Effects of infection with caprine arthritis-encephalitis virus on milk production in goats

A recently assembled commercial herd of Alpine goats was studied. Milk production criteria--305-day milk production (M), butter fat content (BF), and solids nonfat content (SNF)--and somatic cell counts (linear score) were monitored by Dairy Herd Improvement Association test records. Milk samples from all milking goats in the herd were obtained for bacteriologic culture for mastitis organisms on 2 occasions; the infection rate ascribed to major pathogens was 3%. In November 1985, serum specimens were obtained from 154 does in first lactation. Of these, 56 (36%) were seropositive for caprine arthritis-encephalitis (CAE) antibodies by agar gel immunodiffusion (AGID), 91 (59%) were seronegative, and serotest results for 7 (5%) were inconclusive. In December, 80 seronegative and 48 seropositive goats remained in the herd and had 305-day projections available. The median production values for seronegative goats (1,539.5 lb of M, 52 lb of BF, 46 lb of SNF) were higher than those for seropositive goats (1,446 lb of M, 45 lb of BF, 44.5 lb of SNF), but this difference was only significant (t test, P less than 0.05) for BF. Does were ranked by a formula that combined M, BF, and SNF, with a desired minimal daily herd average of 5 lb of M, 3% BF, and 3% SNF. A decision was made not to keep offspring from does of the lowest quartile before CAE test results were obtained. This group consisted of 13 of the 80 (16%) seronegative goats and 18 of the 48 (38%) seropositive goats. Thus, a positive CAE test result by AGID was associated (chi 2, P less than 0.01) with poor production.(ABSTRACT TRUNCATED AT 250 WORDS)