Effect of Pathogen-Specific Clinical Mastitis on Milk Yield in Dairy Cows

Abstract

Our objective was to estimate the effects of the first occurrence of pathogen-specific clinical mastitis (CM) on milk yield in 3071 dairy cows in 2 New York State farms. The pathogens studied were Streptococcus spp.,Staphylococcus aureus, Staphylococcus spp., Escherichia coli, Klebsiella spp., Arcanobacterium pyogenes, other pathogens grouped together, and "no pathogen isolated." Data were collected from October 1999 to July 2001. Milk samples were collected from cows showing signs of CM and were sent to the Quality Milk Production Services laboratory at Cornell University for microbiological culture. The SAS statistical procedure PROC MIXED, with an autoregressive covariance structure, was used to quantify the effect of CM and several other control variables (herd, calving season, parity, month of lactation, J-5 vaccination status, and other diseases) on weekly milk yield. Separate models were fitted for primipara and multipara, because of the different shapes of their lactation curves. To observe effects of mastitis, milk weights were divided into several periods both pre- and postdiagnosis, according to when they were measured in relation to disease occurrence. Another category contained cows without the type of CM being modeled. Because all pathogens were modeled simultaneously, a control cow was one without CM. Among primipara, Staph. aureus, E. coli, Klebsiella spp., and "no pathogen isolated" caused the greatest losses. Milk yield generally began to drop 1 or 2 wk before diagnosis; the greatest loss occurred immediately following diagnosis. Mastitic cows often never recovered their potential yield. Among older cows, Streptococcus spp., Staph. aureus, A. pyogenes, E. coli, and Klebsiella spp. caused the most significant losses. Many multipara that developed CM were actually higher producers before diagnosis than their nonmastitic herd-mates. As in primipara, milk yield in multipara often began to decline shortly before diagnosis; the greatest loss occurred immediately following diagnosis. Milk loss persisted until at least 70 d after diagnosis for Streptococcus spp., Klebsiella spp., and A. pyogenes. The tendency for higher producing cows to contract CM may mask its impact on cow health and production. These findings provide dairy producers with more information on which pathogen-specific CM cases should receive treatment and how to manage these cows, thereby reducing CM impact on cow well being and profitability.

Genetic parameters for production, health, fertility and longevity traits in dairy cows

“…The association between health and milk yield is well documented in the literature for both mastitis (Grö hn et al, 2004;Windig et al, 2005;Hagnestam et al, 2007) and lameness (Barkema et al, 1994). Genetic correlations between both health traits with milk production yield traits were all positive, indicating that animals genetically above average for yield traits were more liable to mastitis and lameness.…”

“…The greatest economic loss due to subclinical and clinical mastitis is reduced milk yield. The magnitude of losses depend very much upon the type of infection, the stage of lactation and parity (Grö hn et al, 2004). Bar et al (2007) estimated milk losses due to mastitis including repeated cases within and across lactations.…”

Molecular Epidemiology of TwoKlebsiella pneumoniaeMastitis Outbreaks on a Dairy Farm in New York State

“…CM due to Klebsiella infection results in high milk losses and mortality of the affected cows (13). Antimicrobial therapy and vaccination have limited effects against Klebsiella CM (15,27).…”

Mediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections

“…Total losses were estimated at 8.7 kg (for the average CFU of 'PPP' cows). Gröhn et al (2003) and Hertl et al (2014) observed a drop of >8 kg in the week following a first case of clinical mastitis due to S. aureus.…”