Production Effects of Pathogens Causing Bovine Leukosis, Bovine Viral Diarrhea, Paratuberculosis, and Neosporosis

Abstract

The primary purpose of this research was to determine associations among seropositivity for bovine leukemia virus (BLV), bovine viral diarrhea virus (BVDV), Mycobacterium avium ssp. paratuberculosis (MAP), and Neospora caninum (NC) and each of 3 outcome variables (305-d milk, fat, and protein production) in Canadian dairy cattle. Serum samples from up to 30 randomly selected cows from 342 herds on monthly milk testing were tested for antibodies against BLV (IDEXX ELISA; IDEXX Corporation, Westbrook, ME), MAP (IDEXX or Biocor ELISA; Biocor Animal Health, Inc., Omaha, NE), and NC (IDEXX or Biovet ELISA; Biovet Inc., St. Hyacinthe, Quebec, Canada). Up to 5 unvaccinated cattle over 6 mo of age were tested for virus-neutralizing antibodies to the Singer strain of type 1 BVDV. Dairy Herd Improvement records were obtained electronically for all sampled cows. Linear mixed models with herd and cow as random variables were fit, with significant restricted maximum likelihood estimates of outcome effects being obtained, while controlling for potential confounding variables. Bovine leukemia virus seropositivity was not associated with 305-d milk, 305-d fat, or 305-d protein production. Cows in BVDV-seropositive herds (at least one unvaccinated animal with a titer > or =1:64) had reductions in 305-d milk, fat, and protein of 368, 10.2, and 9.5 kg, respectively, compared with cows in BVDV-seronegative herds. Mycobacterium avium ssp. paratuberculosis seropositivity was associated with lower 305-d milk of 212 kg in 4+-lactation cows compared with MAP-seronegative 4+-lactation cows. Neospora caninum seropositivity in primiparous cows was associated with lower 305-d milk, fat, and protein of 158, 5.5, and 3.3 kg, respectively, compared with NC-seronegative primiparous cows. There were no interactions among seropositivity for any of the pathogens and their effects on any of the outcomes examined, although the low MAP seroprevalence limited this analysis. Results from this research will contribute to understanding the economic impacts of these pathogens and justify their control.

Effects of paratuberculosis on Friesian cattle carcass weight and age at culling

“…In fact, the economic consequences of these two items have been estimated to account for nearly 70% of overall direct economic losses occurring in MAP infections (Ott et al, 1999;Groenendaal et al, 2002). Consistent results regarding the relationship between lower milk yields and PTB are easily found in the literature (Buergelt & Duncan, 1978;Ott et al, 1999;Kudahl et al, 2004;Hendrick et al, 2005;Tiwari et al, 2007;Smith et al, 2009;Aly et al, 2010). In addition to this, some researchers have suggested that PTB is associated with increased mortality rates, higher infertility rates (Merkal et al, 1975;Buergelt & Duncan, 1978;Johnson-Ifearulundu et al, 1999), greater susceptibility to other secondary pathologies such as mastitis (Buergelt & Duncan, 1978) and decreased slaughter value.…”

Effects of bovine leukemia virus infection on crossbred and purebred dairy cattle productive performance in Brazil

“…Furthermore, other percentages of milk production losses were also described, such as 2.7% reported by Ott, Johnson and Wells (2003), or 3.5% found by Brenner et al (1989). In opposite, some studies have shown that BLV infection has no influence on milk production (KALE et al, 2007;TIWARI et al, 2007) and also in others, BLVpositive cows have even shown an increase in milk production (JACOBS et al, 1991;POLLARI et al, 1992). …”

Effects of subclinical Mycobacterium avium ssp. paratuberculosis infection on some physiological parameters, health status and production in dairy cows

“…There are several studies analysing the effects of MAP infection on the milk yield of dairy cows where a decrease in milk yield is reported (Benedictus et al, 1987;Wilson et al, 1993;Nordlund et al, 1996). The decrease in the milk production of subclinically infected cows tends to be progressive, but statistical differences may only be confirmed in the fourth or later lactations (Tiwari et al, 2007(Tiwari et al, , 2008. However, other authors did not find any difference (Johnson et al, 2001) or even reported an increased milk yield (McNab et al, 1991) in MAP-infected cows.…”