The effect of the stage of lactation on blood redox homeostasis of bovine and buffalo cows was evaluated. The investigation was carried out on early lactating and mid-late lactating cows, reared in a farm located in Campania (southern Italy). Plasma concentration of α-tocopherol and ascorbate, the total antioxidant capacity (TAC), glutathione peroxidase (GPx), and superoxide dismutase activities were higher (P < 0.01) in mid-late lac-tating cows, thus suggesting a higher consumption of antioxidants during early lactation. Plasma concentration of protein-bound carbonyls (PC) and nitrotyrosine (N-Tyr), and the level of lipid hydroperoxides (LPO) were higher (P < 0.01) in early lactating cows, thus suggesting that lipid peroxidation and peroxynitrite production are crucial in determining oxidative modifications in plasma. TAC was positively correlated with ascorbate concentration (P < 0.03), and negatively correlated with PC concentration (P < 0.002), and ascorbate was negatively correlated with PC (P < 0.03) in mid-late lactating group. These findings demonstrate that circulating ascorbate plays a major role in preventing protein modifications induced by carbonyls, and that ascorbate scavenging effect is impaired during early lactation. We calculated a protein oxidative stress index as the ratio (PC + N-Tyr)/TAC multiplied by 100, and we found that this parameter was higher (P < 0.0001) in early lactating cows. Therefore, it could be useful for assessing the extent of protein oxidative damage in relation to the whole antioxidant status. Further, we suggest that the LPO/GPx ratio multiplied by 100 might be used as lipid oxidative stress index in lactating cows. This index was higher (P < 0.0001) in early lactating cows, and might represent a standard parameter for evaluating the lipid damage depending on a deficiency of the enzymatic antioxidant defence. These parameters are proposed for a possible effective description of physiological changes associated with lactation.

Quarter milk samples were taken from 48 clinically healthy, pregnant Finnish Ayrshire and Friesian dairy cows at the last milking before drying-off, and 2 and 6 days later to determine the lactoferrin and citrate concentrations in the udder secretion. The mean lactoferrin concentration in the milk increased from 5.29 mg ml(-1) on the last day of drying-off process to 8.09 and 11.26 mg ml(-1), 2 and 6 days later, respectively. Citrate concentration decreased from 1.85 mg ml(-1) to 1.54 and 1.09 mg ml(-1), respectively. Median molar ratio (citrate to native-Lf) decreased from 153 to 86 and further to 44. Lf and citrate concentrations in milk varied greatly among cows. Sampling time had a statistically significant effect on lactoferrin and citrate concentrations in milk while the breed and the parity of the cows had no effect on either of these variables.

The effect of bovine lactoferrin (Lf) was studied in experimental Escherichia coli mastitis, using enrofloxacin as a comparator. Mastitis was induced in six clinically healthy primiparous dairy cows by infusing 1500 colony-forming units of E. coli into a single udder quarter. The challenge was repeated into a contralateral quarter of the same cows 3 weeks later. At the first challenge, three cows were treated with 1.5 g of bovine lactoferrin intramammarily three times (12, 20 and 36 h postchallenge, PC), and the other three cows received 5 mg/kg of enrofloxacin (Baytril) parenterally (12, 36 and 60 h PC). Flunixin meglumine (2.2 mg/kg) was administered to all cows twice at 24-h intervals. During the second challenge, the treatments for the two groups were reversed. Intramammary challenge with E. coli produced clinical mastitis in all cows, but the severity of the disease varied markedly. No statistically significant differences between treatment groups were observed in clinical signs such as rectal temperature, rumen motility and general attitude. Milk somatic cell count, daily milk yield and bacterial counts in cows treated with Lf and those receiving enrofloxacin also did not differ significantly. However, a trend for a more rapid elimination of bacteria was seen in the cows treated with enrofloxacin. Milk NAGase activity also decreased significantly faster in the group treated with enrofloxacin. The concentration of lipopolysaccharide in milk compared with the number of bacteria was significantly lower in Lf than in enrofloxacin-treated cows (20 h PC).

Staphylococcus aureus (S. aureus), and coagulase-negative staphylococci (CNS) as well as on Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae), originally isolated from bovine mastitis. Concentrations of Lf used were 0.67 mg/ml, 1.67 mg/ml, and 2.67 mg/ml. Growth of udder pathogens was monitored by turbidometry either in broth culture or in whey prepared from normal milk. We focused on 3 different growth variables: lag time, slope, and maximum absorbance of bacterial growth curves. Growth inhibition was seen in the broth but hardly at all in whey. The isolates of E. coli and CNS did not grow sufficiently well in whey to draw any conclusions. The most effective inhibitory activity of Lf was seen against E. coli and P. aeruginosa. All 5 E. coli isolates had similar growth patterns. Inhibition of growth by Lf was concentration-dependent. The concentration of 0.67 mg/ml in broth and whey was generally too low for a significant inhibitory effect. mastitis pathogens; growth inhibition.

Disposition kinetics of lactoferrin (Lf) purified from cheese whey was studied in the milk of Finnish Ayrshire cows after intramammary administration of 1 g of Lf into one udder quarter. Intramammary administration of 1 g of Lf increased Lf concentration in milk for several hours. Mean elimination half-life of Lf was 2.2 h and a mean maximum concentration of 6.3 g/L was reached between 1 and 4 h. After 8 h of administration, Lf concentrations in milk decreased to almost the same level as before the infusion. Forty-eight hours postinfusion, the mean Lf concentration was again higher than in the milk samples taken before the infusion of Lf, being on average 1.5 g/L. Lactoferrin caused some local tissue irritation in the udder quarter. Severity of the irritation reactions varied between cows. The udder quarters of primiparous cows reacted faster than those of multiparous cows, but irritation reactions decreased more rapidly in the older cows than in primiparous cows. The cows had no general signs such as fever or anorexia. The somatic cell count returned to baseline level 4 days after the administration.