Prevalence of cattle persistently infected with bovine viral diarrhea virus in 20 dairy herds in two counties in central Michigan and comparison of prevalence of antibody-positive cattle among herds with different infection and vaccination status.

All cattle in 20 dairy herds randomly selected from herds participating in the Dairy Herd Improvement Association program in 2 counties in central Michigan were tested for the presence of bovine viral diarrhea virus (BVDV). Virus-positive animals were retested to ascertain persistent infection with the virus. A total of 5,481 animals were tested for presence of BVDV. In 9 of the herds, all animals were also tested for virus neutralizing antibody titer. Based on infection and vaccination status, these 9 herds were divided into 3 different herd categories: A, 5 herds with currently no cattle persistently infected (PI) with BVDV and without any vaccination program against BVDV in recent years; B, 2 herds with no current PI cattle but using killed BVDV vaccines; and C, 2 herds with PI cattle. PI cattle were detected in 3 out of 20 herds (15%). A total of 7 of 5,481 animals (0.13%) were PI. The mean prevalences of antibody carriers in herd categories A, B, and C were 28.8%, 76.4% and 90.6%, respectively. For one herd in category A, antibody analyses indicated that mostly young stock was seropositive, suggested recent BVDV infection in a previously closed and naive herd. Cattle in category B herds were vaccinated with killed vaccine from the age of 15 months. These herds had several antibody negative animals among the younger cows, suggesting incomplete protection against BVDV infection. In the 3 herds in which PI animals were detected, all cattle had been vaccinated with killed vaccine. The antibody-positive animals had antibody titers that were significantly different both among herds and among herd categories.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vitamin E and selenium on immune responses of peripheral blood, colostrum, and milk leukocytes of sows.

This study was designed to assess how dietary vitamin E (E) and (or) selenium (Se) concentrations affect immune responses of gestating and peripartum sows. Multiparous sows (24), assigned to one of four groups at breeding, were fed ensiled, shelled corn-soybean meal-based diets without supplemental E or Se (-E-Se), with .3 mg of Se/kg (-E+Se), with 60 IU of E/kg (+E-Se), or with both supplemental E and Se (+E+Se) during gestation and to d 4 of lactation. Blood was obtained on 0, 30, 60, and 90 d of gestation and at parturition for serum E and Se assays. Lymphocytes and polymorphonuclear cells (PMN) were isolated from the blood, colostrum, and 4-d milk samples for immune studies. Compared with the control (+E+Se) diet, the -E-Se diet reduced (P < .05) the serum tocopherol and Se concentrations, the mitogenic responses of lymphocytes of peripheral blood (PBL) and colostrum (CL), the phagocytic activity of blood and colostral PMN, and the microbicidal activity of blood, colostral, and milk PMN. The -E+Se diet reduced (P < .05) the serum tocopherol concentrations, the mitogenic responses of PBL and CL, and the phagocytic activity of PBL. The +E-Se diet reduced (P < .05) serum Se concentrations and the phagocytic activity of PMN. The data indicated that E restriction depressed PBL and PMN immune functions, whereas Se restriction depressed mainly PMN function.

The influence of gestational dietary calcium on serum 1, 25-dihydroxycholecalciferol in sows and their pigs.

Fifteen multiparous sows (three groups of five) were studied during one gestation-lactation cycle to measure the influence of dietary Ca (.5, .8[control], and 1.1%) on 1,25-dihydroxycholecalciferol (1, 25-(OH)2D3) in serum and colostrum of the sows and serum of their pigs. Concentrations of 1,25-(OH)2D3 and Ca, Mg, P, Cu, and Zn were determined on d 15 and 45 of gestation, at parturition, and at 3 wk postpartum in sow serum and at birth and d 10 and 21 in pig serum. Colostrum was assayed for 1,25-(OH)2D3. Serum 1,25-(OH)2D3 in sows was affected inversely (P less than .05) by dietary Ca within d 15 of gestation and was correlated (r = -.88) with serum Ca during gestation and lactation. Serum Ca was correlated (r = .52) with dietary Ca at d 15 and 45 of gestation and at farrowing. Sow serum Mg was inversely related (r = -.49) to serum Ca during gestation and early lactation. Serum 1,25-(OH)2D3 of the pigs at birth ranged from 38.7 to 44.2 pg/ml was decreased (P less than .05) by 1.1% maternal Ca intake. Sow colostrum 1,25-(OH)2D3 was related (P less than .05) inversely (r = -.40) to sow dietary Ca and directly (r = .90) to sow serum 1,25-(OH)2D3. Serum 1,25-(OH)2D3 of 10- and 21-d-old pigs was inversely related (P less than .05) to their dams' dietary Ca. These results indicate that 1,25-(OH)2D3 production in sows is quickly affected by modest changes in dietary Ca.(ABSTRACT TRUNCATED AT 250 WORDS)