent disease in calves. Records on absence or presence of RD before 180 d of age for 250,212 calves (progeny of 728 Norwegian Red artificial insemination sires) were analyzed with a threshold model. A total of 0.7% of the calves had veterinary treatment of RD before 180 d of age. Heritability of RD in the underlying scale was 0.05, with a 95% credibility interval from 0.02 to 0.09. The "worst" sire had a predicted probability of RD that was more than twice as high as that of the "best" one (1.15 vs. 0.44%). Their 95% credibility intervals for predicted probability of RD, however, overlapped. With improved and more extensive recording of calf diseases, the precision in genetic evaluation of sires could increase considerably. The frequency of RD is very low in the Norwegian Red population at present, so there is not much scope for genetic improvement. However, this study indicates that reasonably precise genetic evaluation of sires for resistance to RD could be feasible.