Free radicals, lipid peroxidation and the antioxidant system in the blood of cows and newborn calves around calving.

The oxidative stress of birth in cattle (Bos taurus) was evaluated by measuring steady state concentration of free radicals in whole blood, rate of lipid peroxidation and activity of antioxidant enzymes in erythrocytes, antioxidant capacity of blood plasma in 14 calves at birth and four times after birth until 3 weeks of age and also in their mothers at calving. The same parameters were also measured in 58 dairy cows before calving, at parturition and after calving. Free radical concentration in the blood of newborn calves was higher than in cows confirming that birth means oxidative stress for calves. Red blood cell malondialdehyde in calves was the highest at birth and following the first solid feed intake at the third week. Superoxide dismutase activity increased in calves during the first three weeks of life. Ferric reducing ability of plasma was higher in calves at birth than in cows and decreased thereafter. Higher superoxide dismutase activity in red blood cells and lower ferric reducing ability of plasma in dairy cows was found at calving compared to the average of all pre- and post-calving results. We conclude that the blood of newborn calves is well prepared to deal with the oxidative stress of birth, and that such a stress is present even when some fingerprint markers of redox imbalance show no apparent alterations. Stress of calving has minor effects on the antioxidant system of cows.

Evaluation of vaccine-induced maternal immunity against classical swine fever.

The vaccine-induced maternal immunity against classical swine fever (CSF) was investigated in this study. Eight sows were vaccinated with the Chinese strain of classical swine fever virus (CSFV). The length of time between vaccination and farrowing was 167-217 days. Milk samples from the front, middle and back udder sections and blood samples were taken from the sows on days 3 and 14 after farrowing. Blood samples were obtained from the piglets at the age of 3, 6 and 10 weeks. The antibody level of the milk was examined by ELISA, and that of blood samples by the virus neutralization (VN) test as well. In all 3-week-old piglets and in 80% of the 6-week-old animals the neutralizing antibody level reached the titre of 1:40. In none of the 10-week-old piglets did the titre exceed the value of 1:20, but in about 25% of the piglets it reached 1:20; the half of these piglets came from two litters. In none of the piglets did the antibody level reach the negative threshold in the ELISA test during the study. No significant differences were found between the udder sections in milk antibody level by ELISA.

Eradication of bovine leukosis from a heavily infected herd by the use of own offspring.

In a Holstein-Friesian dairy herd (n = 1,248) kept in loose housing system and showing 62% prevalence of infection with bovine leukosis virus (BLV), the newborn calves were separated from their dams and placed into individual pens. They were given freeze-stored colostrum derived from a BLV-free farm and then a calf starter diet. Strict hygienic measures of leukosis control were observed. Serum samples were taken from the calves and tested by agar gel immunodiffusion (AGID) before and after colostrum uptake, at 2.5 and 6 months of age, and then at the heifer-rearing farm at 2-month intervals. Animals giving a positive reaction were culled. No AGID positivity occurred before the uptake of colostrum. Subsequently, six times as many calves became positive among the offspring of infected cows than among calves born to negative animals. As no separate barn was available, the infected farm was divided into a "black" and a "white" part with a foil to prevent aerogenic infection. The negative heifers being in the 7th month of pregnancy were placed into the "white" part. A separate calving house was established for them, as the joint calving house proved to be a source of infection. By this method a leukosis-free progeny herd was obtained from 90% of the heifer calves of the cow population showing a high prevalence of infection. In this way the original infected herd was gradually replaced.