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.

-A cross-over study was conducted to investigate the effect of intramammarily infused lipopolysaccharide (LPS) on the acute phase reaction in early (EL) and in late (LL) lactation. Nine cows received intramammary injections of 100 µg of Escherichia coli 0111:B4 LPS during EL and LL. The severity of each cows systemic and local signs and change in milk appearance were recorded and scored throughout the experiment. Systemic and local signs were found to be more serious in EL cows. Tumor necrosis factor α (TNFα) was detected in milk but not in serum. Serum amyloid A (SAA) concentrations increased both in serum and in milk. The milk TNFα concentrations peaked at 8 h post-challenge (PC). SAA concentrations started to increase at 8 h PC, and peak concentrations were seen at 32 and 48 h PC in milk and serum, respectively. The milk TNFα and SAA seemed to be correlated, being on average higher in EL. Serum SAA concentration was not correlated with milk TNFα or SAA, nor with the severity of local or systemic signs, but was correlated with changes in milk appearance. LPS / mastitis / dairy cow / SAA / TNFα

Minimal inhibition concentration (MIC) values of 100 Finnish and 100 Israeli Escherichia coli isolated from clinical bovine mastitis were determined for ampicillin, cephalexin, ceftazidime, dihydrostreptomycin, gentamicin, tetracycline, trimethoprim-sulfadiazine, and ciprofloxacin by an agar dilution method. The in vitro antimicrobial susceptibility of the E. coli isolates was high; only 27% showed resistance to one or more tested antimicrobial agents. Fifteen percent of the Israeli isolates and 14% of the Finnish isolates were resistant to tetracycline, 3 and 16% to cephalexin, 10 and 7% to ampicillin, 13 and 9% to dihydrostreptomycin, and 4 and 2% to trimethoprim-sulfadiazine. No gentamicin-, ceftazidime-, or ciprofloxacin-resistant isolates were detected. Eleven percent of all the isolates were resistant to two or more antimicrobial agents. Tetracycline was most often associated with multiresistant patterns. Most of the multiresistant isolates had very high MIC values, whereas most of those that were resistant to only one tested antibiotic had MIC values close to the susceptibility breakpoint. Antimicrobial resistance appeared to pose no problem in E. coli isolated from mastitic milk of both countries. This is probably due to the controlled use of antimicrobial agents in the treatment of dairy herds. Some differences were present in the resistance patterns, which may reflect the different use of antimicrobial agents in these two countries.

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).

Lactoferrin (Lf) is a molecule naturally present in bovine milk that affects the availability and transport systems of iron. Lf also binds endotoxin (lipopolysaccharide, LPS) of Gram-negative bacteria and modulates the immunological response. In the present study, concentrations of bovine Lf (bLf) and citrate in milk were determined in early (EL) and late (LL) lactating dairy cows, using an experimentally induced endotoxin mastitis model and a crossover design. Nine clinically healthy Finnish Ayrshire cows were challenged twice with 100 μg endotoxin infused into one udder quarter. Milk samples were collected from the challenged and control quarters of each cow before and after endotoxin infusion during 3 d, and bLf and citrate concentrations were measured. In all cows, clinical signs of mastitis were seen at both times of challenge, but the response was more severe in EL than in LL. Concentration of bLf in the milk started to rise approximately 8 h after endotoxin infusion and was still higher than normal on the third day, especially in the late-lactating cows. In milk of the LL group, concentrations of bLf were significantly higher than in the EL group. In contrast, concentrations of citrate were higher in milk of the EL cows compared with the LL cows. Concentration of bLf and citrate varied substantially among cows. The molar ratio of citrate to bLf before and after challenge was significantly higher during the EL period. The results of this study partly explain why cows in early lactation are more susceptible to intramammary infections and why mastitis is more severe in them.