Trop Anim Health Prod (2014) 46:391–397 DOI 10.1007/s11250-013-0502-4
REGULAR ARTICLES
Milk yield and reproductive performance of brucellosis-vaccinated but seropositive Holstein cows Miguel Mellado & Angel M. Garcia & Beatriz Arellano-Reynoso & Efren Diaz-Aparicio & Jose E. Garcia
Accepted: 4 November 2013 / Published online: 20 November 2013 # Springer Science+Business Media Dordrecht 2013
Abstract The aim of this research was to study if seropositivity for brucellosis in vaccinated cows against this disease hampers reproductive performance and milk production in high-yielding Holstein cows. For this purpose 1,026 healthy cows and 372 cows seropositive for brucellosis were enrolled in this study. Cows positive to card test and subsequently to the rivanol test were further subjected to the radial immunodiffusion (RID) test. It was found that only 11 % of the presumably infected cows by brucellosis screening tests were really infected with this disease. The reproductive performance of the group of cows with 11 % Brucella -infected animals was not impaired; overall pregnancy rate did not differ between seropositive and healthy cows (30.9 vs. 29.6 %). The abortion rates were similar between seropositive cows (5.3 %) and seronegative animals (6.9 %). Cows in the herd with 11 % Brucella-infected animals produced significantly more milk than unaffected cows over a 305-day lactation (10,684±1,720 vs. 10,345±1,736; mean ± SD; P 0.1) in pregnancy rate was detected between seropositive and seronegative cows (Table 1). The low values for this variable are similar to those reported in this zone for dairy cattle (Mellado et al. 2013) and are due to a drastic heat stress experienced by cows, associated with great metabolic heat load due to the high milk yield (Wheelock et al. 2010) derived from three times milking and exacerbated by the environmental heat gain through intense solar radiation input, elevated ambient temperature for the most part of the year, mild air movement, and poor night cooling. The similar pregnancy rates between seropositive and seronegative cows were quite surprising because B. abortus mainly affects the reproductive organs of infected cows. The current study provides no evidence to support the hypothesis that reproductive function is impaired in herds of cows where 11 % of animals present brucellosis. One explanation for this lack of difference in pregnancy rate between groups of cows could be that the present study evaluated responses after chronic infection, whereas other studies have evaluated responses after acute infection. The similar pregnancy rate in the group of cows where 11 % of animals were infected with Brucella and the healthy animals is likely to be due to adequate immune responses against Brucella in the affected cows, after the acute phase of brucellosis, so the pregnancy rate of cows was not compromised. Additionally, vaccination of animals between 3 and 6 months of age with revaccination when heifers reach sexual maturity provoked that differences in reproductive performance were not recorded between healthy cows and cows serologically positive for brucellosis. B. abortus establishes inside host cells and creates a chronic infection. The chronicity of infection results from the capacity of brucellae to survive in host cells following phagocytosis, by thwarting the host's normal innate immune defenses (Roop et al. 2004; Cutler et al. 2005). However, cows elicit effective immune responses against this intracellular pathogen. The first line of defense mechanisms against invading Brucella is the innate immune system. This works by the recognition of pathogen-associated molecular patterns by pattern recognition receptors (Mogensen 2009). Subsequently, Brucella infection triggers a cell-mediated immunity, which includes CD4+ and CD8+ T lymphocytes, Th1-type cytokines such as IFN-γ and TNF-α, and activated macrophages and dendritic cells (Golding et al. 2001; Martisosyan and Gorvel 2013). Pregnancy rate at first, third, and sixth artificial insemination did not differ between groups of cows, but more services (P
REGULAR ARTICLES
Milk yield and reproductive performance of brucellosis-vaccinated but seropositive Holstein cows Miguel Mellado & Angel M. Garcia & Beatriz Arellano-Reynoso & Efren Diaz-Aparicio & Jose E. Garcia
Accepted: 4 November 2013 / Published online: 20 November 2013 # Springer Science+Business Media Dordrecht 2013
Abstract The aim of this research was to study if seropositivity for brucellosis in vaccinated cows against this disease hampers reproductive performance and milk production in high-yielding Holstein cows. For this purpose 1,026 healthy cows and 372 cows seropositive for brucellosis were enrolled in this study. Cows positive to card test and subsequently to the rivanol test were further subjected to the radial immunodiffusion (RID) test. It was found that only 11 % of the presumably infected cows by brucellosis screening tests were really infected with this disease. The reproductive performance of the group of cows with 11 % Brucella -infected animals was not impaired; overall pregnancy rate did not differ between seropositive and healthy cows (30.9 vs. 29.6 %). The abortion rates were similar between seropositive cows (5.3 %) and seronegative animals (6.9 %). Cows in the herd with 11 % Brucella-infected animals produced significantly more milk than unaffected cows over a 305-day lactation (10,684±1,720 vs. 10,345±1,736; mean ± SD; P 0.1) in pregnancy rate was detected between seropositive and seronegative cows (Table 1). The low values for this variable are similar to those reported in this zone for dairy cattle (Mellado et al. 2013) and are due to a drastic heat stress experienced by cows, associated with great metabolic heat load due to the high milk yield (Wheelock et al. 2010) derived from three times milking and exacerbated by the environmental heat gain through intense solar radiation input, elevated ambient temperature for the most part of the year, mild air movement, and poor night cooling. The similar pregnancy rates between seropositive and seronegative cows were quite surprising because B. abortus mainly affects the reproductive organs of infected cows. The current study provides no evidence to support the hypothesis that reproductive function is impaired in herds of cows where 11 % of animals present brucellosis. One explanation for this lack of difference in pregnancy rate between groups of cows could be that the present study evaluated responses after chronic infection, whereas other studies have evaluated responses after acute infection. The similar pregnancy rate in the group of cows where 11 % of animals were infected with Brucella and the healthy animals is likely to be due to adequate immune responses against Brucella in the affected cows, after the acute phase of brucellosis, so the pregnancy rate of cows was not compromised. Additionally, vaccination of animals between 3 and 6 months of age with revaccination when heifers reach sexual maturity provoked that differences in reproductive performance were not recorded between healthy cows and cows serologically positive for brucellosis. B. abortus establishes inside host cells and creates a chronic infection. The chronicity of infection results from the capacity of brucellae to survive in host cells following phagocytosis, by thwarting the host's normal innate immune defenses (Roop et al. 2004; Cutler et al. 2005). However, cows elicit effective immune responses against this intracellular pathogen. The first line of defense mechanisms against invading Brucella is the innate immune system. This works by the recognition of pathogen-associated molecular patterns by pattern recognition receptors (Mogensen 2009). Subsequently, Brucella infection triggers a cell-mediated immunity, which includes CD4+ and CD8+ T lymphocytes, Th1-type cytokines such as IFN-γ and TNF-α, and activated macrophages and dendritic cells (Golding et al. 2001; Martisosyan and Gorvel 2013). Pregnancy rate at first, third, and sixth artificial insemination did not differ between groups of cows, but more services (P
