Bovine respiratory syncytial virus reinfections and decreased milk yield in dairy cattle

Abstract

(BRSV) reinfections on the daily milk yield was studied by evaluating the milk production of 32 BRSV reinfected cows. For the estimation of milk production losses, four lactation curve models were used, including a gamma function, a second degree polynomial, and both of these models with a lag variable. Bovine respiratory syncytial virus reinfections seemed to have only a small effect on the daily milk production. Comparison of the true production with an estimated production according to the gamma function showed that the production for first lactation cows dropped 0.14 kg on average and for cows in their second or later lactation 0.56 kg on average, during 5 consecutive days in the infection period. For the seconddegree polynomial model these values were respectively 0.42 kg and 0.80 kg. All calculated average production losses were relatively small and not significant (P>0.15). The models without lag variable were more suitable than the models with the lag variable to estimate small production losses caused by BRSV reinfections. The power of this study was sufficient to detect a decrease in production of approximately 1 -1.5 kg milk per cow per day. It was therefore concluded that BRSV reinfections were not associated with an important loss of milkproduction.

Associations between bovine coronavirus and bovine respiratory syncytial virus infections and animal performance in Swedish dairy herds

“…These results are in accordance in direction with those reported by Norström et al (2001) in case of a declared outbreak, but the magnitude of the decrease observed here (on average, a 0.9 kg/d reduction over a 7-mo period) was much higher than that in the latter study (0.7 kg/d over a 1-wk period). However, Norström et al (2001) hypothesized that their result could be largely underestimated; their estimate was similar to the one reported by Van der Poel et al (1995) in case of BRSV reinfections. Information about the relative proportion of primary infected and reinfected cows (assumed to be severely affected and to have a smaller loss in milk yield, respectively) in the affected herds was lacking in their study.…”

Reduced likelihood of bovine coronavirus and bovine respiratory syncytial virus infection on organic compared to conventional dairy farms

“…Bovine coronavirus (BCV) and bovine respiratory syncytial virus (BRSV) infections are widespread, resulting in a high seroprevalence in cattle herds (Van der Poel et al, 1995;Saif, 2004). Bovine coronavirus is an enveloped, positive-stranded RNA virus classified as an antigenic group II member of the family Coronaviridae (Spaan et al, 1988) and is implicated in both respiratory and enteric disease, including calf diarrhoea, winter dysentery in adult dairy cows, and respiratory infections in cattle of all ages (Alenius et al, 1991;Saif, 2004).…”

Bovine respiratory syncytial virus outbreak reduced bulls’ weight gain and feed conversion for eight months in a Norwegian beef herd

“…Large scale epidemiological studies from data records investigating production losses and economic impact of bovine respiratory disease are usually based on clinical diagnosis, without specific information about the etiological agent [1,2,4]. For BRSV specifically, reduced milk yield [5,20] and reduced semen quality [21] are amongst the reported effects. Studies on negative consequences of this infection, relevant for rearing of young stock, are scarce and represent an important knowledge gap in the estimation of the total consequences of BRSV.…”