The impact of spontaneous Neospora caninum infection on pregnancy loss and subsequent
pregnancy in grazing lactating dairy cows was evaluated. Data from 1273 females (878
multiparous and 395 first-calving cows) from six preselected dairy herds were analyzed.
Cows were classified as seropositive (SP) (prevalence, 24%; range, 11%–33%) or seronegative
(SN) by indirect immunofluorescence detection of antibodies against
N caninum. Seropostive cows (prevalence, 40.0%) presented higher (P < 0.001) incidence of
abortion compared with SN cows (prevalence, 4.1%). Neospora caninum DNA was detected
by real-time polymerase chain reaction in 44.4% of intact aborted fetuses from SP cows,
whereas none was found in those aborted from SN cows. The average daily milk production
adjusted to 305 days was lower (P < 0.001) in SP (22.5 0.3 L/day) than in SN cows
(24.8 0.2 L/day). Furthermore, SP cows presented greater occurrence of retained placenta
(17.1% vs. 6.0%; P < 0.001) and acute postpartum metritis (9.8% vs. 2.4%; P < 0.001). Despite
similar pregnancy rates after first postpartum artificial insemination (27.6% vs. 31.8%;
P ¼ 0.40), cumulative pregnancy rates during 300 days in milk (94.7% vs. 98.5%; P ¼ 0.005)
were greater in SN cows. A reduced (P ¼ 0.0001) Cox proportional hazard of pregnancy rate
at 300 days inmilk and a longer interval from parturition or abortion to conception (median,
111 vs. 101 days) were observed in SP compared with SN cows. Spontaneous N caninum
infection is a significant contributing factor of pregnancy loss and occurrence of uterine
disease (i.e., retained placenta and metritis), negatively affecting subsequent pregnancy in
grazing lactating dairy cows.
The impact of spontaneous Neospora caninum infection on pregnancy loss and subsequentpregnancy in grazing lactating dairy cows was evaluated. Data from 1273 females (878multiparous and 395 first-calving cows) from six preselected dairy herds were analyzed.Cows were classified as seropositive (SP) (prevalence, 24%; range, 11%–33%) or seronegative(SN) by indirect immunofluorescence detection of antibodies againstN caninum. Seropostive cows (prevalence, 40.0%) presented higher (P < 0.001) incidence ofabortion compared with SN cows (prevalence, 4.1%). Neospora caninum DNA was detectedby real-time polymerase chain reaction in 44.4% of intact aborted fetuses from SP cows,whereas none was found in those aborted from SN cows. The average daily milk productionadjusted to 305 days was lower (P < 0.001) in SP (22.5 0.3 L/day) than in SN cows(24.8 0.2 L/day). Furthermore, SP cows presented greater occurrence of retained placenta(17.1% vs. 6.0%; P < 0.001) and acute postpartum metritis (9.8% vs. 2.4%; P < 0.001). Despitesimilar pregnancy rates after first postpartum artificial insemination (27.6% vs. 31.8%;P ¼ 0.40), cumulative pregnancy rates during 300 days in milk (94.7% vs. 98.5%; P ¼ 0.005)were greater in SN cows. A reduced (P ¼ 0.0001) Cox proportional hazard of pregnancy rateat 300 days inmilk and a longer interval from parturition or abortion to conception (median,111 vs. 101 days) were observed in SP compared with SN cows. Spontaneous N caninuminfection is a significant contributing factor of pregnancy loss and occurrence of uterinedisease (i.e., retained placenta and metritis), negatively affecting subsequent pregnancy ingrazing lactating dairy cows.
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